0001628280-24-006393 | 10-K | XBRL Viewer

Print Document View Excel Document

Equity Incentive Plans - Valuation Assumptions for Stock Options (Details) - Stock options	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (years)	5 years 1 month 6 days	4 years 10 months 24 days	5 years
Expected volatility	97.60%	92.10%	77.00%
Risk-free interest rate	3.80%	2.20%	4.70%
Dividend yield	0.00%	0.00%	0.00%

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 35
-Paragraph 1D
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480483/718-10-35-1D

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 35
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480483/718-10-35-3

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)(1)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)(2)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)(3)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(i)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(ii)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iii)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iv)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iv)(01)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iv)(02)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iv)(03)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iv)(04)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(i)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(ii)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 16: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 17: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(01)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 18: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(02)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 19: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(03)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 20: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (d)(1)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 21: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (d)(2)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 22: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (e)(1)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 23: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (e)(2)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 24: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (f)(2)(i)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 25: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (f)(2)(ii)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 26: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (f)(2)(iii)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 27: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (f)(2)(iv)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 28: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (f)(2)(v)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

+ Details

Fair Value Measurements - Narrative (Details) - USD ($)	Dec. 31, 2023	Dec. 31, 2022
Fair Value Disclosures [Abstract]
Allowance for credit loss on available-for-sale debt securities	$ 0	$ 0

Fair Value Measurements

12 Months Ended

Dec. 31, 2023

Fair Value Disclosures [Abstract]

Fair Value Measurements

FAIR VALUE MEASUREMENTS

Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs.

The three-level hierarchy for the inputs to valuation techniques is briefly summarized as follows:

Level 1 – Valuations are based on quoted prices in active markets for identical assets or liabilities and readily accessible to us at the reporting date.

Level 2 – Valuations based on inputs other than Level 1 that are observable, either directly or indirectly, such as quoted prices for similar assets or liabilities; quoted prices in markets that are not active; or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities.

Level 3 – Valuations based on unobservable inputs for which there is little or no market data, which require us to develop our own assumptions.

The following table sets forth the fair value of our financial assets and liabilities that are measured or disclosed on a recurring basis by level within the fair value hierarchy (in thousands):


	December 31, 2023
	Total Fair Value		Level 1		Level 2		Level 3
Assets:
Money market funds	$	18,641	$	18,641	$	—	$	—
U.S. government-sponsored agency bonds	102,093		—		102,093		—
Commercial paper	49,654		—		49,654		—
Asset-backed securities	8,625		—		8,625		—
U.S. treasury securities	2,457		—		2,457		—

Total	$	181,470	$	18,641	$	162,829	$	—

Liabilities:
Derivative liabilities for exit fee	$	675	$	—	$	—	$	675
Total	$	675	$	—	$	—	$	675


	December 31, 2022
	Total Fair Value		Level 1		Level 2		Level 3
Assets:
Money market funds	$	84,313	$	84,313	$	—	$	—
Commercial paper	25,291		—		25,291		—
U.S. government-sponsored agency bonds	1,479		—		1,479		—
Corporate bonds	999		—		999		—


Total	$	112,082	$	84,313	$	27,769	$	—

Liabilities:
Derivative liability for exit fees	$	1,656	$	—	$	—	$	1,656
Total	$	1,656	$	—	$	—	$	1,656

Where quoted prices are available in an active market, securities are classified as Level 1. We classify money market funds as Level 1. When quoted market prices are not available for the specific security, we estimate fair value by using benchmark yields, reported trades, broker/dealer quotes and issuer spreads. We classify U.S. government-sponsored agency bonds, U.S. treasury securities, corporate bonds, commercial paper, and asset-backed securities as Level 2. In certain cases, where there is limited activity or less transparency around inputs to valuation, securities or derivative liabilities, such as the 2018 Exit Fee and 2022 Exit Fee, as defined and discussed in Note 10. Derivative Liabilities, are classified as Level 3.

The carrying amounts reflected in the balance sheets for cash equivalents, short-term investments, accounts receivable, prepaid expenses and other current assets, accounts payable and accrued expenses approximate their fair values at both December 31, 2023 and 2022, due to their short-term nature.

Based on our procedures under the expected credit loss model, including an assessment of unrealized losses in our portfolio, we concluded that any unrealized losses on our marketable securities were not attributable to credit and, therefore, we have not recorded an allowance for credit losses for these securities as of December 31, 2023 and 2022.

Fair Value of Debt

The principal amount outstanding under our term loan facilities is subject to a variable interest rate. Therefore, we believe the carrying amount of the term loan facility approximates fair value as of December 31, 2023 and 2022. See Note 9. Borrowings for a description of the Level 2 inputs used to estimate the fair value of the liability.

The carrying value of the deferred royalty obligation related to the sale of future royalties approximates its fair value as of December 31, 2023 and is based on our current estimates of future royalties and commercialization milestones expected to be paid to us by Kyowa Kirin Co., Ltd. (KKC) over the life of the agreement. See Note 8. Deferred Royalty Obligation Related to the Sale of Future Royalties for a description of the Level 3 inputs used to estimate the fair value of the liability.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Summary of Significant Accounting Policies - Narrative (Details) - USD ($) $ in Thousands	1 Months Ended
	Jun. 30, 2022	Jun. 30, 2015	Dec. 31, 2023	Oct. 31, 2023	Sep. 30, 2023	Dec. 31, 2022
Summary of significant accounting policies
Inventory			$ 12,448			$ 3,282
ISBRELA And XPHOZAH Units, Previously Expensed In Period Prior To Commencement Of Capitalization Of Inventory Costs
Summary of significant accounting policies
Inventory			$ 21,800			$ 28,000
Minimum
Summary of significant accounting policies
Estimated useful lives			3 years
Maximum
Summary of significant accounting policies
Estimated useful lives			5 years
AstraZeneca \| AZ Termination Agreement
Summary of significant accounting policies
Percentage of royalty revenue		10.00%
Percentage of non royalty revenue		20.00%
Maximum potential payment per agreement		$ 75,000
Aggregate cost of revenue recognized			$ 27,600
Healthcare royalty partners IV, L.P \| Licensing revenue
Summary of significant accounting policies
Royalty payments and commercial milestone payments	$ 20,000
Upfront payment	10,000
Payment to be received	$ 5,000			$ 5,000	$ 5,000

Net Loss Per Share - Computation of Net Loss Per Common Share (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Numerator:
Net loss	$ (66,067)	$ (67,207)	$ (158,165)
Denominator:
Weighted average common shares outstanding - basic (in shares)	219,331,253	158,690,083	104,205,645
Weighted average common shares outstanding - diluted (in shares)	219,331,253	158,690,083	104,205,645
Net loss per share - basic (in dollars per share)	$ (0.30)	$ (0.42)	$ (1.52)
Net loss per share - diluted (in dollars per share)	$ (0.30)	$ (0.42)	$ (1.52)

- Definition

The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483443/250-10-50-3

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 260
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 15
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482635/260-10-55-15

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 40
-Name Accounting Standards Codification
-Section 65
-Paragraph 1
-Subparagraph (e)(4)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480175/815-40-65-1

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 40
-Name Accounting Standards Codification
-Section 65
-Paragraph 1
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480175/815-40-65-1

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 11
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483443/250-10-50-11

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 11
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483443/250-10-50-11

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 7
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483443/250-10-50-7

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 260
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482689/260-10-45-2

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 260
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 60B
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482689/260-10-45-60B

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483443/250-10-50-4

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 260
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482662/260-10-50-1

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 260
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 10
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482689/260-10-45-10

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(25))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483621/220-10-S99-2

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04(27))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483589/942-220-S99-1

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(23))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483586/944-220-S99-1

Reference 16: http://www.xbrl.org/2003/role/exampleRef
-Topic 260
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 52
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482635/260-10-55-52

Reference 17: http://www.xbrl.org/2003/role/disclosureRef
-Topic 260
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 7
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482689/260-10-45-7

+ Details

- Definition

The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483443/250-10-50-3

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 260
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 15
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482635/260-10-55-15

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 40
-Name Accounting Standards Codification
-Section 65
-Paragraph 1
-Subparagraph (e)(4)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480175/815-40-65-1

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 40
-Name Accounting Standards Codification
-Section 65
-Paragraph 1
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480175/815-40-65-1

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 11
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483443/250-10-50-11

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 11
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483443/250-10-50-11

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 7
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483443/250-10-50-7

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 260
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482689/260-10-45-2

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 260
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 60B
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482689/260-10-45-60B

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483443/250-10-50-4

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 260
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482662/260-10-50-1

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(25))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483621/220-10-S99-2

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04(27))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483589/942-220-S99-1

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(23))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483586/944-220-S99-1

Reference 15: http://www.xbrl.org/2003/role/exampleRef
-Topic 260
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 52
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482635/260-10-55-52

Reference 16: http://www.xbrl.org/2003/role/disclosureRef
-Topic 260
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 7
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482689/260-10-45-7

+ Details

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(g)(1)(ii))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480678/235-10-S99-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 323
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481687/323-10-50-3

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 825
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 28
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482907/825-10-50-28

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482765/220-10-50-6

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483443/250-10-50-3

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (b)(2)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483443/250-10-50-1

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 40
-Name Accounting Standards Codification
-Section 65
-Paragraph 1
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480175/815-40-65-1

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 8
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483443/250-10-50-8

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 9
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483443/250-10-50-9

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 11
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483443/250-10-50-11

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 11
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483443/250-10-50-11

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483443/250-10-50-4

Reference 13: http://www.xbrl.org/2003/role/exampleRef
-Topic 946
-SubTopic 830
-Name Accounting Standards Codification
-Section 55
-Paragraph 10
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480167/946-830-55-10

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 220
-Name Accounting Standards Codification
-Section 45
-Paragraph 7
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483581/946-220-45-7

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(18))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483586/944-220-S99-1

Reference 16: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 22
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-22

Reference 17: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6-07(9))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483575/946-220-S99-1

Reference 18: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 3
-Subparagraph (SX 210.6-09(1)(d))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483575/946-220-S99-3

Reference 19: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(i))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480097/470-10-S99-1A

Reference 20: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(ii))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480097/470-10-S99-1A

Reference 21: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(iii)(A))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480097/470-10-S99-1A

Reference 22: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(iv))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480097/470-10-S99-1A

Reference 23: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(5))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480097/470-10-S99-1A

Reference 24: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(i))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480097/470-10-S99-1B

Reference 25: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(iii)(A))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480097/470-10-S99-1B

Reference 26: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(iii)(B))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480097/470-10-S99-1B

Reference 27: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(iv))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480097/470-10-S99-1B

Reference 28: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(5))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480097/470-10-S99-1B

Reference 29: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 30
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-30

Reference 30: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 32
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-32

Reference 31: http://www.xbrl.org/2003/role/disclosureRef
-Topic 260
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 60B
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482689/260-10-45-60B

Reference 32: http://www.xbrl.org/2003/role/exampleRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 31
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-31

Reference 33: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 32
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-32

Reference 34: http://www.xbrl.org/2003/role/disclosureRef
-Topic 205
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 7
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483499/205-20-50-7

Reference 35: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 230
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 28
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482740/230-10-45-28

Reference 36: http://www.xbrl.org/2003/role/disclosureRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 1A
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482790/220-10-45-1A

Reference 37: http://www.xbrl.org/2003/role/disclosureRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 1B
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482790/220-10-45-1B

Reference 38: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(20))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483621/220-10-S99-2

Reference 39: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 942
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04(22))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483589/942-220-S99-1

+ Details

Cash, Cash Equivalents and Short-Term Investments - Narrative (Details)	12 Months Ended
	Dec. 31, 2023 USD ($) investment	Dec. 31, 2022 USD ($) investment
Cash and Cash Equivalents [Abstract]
Short-term securities, contractual maturities, maximum	1 year	1 year
Investment in continuous unrealized loss position for more than one year \| investment	0	0
Allowance for credit loss on available-for-sale debt securities \| $	$ 0	$ 0

Income Taxes - Components of Deferred Tax Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Deferred tax assets:
Amortization and depreciation	$ 64,919	$ 64,111
Net operating loss carryforwards	98,702	86,547
Tax credits	15,375	14,411
Stock-based compensation	6,946	5,244
Deferred royalty obligation	4,907	2,577
Other	6,707	4,909
Gross deferred tax assets	197,556	177,799
Valuation allowance	(196,197)	(175,670)
Deferred tax assets net of valuation allowance	1,359	2,129
Deferred tax liabilities:
Right-of-use asset	(1,359)	(2,129)
Other	0	0
Net deferred tax assets	$ 0	$ 0

Stockholders' Equity (Details) - USD ($) $ / shares in Units, shares in Millions	1 Months Ended	3 Months Ended	12 Months Ended			14 Months Ended	29 Months Ended
	Jan. 31, 2023	Mar. 31, 2023	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2021	Dec. 31, 2023	Aug. 31, 2021	Jul. 31, 2020
Subsidiary, Sale of Stock [Line Items]
Proceeds from issuance of common stock in at the market offering, net of issuance costs			$ 119,236,000	$ 71,625,000	$ 101,146,000
2020 Open Market Sales Agreement
Subsidiary, Sale of Stock [Line Items]
Offering sales commission (percent)			3.00%
Common stock sold and issued (in shares)					23.3
Proceeds from issuance of common stock in at the market offering, net of issuance costs					$ 100,000,000
Weighted-average share price (in dollars per share)						$ 4.30
2021 Open Market Sales Agreement
Subsidiary, Sale of Stock [Line Items]
Offering sales commission (percent)							3.00%
Common stock sold and issued (in shares)		15.5
Proceeds from issuance of common stock in at the market offering, net of issuance costs		$ 51,900,000
Weighted-average share price (in dollars per share)		$ 3.35					$ 1.57
Total of gross proceeds		$ 150,000,000
2023 Open Market Sales Agreement
Subsidiary, Sale of Stock [Line Items]
Offering sales commission (percent)	3.00%
Common stock sold and issued (in shares)			16.8
Proceeds from issuance of common stock in at the market offering, net of issuance costs			$ 70,000,000
Weighted-average share price (in dollars per share)			$ 4.17
Common stock
Subsidiary, Sale of Stock [Line Items]
Maximum aggregate offering price	$ 250,000,000								$ 250,000,000
Common stock \| 2020 Open Market Sales Agreement
Subsidiary, Sale of Stock [Line Items]
Maximum aggregate offering price									$ 100,000,000
Common stock \| 2021 Open Market Sales Agreement
Subsidiary, Sale of Stock [Line Items]
Maximum aggregate offering price								$ 150,000,000
Common stock \| 2023 Open Market Sales Agreement
Subsidiary, Sale of Stock [Line Items]
Maximum aggregate offering price	$ 150,000,000

Income Taxes

12 Months Ended

Dec. 31, 2023

Income Tax Disclosure [Abstract]

Income Taxes

INCOME TAXES

The components of our provision for income taxes for the years ended December 31, 2023, 2022 and 2021, are as follows (in thousands):


	Year Ended December 31,
	2023		2022		2021
Current:
State	$	47	$	8	$	4
Foreign	500		—		—
Total current	547		8		4
Deferred:
Federal	—		—		—
Total deferred	—		—		—
Provision for income taxes	$	547	$	8	$	4

A reconciliation of the statutory federal income tax rate to our effective tax rate is as follows:


	Year Ended December 31,
	2023		2022		2021
Income tax at the federal statutory rate	21.0	%	21.0	%	21.0	%
State taxes, net of federal benefit	3.4		1.9		0.4
Tax credits	1.7		1.5		1.0
Stock based compensation	0.1		(2.3)		(1.3)
Foreign withholding tax	(0.8)		—		—
Executive compensation disallowed under IRC Sec 162(m)	(1.9)		(1.6)		(1.1)
Other	—		(0.8)		—
Change in valuation allowance	(24.3)		(19.7)		(20.0)
Income tax provision	(0.8)	%	—	%	—	%

Deferred income taxes reflect the tax effects of temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes. Significant components of our deferred tax assets are as follows as of December 31, 2023 and 2022 (in thousands):


	December 31,
	2023		2022
Deferred tax assets:
Amortization and depreciation	$	64,919	$	64,111
Net operating loss carryforwards	98,702		86,547
Tax credits	15,375		14,411
Stock-based compensation	6,946		5,244
Deferred royalty obligation	4,907		2,577
Other	6,707		4,909
Gross deferred tax assets	197,556		177,799
Valuation allowance	(196,197)		(175,670)
Deferred tax assets net of valuation allowance	1,359		2,129
Deferred tax liabilities:
Right-of-use asset	(1,359)		(2,129)

Other	—		—
Net deferred tax assets	$	—	$	—

Realization of deferred tax assets is dependent on future taxable income, if any, the timing and the amount of which are uncertain. We assess the available positive and negative evidence to estimate whether sufficient future taxable income will be generated to permit use of the existing deferred tax assets. A significant component of objective negative evidence evaluated was our cumulative loss incurred over the three-year period ended December 31, 2023. Such objective evidence limits the ability to consider other subjective evidence, such as our projections for future growth. On the basis of this evaluation, as of December 31, 2023, 2022 and 2021, a full valuation allowance has been recorded against our net deferred tax asset. The valuation allowance increased by $20.5 million in 2023 primarily due to increases in net operating losses. The amount of the deferred tax asset considered realizable, however, could be adjusted if estimates of future taxable income during the carryforward period are reduced or increased or if objective negative evidence in the form of cumulative losses is no longer present and additional weight is given to subjective evidence such as our projections for growth.

As of December 31, 2023, we had net operating loss carryforwards for federal income tax purposes of approximately $479.0 million, of which approximately $328.8 million can be carried forward indefinitely and the remaining net operating losses expire beginning in 2030, if not utilized. Federal research and development tax credit carryforwards of approximately $17.8 million that expire beginning in 2027, if not utilized, and foreign tax credit carryforwards of approximately $1.7 million that begin to expire in 2027, if not utilized.

In addition, we had net operating loss carryforwards for California income tax purposes of approximately $92.9 million that expire beginning of 2030, if not utilized, and state research and development tax credit carryforwards of approximately $8.9 million which can be carried forward indefinitely. We had approximately $0.1 million of minimum tax credit carryovers for California income tax purposes. The minimum tax credits have no expiration date. We had other state net operating losses of approximately $50.5 million that begin to expire in 2031.

The future utilization of net operating loss and tax credit carryforwards and credits may be subject to an annual limitation, pursuant to Internal Revenue Code Sections 382 and 383, as a result of ownership changes that may have occurred previously or that could occur in the future. Due to the existence of the valuation allowance, limitations under Section 382 and 383 will not impact our effective tax rate.

Under the Tax Cuts and Jobs Act of 2017, research and development costs are no longer fully deductible and are required to be capitalized and amortized for U.S. tax purposes effective January 1, 2022. The mandatory capitalization requirement did not have a material impact on our deferred tax assets and did not result in a cash tax liability as we have historically elected to capitalized research and development expenses for tax purposes.

A reconciliation of the beginning and ending amount of unrecognized tax benefits is as follows (in thousands):


	December 31,
	2023		2022		2021
Balance at beginning of year	$	24,075	$	24,426	$	23,624
Additions based on tax positions related to current year	262		460		1,613
Additions based on tax positions related to prior year	99		—		—
Subtractions based on tax positions related to prior year	(811)		(811)		(811)
Balance at end of year	$	23,625	$	24,075	$	24,426

We recognize a tax benefit from an uncertain tax position when it is more likely than not that the position will be sustained upon examination, including resolutions of any related appeals or litigation processes, based on the technical merits. Income tax positions must meet a more likely than not recognition at the effective date to be recognized. None of our unrecognized tax benefits would impact the effective tax rate if recognized, because the benefit would be offset by an increase in the valuation allowance.

We have elected to include interest and penalties as a component of tax expense. During the years ended December 31, 2023, 2022 and 2021, we did not recognize accrued interest and penalties related to unrecognized tax benefits. Although the timing and outcome of an income tax audit is highly uncertain, we do not anticipate that the amount of existing unrecognized tax benefits will significantly change during the next 12 months.

We file a U.S. federal income tax return and income tax returns in various state and local jurisdictions. Due to our net operating loss and tax credit carryforwards, the income tax returns remain open to U.S. federal and state tax examinations. We are not currently under examination in any tax jurisdiction.

- Definition

The entire disclosure for income taxes. Disclosures may include net deferred tax liability or asset recognized in an enterprise's statement of financial position, net change during the year in the total valuation allowance, approximate tax effect of each type of temporary difference and carryforward that gives rise to a significant portion of deferred tax liabilities and deferred tax assets, utilization of a tax carryback, and tax uncertainties information.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480990/946-20-50-13

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(h)(2))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480678/235-10-S99-1

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-Name Accounting Standards Codification
-Publisher FASB
-URI https://asc.fasb.org//740/tableOfContent

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 14
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482685/740-10-50-14

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 21
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482685/740-10-50-21

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 270
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482526/740-270-50-1

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 17
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482685/740-10-50-17

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SAB TOPIC 6.I.5.Q1)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479360/740-10-S99-1

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Subparagraph (SAB Topic 11.C)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479360/740-10-S99-2

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482603/740-30-50-2

+ Details

Deferred Royalty Obligation Related To The Sale Of Future Royalties (Details) - USD ($)	1 Months Ended	12 Months Ended
	Jun. 30, 2022	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Oct. 31, 2023	Sep. 30, 2023
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Amortization of the deferred royalty obligation		$ 3,924,000	$ 1,673,000	$ 0
Proceeds from royalties received		0
Healthcare royalty partners IV, L.P \| License
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Royalty payments and commercial milestone payments	$ 20,000,000
Upfront payment	10,000,000
Payment to be received	$ 5,000,000				$ 5,000,000	$ 5,000,000
Transaction costs		$ 400,000
Amortization, effective interest rate, percent		34.70%

Leases - Undiscounted Cash Payment Obligations (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Undiscounted cash payment obligations
2024	$ 4,715
2025	1,450
2026	329
Thereafter	0
Total undiscounted operating lease payments	6,494
Imputed interest expenses	(334)
Total operating lease liabilities	6,160	$ 9,749
Less: Current portion of operating lease liability	(4,435)	(3,894)
Operating lease liability, net of current portion	$ 1,725	$ 5,855

Inventory - Narrative (Details) - USD ($)	Dec. 31, 2023	Dec. 31, 2022
Inventory Disclosure [Abstract]
Prepaid commercial manufacturing	$ 23,200,000	$ 13,600,000
Prepaid commercial manufacturing, non-current	$ 4,235,000	$ 0

Audit Information	12 Months Ended
Audit Information	Dec. 31, 2023
Audit Information [Abstract]
Auditor Name	Ernst & Young LLP
Auditor Location	Boston, MA
Auditor Firm ID	42

Borrowing - Future Payment Obligations (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Future payment obligations
2024	$ 0
2025	0
2026	0
2027	52,475
Thereafter	0
Total repayment obligations	52,475
Less: Unamortized discount and debt issuance costs	(912)
Less: Unaccreted value of final fee	(1,741)
Long-term debt	49,822
Less: Current portion of long-term debt	0	$ (26,711)
Long-term debt, net of current portion	$ 49,822	$ 0

Property and Equipment, Net (Tables)

12 Months Ended

Dec. 31, 2023

Property, Plant and Equipment [Abstract]

Schedule of Property and Equipment

Property and equipment consist of the following (in thousands):


	December 31,
	2023		2022
Laboratory equipment	$	46	$	46
Office equipment and furniture	2,433		2,089
Leasehold improvements	8,731		8,745
Property and equipment, gross	11,210		10,880
Less: accumulated depreciation	(10,201)		(9,657)
Total property and equipment, net	$	1,009	$	1,223

Income Taxes - Components of Provision for Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Current:
State	$ 47	$ 8	$ 4
Foreign	500	0	0
Total current	547	8	4
Deferred:
Federal	0	0	0
Total deferred	0	0	0
Provision for income taxes	$ 547	$ 8	$ 4

- Definition

Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

+ References + Details

Revenue - Revenue from Customers as a Percentage of Total Product Revenue, Net (Details) - Gross product revenue - Customer	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
BioRidge Pharma, LLC
Disaggregation of Revenue [Line Items]
Concentration risk (percent)	26.30%	0.00%
Cardinal
Disaggregation of Revenue [Line Items]
Concentration risk (percent)	21.60%	23.10%
AmerisourceBergen Drug Corporation
Disaggregation of Revenue [Line Items]
Concentration risk (percent)	20.90%	26.80%
McKesson Corporation
Disaggregation of Revenue [Line Items]
Concentration risk (percent)	17.20%	21.60%

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References + Details

Borrowing (Tables)

12 Months Ended

Dec. 31, 2023

Debt Disclosure [Abstract]

Schedule of Future Debt Payment Obligations

As of December 31, 2023, our future payment obligations related to the 2022 Loan, excluding interest payments and the 2022 final fee, were as follows (in thousands):



2024	$	—
2025	—
2026	—
2027	52,475
Thereafter	—
Total repayment obligations	52,475
Less: Unamortized discount and debt issuance costs	(912)
Less: Unaccreted value of final fee	(1,741)
Long-term debt	49,822
Less: Current portion of long-term debt	—
Long-term debt, net of current portion	$	49,822

Cash, Cash Equivalents and Short-Term Investments - Securities Classified as Cash and Short-Term Investments (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Cash and cash equivalents:
Fair value	$ 21,470	$ 96,140
Short-term investments:
Amortized Cost	162,605	27,823
Gross Unrealized Gains	280	6
Gross Unrealized Losses	(56)	(60)
Fair Value	162,829	27,769
Total cash equivalents and investments, Cost	184,075	123,963
Total cash equivalents and investments, Gross Unrealized Gains	280	6
Total cash equivalents and investments, Gross Unrealized Losses	(56)	(60)
Total cash equivalents and investments, Fair Value	184,299	123,909
U.S. government-sponsored agency bonds
Short-term investments:
Amortized Cost	101,892	1,487
Gross Unrealized Gains	235	0
Gross Unrealized Losses	(34)	(8)
Fair Value	102,093	1,479
Commercial paper
Short-term investments:
Amortized Cost	49,630	25,336
Gross Unrealized Gains	41	6
Gross Unrealized Losses	(17)	(51)
Fair Value	49,654	25,291
Corporate bonds
Short-term investments:
Amortized Cost		1,000
Gross Unrealized Gains		0
Gross Unrealized Losses		(1)
Fair Value		999
Asset-backed securities
Short-term investments:
Amortized Cost	8,628
Gross Unrealized Gains	2
Gross Unrealized Losses	(5)
Fair Value	8,625
U.S. treasury securities
Short-term investments:
Amortized Cost	2,455
Gross Unrealized Gains	2
Gross Unrealized Losses	0
Fair Value	2,457
Cash
Cash and cash equivalents:
Fair value	2,829	11,827
Money market funds
Cash and cash equivalents:
Fair value	$ 18,641	$ 84,313

STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Operating activities
Net loss	$ (66,067)	$ (67,207)	$ (158,165)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization expense	1,292	1,144	2,807
Non-cash lease expense	3,624	3,457	3,085
Stock-based compensation	13,530	10,750	12,039
Non-cash interest expense	4,220	1,962	283
Gain on sale of equipment	0	(1,260)	0
Other, net	(2,930)	685	(678)
Changes in operating assets and liabilities:
Accounts receivable	(14,298)	(7,231)	(502)
Inventory	(21,141)	(28,346)	0
Prepaid commercial manufacturing	(9,593)	(4,161)	(9,406)
Prepaid expenses and other assets	(6,035)	2,299	502
Accounts payable	279	6,582	(1,349)
Accrued compensation and benefits	5,049	2,126	(250)
Operating lease liabilities	(3,928)	(3,491)	(2,853)
Accrued and other liabilities	3,691	4,138	1,386
Deferred revenue	2,590	8,509	550
Net cash used in operating activities	(89,717)	(70,044)	(152,551)
Investing activities
Proceeds from maturities and redemptions of investments	84,321	67,000	125,550
Purchases of investments	(215,225)	(50,328)	(72,735)
Proceeds from sale of property and equipment	0	1,798	0
Purchases of property and equipment	(344)	(55)	(1,867)
Net cash (used in) provided by investing activities	(131,248)	18,415	50,948
Financing activities
Proceeds from issuance of common stock in at the market offering, net of issuance costs	119,236	71,625	101,146
Proceeds from 2022 Loan, net of issuance costs	22,386	26,971	0
Proceeds from the sale of future royalties, net of issuance costs	5,000	9,581	0
Proceeds from issuance of common stock under equity incentive and stock purchase plans	1,173	202	1,403
Payment of the 2018 Exit Fee	(1,500)	0	0
Payments for the 2018 Loan, net of costs	0	(33,038)	(19,444)
Payments for taxes related to net share settlement of equity awards	0	0	(106)
Net cash provided by financing activities	146,295	75,341	82,999
Net (decrease) increase in cash and cash equivalents	(74,670)	23,712	(18,604)
Cash and cash equivalents at beginning of period	96,140	72,428	91,032
Cash and cash equivalents at end of period	21,470	96,140	72,428
Supplementary disclosure of cash flow information:
Cash paid for interest	4,240	2,901	3,469
Cash paid for income taxes	51	6	4
Supplementary disclosure of non-cash activities:
Right-of-use assets obtained in exchange for lease obligations	339	0	1,604
Issuance of common stock for services	337	390	190
Issuance of derivative in connection with issuance of loan payable	$ 0	$ 375	$ 0

Summary of Significant Accounting Policies - Liquidity (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Accounting Policies [Abstract]
Cash and short-term investments	$ 184,299	$ 123,909
Accumulated deficit	$ 846,204	$ 780,137

- Definition

Amount of accumulated undistributed earnings (deficit).

+ References + Details

Net Loss Per Share

12 Months Ended

Dec. 31, 2023

Earnings Per Share [Abstract]

Net Loss Per Share

NET LOSS PER SHARE

Basic net loss per share is calculated by dividing net loss by the weighted-average number of common shares outstanding during the period and excludes any dilutive effects of stock-based awards and warrants. Diluted net loss per common share is computed giving effect to all potential dilutive common shares, including common stock issuable upon exercise of stock options, and unvested restricted common stock and stock units. As we had net losses for the years ended December 31, 2023, 2022 and 2021, all potential common shares were determined to be anti-dilutive.

The following table sets forth the computation of net loss per common share (in thousands, except per share dollar amounts):


	Year Ended December 31,
	2023		2022		2021
Numerator:
Net loss	$	(66,067)	$	(67,207)	$	(158,165)
Denominator:
Weighted average common shares outstanding - basic and diluted	219,331		158,690		104,206
Net loss per share - basic and diluted	$	(0.30)	$	(0.42)	$	(1.52)

For the years ended December 31, 2023, 2022 and 2021, the total numbers of securities that could potentially dilute net income per share in the future that were not considered in the diluted net loss per share calculations because the effect would have been anti-dilutive were as follows (in thousands):


	Year Ended December 31,
	2023	2022	2021
Options to purchase common stock	20,877	13,522	11,871
Restricted stock units	3,086	2,694	1,602
ESPP shares issuable	249	166	207

Total	24,212	16,382	13,680

The number of potential common shares that would have been included in diluted income per share had it not been for the anti-dilutive effect caused by the net loss, computed by converting these securities using the treasury stock method during the years ended December 31, 2023, 2022 and 2021, was approximately 6.3 million, 0.6 million and 1.1 million, respectively.

Organization and Basis of Presentation	12 Months Ended
Organization and Basis of Presentation	Dec. 31, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization and Basis of Presentation	ORGANIZATION AND BASIS OF PRESENTATION Ardelyx, Inc. (Company, we, us or our) is a biopharmaceutical company founded with a mission to discover, develop and commercialize innovative, first-in-class medicines that meet significant unmet medical needs. We developed a unique and innovative platform that enabled the discovery of new biological mechanisms and pathways to develop potent and efficacious therapies that minimize the side effects and drug-drug interactions frequently encountered with traditional, systemically absorbed medicines. The first molecule we discovered and developed was tenapanor, a minimally absorbed, first-in-class, oral, small molecule therapy. Tenapanor, branded as IBSRELA®, is approved in the U.S. for the treatment of adults with irritable bowel syndrome with constipation (IBS-C). Tenapanor, branded as XPHOZAH®, was approved by the U.S. Food and Drug Administration (U.S. FDA) on October 17, 2023, to reduce serum phosphorus in adults with chronic kidney disease (CKD) on dialysis as add-on therapy in patients who have an inadequate response to phosphate binders or who are intolerant of any dose of phosphate binder therapy. We also have a development stage asset, RDX013 for adult patients with CKD and/or heart failure with hyperkalemia, or elevated serum potassium, and a discovery phase asset, RDX020 for adult patients with metabolic acidosis, a serious electrolyte disorder, in patients with CKD. We operate in one business segment, which is the development and commercialization of biopharmaceutical products.

BALANCE SHEETS (Parenthetical) - $ / shares	Dec. 31, 2023	Dec. 31, 2022
Statement of Financial Position [Abstract]
Preferred stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Preferred stock, shares authorized (in shares)	5,000,000	5,000,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized (in shares)	500,000,000	300,000,000
Common stock, shares issued (in shares)	232,453,190	198,575,016
Common stock, shares outstanding (in shares)	232,453,190	198,575,016

Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Payables and Accruals [Abstract]
Accrued payments due to AstraZeneca	$ 3,680	$ 3,385
Accrued gross to net revenue liabilities	3,258	1,991
Accrued contract manufacturing expenses	1,946	1,657
Accrued sales and marketing expenses	3,223	587
Accrued professional and consulting services	486	808
Derivative liability for exit fees	675	1,656
Accrued clinical expenses	377	223
Accrued non-clinical research and development expenses	30	1,188
Other	1,366	885
Total accrued expenses and other current liabilities	$ 15,041	$ 12,380

Pay vs Performance Disclosure - USD ($) $ in Thousands	12 Months Ended
Pay vs Performance Disclosure - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Pay vs Performance Disclosure
Net loss	$ (66,067)	$ (67,207)	$ (158,165)

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References

+ Details

Summary of Significant Accounting Policies	12 Months Ended
Summary of Significant Accounting Policies	Dec. 31, 2023
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Basis of Presentation The accompanying financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”). Use of Estimates The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and judgments that affect the amounts reported in the financial statements and accompanying notes thereto. On an ongoing basis, management evaluates its estimates, including those related to recognition of revenue, clinical trial accruals, contract manufacturing accruals, expected demand for inventory, fair value of assets and liabilities, income taxes and stock-based compensation. Management bases its estimates on historical experience and on various other market-specific and relevant assumptions that management believes to be reasonable under the circumstances. Actual results could materially differ from those estimates. Liquidity As of December 31, 2023, we had cash, cash equivalents and short-term investments of approximately $184.3 million. We have incurred operating losses since inception in 2007 and our accumulated deficit as of December 31, 2023 is $846.2 million. Since December 31, 2021 and prior to September 30, 2023, our liquidity position raised substantial doubt about our ability to continue as a going concern. We have addressed our operating cash flow requirements through cash generated from product sales of IBSRELA and XPHOZAH, proceeds from the sale of shares of our common stock under our at-the-market offering, from the receipt of milestones payments from our collaboration partners and payments from our Japanese collaboration partner under the second amendment to our License Agreement, and through funds from our loan agreements with SLR Investment Corp. (SLR), as amended. We believe our available cash, cash equivalents and short-term investments as of December 31, 2023 will be sufficient to fund our planned operations for at least a period of one year from the issuance of these financial statements. Cash and Cash Equivalents We consider all highly liquid investments purchased with an original maturity date of 90 days or less on the date of purchase to be cash equivalents. Short-Term Investments Short-term investments consist of debt securities classified as available-for-sale and have maturities greater than 90 days, but less than one year, from the date of acquisition. Short-term investments are carried at fair value based upon quoted market prices. Unrealized gains and losses on available-for-sale securities are included in accumulated other comprehensive income (loss) on our balance sheets. The cost of available-for-sale securities sold is based on the specific-identification method. Concentration of Credit Risk Financial instruments that potentially subject us to significant concentrations of credit risk consist primarily of cash, cash equivalents, short-term investments and accounts receivable. We are exposed to credit risks in the event of default by the counterparties to the extent of the amount recorded in our balance sheet. Cash, cash equivalents and short-term investments are invested through banks and other financial institutions in the U.S. Foreign Currency We manage our foreign currency exposures with the use of foreign currency purchases. We primarily conduct business in U.S. dollars; however, a portion of our expense and capital activities are transacted in foreign currencies which are subject to exchange rate fluctuations that can affect cash or earnings. We have been in a loss position and therefore our primary objective is to conserve and manage cash. There are generally two methods by which we may manage the cash flow risk of foreign exchange fluctuations when a contract is signed (i) we can purchase the foreign funds, in full or in part, upon the execution of the contract, or (ii) we can obtain the right to purchase such funds, in full or in part, at the execution of the contract, i.e., obtain a forward contract from an appropriate bank, that can be exercised to obtain the currency of interest at a particular point in time. The derivative instruments that we may use to hedge the exposure shall generally not be designated as cash flow hedges, and as a result, changes in their fair value would be recorded in other income (expense), net, in our statements of operations and comprehensive loss. The fair values of forward foreign currency exchange contracts would be estimated using current exchange rates and interest rates and the current creditworthiness of the counterparties is taken into consideration. Property and Equipment Property and equipment are stated at cost, less accumulated depreciation and amortization. Depreciation is computed using the straight-line method over the estimated useful lives of the respective assets, with ranges generally from three to five years. Leasehold improvements are amortized over the lesser of the estimated useful lives or the related remaining lease term. Impairment of Long-Lived Assets The carrying values of long-lived assets, including property and equipment, are reviewed for impairment whenever events or changes in circumstances indicate that the asset may not be recoverable. An impairment loss is recognized when the total of estimated future undiscounted cash flows, expected to result from the use of the asset and its eventual disposition, are less than the asset’s carrying amount. Impairment, if any, would be assessed using discounted cash flows or other appropriate measures of fair value. Income Taxes We use the asset and liability method of accounting for income taxes. Under this method, deferred tax assets and liabilities are determined based on the differences between the financial reporting and the tax bases of assets and liabilities and are measured using the enacted tax rates and laws that will be in effect when the differences are expected to reverse. A valuation allowance is provided when it is more likely than not that some portion or all of a deferred tax asset will not be realized. Accounts Receivable Accounts receivable are stated at amortized cost less allowance for credit losses. The allowance for credit losses reflects the best estimate of future losses over the contractual life of outstanding accounts receivable and is determined on the basis of historical experience, specific allowances for known troubled accounts, other currently available information including customer financial condition and both current and forecasted economic conditions. To date, we have determined that an allowance for doubtful accounts is not required. As of December 31, 2023 our accounts receivable balance was comprised of $4.9 million from our collaboration agreements and $17.1 million from commercial customers. As of December 31, 2022 our accounts receivable balance was comprised of $0.7 million from our collaboration agreements and $7.0 million from commercial customers. Inventory We capitalize inventory costs associated with the production of our products after regulatory approval or when, based on management’s judgment, future commercialization is considered probable and the future economic benefit is expected to be realized. Otherwise, such costs are expensed as research and development. Prior to the regulatory approval of drug product candidates, we incurred expenses for the manufacture of drug product that could potentially be available to support the commercial launch of our products or could be sold to our international partners under product supply agreements. We began to capitalize inventory costs associated with IBSRELA during the fourth quarter of 2021, when our intent to commercialize IBSRELA was established and we commenced preparation for the commercial launch of IBSRELA, which was when it was determined that the inventory had a probable future economic benefit. We began to capitalize inventory costs associated with XPHOZAH during the fourth quarter of 2023, following approval by the U.S. FDA to market XPHOZAH in the U.S., which was when it was determined that the inventory had a probable future economic benefit. Inventory is stated at the lower of cost or estimated net realizable value with cost determined under the specific identification method. Inventory costs include the cost of materials, third-party contract manufacturing, third-party packaging services, freight, labor costs for personnel involved in the manufacturing process, and indirect overhead costs. We primarily use actual costs to determine the cost basis for inventory. The determination of whether inventory costs will be realizable requires management review of the expiration dates of IBSRELA and XPHOZAH compared to our forecasted sales. If actual market conditions are less favorable than projected by management, write-downs of inventory may be required, which would be recorded as cost of revenue in the statement of operations and comprehensive loss. As of December 31, 2023, we have not recorded any write-offs for excess and obsolete inventory. A portion of inventory that represents product that is not expected to be sold or used within the next 12 months is classified as non-current on our balance sheets. Product Sales, Net We account for our commercial product sales, net in accordance with Topic 606 – Revenue from Contracts with Customers. We received approval from the FDA to market IBSRELA in the U.S. in September 2019 and to market XPHOZAH in the U.S. in October 2023. We began selling IBSRELA and XPHOZAH in the U.S. in March 2022 and November 2023, respectively. We distribute IBSRELA principally through major wholesalers, specialty pharmacies and group purchasing organizations (GPOs) (collectively, our IBSRELA Customers). XPHOZAH is principally distributed through a specialty wholesaler (XPHOZAH Customer) to select specialty pharmacies (collectively, IBSRELA Customers and XPHOZAH Customers, “Customers”). Our Customers subsequently sell IBSRELA and XPHOZAH to pharmacies and patients. Separately, we enter into arrangements with third parties that provide for government-mandated rebates, chargebacks and discounts. Revenue from product sales is recognized when our performance obligations are satisfied, which is when Customers obtain control of our product and occurs upon delivery. Reserves for Variable Consideration Revenues from product sales are recorded at the net sales price (transaction price), which includes estimates of variable consideration which may be settled in the form of off-invoice discounts, chargebacks, or rebates. Variable consideration includes discounts to customers and government programs, wholesaler fees, group purchasing organization administrative fees, patient copay assistance, and estimated product returns. These estimates are based on the amounts earned or to be claimed for related sales and are classified as reductions of gross accounts receivable if settlement is expected to occur through a reduction in the amounts paid by our Customers or a current liability if settlement is expected to occur through a payment from us. Where appropriate, these estimates are based on factors such as industry data and forecasted customer buying and payment patterns, our experience, current contractual and statutory requirements, specific known market events and trends. These reductions to gross sales reflect our best estimates of the amount of consideration to which we are entitled based on the terms of the contract. Variable consideration is included in the transaction price only to the extent that it is probable that a significant reversal in the amount of cumulative revenue recognized will not occur when the uncertainty associated with the variable consideration is subsequently resolved. Actual amounts of consideration ultimately received may differ from our estimates. If actual results in the future vary from our estimates, we adjust these estimates, which would affect product revenue and earnings in the period such variances become known. As we gain more experience, estimates will be more heavily based on the expected utilization from historical data we have accumulated since the IBSRELA and XPHOZAH product launches. Changes in estimates recorded through December 31, 2023 have not been material. Rebates: Rebates include wholesaler fees, GPO fees, as well as mandated discounts under the Medicaid Drug Rebate Program (Medicaid) and the Medicare Coverage Gap Program (Medicare). Estimates for rebates are recorded in the same period the related gross revenue is recognized, resulting in a reduction of product revenue and the establishment of a current liability which is included in accrued expenses on the balance sheets. We estimate our Medicaid and Medicare rebates based upon the estimated payor mix, and statutory discount rates. Our estimates for payor mix are guided by payor information received from specialty pharmacies, expected utilization for wholesaler sales to pharmacies, and available industry payor information and, therefore, require the most estimation and judgment of our gross to net deductions. Chargebacks: Chargebacks are discounts that occur when certain contracted purchasers purchase directly from our wholesalers at a discounted price. The wholesaler, in turn, charges back the difference between the price initially paid to us by the wholesaler and the discounted price paid to the wholesaler by the contracted purchaser. Amounts for estimated chargebacks are established in the same period that the related gross revenue is recognized, resulting in a reduction of product revenue and accounts receivable. The accrual for wholesaler chargebacks is estimated based on known chargeback rates, known sales to wholesalers, and known sales from wholesalers to their chargeback-eligible customers. Discounts and Fees: Our payment terms are generally 30 to 60 days. Wholesalers, GPOs and specialty pharmacies are offered various forms of consideration, including off-invoice discounts which may be paid to GPOs and specialty pharmacies. Wholesalers and GPOs may also receive prompt pay discounts for payment within a specified period. We expect discounts to be earned when offered and, therefore, we deduct the full amount of these discounts from product sales when revenue is recognized, resulting in a reduction of product revenue and accounts receivable. Other Reserves: Patients who have commercial insurance may receive copay assistance when product is dispensed by pharmacies to patients. We estimate the amount of copay assistance provided to eligible patients based on the terms of the program, and redemption information provided by third-party claims processing organizations. We also estimate the amount of copay assistance that will be provided to patients associated with product which we have sold but which has not yet been dispensed to commercial patients, which requires significant estimation and judgment. Our estimates are recorded in accounts payable and accrued expenses and other current liabilities on the balance sheets. Other reserves include estimated product returns which are recorded in the same period the related gross revenue is recognized, resulting in a reduction of product revenue as well as accounts receivable. We estimate our product returns reserve based upon our experience and specific known market events and trends. As we have experienced limited product returns, establishing the appropriate level of returns reserve require estimation and judgment. Collaboration Revenue Recognition We generate collaboration revenue primarily from research and collaboration and license agreements with customers. Goods and services in the agreements may include the grant of licenses for the use of our technology, the provision of services associated with the research and development of product candidates, manufacturing services, and participation in joint steering committees. The terms of these arrangements typically include payment to us of one or more of the following: non-refundable, up-front license fees; research, development, regulatory and commercial milestone payments; reimbursement of research and development services; option payments; reimbursement of certain costs; payments for manufacturing supply services; and future royalties on net sales of licensed products. When two or more contracts are entered into with the same customer at or near the same time, we evaluate the contracts to determine whether the contracts should be accounted for as a single arrangement. Contracts are combined and accounted for as a single arrangement if one or more of the following criteria are met: (i) the contracts are negotiated as a package with a single commercial objective; (ii) the amount of consideration to be paid in one contract depends on the price or performance of the other contract; or (iii) the goods or services promised in the contracts (or some goods or services promised in each of the contracts) are a single performance obligation. In determining the appropriate amount of revenue to be recognized as we fulfill our obligations under each of our agreements, management performs the following steps: (i) identification of the promised goods or services in the contract; (ii) determination of whether the promised goods or services are performance obligations including whether they are distinct in the context of the contract; (iii) measurement of the transaction price, including any constraints on variable consideration; (iv) allocation of the transaction price to the performance obligations; and (v) recognition of revenue when (or as) we satisfy each performance obligation. As part of the accounting for contracts with customers, we develop assumptions that require judgment to determine whether promised goods and services represent distinct performance obligations and the standalone selling price for each performance obligation identified in the contract. This evaluation is subjective and requires us to make judgments about the promised goods and services and whether those goods and services are separable from other aspects of the contract. Further, determining the standalone selling price for performance obligations requires significant judgment, and when an observable price of a promised good or service is not readily available, we consider relevant assumptions to estimate the standalone selling price, including, as applicable, market conditions, development timelines, probabilities of technical and regulatory success, reimbursement rates for personnel costs, forecasted revenues, potential limitations to the selling price of the product and discount rates. We apply judgment in determining whether a combined performance obligation is satisfied at a point in time or over time, and, if over time, concluding upon the appropriate method of measuring progress to be applied for purposes of recognizing revenue. We evaluate the measure of progress each reporting period and, as estimates related to the measure of progress change, related revenue recognition is adjusted accordingly. Changes in our estimated measure of progress are accounted for prospectively as a change in accounting estimate. We recognize collaboration revenue by measuring the progress toward complete satisfaction of the performance obligation using an input measure. In order to recognize revenue over the research and development period, we measure actual costs incurred to date compared to the overall total expected costs to satisfy the performance obligation. Revenues are recognized as the program costs are incurred. We will re-evaluate the estimate of expected costs to satisfy the performance obligation each reporting period and make adjustments for any significant changes. Amounts received prior to satisfying the revenue recognition criteria are recorded as contract liabilities in our balance sheets. If the related performance obligation is expected to be satisfied within the next twelve months, this will be classified in current liabilities. Amounts recognized as revenue prior to receipt are recorded as contract assets in our balance sheets. If we expect to have an unconditional right to receive the consideration in the next twelve months, this will be classified in current assets. A net contract asset or liability is presented for each contract with a customer. Milestone Payments: At the inception of each arrangement that includes research and development milestone payments, we evaluate whether the milestones are considered probable of being reached and estimate the amount to be included in the transaction price using the most likely amount method. Amounts of variable consideration are included in the transaction price to the extent that it is probable that a significant reversal in the amount of cumulative revenue recognized will not occur and when the uncertainty associated with the variable consideration is subsequently resolved. Milestone payments that are not within the control of us or the licensee, such as regulatory approvals, are not considered probable of being achieved until those approvals are received. The transaction price is then allocated to each performance obligation on a relative standalone selling price basis, for which we recognize revenue as or when the performance obligations under the contract are satisfied. At the end of each subsequent reporting period, we re-evaluate the probability of achievement of such development milestones and any related constraints, and if necessary, adjust our estimate of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis, which would affect earnings in the period of adjustment. Manufacturing supply services: Arrangements that include a promise for the future supply of drug substance or drug product for either clinical development or commercial supply at the customer’s discretion are generally considered as options. We assess if these options provide a material right to the licensee and if so, they are accounted for as separate performance obligations. If we are entitled to additional payments when the customer exercises these options, any payments are recorded in product supply revenue when the customer obtains control of the goods, which is upon delivery. Royalties: For arrangements that include sales-based royalties, including milestone payments based on the level of sales, and where the license is deemed to be the predominant item to which the royalties relate, we recognize revenue at the later of (i) when the related sales occur, or (ii) when the performance obligation to which some or all of the royalty has been allocated has been satisfied (or partially satisfied). To date, royalty revenue resulting from licensing arrangements has not been material. Licenses of intellectual property: If a license granted to a customer to use our intellectual property is determined to be distinct from the other performance obligations identified in the arrangement, we recognize revenue from consideration allocated to the license when the license is transferred to the licensee and the licensee is able to use and benefit from the license. For licenses that are bundled with other promises, we apply judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, to conclude upon the appropriate method of measuring progress for purposes of recognizing revenue related to consideration allocated to the performance obligation. Options: Customer options, such as options granted to allow a licensee to choose to research, develop and commercialize licensed compounds are evaluated at contract inception in order to determine whether those options provide a material right (i. e., an optional good or service offered for free or at a discount) to the customer. If the customer options represent a material right, the material right is treated as a separate performance obligation at the outset of the arrangement. We allocate the transaction price to material rights based on the standalone selling price, and revenue is recognized when or as the future goods or services are transferred or when the option expires. Customer options that are not material rights do not give rise to a separate performance obligation, and as such, the additional consideration that would result from a customer exercising an option in the future is not included in the transaction price for the current contract. Instead, the option is deemed a marketing offer, and additional option fee payments are recognized or being recognized as revenue when the licensee exercises the option. The exercise of an option that does not represent a material right is treated as a separate contract for accounting purposes. Contract modifications: Contract modifications, defined as changes in the scope or price (or both) of a contract that are approved by the parties to the contract, such as a contract amendment, exist when the parties to a contract approve a modification that either creates new or changes existing enforceable rights and obligations of the parties to the contract. Depending on facts and circumstances, we account for a contract modification as one of the following: (i) a separate contract; (ii) a termination of the existing contract and a creation of a new contract; or (iii) a combination of the preceding treatments. A contract modification is accounted for as a separate contract if the scope of the contract increases because of the addition of promised goods or services that are distinct and the price of the contract increases by an amount of consideration that reflects our standalone selling prices of the additional promised goods or services. When a contract modification is not considered a separate contract and the remaining goods or services are distinct from the goods or services transferred on or before the date of the contract modification, we account for the contract modification as a termination of the existing contract and a creation of a new contract. When a contract modification is not considered a separate contract and the remaining goods or services are not distinct, we account for the contract modification as an add-on to the existing contract and as an adjustment to revenue on a cumulative catch-up basis. We receive payments from our licensees as established in each contract. Upfront payments and fees are recorded as deferred revenue upon receipt or when due and may require deferral of revenue recognition to a future period until we perform our obligations under these arrangements. Where applicable, amounts are recorded as unbilled revenue when our right to consideration is unconditional. We do not assess whether a contract with a customer has a significant financing component if the expectation at contract inception is such that the period between payment by the licensees and the transfer of the promised goods or services to the licensees will be one year or less. Cost of Goods Sold Cost of product sales consists of the cost of commercial goods sold to our Customers. Other cost of revenue consists of the cost of materials sold to our international partners under product supply agreements, as well as payments due to AstraZeneca AB (AstraZeneca) based on sales of tenapanor. We capitalize inventory costs associated with the production of our products after regulatory approval or when, based on management’s judgment, future commercialization is considered probable and the future economic benefit is expected to be realized. Otherwise, such costs are expensed as research and development. A portion of the costs of IBSRELA and XPHOZAH units recognized as revenue during the years ended December 31, 2023 and 2022 were expensed in periods prior to the commencement of capitalization of inventory costs for each respective product. As of December 31, 2023 and December 31, 2022, we had approximately $21.8 million and $28.0 million, respectively, of inventory on hand that was previously expensed as research and development expense and will not be reported as cost of goods sold in future periods when sales of IBSRELA and XPHOZAH are recognized as revenue. Other cost of revenue includes payments due to AstraZeneca, which under the terms of a termination agreement entered into in 2015 (AstraZeneca Termination Agreement) is entitled to (i) future royalties at a rate of 10% of net sales of tenapanor or other NHE3 products by us or our licensees, and (ii) 20% of non-royalty revenue received from our collaboration partners in connection with the development and commercialization of tenapanor or other NHE3 products. We have agreed to pay AstraZeneca up to a maximum of $75.0 million in the aggregate for (i) and (ii). We recognize these expenses as other cost of revenue when we recognize the corresponding revenue that gives rise to payments due to AstraZeneca. To date, we have recognized an aggregate of $27.6 million as other cost of revenue under the AstraZeneca Termination Agreement. See details in Note 7, Collaboration and Licensing Agreements, under AstraZeneca, in the notes to our financial statement of this Annual Report on Form 10-K. Research and Development Costs Research and development costs are charged to expense as incurred and consisted of costs incurred to further our research and development activities and include salaries and related employee benefits, costs associated with clinical trials, costs related to pre-commercialization manufacturing activities such as manufacturing process validation activities and the manufacturing of clinical drug supply, nonclinical research and development activities, regulatory activities, research-related overhead expenses and fees paid to external service providers and contract research and manufacturing organizations that conduct certain research and development activities on our behalf. Accrued Expenses As part of the process of preparing our financial statements, we are required to estimate our accrued expenses. This process involves reviewing open contracts and purchase orders, communicating with our personnel to identify services that have been performed on our behalf and estimating the level of service performed and the associated cost incurred for the service when we have not yet been invoiced or otherwise notified of the actual cost. The majority of our service providers invoice us monthly in arrears for services performed or when contractual milestones are met. We make estimates of our accrued expenses as of each balance sheet date in our financial statements based on facts and circumstances known to us at that time. We periodically confirm the accuracy of our estimates with our service providers and make adjustments if necessary. In accruing service fees, we estimate the time period over which each component of a service will be performed, and estimate, with vendor input if appropriate. If the actual timing of the performance of services or the level of effort varies from our estimate, we adjust the accrued or prepaid expense balance accordingly. Although we do not expect our estimates to be materially different from amounts actually incurred, if our estimates of the status and timing of services performed differ from the actual status and timing of services performed, we may report amounts that are too high or too low in any particular period. Stock-Based Compensation We recognize compensation expense for all stock-based payment awards made to employees, non-employees and directors based on estimated fair values. For employee and non-employee stock options, we determine the grant date fair value of the awards using the Black-Scholes option-pricing model and generally recognize the fair value as stock-based compensation expense on a straight-line basis over the vesting period of the respective awards. For restricted stock and performance-based restricted stock, to the extent they are probable, the compensation cost for these awards is based on the closing price of our common stock on the date of grant and recognized as compensation expense on a straight-line basis over the requisite service period. Stock-based compensation expense is based on the value of the portion of stock-based payment awards that is ultimately expected to vest. As such, our stock-based compensation is reduced for the estimated forfeitures at the date of grant and revised, if necessary, in subsequent periods if actual forfeitures differ from those estimates. Derivatives and Hedging Activities We account for our derivative instruments as either assets or liabilities on the balance sheet and measure them at fair value. Derivatives are adjusted to fair value through other income (expense), net in the statements of operations and comprehensive loss. Non-cash Interest Expense on Deferred Royalty Obligation Non-cash interest expense related to the sale of future royalties represents the imputed interest expense on our deferred royalty obligation related to the sale of future royalties using the effective interest method. As further described in Note 8. Deferred Royalty Obligation Related to the Sale of Future Royalties, in June 2022, we and HealthCare Royalty Partners IV, L.P. (HCR) entered into a Royalty and Sales Milestone Interest Acquisition Agreement (HCR Agreement). Under the terms of the HCR Agreement, HCR agreed to pay us up to $20.0 million in exchange for the royalty payments and commercial milestone payments (collectively the Royalty Interest Payments) that we may receive under our 2017 License Agreement with Kyowa Kirin, as amended, based upon Kyowa Kirin's net sales of tenapanor in Japan for hyperphosphatemia. As part of the HCR Agreement, we received a $10.0 million upfront payment from HCR in June 2022 and recorded it as a deferred royalty obligation on our balance sheet. In September 2023, we announced that Kyowa Kirin received approval from the Japanese MHLW for the New Drug Application for tenapanor for the improvement of hyperphosphatemia in adult patients with chronic kidney disease on dialysis, which entitled us to a $5.0 million payment under the terms of the HCR Agreement, which we received in October 2023. Non-cash interest expense will be recognized over the life of the HCR Agreement using the effective interest method based on the imputed interest rate derived from estimated amounts and timing of future royalty payments to be received from Kyowa Kirin. Leases We determine if an arrangement is a lease at the inception of the arrangement. Operating leases are included in right-of-use assets, current portion of operating lease liability, and operating lease liability, net of current portion in our balance sheets. Right-of-use assets represent our right to use an underlying asset for the lease term and lease liabilities represent our obligation to make lease payments arising from the lease. Operating lease right-of-use assets and liabilities are recognized at the lease commencement date based on the present value of lease payments over the lease term. In determining the present value of lease payments, we use our incremental borrowing rate based on the information available at the lease commencement date. The operating lease right-of-use assets also include any lease payments made and exclude lease incentives. Our lease terms may include options to extend or terminate the lease when it is reasonably certain that we will exercise any such options. Lease expense is recognized on a straight-line basis over the expected lease term. We have elected not to separate lease and non-lease components, such as common area maintenance charges, and instead it accounts for these as a single lease component. Net Loss per Share Basic net loss per common share is calculated by dividing the net loss by the weighted-average number of shares of common stock outstanding during the period, without consideration of potential shares of common stock. Diluted net loss per common share in the periods presented is the same as basic net loss per common share, since the effects of potentially dilutive securities are antidilutive due to the net loss for all periods presented. Recent Accounting Pronouncements New Accounting Pronouncements - Recently Adopted In July 2023, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2023-03, Presentation of Financial Statements (Topic 205), Income Statement - Reporting Comprehensive Income (Topic 220), Distinguishing Liabilities from Equity (Topic 480), Equity (Topic 505), and Compensation - Stock Compensation (Topic 718) Presentation of Financial Statements (ASU 2023-03). ASU 2023-03 amends the FASB Accounting Standards Codification to include Amendments to SEC Paragraphs pursuant to SEC Staff Accounting Bulletin No. 120, SEC Staff Announcement at the March 24, 2022 EITF Meeting, and SEC Staff Accounting Bulletin Topic 6.B, Accounting Series Release 280 - General Revision of Regulation S-X: Income or Loss Applicable to Common Stock. As the ASU does not provide any new guidance, there is no transition or effective date associated with its adoption. Accordingly, we adopted ASU 2023-03 immediately upon its issuance. The adoption of ASU 2023-03 did not have any impact on our financial statement presentation or related disclosures. Recent Accounting Pronouncements Not Yet Adopted In October 2023, the FASB issued ASU No. 2023-06, Disclosure Improvements - Codification Amendments in Response to the SEC’s Disclosure Update and Simplification Initiative. The amendments in this Update modify the disclosure or presentation requirements of a variety of Topics in the Codification. The amendments are in response to the U.S. Securities and Exchange Commission's (SEC) Release No. 33-10532, Disclosure Update and Simplification, in which the SEC referred certain of its disclosure requirements that overlap with, but require incremental information to, generally accepted accounting principles to the FASB for potential incorporation into the Codification. For entities subject to the SEC’s existing disclosure requirements and for entities required to file or furnish financial statements with or to the SEC in preparation for the sale of or for purposes of issuing securities that are not subject to contractual restrictions on transfer, the effective date for each amendment will be the date on which the SEC’s removal of that related disclosure from Regulation S-X or Regulation S-K becomes effective, with early adoption prohibited. For all other entities, the amendments will be effective two years later. For all entities, if by June 30, 2027, the SEC has not removed the applicable requirement from Regulation S-X or Regulation S-K, the pending content of the related amendment will be removed from the Codification and will not become effective for any entity. Management is currently assessing the impact of this standard on the Company’s financial statements. In November 2023, the FASB issued ASU No. 2023-07, Segment Reporting (Topic 280) - Improvements to Reportable Segment Disclosures. The amendments in this Update improve reportable segment disclosure requirements, primarily through enhanced disclosures about significant segment expenses. The amendments in this update improve financial reporting by requiring disclosure of incremental segment information on an annual and interim basis for all public entities to enable investors to develop more decision-useful financial analyses. The amendments in this update are effective for fiscal years beginning after December 15, 2023, and interim periods within fiscal years beginning after December 15, 2024. Early adoption is permitted. Management is currently assessing the impact of this standard on the Company’s financial statements. In December 2023, the FASB issued ASU No. 2023-09, Income Taxes (Topic 740) - Improvements to Income Tax Disclosures, an amendment which modifies the measurement and recognition of credit losses for most financial assets and certain other instruments. The amendments in this Update provide more transparency about income tax information through improvements to income tax disclosures primarily related to the rate reconciliation and income taxes paid information. For public business entities, the amendments in this Update are effective for annual periods beginning after December 15, 2024. Early adoption is permitted on a prospective basis for annual financial statements that have not yet been issued or made available for issuance. Management is currently assessing the impact of this standard on the Company’s financial statements. There were various other accounting standards and interpretations issued recently, none of which are expected to have a material impact on our financial position, operations or cash flows.

Derivative Liabilities - Narrative (Details) - USD ($) $ in Millions	1 Months Ended
	Feb. 28, 2022	Dec. 31, 2023	Oct. 17, 2023	Dec. 31, 2022	May 31, 2018
2018 Exit Fee
Derivative [Line Items]
Agreed amount for exit fee upon change of control or regulatory approval					$ 1.5
Estimated fair value		$ 0.0		$ 1.2
2022 Exit Fee
Derivative [Line Items]
Estimated fair value		$ 0.7		$ 0.4
Exit fee (percent)			2.00%
Exit fee, net product revenue threshold	$ 100.0
2022 Exit Fee \| Level 3
Derivative [Line Items]
Fair value analysis, percentage change in probability of occurrence		10.00%

- Definition

Nominal or face amount used to calculate payments on the derivative liability.

+ References + Details

Deferred Royalty Obligation Related To The Sale Of Future Royalties	12 Months Ended
	Dec. 31, 2023
Advance Royalties [Abstract]
Deferred Royalty Obligation Related To The Sale Of Future Royalties	DEFERRED ROYALTY OBLIGATION RELATED TO THE SALE OF FUTURE ROYALTIES In June 2022, we and HealthCare Royalty Partners IV, L.P. (HCR) entered into a Royalty and Sales Milestone Interest Acquisition Agreement (HCR Agreement). Under the terms of the HCR Agreement, HCR has agreed to pay us up to $20.0 million in exchange for the royalty payments and commercial milestone payments (collectively the Royalty Interest Payments) that we may receive under our 2017 License Agreement with Kyowa Kirin, as amended, based upon Kyowa Kirin's net sales of tenapanor in Japan for hyperphosphatemia. As consideration for the sale of the Royalty Interest Payments, HCR paid to us a $10.0 million upfront payment, and we were eligible to receive a $5.0 million payment as a result of Kyowa Kirin's receipt of regulatory approval to market tenapanor for hyperphosphatemia in Japan, and another $5.0 million payment in the event net sales by Kyowa Kirin in Japan exceed a certain annual target level by the end of 2025. In September 2023, we announced that Kyowa Kirin received approval from the Japanese MHLW for the New Drug Application for tenapanor for the improvement of hyperphosphatemia in adult patients with chronic kidney disease on dialysis, which entitled us to a $5.0 million payment under the terms of the HCR Agreement. We received the payment in October 2023. The HCR Agreement is effective until terminated by the mutual agreement of the parties and contains customary representations and warranties and customary affirmative and negative covenants, including, among others, requirements as to prosecution, maintenance, defense and enforcement of certain patent rights in Japan, restrictions regarding our ability to forgive, release or reduce any Royalty Interest Payments due to us under the 2017 Kyowa Kirin Agreement, to create or incur any liens with respect to the Royalty Interest Payments, the 2017 Kyowa Kirin Agreement or certain patents, or to sell, license or transfer certain patents in the field and territory described in the 2017 Kyowa Kirin Agreement. In addition, the HCR Agreement contains customary events of default with respect to which we may incur indemnification obligations to HCR for any losses incurred by HCR and related parties as a result of the event of default, subject to a specified limitation of liability cap. Under the HCR Agreement, an event of default will occur if, among other things, any of the representations and warranties included in the HCR Agreement proves not to have been true and correct in all material respects, at the time it was made, we breach any of our covenants under the HCR Agreement, subject to specified cure periods with respect to certain breaches, we are in breach or default under the 2017 Kyowa Kirin Agreement in any manner which is likely to cause a material adverse effect on the Royalty Interest Payments, the occurrence of a termination of the 2017 Kyowa Kirin Agreement under certain circumstances or we or our assets become subject to certain legal proceedings, such as bankruptcy proceedings, or we are unable to pay our debts as they become due. The $10.0 million upfront payment from HCR received in June 2022 and the $5.0 million payment received in October 2023 have been recorded as a deferred royalty obligation related to the sale of future royalties (deferred royalty obligation) on our balance sheets. Due to our ongoing manufacturing obligations under the 2017 Kyowa Kirin Agreement, we account for the proceeds as imputed debt and therefore will recognize royalties earned under the arrangement as non-cash royalty revenue. Non-cash interest expense will be recognized over the life of the HCR Agreement using the effective interest method based on the imputed interest rate derived from estimated amounts and timing of future royalty payments to be received from Kyowa Kirin. As part of the sale, we incurred approximately $0.4 million in transaction costs, which, along with the deferred royalty obligation, are being amortized to non-cash interest expense over the estimated life of the HCR Agreement using the effective interest method. As future royalties are remitted to us by Kyowa Kirin, and subsequently from us to HCR, the balance of the deferred royalty obligation will be effectively repaid over the life of the HCR Agreement. There are a number of factors that could materially affect the fair value of the deferred royalty obligation. Such factors include, but are not limited to, the amount and timing of potential future royalty payments to be received from Kyowa Kirin under the 2017 Kyowa Kirin agreement, changing standards of care, the introduction of competing products, manufacturing or other delays, intellectual property matters, adverse events that result in governmental health authority imposed restrictions on the use of the drug products, significant changes in foreign exchange rates as the royalties remitted to HCR are made in U.S. dollars while the underlying sales of the products by Kyowa Kirin are made in Japanese yen, and other events or circumstances that could result in reduced royalty payments from Kyowa Kirin, which are not within our control, and all of which would result in a reduction of non-cash royalty revenues and the non-cash interest expense over the life of the deferred royalty obligation. We periodically assess the estimated royalty payments from Kyowa Kirin and, to the extent that the amount or timing of such payments is materially different than our original estimates, we prospectively adjust the imputed interest rate and the related amortization of the deferred royalty obligation. As of December 31, 2023, our effective interest rate used to amortize the liability is 34.7%. During the years ended December 31, 2023 and 2022, we recognized approximately $3.9 million and $1.7 million, respectively, of non-cash interest expense related to the deferred royalty obligation. As of December 31, 2023, we have received no royalty payments from Kyowa Kirin and, therefore, the deferred royalty obligation has not begun to be reduced.

Insider Trading Arrangements

3 Months Ended

12 Months Ended

Dec. 31, 2023

Trading Arrangements, by Individual

Non-Rule 10b5-1 Arrangement Adopted

false

Rule 10b5-1 Arrangement Terminated

false

Non-Rule 10b5-1 Arrangement Terminated

false

Michael Raab [Member]

Trading Arrangements, by Individual

Name

Michael Raab

Title

President and Chief Executive Officer

Rule 10b5-1 Arrangement Adopted

true

Adoption Date

December 13, 2023

Arrangement Duration

390 days

Aggregate Available

331,300

Elizabeth Grammer [Member]

Trading Arrangements, by Individual

Name

Elizabeth Grammer

Title

Chief Legal Officer

Rule 10b5-1 Arrangement Adopted

true

Adoption Date

December 20, 2023

Arrangement Duration

209 days

Aggregate Available

131,000

Robert Blanks [Member]

Trading Arrangements, by Individual

Name

Robert Blanks

Title

Chief Regulatory Officer

Rule 10b5-1 Arrangement Adopted

true

Adoption Date

December 21, 2023

Arrangement Duration

183 days

Aggregate Available

48,000

Laura Williams [Member]

Trading Arrangements, by Individual

Name

Laura Williams

Title

Chief Medical Officer

Rule 10b5-1 Arrangement Adopted

true

Adoption Date

December 27, 2023

Arrangement Duration

91 days

Aggregate Available

79,949

Officer Trading Arrangement [Member]

Trading Arrangements, by Individual

Material Terms of Trading Arrangement

During the three months ended December 31, 2023, our Section 16 officers and directors adopted or terminated contracts, instructions or written plans for the purchase or sale of our securities as noted below:

Name and Title of Director or Officer

Action

Date

Trading Arrangement

Total Shares Available to be Sold

Expiration Date

Rule 10b5-1*

Non-Rule 10b5-1**

Michael Raab, President and Chief Executive Officer

Adoption

December 13, 2023

331,300

January 6, 2025

Elizabeth Grammer, Chief Legal Officer

Adoption

December 20, 2023

131,000

July 16, 2024

Robert Blanks, Chief Regulatory Officer

Adoption

December 21, 2023

48,000

June 21, 2024

Laura Williams, Chief Medical Officer

Adoption

December 27, 2023

79,949

March 27, 2024

*Intended to satisfy the affirmative defense conditions of Rule 10b5-1(c)

** Not intended to satisfy the affirmative defense conditions of Rule 10b5-1(c)

Equity Incentive Plans - Stock-Based Compensation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation	$ 13,530	$ 10,750	$ 12,039
Selling, general and administrative
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation	9,952	7,525	7,923
Research and development
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation	$ 3,578	$ 3,225	$ 4,116

Collaboration and Licensing Agreements (Tables)

12 Months Ended

Dec. 31, 2023

Collaboration and Licensing Agreements [Abstract]

Schedule of Deferred Revenue Balances

The following tables present changes in our current and non-current deferred revenue balances during the reporting period, which are all attributable to the 2017 Kyowa Kirin Agreement (in thousands):


	2023				2022
	Current		Non-Current		Current		Non-Current
Balance at January 1,	$	4,211	$	9,025	$	—	$	4,727
Amounts invoiced as prepayments for product supply	1,547		5,629		250		8,259
Decrease for revenue recognized for product supply	(4,586)		—		—		—
Reclassify amounts to be recognized in the next twelve months	6,010		(6,010)		3,961		(3,961)
Balance at December 31,	$	7,182	$	8,644	$	4,211	$	9,025

Property and Equipment, Net - Balances (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 11,210	$ 10,880
Less: accumulated depreciation	(10,201)	(9,657)
Total property and equipment, net	1,009	1,223
Laboratory equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	46	46
Office equipment and furniture
Property, Plant and Equipment [Line Items]
Property and equipment, gross	2,433	2,089
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 8,731	$ 8,745

Leases

12 Months Ended

Dec. 31, 2023

Leases [Abstract]

Leases

LEASES

We have recorded right-of-use operating lease assets under three lease agreements. We have evaluated our facility leases and determined that, effective upon the adoption of Topic 842, the leases evaluated are all operating leases. We have performed an evaluation of our other contracts with suppliers and collaborators in accordance with Topic 842 and have determined that, except for the facility leases described below, none of our contracts contain a lease.

We recorded right-of-use operating lease assets for our facility in Waltham, Massachusetts under a lease agreement entered into during December 2020 with lease commencement dates during April and May 2021. In August 2023, we entered into an amendment to the lease agreement to expand the leased premises to include an additional 4,247 square feet of office space. As of December 31, 2023, the Waltham office space consists of 17,111 square feet with the lease terminating in June 2026. We have an option to extend the lease term for one additional five year period. This option to extend the lease term has not been included in the calculation of the right-of-use asset and lease liability since the exercise of the option is uncertain and therefore deemed not probable. We recorded a $1.6 million right-of-use asset and lease liability for the Waltham lease upon commencement of the lease and an additional $0.3 million right-of-use asset and lease liability upon commencement of the lease amendment.

We have also recorded a right-of-use operating lease asset for our facility located in Fremont, California under a lease agreement entered into in September 2008 that was amended multiple times to add space and to extend the lease term through March 2025. The office space consists of 72,500 square feet. We do not have an option to renew the lease at our current Fremont location beyond March 2025. In March 2023, we entered into a sub-lease Agreement (Sub-lease) with Chronus Health, Inc. (Chronus). We have sub-leased to Chronus approximately 21,644 square feet of the 72,500 square foot building's interior space, plus corresponding exterior support space and parking. The term of the Sub-lease expires on February 1, 2025. In accordance with the Sub-lease, we recognized an impairment of long-lived assets totaling $0.4 million during the three months ended March 31, 2023, which consisted primarily of impairment to the Fremont facility right-of-use asset, as determined by measuring the undiscounted future cash flows from the sub-leased space. The Sub-lease commenced in April 2023 and we recognized $0.8 million of income from the Sub-lease during the year ended December 31, 2023.

We have recorded a right-of-use operating lease asset for our facility located in Milwaukee, Wisconsin under a lease agreement entered into in October 2020 with a lease commencement date in November 2020. The office space consists of 4,768 square feet with the lease terminating in February 2026. We have an option to extend the lease term by one additional five-year period. This option to extend the lease term has not been included in the calculation of the right-of-use asset and lease liability since the exercise of the option is uncertain and therefore deemed not probable. We recorded a $0.4 million right-of use asset and lease liability for the Milwaukee lease upon commencement of the lease.

All of our leases are operating leases and each contain customary rent escalation clauses. Certain of the leases have both lease and non-lease components. We have elected to account for each separate lease component and the non-lease components associated with that lease component as a single lease component for all classes of underlying assets.

The following table provides additional details of our facility leases presented in our balance sheets (dollars in thousands):


	December 31,
Facilities	2023			2022
Right-of-use assets	$	5,589		$	9,295

Current portion of lease liabilities	4,435			3,894
Operating lease liability, net of current portion	1,725			5,855
Total lease liabilities	$	6,160		$	9,749

Weighted-average remaining life (years)	1.6			2.4
Weighted-average discount rate	6.8		%	6.8		%

The lease costs, which are included in operating expenses in our statements of operations, were as follows (in thousands):


	Year Ended December 31,
	2023		2022		2021
Operating lease expense	$	3,857	$	4,257	$	3,671
Cash paid for operating lease	$	4,481	$	4,292	$	3,438

The following table summarizes our undiscounted cash payment obligations for our operating lease liabilities as of December 31, 2023 (in thousands):


Ending December 31,
2024	$	4,715
2025	1,450
2026	329

Thereafter	—
Total undiscounted operating lease payments	6,494
Imputed interest expenses	(334)
Total operating lease liabilities	6,160
Less: Current portion of operating lease liability	(4,435)
Operating lease liability, net of current portion	$	1,725

Commitments and Contingencies	12 Months Ended
Commitments and Contingencies	Dec. 31, 2023
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	COMMITMENTS AND CONTINGENCIES Guarantees and Indemnifications We indemnify each of our officers and directors for certain events or occurrences, subject to certain limits, while the officer or director is or was serving at our request in such capacity, as permitted under Delaware law and in accordance with our certificate of incorporation and bylaws. The term of the indemnification period lasts as long as an officer or director may be subject to any proceeding arising out of acts or omissions of such officer or director in such capacity. The maximum amount of potential future indemnification is unlimited; however, we currently hold director and officer liability insurance, which allows the transfer of risk associated with our exposure and may enable us to recover a portion of any future amounts paid. We believe that the fair value of these indemnification obligations is minimal. Accordingly, we have not recognized any liabilities relating to these obligations for any period presented. Legal Proceedings and Claims On July 30 and August 12, 2021, two putative securities class action lawsuits were commenced in the U.S. District Court for the Northern District of California naming as defendants Ardelyx and two current officers captioned Strezsak v. Ardelyx, Inc., et al., Case No. 4:21-cv-05868-HSG, and Siegel v. Ardelyx, Inc., et al., Case No. 5:21-cv-06228-HSG (together, the Securities Class Actions). The complaints allege that the defendants violated Sections 10(b) and 20(a) of the Securities Exchange Act of 1934, as amended, and Rule 10b-5 thereunder, by making false and misleading statements and omissions of material fact related to tenapanor. The plaintiffs seek damages and interest, and an award of costs, including attorneys’ fees. On July 19, 2022, the court consolidated the two putative class actions and appointed a lead plaintiff and lead counsel. The lead plaintiff filed an amended complaint on September 29, 2022. Defendants filed a motion to dismiss the amended complaint on December 2, 2022. In January and February 2023, in lieu of filing a response to defendant’s motion to dismiss, plaintiffs filed a motion seeking leave to further amend their complaint and defendants filed an opposition to the motion for leave to further amend the complaint. On April 6, 2023, the court granted plaintiff’s motion for leave to further amend the complaint. With the second amended complaint, the plaintiffs seek to represent all persons who purchased or otherwise acquired Ardelyx securities between March 6, 2020 and July 19, 2021. Defendants filed a motion to dismiss the amended complaint on June 2, 2023. On August 22, 2023, the court cancelled the hearing scheduled for September 14, 2023 on the motion to dismiss the amended complaint and indicated its decisions to instead rule on the filed briefs. We believe the plaintiff’s claims are without merit and we have not recorded any accrual for a contingent liability associated with these legal proceedings. On December 7, 2021 and March 29, 2022, two verified shareholders derivative lawsuits were filed in the U.S. District Court for the Northern District of California purportedly on behalf of Ardelyx against certain of Ardelyx’s executive officers and members of our board of directors, captioned Go v. Raab, et al., Case No. 4:21-cv-09455-HSG, and Morris v. Raab, et al., Case No. 4:22-cv-01988-JSC. The complaints allege that the defendants' violations of Section 14(a) of the Securities Exchange Act of 1934, as amended, breaches of fiduciary duties, unjust enrichment, abuse of control, gross mismanagement, and waste of corporate assets for personally making and/or causing Ardelyx to make materially false and misleading statements regarding the Company’s business, operations and prospects. The complaint seeks contribution under Sections 10(b) and 21D of the Securities Exchange Act of 1934 from two executive officers. On January 19, and April 27, 2022, the court granted the parties’ stipulation to stay the Go and Morris actions, respectively, until resolution of the anticipated motion(s) to dismiss in the Securities Class Actions. On October 25, 2022, the parties filed a stipulation to consolidate and stay the Go and Morris actions, and on October 27, 2022, the court consolidated the Go and Morris action and stayed the consolidated action pending resolution of the anticipated motion(s) to dismiss in the Securities Class Action. We believe the plaintiff’s claims are without merit and we have not recorded any accrual for a contingent liability associated with these legal proceedings. From time to time, we may be involved in legal proceedings arising in the ordinary course of business. As of December 31, 2023, there is no litigation pending that would reasonably be expected to have a material adverse effect on our results of operations and financial condition, and no contingent liabilities were accrued as of December 31, 2023.

Income Taxes - Narrative (Details) $ in Millions	12 Months Ended
Income Taxes - Narrative (Details) $ in Millions	Dec. 31, 2023 USD ($)
Income Tax Disclosure [Line Items]
Increase in valuation allowance	$ 20.5
Federal
Income Tax Disclosure [Line Items]
Net operating loss carryforwards	479.0
Net operating loss carryforwards, indefinite	328.8
Federal \| Research and development tax credit
Income Tax Disclosure [Line Items]
Tax credit carryforwards	17.8
Foreign
Income Tax Disclosure [Line Items]
Tax credit carryforwards	1.7
State \| California
Income Tax Disclosure [Line Items]
Net operating loss carryforwards	92.9
State \| California \| Research and development tax credit
Income Tax Disclosure [Line Items]
Tax credit carryforwards	8.9
State \| California \| Minimum tax credit carryforwards
Income Tax Disclosure [Line Items]
Tax credit carryforwards	0.1
State \| Other states
Income Tax Disclosure [Line Items]
Net operating loss carryforwards	$ 50.5

Leases - Additional Lease Information (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Facilities - right-of-use assets and lease liabilities
Right-of-use assets	$ 5,589	$ 9,295
Current portion of lease liabilities	4,435	3,894
Operating lease liability, net of current portion	1,725	5,855
Total operating lease liabilities	$ 6,160	$ 9,749
Additional details
Weighted-average remaining life (years)	1 year 7 months 6 days	2 years 4 months 24 days
Weighted-average discount rate	6.80%	6.80%

Accrued Expenses and Other Current Liabilities

12 Months Ended

Dec. 31, 2023

Payables and Accruals [Abstract]

Accrued Expenses and Other Current Liabilities

ACCRUED EXPENSES AND OTHER CURRENT LIABILITIES

Accrued expenses and other current liabilities consist of the following (in thousands):


	December 31,
	2023		2022
Accrued payments due to AstraZeneca	$	3,680	$	3,385
Accrued gross to net revenue liabilities	3,258		1,991
Accrued contract manufacturing expenses	1,946		1,657
Accrued sales and marketing expenses	3,223		587
Accrued professional and consulting services	486		808
Derivative liability for exit fees	675		1,656
Accrued clinical expenses	377		223
Accrued non-clinical research and development expenses	30		1,188

Other	1,366		885
Total accrued expenses and other current liabilities	$	15,041	$	12,380

Equity Incentive Plans - Valuation Assumptions for ESPP (Details) - ESPP	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (years)	6 months	6 months	6 months
Expected volatility	86.00%	97.20%	123.00%
Risk-free interest rate	5.30%	1.90%	0.70%
Dividend yield	0.00%	0.00%	0.00%

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

+ Details

Borrowing

12 Months Ended

Dec. 31, 2023

Debt Disclosure [Abstract]

Borrowing

BORROWING

Solar Capital and Western Alliance Bank Loan Agreement

In May 2018, we entered into a loan and security agreement (as amended on October 9, 2020, March 1, 2021, May 5, 2021, and July 29, 2021) (2018 Loan Agreement) with Solar Capital Ltd. and Western Alliance Bank (collectively, the 2018 Lenders). The 2018 Loan Agreement provided for a loan facility for up to $50.0 million with a maturity date of November 1, 2022 (2018 Loan). As of the Closing Date for the 2022 Loan, as discussed below, we owed $25.0 million in principal payments from the 2018 Loan, which we repaid in full at that time.

As discussed in Note 10. Derivative Liabilities, in connection with entering into the 2018 Loan Agreement, we entered into an agreement pursuant to which we agreed to pay $1.5 million in cash upon the occurrence of certain conditions (2018 Exit Fee). Our obligations for the 2018 Exit Fee remained outstanding following the full repayment of the 2018 Loan in February 2022 until October 2023 when we received approval from the U.S. FDA for XPHOZAH to reduce serum phosphorus in adults with CKD on dialysis as add-on therapy in patients who have an inadequate response to phosphate binders or who are intolerant of any dose of phosphate binder therapy. This triggered our obligation to pay the 2018 Exit Fee to the 2018 Lenders and we subsequently paid the 2018 Exit Fee in October 2023.

SLR Investment Corp. Loan Agreement

On February 23, 2022 (Closing Date), we entered into a loan and security agreement (2022 Loan Agreement) with SLR Investment Corp. as collateral agent (Agent), and the lenders listed in the 2022 Loan Agreement (collectively, the 2022 Lenders). The 2022 Loan Agreement was subsequently amended in August 2022 (the First Amendment) and February 2023 (the Second Amendment). We concluded that the First Amendment and the Second Amendment were modifications to the 2022 Loan Agreement. The 2022 Loan Agreement, as amended by the First Amendment and the Second Amendment, provided for a senior secured loan facility, with $27.5 million (Term A Loan) funded on the Closing Date and an additional $22.5 million which we may borrow on or prior to December 20, 2023; provided that (i) we have received approval by the U.S. FDA for our NDA for XPHOZAH by November 30, 2023, and (ii) we have achieved certain product revenue milestone targets described in the 2022 Loan Agreement (Term B Loan, and together with the Term A Loan, the 2022 Original Loans). The 2022 Term A Loan funds were used to repay the 2018 Loan with the 2018 Lenders.

On October 17, 2023, we entered into a Third Amendment (the Third Amendment) to the 2022 Loan Agreement by and between us and the 2022 Lenders. The Third Amendment, among other things, (1) provides us with the option to draw an additional $50.0 million of committed capital by March 15, 2024 (the Term C Loan) provided we have drawn the Term B Loan; and (2) provides us with the option to draw up to an additional $50.0 million of uncommitted capital by December 31, 2026, subject to approval by the Agent’s investment committee (the Term D Loan and together with the Term A, B, and C Loans, the Four 2022 Loans). We concluded that the Third Amendment was a modification to the 2022 Loan Agreement and is accounted for accordingly. We expect to provide the Agent with notice of our decision to draw the Term C Loan prior to the expiry of the option on March 15, 2024 to further support the commercial launch of XPHOZAH.

Under the Third Amendment, the maturity date for the Four 2022 Loans is March 1, 2027. The interest rate for each of the Term A Loan and the Term B Loan is 7.95% plus a SOFR value equal to 0.022% plus the 1-month CME Term SOFR reference rate as published by the CME Term SOFR Administrator on the CME Term SOFR Administrator’s Website, subject to a SOFR floor of one percent. The interest rate for each of the Term C Loan and the Term D Loan is 4.25% plus a SOFR value equal to 0.022% plus the 1-month CME Term SOFR reference rate as published by the CME Term SOFR Administrator on the CME Term SOFR Administrator’s Website, subject to a SOFR floor of 4.7%.

In addition, the period under which we are permitted to make interest-only payments on the Four 2022 Loans was extended to December 31, 2026, effective upon our decision to draw the Term B Loan in the amount of $22.5 million. In October 2023, we provided the Agent with notice of our decision to draw the Term B Loan to support the commercial launch of XPHOZAH and received the proceeds of the Term B Loan.

We were obligated to pay $0.2 million, upon the closing of the Term A Loan, and we were obligated to pay $0.1 million on the funding date of the Term B Loan. We are obligated to pay $0.3 million on the earliest of (1) the funding date of the Term C Loan, (2) March 15, 2024, and (3) the prepayment, refinancing, substitution or replacement of the Term B Loans on or prior to March 15, 2024. In addition, we will be obligated to pay 0.5% of the aggregate original principal amount of the Term D Loan commitment, if requested by us and approved by the Agent’s investment committee, which shall be due on the earliest of (1) the funding of the Term D Loan, (2) if we request and the 2022 Lenders provide the Term D Loan commitment, the day immediately preceding the amortization date, and (3) if we request and the 2022 Lenders provide the Term D Loan commitment, the prepayment, refinancing, substitution or replacement of the Term C Loan on or prior to the date immediately preceding the amortization date.

We are obligated to pay a final fee equal to 4.95% of the aggregate original principal amount of the Four 2022 Loans, to the extent such loans are funded, upon the earliest to occur of the maturity date, the acceleration of the Four 2022 Loans, and the prepayment, refinancing, substitution, or replacement of the Four 2022 Loans.

We may voluntarily prepay all amounts outstanding under the Four 2022 Loans, subject to a prepayment premium of (i) 3% of the outstanding principal amount of the Four 2022 Loans if prepaid prior to or on October 17, 2024, (ii) 2% of the outstanding principal amount of the Four 2022 Loans if prepaid after October 17, 2024 through and including October 17, 2025, or (iii) 1% of the outstanding principal amount of the Four 2022 Loans if prepaid after October 17, 2025 and prior to the maturity date. The Four 2022 Loans are secured by substantially all of our assets, except for our intellectual property and certain other customary exclusions. Additionally, as discussed in Note 10. Derivative Liabilities, in connection with the 2022 Original Loans, we entered into an agreement whereby we agreed to pay an exit fee in the amount of 2% of the 2022 Original Loans funded (2022 Exit Fee). Notwithstanding the prepayment or termination of the 2022 Loan, the 2022 Exit Fee will expire 10 years from the Closing Date.

The 2022 Loan Agreement, as amended, contains customary representations and warranties and customary affirmative and negative covenants, including, among others, requirements as to financial reporting and insurance and restrictions on our ability to dispose of our business or property, to change our line of business, to liquidate or dissolve, to enter into any change in control transaction, to merge or consolidate with any other entity or to acquire all or substantially all the capital stock or property of another entity, to incur additional indebtedness, to incur liens on our property, to pay any dividends or other distributions on capital stock other than dividends payable solely in capital stock or to redeem capital stock. We have agreed to not allow our cash and cash equivalents to be less than the eighty percent (80%) of the outstanding Four 2022 Term Loan balance for any period in which our net revenue from the sale of any products, calculated on a trailing six (6) month basis and tested monthly, is less than sixty percent (60%) of the outstanding Four 2022 Loan balance.

In addition, the 2022 Loan Agreement, as amended, contains customary events of default that entitle the Agent to cause our indebtedness under the 2022 Loan Agreement to become immediately due and payable, and to exercise remedies against us and the collateral securing the Four 2022 Term Loans, including our cash. Under the 2022 Loan Agreement, an event of default will occur if, among other things, we fail to make payments under the 2022 Loan Agreement, we breach any of our covenants under the 2022 Loan Agreement, subject to specified cure periods with respect to certain breaches, certain Lenders determine that a material adverse change has occurred, we or our assets become subject to certain legal proceedings, such as bankruptcy proceedings, we are unable to pay our debts as they become due or we default on contracts with third parties which would permit the holder of indebtedness to accelerate the maturity of such indebtedness or that could have a material adverse change on us. Upon the occurrence and for the duration of an event of default, an additional default interest rate equal to 4% per annum will apply to all obligations owed under the 2022 Loan Agreement. We have classified the 2022 Original Loan balance as a non-current liability as of December 31, 2023 due to principal repayments beginning in January 2027. We have concluded that the provisions that could cause acceleration of the principal repayments are remote.

As of December 31, 2023, our future payment obligations related to the 2022 Loan, excluding interest payments and the 2022 final fee, were as follows (in thousands):



2024	$	—
2025	—
2026	—
2027	52,475
Thereafter	—
Total repayment obligations	52,475
Less: Unamortized discount and debt issuance costs	(912)
Less: Unaccreted value of final fee	(1,741)
Long-term debt	49,822
Less: Current portion of long-term debt	—
Long-term debt, net of current portion	$	49,822

- Definition

The entire disclosure for information about short-term and long-term debt arrangements, which includes amounts of borrowings under each line of credit, note payable, commercial paper issue, bonds indenture, debenture issue, own-share lending arrangements and any other contractual agreement to repay funds, and about the underlying arrangements, rationale for a classification as long-term, including repayment terms, interest rates, collateral provided, restrictions on use of assets and activities, whether or not in compliance with debt covenants, and other matters important to users of the financial statements, such as the effects of refinancing and noncompliance with debt covenants.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Subparagraph (h)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1B

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(c))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480678/235-10-S99-1

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 470
-Name Accounting Standards Codification
-Publisher FASB
-URI https://asc.fasb.org//470/tableOfContent

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1B

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Subparagraph (g)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1B

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Subparagraph (i)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1B

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1C
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1C

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1C
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1C

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1C
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1C

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1E
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1E

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1I
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1I

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1I
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1I

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1I
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1I

+ Details

Net Loss Per Share - Anti-Dilutive Securities and Potential Common Shares (Details) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities not included in computation of diluted net loss per share	24,212	16,382	13,680
Potential common shares that would have been included if not for anti-dilutive effect of securities	6,300	600	1,100
Options to purchase common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities not included in computation of diluted net loss per share	20,877	13,522	11,871
Restricted stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities not included in computation of diluted net loss per share	3,086	2,694	1,602
ESPP shares issuable
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities not included in computation of diluted net loss per share	249	166	207

Accrued Expenses and Other Current Liabilities (Tables)

12 Months Ended

Dec. 31, 2023

Payables and Accruals [Abstract]

Schedule of Accrued Expenses and Other Current Liabilities

Accrued expenses and other current liabilities consist of the following (in thousands):


	December 31,
	2023		2022
Accrued payments due to AstraZeneca	$	3,680	$	3,385
Accrued gross to net revenue liabilities	3,258		1,991
Accrued contract manufacturing expenses	1,946		1,657
Accrued sales and marketing expenses	3,223		587
Accrued professional and consulting services	486		808
Derivative liability for exit fees	675		1,656
Accrued clinical expenses	377		223
Accrued non-clinical research and development expenses	30		1,188

Other	1,366		885
Total accrued expenses and other current liabilities	$	15,041	$	12,380

STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Deficit	Accumulated Other Comprehensive (Loss) Income
Beginning balance (in shares) at Dec. 31, 2020		93,599,975
Beginning balance at Dec. 31, 2020	$ 126,112	$ 9	$ 680,872	$ (554,765)	$ (4)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock under employee stock purchase plan (in shares)		386,664
Issuance of common stock under employee stock purchase plan	819		819
Issuance of common stock for services (in shares)		25,989
Issuance of common stock for services	190		190
Issuance of common stock upon exercise of options (in shares)		331,310
Issuance of common stock upon exercise of options	584		584
Issuance of common stock upon vesting of restricted stock units (in shares)		167,158
Taxes paid for net share settlement of equity awards	(106)		(106)
Issuance of common stock in at the market offering (in shares)		35,671,439
Issuance of common stock in at the market offering	101,146	$ 4	101,142
Stock-based compensation	12,039		12,039
Unrealized gains (losses) on available-for-sale securities	(2)				(2)
Net loss	(158,165)			(158,165)
Ending balance (in shares) at Dec. 31, 2021		130,182,535
Ending balance at Dec. 31, 2021	82,617	$ 13	795,540	(712,930)	(6)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock under employee stock purchase plan (in shares)		308,356
Issuance of common stock under employee stock purchase plan	195		195
Issuance of common stock for services (in shares)		711,675
Issuance of common stock for services	390		390
Issuance of common stock upon exercise of options (in shares)		14,080
Issuance of common stock upon exercise of options	7		7
Issuance of common stock upon vesting of restricted stock units (in shares)		3,243,828
Issuance of common stock in at the market offering (in shares)		64,114,542
Issuance of common stock in at the market offering	71,625	$ 7	71,618
Stock-based compensation	10,750		10,750
Unrealized gains (losses) on available-for-sale securities	(48)				(48)
Net loss	(67,207)			(67,207)
Ending balance (in shares) at Dec. 31, 2022		198,575,016
Ending balance at Dec. 31, 2022	98,329	$ 20	878,500	(780,137)	(54)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock under employee stock purchase plan (in shares)		435,708
Issuance of common stock under employee stock purchase plan	808		808
Issuance of common stock for services (in shares)		86,095
Issuance of common stock for services	$ 337		337
Issuance of common stock upon exercise of options (in shares)	226,000	225,988
Issuance of common stock upon exercise of options	$ 365		365
Issuance of common stock upon vesting of restricted stock units (in shares)		855,642
Issuance of common stock in at the market offering (in shares)		32,274,741
Issuance of common stock in at the market offering	119,236	$ 3	119,233
Stock-based compensation	13,530		13,530
Unrealized gains (losses) on available-for-sale securities	278				278
Net loss	(66,067)			(66,067)
Ending balance (in shares) at Dec. 31, 2023		232,453,190
Ending balance at Dec. 31, 2023	$ 166,816	$ 23	$ 1,012,773	$ (846,204)	$ 224

STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Revenues:
Total revenues	$ 124,456	$ 52,158	$ 10,097
Cost of goods sold:
Total cost of goods sold	17,795	4,117	1,000
Operating expenses:
Research and development	35,536	35,201	91,140
Selling, general and administrative	134,401	76,599	72,303
Total operating expenses	169,937	111,800	163,443
Loss from operations	(63,276)	(63,759)	(154,346)
Interest expense	(4,950)	(3,400)	(4,502)
Non-cash interest expense related to the sale of future royalties	(3,924)	(1,673)	0
Other income, net	6,630	1,633	687
Loss before provision for income taxes	(65,520)	(67,199)	(158,161)
Provision for income taxes	547	8	4
Net loss	$ (66,067)	$ (67,207)	$ (158,165)
Net loss per share of common stock - basic (in dollars per share)	$ (0.30)	$ (0.42)	$ (1.52)
Net loss per share of common stock - diluted (in dollars per share)	$ (0.30)	$ (0.42)	$ (1.52)
Shares used in computing net loss per share - basic (in shares)	219,331,253	158,690,083	104,205,645
Shares used in computing net loss per share - diluted (in shares)	219,331,253	158,690,083	104,205,645
Comprehensive loss:
Net loss	$ (66,067)	$ (67,207)	$ (158,165)
Unrealized gains (losses) on available-for-sale securities	278	(48)	(2)
Comprehensive loss	(65,789)	(67,255)	(158,167)
Product sales, net
Revenues:
Total revenues	82,526	15,600	0
Cost of goods sold:
Total cost of goods sold	2,323	566	0
Licensing revenue
Revenues:
Total revenues	35,809	35,031	5,013
Product supply revenue
Revenues:
Total revenues	6,121	1,527	907
Collaborative development revenue
Revenues:
Total revenues	0	0	4,177
Other cost of revenue
Cost of goods sold:
Total cost of goods sold	$ 15,472	$ 3,551	$ 1,000

Inventory - Schedule (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Inventory Disclosure [Abstract]
Raw materials	$ 22,920	$ 22,299
Work in process	24,582	5,324
Finished goods	1,985	723
Inventory	12,448	3,282
Inventory, non-current	37,039	25,064
Total	$ 49,487	$ 28,346

BALANCE SHEETS - USD ($)	Dec. 31, 2023	Dec. 31, 2022
Current assets:
Cash and cash equivalents	$ 21,470,000	$ 96,140,000
Short-term investments	162,829,000	27,769,000
Accounts receivable	22,031,000	7,733,000
Inventory	12,448,000	3,282,000
Prepaid commercial manufacturing	18,925,000	13,567,000
Prepaid expenses and other current assets	8,408,000	5,112,000
Total current assets	246,111,000	153,603,000
Property and equipment, net	1,009,000	1,223,000
Inventory, non-current	37,039,000	25,064,000
Prepaid commercial manufacturing, non-current	4,235,000	0
Right-of-use assets	5,589,000	9,295,000
Other assets	3,596,000	881,000
Total assets	297,579,000	190,066,000
Current liabilities:
Accounts payable	11,138,000	10,859,000
Accrued compensation and benefits	12,597,000	7,548,000
Current portion of operating lease liability	4,435,000	3,894,000
Current portion of long-term debt	0	26,711,000
Deferred revenue	7,182,000	4,211,000
Accrued expenses and other current liabilities	15,041,000	12,380,000
Total current liabilities	50,393,000	65,603,000
Operating lease liability, net of current portion	1,725,000	5,855,000
Long-term debt, net of current portion	49,822,000	0
Deferred revenue, non-current	8,644,000	9,025,000
Deferred royalty obligation related to the sale of future royalties	20,179,000	11,254,000
Total liabilities	130,763,000	91,737,000
Commitments and contingencies (Note 20)
Stockholders’ equity:
Preferred stock, $0.0001 par value; 5,000,000 shares authorized; no shares issued and outstanding	0	0
Common stock, $0.0001 par value; 500,000,000 and 300,000,000 shares authorized; 232,453,190 and 198,575,016 shares issued and outstanding as of December 31, 2023 and December 31, 2022, respectively.	23,000	20,000
Additional paid-in capital	1,012,773,000	878,500,000
Accumulated deficit	(846,204,000)	(780,137,000)
Accumulated other comprehensive income (loss)	224,000	(54,000)
Total stockholders’ equity	166,816,000	98,329,000
Total liabilities and stockholders’ equity	$ 297,579,000	$ 190,066,000

Revenue

12 Months Ended

Dec. 31, 2023

Revenue from Contract with Customer [Abstract]

Revenue

REVENUE

Total revenues during the years ended December 31, 2023, 2022, and 2021 were as follows (in thousands):


	Year Ended December 31,
	2023		2022		2021
Product sales, net:
IBSRELA	$	80,062	$	15,600	$	—
XPHOZAH	2,464		—		—
Total product sales, net	82,526		15,600		—
Licensing revenue	35,809		35,031		5,013
Product supply revenue	6,121		1,527		907
Collaborative development revenue	—		—		4,177
Total revenues	$	124,456	$	52,158	$	10,097

Revenue from the following Customers who contributed greater than 10% of our gross product revenue during the years ended December 31, 2023 and 2022 as a percentage of total gross product revenue was as follows:


	Year Ended December 31,
		2023		2022
BioRidge Pharma, LLC		26.3	%	—	%
Cardinal Health		21.6	%	23.1	%
AmerisourceBergen Drug Corporation		20.9	%	26.8	%
McKesson Corporation		17.2	%	21.6	%

The activities and ending reserve balances for each significant category of discounts and allowances, which constitute variable consideration, were as follows (in thousands):


	Discounts and Chargebacks		Rebates, Wholesaler and GPO Fees		Copay and Returns		Total
Balance as of December 31, 2021	$	—	$	—	$	—	$	—
Provisions	825		2,721		2,502		6,048
Credits/payments	(683)		(1,277)		(1,244)		(3,204)
Balance as of December 31, 2022	142		1,444		1,258		2,844
Provisions	5,341		15,365		10,629		31,335
Credits/payments	(5,005)		(12,575)		(7,971)		(25,551)
Balance as of December 31, 2023	$	478	$	4,234	$	3,916	$	8,628

Adjustments to prior period provisions recorded in the current period were not material.

- Definition

The entire disclosure of revenue from contract with customer to transfer good or service and to transfer nonfinancial asset. Includes, but is not limited to, disaggregation of revenue, credit loss recognized from contract with customer, judgment and change in judgment related to contract with customer, and asset recognized from cost incurred to obtain or fulfill contract with customer. Excludes insurance and lease contracts.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 9
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479806/606-10-50-9

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 10
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479806/606-10-50-10

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 15
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479806/606-10-50-15

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 12
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479806/606-10-50-12

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 12
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479806/606-10-50-12

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 12
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479806/606-10-50-12

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 12
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479806/606-10-50-12

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 12
-Subparagraph (e)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479806/606-10-50-12

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (b)(2)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479806/606-10-50-13

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Name Accounting Standards Codification
-Topic 606
-Publisher FASB
-URI https://asc.fasb.org//606/tableOfContent

+ Details

Restructuring	12 Months Ended
Restructuring	Dec. 31, 2023
Restructuring and Related Activities [Abstract]
Restructuring	RESTRUCTURING During 2021, we implemented restructuring plans in August and October following the receipt of a Complete Response Letter (CRL) from the U.S. FDA relating to our NDA for XPHOZAH and following the conclusion of an End of Review Type A meeting with the U.S. FDA, respectively. Both restructuring plans were substantially completed in December 2021 and most of the cash payments related to the reduction in workforce were disbursed prior to December 31, 2021. In connection with restructuring, we incurred restructuring charges of $6.2 million, which were recorded during the year ended December 31, 2021, related to one-time termination notice and severance payments and other employee-related costs. We did not incur any significant contract termination costs pursuant to restructuring. Of the charges, $2.7 million was recorded in research and development expenses, and $3.5 million was recorded in selling, general and administrative expense in the accompanying statements of operations and comprehensive loss.

Leases - Narrative (Details) $ in Thousands	1 Months Ended	3 Months Ended	12 Months Ended
Leases - Narrative (Details) $ in Thousands	Nov. 30, 2020 USD ($) ft² renewal_option	Mar. 31, 2023 USD ($) ft²	Dec. 31, 2023 USD ($) ft² lease_agreement renewal_option	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Aug. 31, 2023 USD ($) ft²	May 31, 2021 USD ($)
Lessee, Lease, Description [Line Items]
Number of lease agreements \| lease_agreement			3
Right-of-use assets			$ 5,589	$ 9,295
Operating lease, liability			6,160	9,749
Sublease Income			800
Right-of-use assets obtained in exchange for lease obligations			$ 339	$ 0	$ 1,604
Waltham, Massachusetts
Lessee, Lease, Description [Line Items]
Office space area (sq ft) \| ft²						4,247
Waltham facility
Lessee, Lease, Description [Line Items]
Number of options to extend \| renewal_option			1
Term of lease extension			5 years
Right-of-use assets						$ 300	$ 1,600
Operating lease, liability						$ 300	$ 1,600
Waltham facility \| Minimum
Lessee, Lease, Description [Line Items]
Office space area (sq ft) \| ft²			17,111
Fremont facility \| Maximum
Lessee, Lease, Description [Line Items]
Office space area (sq ft) \| ft²		72,500
Milwaukee facility
Lessee, Lease, Description [Line Items]
Office space area (sq ft) \| ft²	4,768
Number of options to extend \| renewal_option	1
Term of lease extension	5 years
Existence of option to extend	true
Right-of-use assets obtained in exchange for lease obligations	$ 400
Sublease Facility, Fremont California
Lessee, Lease, Description [Line Items]
Operating lease, impairment loss		$ 400
Sublease Facility, Fremont California \| Minimum
Lessee, Lease, Description [Line Items]
Office space area (sq ft) \| ft²		21,644

Cover - USD ($)	12 Months Ended
Cover - USD ($)	Dec. 31, 2023	Feb. 16, 2024	Jun. 30, 2023
Cover [Abstract]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2023
Current Fiscal Year End Date	--12-31
Document Transition Report	false
Entity File Number	001-36485
Entity Registrant Name	ARDELYX, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	26-1303944
Entity Address, Address Line One	400 FIFTH AVE.
Entity Address, Address Line Two	SUITE 210
Entity Address, City or Town	WALTHAM
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02451
City Area Code	510
Local Phone Number	745-1700
Title of 12(b) Security	Common Stock, par value $0.0001 per share
Trading Symbol	ARDX
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Document Financial Statement Error Correction [Flag]	false
Entity Shell Company	false
Entity Public Float			$ 724,838,738
Entity Common Stock, Shares Outstanding		232,686,008
Entity Central Index Key	0001437402
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	FY
Amendment Flag	false
Documents Incorporated by Reference	Portions of the Registrant’s Definitive Proxy Statement for its 2024 Annual Meeting of Stockholders, which will be filed with the Commission within 120 days of December 31, 2023, the close of the Registrant’s 2023 fiscal year, are incorporated by reference into Part III of this Report.

Borrowing - Narrative (Details) - USD ($)	Oct. 17, 2023	Feb. 23, 2022	Dec. 31, 2023	May 31, 2018
Term Loans
Principal outstanding			$ 52,475,000
2018 Exit Fee
Term Loans
Agreed amount for exit fee upon occurrence of certain conditions				$ 1,500,000
2022 Exit Fee
Term Loans
Exit fee (percent)	2.00%
Exit fee, term (in years)	10 years
2018 Term Loan \| Term loan
Term Loans
Term loan amount				$ 50,000,000
Principal outstanding		$ 25,000,000
2022 Term Loan \| Term loan
Term Loans
Final fee due upon maturity, acceleration, prepayment, or termination (percent)		4.95%
Loan agreement covenant, cash and cash equivalents as percentage of outstanding loan balance, minimum		80.00%
Loan agreement, covenant, cash and cash equivalents as percentage of outstanding loan balance, calculation period		6 months
Loan agreement covenant, net product revenue as percentage of outstanding loan balance, minimum		60.00%
Additional default interest rate		4.00%
2022 Term Loan \| Term loan \| Prior to first anniversary of closing date
Term Loans
Prepayment premium (as a percent)	3.00%
2022 Term Loan \| Term loan \| After first anniversary through second anniversary of closing date
Term Loans
Prepayment premium (as a percent)	2.00%
2022 Term Loan \| Term loan \| After second anniversary to maturity date
Term Loans
Prepayment premium (as a percent)	1.00%
Term Loan A \| Term loan
Term Loans
Proceeds from loan payable, net of issuance costs		$ 27,500,000
Interest rate (as percent)	7.95%
Closing fee	$ 200,000
Term Loan A \| Term loan \| Secured Overnight Financing Rate (SOFR)
Term Loans
Floating per annum rate (percent)	0.022%
Term Loan A \| Term loan \| Floor Rate
Term Loans
Floating per annum rate (percent)	1.00%
Term Loan B \| Term loan
Term Loans
Remaining funding based on milestone achievement		22,500,000
Interest rate (as percent)	7.95%
Future obligation upon loan funding or other events		$ 100,000
Term Loan B \| Term loan \| Secured Overnight Financing Rate (SOFR)
Term Loans
Floating per annum rate (percent)	0.022%
Term Loan B \| Term loan \| Floor Rate
Term Loans
Floating per annum rate (percent)	1.00%
Term Loan C \| Term loan
Term Loans
Additional committed capital	$ 50,000,000
Interest rate (as percent)	4.25%
Closing fee	$ 300,000
Term Loan C \| Term loan \| Secured Overnight Financing Rate (SOFR)
Term Loans
Floating per annum rate (percent)	0.022%
Term Loan C \| Term loan \| Floor Rate
Term Loans
Floating per annum rate (percent)	4.70%
Term Loan D \| Term loan
Term Loans
Additional uncommitted capital	$ 50,000,000
Interest rate (as percent)	4.25%
Closing fee percentage	0.50%
Term Loan D \| Term loan \| Secured Overnight Financing Rate (SOFR)
Term Loans
Floating per annum rate (percent)	0.022%
Term Loan D \| Term loan \| Floor Rate
Term Loans
Floating per annum rate (percent)	4.70%

Leases - Lease Costs (Details) - USD ($) $ in Thousands	12 Months Ended
Leases - Lease Costs (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Lease costs
Operating lease expense	$ 3,857	$ 4,257	$ 3,671
Cash paid for operating lease	$ 4,481	$ 4,292	$ 3,438

Geographic Information and Concentrations (Tables)

12 Months Ended

Dec. 31, 2023

Risks and Uncertainties [Abstract]

Schedule of Revenue by Geographic Areas

A summary of our revenue by geographic areas for the years ended December 31, 2023, 2022 and 2021, is as follows (in thousands):


	Year Ended December 31,
	2023		2022		2021
United States (1)	$	83,276	$	15,600	$	—
International:
Asia Pacific (2)	41,121		36,527		10,084
North America (3)	59		31		13
Total revenue	$	124,456	$	52,158	$	10,097

(1)Revenues from the United States are primarily comprised of amounts earned from sales of IBSRELA and XPHOZAH, as well as the upfront license fee from the METiS Agreement.

(2)Revenues from Asia Pacific are primarily comprised of amounts earned in accordance with the 2017 Kyowa Kirin Agreement, the 2019 Kyowa Kirin Agreement and the Fosun Agreement.

(3)Revenues from North America are comprised of amounts earned from Canada in accordance with the Knight Agreement.

Schedule of Revenues from Customers and Collaboration Partnerships


	Year Ended December 31,
		2023		2022
BioRidge Pharma, LLC		26.3	%	—	%
Cardinal Health		21.6	%	23.1	%
AmerisourceBergen Drug Corporation		20.9	%	26.8	%
McKesson Corporation		17.2	%	21.6	%

Revenues from Customers and collaboration partnerships accounting for more than 10% of total revenues during the years ended December 31, 2023, 2022 and 2021 were as follows:


	Year Ended December 31,
	2023		2022		2021
Kyowa Kirin	29.0	%	70.0	%	100.0	%
Bioridge Phama	24.0	%	3.2	%	—	%
Cardinal	19.8	%	9.6	%	—	%


AmerisourceBergen Drug Corporation	19.1	%	11.1	%	—	%
McKesson	15.7	%	8.9	%	—	%

Restructuring (Details) $ in Millions	12 Months Ended
Restructuring (Details) $ in Millions	Dec. 31, 2021 USD ($)
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 6.2
Research and development expenses
Restructuring Cost and Reserve [Line Items]
Restructuring charges	2.7
General and administrative expense
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 3.5

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References + Details

Geographic Information and Concentrations - Revenue by Geographical Area (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	$ 124,456	$ 52,158	$ 10,097
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	83,276	15,600	0
Asia Pacific
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	41,121	36,527	10,084
North America
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	$ 59	$ 31	$ 13

- Definition

Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 924
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 11.L)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479941/924-10-S99-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479806/606-10-50-5

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 30
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-30

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 42
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-42

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 22
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-22

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 32
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-32

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 40
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-40

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 22
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-22

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 32
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-32

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 41
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-41

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479806/606-10-50-4

+ Details

Summary of Significant Accounting Policies (Policies)	12 Months Ended
Summary of Significant Accounting Policies (Policies)	Dec. 31, 2023
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”).
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and judgments that affect the amounts reported in the financial statements and accompanying notes thereto. On an ongoing basis, management evaluates its estimates, including those related to recognition of revenue, clinical trial accruals, contract manufacturing accruals, expected demand for inventory, fair value of assets and liabilities, income taxes and stock-based compensation. Management bases its estimates on historical experience and on various other market-specific and relevant assumptions that management believes to be reasonable under the circumstances. Actual results could materially differ from those estimates.
Cash and Cash Equivalents	Cash and Cash Equivalents We consider all highly liquid investments purchased with an original maturity date of 90 days or less on the date of purchase to be cash equivalents.
Short-Term Investments	Short-Term Investments Short-term investments consist of debt securities classified as available-for-sale and have maturities greater than 90 days, but less than one year, from the date of acquisition. Short-term investments are carried at fair value based upon quoted market prices. Unrealized gains and losses on available-for-sale securities are included in accumulated other comprehensive income (loss) on our balance sheets. The cost of available-for-sale securities sold is based on the specific-identification method.
Concentration of Credit Risk	Concentration of Credit Risk Financial instruments that potentially subject us to significant concentrations of credit risk consist primarily of cash, cash equivalents, short-term investments and accounts receivable. We are exposed to credit risks in the event of default by the counterparties to the extent of the amount recorded in our balance sheet. Cash, cash equivalents and short-term investments are invested through banks and other financial institutions in the U.S.
Foreign Currency	Foreign Currency We manage our foreign currency exposures with the use of foreign currency purchases. We primarily conduct business in U.S. dollars; however, a portion of our expense and capital activities are transacted in foreign currencies which are subject to exchange rate fluctuations that can affect cash or earnings. We have been in a loss position and therefore our primary objective is to conserve and manage cash. There are generally two methods by which we may manage the cash flow risk of foreign exchange fluctuations when a contract is signed (i) we can purchase the foreign funds, in full or in part, upon the execution of the contract, or (ii) we can obtain the right to purchase such funds, in full or in part, at the execution of the contract, i.e., obtain a forward contract from an appropriate bank, that can be exercised to obtain the currency of interest at a particular point in time. The derivative instruments that we may use to hedge the exposure shall generally not be designated as cash flow hedges, and as a result, changes in their fair value would be recorded in other income (expense), net, in our statements of operations and comprehensive loss. The fair values of forward foreign currency exchange contracts would be estimated using current exchange rates and interest rates and the current creditworthiness of the counterparties is taken into consideration.
Property and Equipment	Property and Equipment Property and equipment are stated at cost, less accumulated depreciation and amortization. Depreciation is computed using the straight-line method over the estimated useful lives of the respective assets, with ranges generally from three to five years. Leasehold improvements are amortized over the lesser of the estimated useful lives or the related remaining lease term.
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets The carrying values of long-lived assets, including property and equipment, are reviewed for impairment whenever events or changes in circumstances indicate that the asset may not be recoverable. An impairment loss is recognized when the total of estimated future undiscounted cash flows, expected to result from the use of the asset and its eventual disposition, are less than the asset’s carrying amount. Impairment, if any, would be assessed using discounted cash flows or other appropriate measures of fair value.
Income Taxes	Income Taxes We use the asset and liability method of accounting for income taxes. Under this method, deferred tax assets and liabilities are determined based on the differences between the financial reporting and the tax bases of assets and liabilities and are measured using the enacted tax rates and laws that will be in effect when the differences are expected to reverse. A valuation allowance is provided when it is more likely than not that some portion or all of a deferred tax asset will not be realized.
Accounts Receivable	Accounts Receivable Accounts receivable are stated at amortized cost less allowance for credit losses. The allowance for credit losses reflects the best estimate of future losses over the contractual life of outstanding accounts receivable and is determined on the basis of historical experience, specific allowances for known troubled accounts, other currently available information including customer financial condition and both current and forecasted economic conditions. To date, we have determined that an allowance for doubtful accounts is not required.
Inventory	Inventory We capitalize inventory costs associated with the production of our products after regulatory approval or when, based on management’s judgment, future commercialization is considered probable and the future economic benefit is expected to be realized. Otherwise, such costs are expensed as research and development. Prior to the regulatory approval of drug product candidates, we incurred expenses for the manufacture of drug product that could potentially be available to support the commercial launch of our products or could be sold to our international partners under product supply agreements. We began to capitalize inventory costs associated with IBSRELA during the fourth quarter of 2021, when our intent to commercialize IBSRELA was established and we commenced preparation for the commercial launch of IBSRELA, which was when it was determined that the inventory had a probable future economic benefit. We began to capitalize inventory costs associated with XPHOZAH during the fourth quarter of 2023, following approval by the U.S. FDA to market XPHOZAH in the U.S., which was when it was determined that the inventory had a probable future economic benefit. Inventory is stated at the lower of cost or estimated net realizable value with cost determined under the specific identification method. Inventory costs include the cost of materials, third-party contract manufacturing, third-party packaging services, freight, labor costs for personnel involved in the manufacturing process, and indirect overhead costs. We primarily use actual costs to determine the cost basis for inventory. The determination of whether inventory costs will be realizable requires management review of the expiration dates of IBSRELA and XPHOZAH compared to our forecasted sales. If actual market conditions are less favorable than projected by management, write-downs of inventory may be required, which would be recorded as cost of revenue in the statement of operations and comprehensive loss. As of December 31, 2023, we have not recorded any write-offs for excess and obsolete inventory. A portion of inventory that represents product that is not expected to be sold or used within the next 12 months is classified as non-current on our balance sheets.
Product Sales, Net and Reserves for Variable Consideration and Collaboration Revenue Recognition	Product Sales, Net We account for our commercial product sales, net in accordance with Topic 606 – Revenue from Contracts with Customers. We received approval from the FDA to market IBSRELA in the U.S. in September 2019 and to market XPHOZAH in the U.S. in October 2023. We began selling IBSRELA and XPHOZAH in the U.S. in March 2022 and November 2023, respectively. We distribute IBSRELA principally through major wholesalers, specialty pharmacies and group purchasing organizations (GPOs) (collectively, our IBSRELA Customers). XPHOZAH is principally distributed through a specialty wholesaler (XPHOZAH Customer) to select specialty pharmacies (collectively, IBSRELA Customers and XPHOZAH Customers, “Customers”). Our Customers subsequently sell IBSRELA and XPHOZAH to pharmacies and patients. Separately, we enter into arrangements with third parties that provide for government-mandated rebates, chargebacks and discounts. Revenue from product sales is recognized when our performance obligations are satisfied, which is when Customers obtain control of our product and occurs upon delivery. Reserves for Variable Consideration Revenues from product sales are recorded at the net sales price (transaction price), which includes estimates of variable consideration which may be settled in the form of off-invoice discounts, chargebacks, or rebates. Variable consideration includes discounts to customers and government programs, wholesaler fees, group purchasing organization administrative fees, patient copay assistance, and estimated product returns. These estimates are based on the amounts earned or to be claimed for related sales and are classified as reductions of gross accounts receivable if settlement is expected to occur through a reduction in the amounts paid by our Customers or a current liability if settlement is expected to occur through a payment from us. Where appropriate, these estimates are based on factors such as industry data and forecasted customer buying and payment patterns, our experience, current contractual and statutory requirements, specific known market events and trends. These reductions to gross sales reflect our best estimates of the amount of consideration to which we are entitled based on the terms of the contract. Variable consideration is included in the transaction price only to the extent that it is probable that a significant reversal in the amount of cumulative revenue recognized will not occur when the uncertainty associated with the variable consideration is subsequently resolved. Actual amounts of consideration ultimately received may differ from our estimates. If actual results in the future vary from our estimates, we adjust these estimates, which would affect product revenue and earnings in the period such variances become known. As we gain more experience, estimates will be more heavily based on the expected utilization from historical data we have accumulated since the IBSRELA and XPHOZAH product launches. Changes in estimates recorded through December 31, 2023 have not been material. Rebates: Rebates include wholesaler fees, GPO fees, as well as mandated discounts under the Medicaid Drug Rebate Program (Medicaid) and the Medicare Coverage Gap Program (Medicare). Estimates for rebates are recorded in the same period the related gross revenue is recognized, resulting in a reduction of product revenue and the establishment of a current liability which is included in accrued expenses on the balance sheets. We estimate our Medicaid and Medicare rebates based upon the estimated payor mix, and statutory discount rates. Our estimates for payor mix are guided by payor information received from specialty pharmacies, expected utilization for wholesaler sales to pharmacies, and available industry payor information and, therefore, require the most estimation and judgment of our gross to net deductions. Chargebacks: Chargebacks are discounts that occur when certain contracted purchasers purchase directly from our wholesalers at a discounted price. The wholesaler, in turn, charges back the difference between the price initially paid to us by the wholesaler and the discounted price paid to the wholesaler by the contracted purchaser. Amounts for estimated chargebacks are established in the same period that the related gross revenue is recognized, resulting in a reduction of product revenue and accounts receivable. The accrual for wholesaler chargebacks is estimated based on known chargeback rates, known sales to wholesalers, and known sales from wholesalers to their chargeback-eligible customers. Discounts and Fees: Our payment terms are generally 30 to 60 days. Wholesalers, GPOs and specialty pharmacies are offered various forms of consideration, including off-invoice discounts which may be paid to GPOs and specialty pharmacies. Wholesalers and GPOs may also receive prompt pay discounts for payment within a specified period. We expect discounts to be earned when offered and, therefore, we deduct the full amount of these discounts from product sales when revenue is recognized, resulting in a reduction of product revenue and accounts receivable. Other Reserves: Patients who have commercial insurance may receive copay assistance when product is dispensed by pharmacies to patients. We estimate the amount of copay assistance provided to eligible patients based on the terms of the program, and redemption information provided by third-party claims processing organizations. We also estimate the amount of copay assistance that will be provided to patients associated with product which we have sold but which has not yet been dispensed to commercial patients, which requires significant estimation and judgment. Our estimates are recorded in accounts payable and accrued expenses and other current liabilities on the balance sheets. Other reserves include estimated product returns which are recorded in the same period the related gross revenue is recognized, resulting in a reduction of product revenue as well as accounts receivable. We estimate our product returns reserve based upon our experience and specific known market events and trends. As we have experienced limited product returns, establishing the appropriate level of returns reserve require estimation and judgment. Collaboration Revenue Recognition We generate collaboration revenue primarily from research and collaboration and license agreements with customers. Goods and services in the agreements may include the grant of licenses for the use of our technology, the provision of services associated with the research and development of product candidates, manufacturing services, and participation in joint steering committees. The terms of these arrangements typically include payment to us of one or more of the following: non-refundable, up-front license fees; research, development, regulatory and commercial milestone payments; reimbursement of research and development services; option payments; reimbursement of certain costs; payments for manufacturing supply services; and future royalties on net sales of licensed products. When two or more contracts are entered into with the same customer at or near the same time, we evaluate the contracts to determine whether the contracts should be accounted for as a single arrangement. Contracts are combined and accounted for as a single arrangement if one or more of the following criteria are met: (i) the contracts are negotiated as a package with a single commercial objective; (ii) the amount of consideration to be paid in one contract depends on the price or performance of the other contract; or (iii) the goods or services promised in the contracts (or some goods or services promised in each of the contracts) are a single performance obligation. In determining the appropriate amount of revenue to be recognized as we fulfill our obligations under each of our agreements, management performs the following steps: (i) identification of the promised goods or services in the contract; (ii) determination of whether the promised goods or services are performance obligations including whether they are distinct in the context of the contract; (iii) measurement of the transaction price, including any constraints on variable consideration; (iv) allocation of the transaction price to the performance obligations; and (v) recognition of revenue when (or as) we satisfy each performance obligation. As part of the accounting for contracts with customers, we develop assumptions that require judgment to determine whether promised goods and services represent distinct performance obligations and the standalone selling price for each performance obligation identified in the contract. This evaluation is subjective and requires us to make judgments about the promised goods and services and whether those goods and services are separable from other aspects of the contract. Further, determining the standalone selling price for performance obligations requires significant judgment, and when an observable price of a promised good or service is not readily available, we consider relevant assumptions to estimate the standalone selling price, including, as applicable, market conditions, development timelines, probabilities of technical and regulatory success, reimbursement rates for personnel costs, forecasted revenues, potential limitations to the selling price of the product and discount rates. We apply judgment in determining whether a combined performance obligation is satisfied at a point in time or over time, and, if over time, concluding upon the appropriate method of measuring progress to be applied for purposes of recognizing revenue. We evaluate the measure of progress each reporting period and, as estimates related to the measure of progress change, related revenue recognition is adjusted accordingly. Changes in our estimated measure of progress are accounted for prospectively as a change in accounting estimate. We recognize collaboration revenue by measuring the progress toward complete satisfaction of the performance obligation using an input measure. In order to recognize revenue over the research and development period, we measure actual costs incurred to date compared to the overall total expected costs to satisfy the performance obligation. Revenues are recognized as the program costs are incurred. We will re-evaluate the estimate of expected costs to satisfy the performance obligation each reporting period and make adjustments for any significant changes. Amounts received prior to satisfying the revenue recognition criteria are recorded as contract liabilities in our balance sheets. If the related performance obligation is expected to be satisfied within the next twelve months, this will be classified in current liabilities. Amounts recognized as revenue prior to receipt are recorded as contract assets in our balance sheets. If we expect to have an unconditional right to receive the consideration in the next twelve months, this will be classified in current assets. A net contract asset or liability is presented for each contract with a customer. Milestone Payments: At the inception of each arrangement that includes research and development milestone payments, we evaluate whether the milestones are considered probable of being reached and estimate the amount to be included in the transaction price using the most likely amount method. Amounts of variable consideration are included in the transaction price to the extent that it is probable that a significant reversal in the amount of cumulative revenue recognized will not occur and when the uncertainty associated with the variable consideration is subsequently resolved. Milestone payments that are not within the control of us or the licensee, such as regulatory approvals, are not considered probable of being achieved until those approvals are received. The transaction price is then allocated to each performance obligation on a relative standalone selling price basis, for which we recognize revenue as or when the performance obligations under the contract are satisfied. At the end of each subsequent reporting period, we re-evaluate the probability of achievement of such development milestones and any related constraints, and if necessary, adjust our estimate of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis, which would affect earnings in the period of adjustment. Manufacturing supply services: Arrangements that include a promise for the future supply of drug substance or drug product for either clinical development or commercial supply at the customer’s discretion are generally considered as options. We assess if these options provide a material right to the licensee and if so, they are accounted for as separate performance obligations. If we are entitled to additional payments when the customer exercises these options, any payments are recorded in product supply revenue when the customer obtains control of the goods, which is upon delivery. Royalties: For arrangements that include sales-based royalties, including milestone payments based on the level of sales, and where the license is deemed to be the predominant item to which the royalties relate, we recognize revenue at the later of (i) when the related sales occur, or (ii) when the performance obligation to which some or all of the royalty has been allocated has been satisfied (or partially satisfied). To date, royalty revenue resulting from licensing arrangements has not been material. Licenses of intellectual property: If a license granted to a customer to use our intellectual property is determined to be distinct from the other performance obligations identified in the arrangement, we recognize revenue from consideration allocated to the license when the license is transferred to the licensee and the licensee is able to use and benefit from the license. For licenses that are bundled with other promises, we apply judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, to conclude upon the appropriate method of measuring progress for purposes of recognizing revenue related to consideration allocated to the performance obligation. Options: Customer options, such as options granted to allow a licensee to choose to research, develop and commercialize licensed compounds are evaluated at contract inception in order to determine whether those options provide a material right (i. e., an optional good or service offered for free or at a discount) to the customer. If the customer options represent a material right, the material right is treated as a separate performance obligation at the outset of the arrangement. We allocate the transaction price to material rights based on the standalone selling price, and revenue is recognized when or as the future goods or services are transferred or when the option expires. Customer options that are not material rights do not give rise to a separate performance obligation, and as such, the additional consideration that would result from a customer exercising an option in the future is not included in the transaction price for the current contract. Instead, the option is deemed a marketing offer, and additional option fee payments are recognized or being recognized as revenue when the licensee exercises the option. The exercise of an option that does not represent a material right is treated as a separate contract for accounting purposes. Contract modifications: Contract modifications, defined as changes in the scope or price (or both) of a contract that are approved by the parties to the contract, such as a contract amendment, exist when the parties to a contract approve a modification that either creates new or changes existing enforceable rights and obligations of the parties to the contract. Depending on facts and circumstances, we account for a contract modification as one of the following: (i) a separate contract; (ii) a termination of the existing contract and a creation of a new contract; or (iii) a combination of the preceding treatments. A contract modification is accounted for as a separate contract if the scope of the contract increases because of the addition of promised goods or services that are distinct and the price of the contract increases by an amount of consideration that reflects our standalone selling prices of the additional promised goods or services. When a contract modification is not considered a separate contract and the remaining goods or services are distinct from the goods or services transferred on or before the date of the contract modification, we account for the contract modification as a termination of the existing contract and a creation of a new contract. When a contract modification is not considered a separate contract and the remaining goods or services are not distinct, we account for the contract modification as an add-on to the existing contract and as an adjustment to revenue on a cumulative catch-up basis. We receive payments from our licensees as established in each contract. Upfront payments and fees are recorded as deferred revenue upon receipt or when due and may require deferral of revenue recognition to a future period until we perform our obligations under these arrangements. Where applicable, amounts are recorded as unbilled revenue when our right to consideration is unconditional. We do not assess whether a contract with a customer has a significant financing component if the expectation at contract inception is such that the period between payment by the licensees and the transfer of the promised goods or services to the licensees will be one year or less.
Cost of Goods Sold	Cost of Goods Sold Cost of product sales consists of the cost of commercial goods sold to our Customers. Other cost of revenue consists of the cost of materials sold to our international partners under product supply agreements, as well as payments due to AstraZeneca AB (AstraZeneca) based on sales of tenapanor. We capitalize inventory costs associated with the production of our products after regulatory approval or when, based on management’s judgment, future commercialization is considered probable and the future economic benefit is expected to be realized. Otherwise, such costs are expensed as research and development. A portion of the costs of IBSRELA and XPHOZAH units recognized as revenue during the years ended December 31, 2023 and 2022 were expensed in periods prior to the commencement of capitalization of inventory costs for each respective product. As of December 31, 2023 and December 31, 2022, we had approximately $21.8 million and $28.0 million, respectively, of inventory on hand that was previously expensed as research and development expense and will not be reported as cost of goods sold in future periods when sales of IBSRELA and XPHOZAH are recognized as revenue. Other cost of revenue includes payments due to AstraZeneca, which under the terms of a termination agreement entered into in 2015 (AstraZeneca Termination Agreement) is entitled to (i) future royalties at a rate of 10% of net sales of tenapanor or other NHE3 products by us or our licensees, and (ii) 20% of non-royalty revenue received from our collaboration partners in connection with the development and commercialization of tenapanor or other NHE3 products. We have agreed to pay AstraZeneca up to a maximum of $75.0 million in the aggregate for (i) and (ii). We recognize these expenses as other cost of revenue when we recognize the corresponding revenue that gives rise to payments due to AstraZeneca. To date, we have recognized an aggregate of $27.6 million as other cost of revenue under the AstraZeneca Termination Agreement. See details in Note 7, Collaboration and Licensing Agreements, under AstraZeneca, in the notes to our financial statement of this Annual Report on Form 10-K.
Research and Development Costs	Research and Development Costs Research and development costs are charged to expense as incurred and consisted of costs incurred to further our research and development activities and include salaries and related employee benefits, costs associated with clinical trials, costs related to pre-commercialization manufacturing activities such as manufacturing process validation activities and the manufacturing of clinical drug supply, nonclinical research and development activities, regulatory activities, research-related overhead expenses and fees paid to external service providers and contract research and manufacturing organizations that conduct certain research and development activities on our behalf.
Accrued Expenses	Accrued Expenses As part of the process of preparing our financial statements, we are required to estimate our accrued expenses. This process involves reviewing open contracts and purchase orders, communicating with our personnel to identify services that have been performed on our behalf and estimating the level of service performed and the associated cost incurred for the service when we have not yet been invoiced or otherwise notified of the actual cost. The majority of our service providers invoice us monthly in arrears for services performed or when contractual milestones are met. We make estimates of our accrued expenses as of each balance sheet date in our financial statements based on facts and circumstances known to us at that time. We periodically confirm the accuracy of our estimates with our service providers and make adjustments if necessary. In accruing service fees, we estimate the time period over which each component of a service will be performed, and estimate, with vendor input if appropriate. If the actual timing of the performance of services or the level of effort varies from our estimate, we adjust the accrued or prepaid expense balance accordingly. Although we do not expect our estimates to be materially different from amounts actually incurred, if our estimates of the status and timing of services performed differ from the actual status and timing of services performed, we may report amounts that are too high or too low in any particular period.
Stock-Based Compensation	Stock-Based Compensation We recognize compensation expense for all stock-based payment awards made to employees, non-employees and directors based on estimated fair values. For employee and non-employee stock options, we determine the grant date fair value of the awards using the Black-Scholes option-pricing model and generally recognize the fair value as stock-based compensation expense on a straight-line basis over the vesting period of the respective awards. For restricted stock and performance-based restricted stock, to the extent they are probable, the compensation cost for these awards is based on the closing price of our common stock on the date of grant and recognized as compensation expense on a straight-line basis over the requisite service period. Stock-based compensation expense is based on the value of the portion of stock-based payment awards that is ultimately expected to vest. As such, our stock-based compensation is reduced for the estimated forfeitures at the date of grant and revised, if necessary, in subsequent periods if actual forfeitures differ from those estimates.
Derivatives and Hedging Activities	Derivatives and Hedging Activities We account for our derivative instruments as either assets or liabilities on the balance sheet and measure them at fair value. Derivatives are adjusted to fair value through other income (expense), net in the statements of operations and comprehensive loss.
Non-cash Interest Expense on Deferred Royalty Obligation	Non-cash Interest Expense on Deferred Royalty Obligation Non-cash interest expense related to the sale of future royalties represents the imputed interest expense on our deferred royalty obligation related to the sale of future royalties using the effective interest method. As further described in Note 8. Deferred Royalty Obligation Related to the Sale of Future Royalties, in June 2022, we and HealthCare Royalty Partners IV, L.P. (HCR) entered into a Royalty and Sales Milestone Interest Acquisition Agreement (HCR Agreement). Under the terms of the HCR Agreement, HCR agreed to pay us up to $20.0 million in exchange for the royalty payments and commercial milestone payments (collectively the Royalty Interest Payments) that we may receive under our 2017 License Agreement with Kyowa Kirin, as amended, based upon Kyowa Kirin's net sales of tenapanor in Japan for hyperphosphatemia. As part of the HCR Agreement, we received a $10.0 million upfront payment from HCR in June 2022 and recorded it as a deferred royalty obligation on our balance sheet. In September 2023, we announced that Kyowa Kirin received approval from the Japanese MHLW for the New Drug Application for tenapanor for the improvement of hyperphosphatemia in adult patients with chronic kidney disease on dialysis, which entitled us to a $5.0 million payment under the terms of the HCR Agreement, which we received in October 2023. Non-cash interest expense will be recognized over the life of the HCR Agreement using the effective interest method based on the imputed interest rate derived from estimated amounts and timing of future royalty payments to be received from Kyowa Kirin.
Leases	Leases We determine if an arrangement is a lease at the inception of the arrangement. Operating leases are included in right-of-use assets, current portion of operating lease liability, and operating lease liability, net of current portion in our balance sheets. Right-of-use assets represent our right to use an underlying asset for the lease term and lease liabilities represent our obligation to make lease payments arising from the lease. Operating lease right-of-use assets and liabilities are recognized at the lease commencement date based on the present value of lease payments over the lease term. In determining the present value of lease payments, we use our incremental borrowing rate based on the information available at the lease commencement date. The operating lease right-of-use assets also include any lease payments made and exclude lease incentives. Our lease terms may include options to extend or terminate the lease when it is reasonably certain that we will exercise any such options. Lease expense is recognized on a straight-line basis over the expected lease term. We have elected not to separate lease and non-lease components, such as common area maintenance charges, and instead it accounts for these as a single lease component.
Net Loss per Share	Net Loss per Share Basic net loss per common share is calculated by dividing the net loss by the weighted-average number of shares of common stock outstanding during the period, without consideration of potential shares of common stock. Diluted net loss per common share in the periods presented is the same as basic net loss per common share, since the effects of potentially dilutive securities are antidilutive due to the net loss for all periods presented.
Recent Accounting Pronouncements	Recent Accounting Pronouncements New Accounting Pronouncements - Recently Adopted In July 2023, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2023-03, Presentation of Financial Statements (Topic 205), Income Statement - Reporting Comprehensive Income (Topic 220), Distinguishing Liabilities from Equity (Topic 480), Equity (Topic 505), and Compensation - Stock Compensation (Topic 718) Presentation of Financial Statements (ASU 2023-03). ASU 2023-03 amends the FASB Accounting Standards Codification to include Amendments to SEC Paragraphs pursuant to SEC Staff Accounting Bulletin No. 120, SEC Staff Announcement at the March 24, 2022 EITF Meeting, and SEC Staff Accounting Bulletin Topic 6.B, Accounting Series Release 280 - General Revision of Regulation S-X: Income or Loss Applicable to Common Stock. As the ASU does not provide any new guidance, there is no transition or effective date associated with its adoption. Accordingly, we adopted ASU 2023-03 immediately upon its issuance. The adoption of ASU 2023-03 did not have any impact on our financial statement presentation or related disclosures. Recent Accounting Pronouncements Not Yet Adopted In October 2023, the FASB issued ASU No. 2023-06, Disclosure Improvements - Codification Amendments in Response to the SEC’s Disclosure Update and Simplification Initiative. The amendments in this Update modify the disclosure or presentation requirements of a variety of Topics in the Codification. The amendments are in response to the U.S. Securities and Exchange Commission's (SEC) Release No. 33-10532, Disclosure Update and Simplification, in which the SEC referred certain of its disclosure requirements that overlap with, but require incremental information to, generally accepted accounting principles to the FASB for potential incorporation into the Codification. For entities subject to the SEC’s existing disclosure requirements and for entities required to file or furnish financial statements with or to the SEC in preparation for the sale of or for purposes of issuing securities that are not subject to contractual restrictions on transfer, the effective date for each amendment will be the date on which the SEC’s removal of that related disclosure from Regulation S-X or Regulation S-K becomes effective, with early adoption prohibited. For all other entities, the amendments will be effective two years later. For all entities, if by June 30, 2027, the SEC has not removed the applicable requirement from Regulation S-X or Regulation S-K, the pending content of the related amendment will be removed from the Codification and will not become effective for any entity. Management is currently assessing the impact of this standard on the Company’s financial statements. In November 2023, the FASB issued ASU No. 2023-07, Segment Reporting (Topic 280) - Improvements to Reportable Segment Disclosures. The amendments in this Update improve reportable segment disclosure requirements, primarily through enhanced disclosures about significant segment expenses. The amendments in this update improve financial reporting by requiring disclosure of incremental segment information on an annual and interim basis for all public entities to enable investors to develop more decision-useful financial analyses. The amendments in this update are effective for fiscal years beginning after December 15, 2023, and interim periods within fiscal years beginning after December 15, 2024. Early adoption is permitted. Management is currently assessing the impact of this standard on the Company’s financial statements. In December 2023, the FASB issued ASU No. 2023-09, Income Taxes (Topic 740) - Improvements to Income Tax Disclosures, an amendment which modifies the measurement and recognition of credit losses for most financial assets and certain other instruments. The amendments in this Update provide more transparency about income tax information through improvements to income tax disclosures primarily related to the rate reconciliation and income taxes paid information. For public business entities, the amendments in this Update are effective for annual periods beginning after December 15, 2024. Early adoption is permitted on a prospective basis for annual financial statements that have not yet been issued or made available for issuance. Management is currently assessing the impact of this standard on the Company’s financial statements. There were various other accounting standards and interpretations issued recently, none of which are expected to have a material impact on our financial position, operations or cash flows.
Fair Value Measurements	The three-level hierarchy for the inputs to valuation techniques is briefly summarized as follows: Level 1 – Valuations are based on quoted prices in active markets for identical assets or liabilities and readily accessible to us at the reporting date. Level 2 – Valuations based on inputs other than Level 1 that are observable, either directly or indirectly, such as quoted prices for similar assets or liabilities; quoted prices in markets that are not active; or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. Level 3 – Valuations based on unobservable inputs for which there is little or no market data, which require us to develop our own assumptions.

Equity Incentive Plans (Tables)

12 Months Ended

Dec. 31, 2023

Share-Based Payment Arrangement [Abstract]

Schedule of Stock Option Activity

A summary of our stock option activity and related information during the year ended December 31, 2023 is as follows (in thousands, except per share dollar amounts and years):


		Options Issued and Outstanding				Weighted Average Remaining Contractual Term (in Years)	Aggregate Intrinsic Value
	Number of Shares		Weighted-Average Exercise Price per Share
Balance at December 31, 2022		13,963		$	4.83

Options granted		8,914		$	3.14
Options exercised		(226)		$	1.61
Options canceled		(483)		$	3.83


Balance at December 31, 2023		22,168		$	4.20	7.3	$	58,606
Vested and expected to vest at December 31, 2023		22,168		$	4.20	7.3	$	58,606
Exercisable at December 31, 2023		12,199		$	5.30	6.1	$	25,116

Schedule of Valuation Assumptions for Stock Options

The estimated grant date fair value of employee stock options was calculated using the Black-Scholes option-pricing model, based on the following weighted-average assumptions:


	Year Ended December 31,
	2023		2022		2021
Expected term (years)	5.1		4.9		5.0
Expected volatility	97.6	%	92.1	%	77.0	%
Risk-free interest rate	3.8	%	2.2	%	4.7	%
Dividend yield	—	%	—	%	—	%

Schedule of Restricted Stock Units Activity

A summary of our RSUs activity and related information for the year ended December 31, 2023 is as follows (in thousands, except per share dollar amounts):


	Number of RSUs	Weighted-Average Grant Date Fair Value Per Share
Non-vested restricted stock units at December 31, 2022	1,406	$	2.17
Granted	3,269	$	3.39
Vested	(942)	$	2.76
Forfeited	(87)	$	3.05
Non-vested restricted stock units at December 31, 2023	3,646	$	3.09

Schedule of Valuation Assumptions for Employee Stock Purchase Plan

The following table illustrates the weighted-average assumptions for the Black-Scholes option-pricing model used in determining the fair value of ESPP purchase rights granted to our employees:


	Year Ended December 31,
	2023		2022		2021
Expected term (years)	0.5		0.5		0.5
Expected volatility	86.0	%	97.2	%	123.0	%
Risk-free interest rate	5.3	%	1.9	%	0.7	%
Dividend yield	—	%	—	%	—	%

Schedule of Stock-Based Compensation Recognized

Stock-based compensation expense recognized for stock options, RSUs, and our ESPP are recorded as operating expenses in our statements of operations and comprehensive loss, as follows (in thousands):


	Year Ended December 31,
	2023		2022		2021
Selling, general and administrative	$	9,952	$	7,525	$	7,923
Research and development	3,578		3,225		4,116
Total	$	13,530	$	10,750	$	12,039

Schedule of Total Unrecognized Stock-Based Compensation Expense, Net of Estimated Forfeitures

A summary of our total unrecognized stock-based compensation expense, net of estimated forfeitures, as of December 31, 2023 is as follows (dollars in thousands):


	December 31, 2023
	Unrecognized Compensation Expense		Average Remaining Vesting Period (Years)
Stock option grants	$	19,960	2.75
RSU grants	$	10,579	3.03
ESPP	$	154	0.2

Organization and Basis of Presentation (Details)	12 Months Ended
Organization and Basis of Presentation (Details)	Dec. 31, 2023 segment
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of operating segments	1

Revenue (Tables)

12 Months Ended

Dec. 31, 2023

Revenue from Contract with Customer [Abstract]

Schedule of Revenue

Total revenues during the years ended December 31, 2023, 2022, and 2021 were as follows (in thousands):


	Year Ended December 31,
	2023		2022		2021
Product sales, net:
IBSRELA	$	80,062	$	15,600	$	—
XPHOZAH	2,464		—		—
Total product sales, net	82,526		15,600		—
Licensing revenue	35,809		35,031		5,013
Product supply revenue	6,121		1,527		907
Collaborative development revenue	—		—		4,177
Total revenues	$	124,456	$	52,158	$	10,097

Schedule of Revenue from Customers as a Percentage of Total Product Revenue, Net


	Year Ended December 31,
		2023		2022
BioRidge Pharma, LLC		26.3	%	—	%
Cardinal Health		21.6	%	23.1	%
AmerisourceBergen Drug Corporation		20.9	%	26.8	%
McKesson Corporation		17.2	%	21.6	%

Revenues from Customers and collaboration partnerships accounting for more than 10% of total revenues during the years ended December 31, 2023, 2022 and 2021 were as follows:


	Year Ended December 31,
	2023		2022		2021
Kyowa Kirin	29.0	%	70.0	%	100.0	%
Bioridge Phama	24.0	%	3.2	%	—	%
Cardinal	19.8	%	9.6	%	—	%


AmerisourceBergen Drug Corporation	19.1	%	11.1	%	—	%
McKesson	15.7	%	8.9	%	—	%

Schedule of Chargebacks, Discounts and Reserve Balances

The activities and ending reserve balances for each significant category of discounts and allowances, which constitute variable consideration, were as follows (in thousands):


	Discounts and Chargebacks		Rebates, Wholesaler and GPO Fees		Copay and Returns		Total
Balance as of December 31, 2021	$	—	$	—	$	—	$	—
Provisions	825		2,721		2,502		6,048
Credits/payments	(683)		(1,277)		(1,244)		(3,204)
Balance as of December 31, 2022	142		1,444		1,258		2,844
Provisions	5,341		15,365		10,629		31,335
Credits/payments	(5,005)		(12,575)		(7,971)		(25,551)
Balance as of December 31, 2023	$	478	$	4,234	$	3,916	$	8,628

Summary of Significant Accounting Policies - Accounts Receivable (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Accounts receivable	$ 22,031	$ 7,733
Collaborators
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Accounts receivable	4,900	700
Commercial customers
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Accounts receivable	$ 17,100	$ 7,000

Collaboration and Licensing Agreements - Narrative (Details) $ in Millions, ¥ in Billions	1 Months Ended				12 Months Ended				74 Months Ended
	Mar. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Nov. 30, 2017 USD ($)	Jun. 30, 2015 USD ($)	Dec. 31, 2023 USD ($)	Dec. 31, 2023 CAD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2023 USD ($)	Mar. 31, 2024 USD ($)	Dec. 31, 2023 JPY (¥)	Sep. 30, 2023 USD ($)	Jul. 31, 2023 USD ($)	Apr. 30, 2023 USD ($)	Oct. 31, 2022 USD ($)	Apr. 30, 2022 USD ($) payment_tranche
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Total revenues					$ 124,456,000		$ 52,158,000	$ 10,097,000
Licensing revenue
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Total revenues					35,809,000		35,031,000	5,013,000
Product supply revenue
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Total revenues					6,121,000		1,527,000	907,000
2017 KKC Agreement \| Licensing revenue
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Total revenues					30,000,000		35,000,000	5,000,000
2017 KKC Agreement \| Product supply revenue
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Total revenues					6,100,000		1,500,000	900,000
Fosun Agreement \| Licensing revenue
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Total revenues					5,000,000		0	0
Knight Agreement \| Licensing revenue
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Total revenues					0		0	0
Kyowa Kirin Co. Ltd \| 2017 KKC Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Upfront license fees			$ 30,000,000
Potential development milestones			$ 55,000,000
Total revenues									$ 35,000,000
Potential commercialization milestones					60,300,000				60,300,000		¥ 8.5
Fee receivable for reduction in royalty rate																$ 40,000,000
Number of payment tranches for fee receivable for reduction in royalty rate \| payment_tranche																2
Kyowa Kirin Co. Ltd \| 2017 KKC Agreement \| Licensing revenue
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Proceeds from milestone payments												$ 30,000,000			$ 35,000,000
Fosun Pharma \| Fosun Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Proceeds from milestone payments					8,000,000				8,000,000				$ 2,000,000
Upfront payment received		$ 12,000,000
Potential development and commercialization milestones					$ 113,000,000
Threshold percentage of net sales for tiered royalties					20.00%	20.00%
Fosun Pharma \| Fosun Agreement \| Subsequent event
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Proceeds from milestone payments										$ 3,000,000
Fosun Pharma \| Knight Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Potential development milestones					$ 5,000,000				5,000,000
Knight \| Knight Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Potential development milestones					700,000				700,000
Upfront payment received	$ 2,300,000
Potential development and commercialization milestones					16,700,000	$ 22.2
METiS Therapeutics Inc \| Licensing revenue
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Total revenues					800,000
Proceeds from milestone payments														$ 243,000,000
Upfront payment														$ 800,000
AstraZeneca \| AZ Termination Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Percentage of royalty revenue				10.00%
Percentage of non royalty revenue				20.00%
Maximum potential payment per agreement				$ 75,000,000
Aggregate cost of revenue recognized					27,600,000				$ 27,600,000
Total cost of goods sold					$ 12,400,000		$ 3,600,000	$ 1,000,000

Derivative Liabilities

12 Months Ended

Dec. 31, 2023

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Derivative Liabilities

DERIVATIVE LIABILITIES

2018 Exit Fee

In May 2018, in connection with entering into the 2018 Loan Agreement, we entered into an agreement pursuant to which we agreed to pay $1.5 million in cash (2018 Exit Fee) upon any change of control transaction in respect of the Company or if we obtain both (i) U.S. FDA approval of XPHOZAH and (ii) U.S. FDA approval of IBSRELA, which was obtained on September 12, 2019 (2018 Exit Fee Agreement). Notwithstanding the February 2022 prepayment of the 2018 Loan, our obligation to pay the 2018 Exit Fee would have expired on May 16, 2028. We concluded that the 2018 Exit Fee was a freestanding derivative which should be accounted for at fair value on a recurring basis.

In October 2023, we received approval from the U.S. FDA for XPHOZAH to reduce serum phosphorus in adults with chronic kidney disease (CKD) on dialysis as add-on therapy in patients who have an inadequate response to phosphate binders or who are intolerant of any dose of phosphate binder therapy. This triggered our obligation to pay the 2018 Exit Fee to the 2018 Lenders, which we subsequently paid in October 2023. The estimated fair value of the 2018 Exit Fee was recorded as a derivative liability and included in accrued expense and other current liabilities on the accompanying balance sheets. As of December 31, 2023 and December 31, 2022, the estimated fair value of the 2018 Exit Fee was zero and $1.2 million, respectively.

The fair value of the derivative liability at December 31, 2022 was determined using a discounted cash flow analysis and was classified as a Level 3 measurement within the fair value hierarchy since our valuation utilized significant unobservable inputs. Specifically, the key assumptions included in the calculation of the estimated fair value of the derivative instrument included: (i) our estimates of both the probability and timing of a potential $1.5 million payment to the 2018 Lenders as a result of the U.S. FDA approvals, and (ii) a discount rate which was derived from our estimated cost of debt, adjusted with current LIBOR.

2022 Exit Fee

In February 2022, in connection with entering into the 2022 Original Loans, we entered into an agreement, whereby we agreed to pay an exit fee in the amount of 2% of the 2022 Original Loan funded (2022 Exit Fee) upon (i) any change of control transaction or (ii) our achievement of net revenue from the sale of any products equal to or greater than $100.0 million, measured on a six (6) months basis (Revenue Milestone), tested monthly at the end of each month. The Term C and Term D Loans do not result in payment of an additional exit fee. Notwithstanding the prepayment or termination of the 2022 Original Loans, the 2022 Exit Fee will expire on February 23, 2032. We concluded that the 2022 Exit Fee is a freestanding derivative which should be accounted for at fair value on a recurring basis. The estimated fair value of the 2022 Exit Fee is recorded as a derivative liability and included in accrued expenses and other current liabilities on the accompanying balance sheets. As of December 31, 2023 and December 31, 2022, the estimated fair value of the 2022 Exit Fee was $0.7 million and $0.4 million, respectively.

The fair value of the derivative liability was determined using a discounted cash flow analysis and is classified as a Level 3 measurement within the fair value hierarchy since our valuation utilized significant unobservable inputs. Specifically, the key assumptions included in the calculation of the estimated fair value of the 2022 Exit Fee derivative liability include: (i) our estimates of both the probability and timing of achieving the Revenue Milestone and (ii) the probability and timing of funding the Term B Loan, which was dependent upon (a) approval by the U.S. FDA for our NDA for the control of serum phosphorus in adult patients with CKD on dialysis by November 30, 2023, and (b) achievement of certain product revenue milestone targets. As of December 31, 2023, uncertainty around two of the noted valuation estimates had been removed, as the Term B Loan had been funded and the U.S. FDA had approved our NDA for the control of serum phosphorus in adult patients with CKD on dialysis prior to November 30, 2023. Generally, increases or decreases in the probability of occurrence would result in a directionally similar impact in the fair value measurement of the derivative liability and it is estimated that a 10% increase (decrease) in the probability of occurrence would not result in a material fair value fluctuation.

Changes in the fair value of recurring measurements included in Level 3 of the fair value hierarchy are presented as other income, net in our statements of operations and comprehensive income (loss) and were as follows for the years ended December 31, 2023, 2022, and 2021 (in thousands):


	2023		2022
Balance at January 1,	$	1,656	$	698
2022 Exit Fee addition at fair value	—		375
Changes in estimated fair value:
2018 Exit Fee	292		510
2022 Exit Fee	227		73
2018 Exit Fee payment	$	(1,500)	$	—
Fair value of exit fee derivative liabilities at December 31,	$	675	$	1,656

Cash, Cash Equivalents and Short-Term Investments (Tables)

12 Months Ended

Dec. 31, 2023

Cash and Cash Equivalents [Abstract]

Schedule of Securities Classified as Cash, Cash Equivalents and Short-Term Investments

Securities classified as cash, cash equivalents and short-term investments as of December 31, 2023 and 2022 are summarized below (in thousands):


	December 31, 2023
			Gross Unrealized
	Amortized Cost		Gains		Losses		Fair Value
Cash and cash equivalents:
Cash	$	2,829	$	—	$	—	$	2,829
Money market funds	18,641		—		—		18,641


Total cash and cash equivalents	21,470		—		—		21,470
Short-term investments:
U.S. government-sponsored agency bonds	$	101,892	$	235	$	(34)	$	102,093
Commercial paper	$	49,630	$	41	$	(17)	$	49,654
Asset-backed securities	8,628		2		(5)		8,625

U.S. treasury securities	2,455		2		—		2,457
Total short-term investments	162,605		280		(56)		162,829


Total cash, cash equivalents and investments	$	184,075	$	280	$	(56)	$	184,299


	December 31, 2022
			Gross Unrealized
	Amortized Cost		Gains		Losses		Fair Value
Cash and cash equivalents:
Cash	$	11,827	$	—	$	—	$	11,827
Money market funds	84,313		—		—		84,313


Total cash and cash equivalents	96,140		—		—		96,140
Short-term investments
Commercial paper	$	25,336	$	6	$	(51)	$	25,291
Corporate bonds	1,000		—		(1)		999
U.S. government-sponsored agency bonds	1,487		—		(8)		1,479

Total short-term investments	27,823		6		(60)		27,769


Total cash, cash equivalents and investments	$	123,963	$	6	$	(60)	$	123,909

Revenue - Schedule of Revenue (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Disaggregation of Revenue [Line Items]
Total revenues	$ 124,456	$ 52,158	$ 10,097
Product sales, net
Disaggregation of Revenue [Line Items]
Total revenues	82,526	15,600	0
IBSRELA
Disaggregation of Revenue [Line Items]
Total revenues	80,062	15,600	0
XPHOZAH
Disaggregation of Revenue [Line Items]
Total revenues	2,464	0	0
Licensing revenue
Disaggregation of Revenue [Line Items]
Total revenues	35,809	35,031	5,013
Product supply revenue
Disaggregation of Revenue [Line Items]
Total revenues	6,121	1,527	907
Collaborative development revenue
Disaggregation of Revenue [Line Items]
Total revenues	$ 0	$ 0	$ 4,177

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References + Details

- Definition

+ References

+ Details

Property and Equipment, Net - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Property, Plant and Equipment [Abstract]
Depreciation and amortization expense	$ 600	$ 700	$ 1,400
Sale of property, plant and equipment		500
Proceeds from sale of property and equipment	$ 0	1,798	$ 0
Gain on disposition of property plant equipment		$ 1,300

Collaboration and Licensing Agreements

12 Months Ended

Dec. 31, 2023

Collaboration and Licensing Agreements [Abstract]

Collaboration and Licensing Agreements

COLLABORATION AND LICENSING AGREEMENTS

Kyowa Kirin Co., Ltd. (Kyowa Kirin)

In November 2017, we entered into an exclusive license agreement with Kyowa Kirin (2017 Kyowa Kirin Agreement), under which we granted Kyowa Kirin an exclusive license to develop and commercialize certain NHE3 inhibitors including tenapanor in Japan for the treatment of cardiorenal diseases and conditions, excluding cancer. We retained the rights to tenapanor outside of Japan, and also retained the rights to tenapanor in Japan for indications other than those stated above. Pursuant to the 2017 Kyowa Kirin Agreement, Kyowa Kirin is responsible for all costs and expenses incurred in the development and commercialization of tenapanor for all licensed indications in Japan. We are responsible for supplying the tenapanor drug substance for Kyowa Kirin’s use in development and commercialization throughout the term of the 2017 Kyowa Kirin Agreement, provided that Kyowa Kirin may exercise an option to manufacture the tenapanor drug substance under certain conditions. In October 2022, we entered into a Commercial Supply Agreement with Kyowa Kirin to further define the obligations of the parties with respect to the commercial supply of tenapanor drug substance (2022 Kyowa Kirin Supply Agreement). As detailed below under the heading Deferred Revenue we have received advanced payments from Kyowa Kirin for the manufacturing of tenapanor drug substance that will be used to satisfy Kyowa Kirin needs.

We assessed these arrangements in accordance with Accounting Standards Update (ASU) No. 2014-09, Revenue from Contracts with Customers (Topic 606) and related amendments (ASC 606) and concluded that the contract counterparty, Kyowa Kirin, is a customer. Under the terms of the 2017 Kyowa Kirin Agreement, we received $30.0 million in upfront license fees, which was recognized as revenue when the agreement was executed. Based on our assessment, management determined that the license and the manufacturing supply services were its material performance obligations at the inception of the 2017 Kyowa Kirin Agreement, and as such, each of the performance obligations is distinct.

We may be entitled to receive up to $55.0 million in total development and regulatory milestones, of which $35.0 million has been received and recognized as revenue as of December 31, 2023. We may also be eligible to receive approximately ¥8.5 billion for commercialization milestones, or approximately $60.3 million at the currency exchange rate on December 31, 2023, as well as reimbursement of costs plus a reasonable overhead for the supply of product and royalties on net sales throughout the term of the agreement. As discussed in Note 8. Deferred Royalty Obligation Related to the Sale of Future Royalties, the future royalties and commercial milestone payments we may receive under the 2017 Kyowa Kirin Agreement will be remitted to HealthCare Royalty Partners IV, L.P. pursuant to a Royalty and Sales Milestone Interest Acquisition Agreement. The variable consideration related to the remaining milestone payments was fully constrained at December 31, 2023.

In April 2022, we entered into a second amendment to the 2017 Kyowa Kirin Agreement (2022 Amendment). Under the terms of the 2022 Amendment, we and Kyowa Kirin agreed to a reduction in the royalty rate payable to us by Kyowa Kirin upon net sales of tenapanor for hyperphosphatemia in Japan. The royalty rate will be reduced from the high teens to low double digits for a two-year period of time following the first commercial sale in Japan, and then to mid-single digits for the remainder of the royalty term. As discussed in Note 8. Deferred Royalty Obligation Related to the Sale of Future Royalties, the future commercial milestones and royalties we may receive under the 2017 Kyowa Kirin Agreement will be remitted to HealthCare Royalty Partners IV, L.P. pursuant to a Royalty and Sales Milestone Interest Acquisition Agreement. As consideration for the reduction in the royalty rate, Kyowa Kirin agreed to pay us up to an additional $40.0 million payable in two tranches, with the first payment due following Kyowa Kirin's filing with the Japanese Ministry of Health, Labour and Welfare (MHLW) of its application for marketing approval for tenapanor and the second payment due following Kyowa Kirin’s receipt of regulatory approval to market tenapanor for hyperphosphatemia in Japan, both of which occurred as of September 30, 2023.

In October 2022, we announced that Kyowa Kirin submitted a New Drug Application (NDA) to the Japanese MHLW for tenapanor for the improvement of hyperphosphatemia in adult patients with CKD on dialysis, which resulted in payment to us from Kyowa Kirin for an aggregate of $35.0 million for milestone payments and payments under the 2022 Amendment. We received these payments during the fourth quarter of 2022 and recorded them as licensing revenue on our statement of operations and comprehensive income (loss).

In September 2023, we announced that Kyowa Kirin received approval from the Japanese MHLW for the NDA for tenapanor for the improvement of hyperphosphatemia in adult patients with CKD on dialysis, which resulted in payment to us from Kyowa Kirin for an aggregate of $30.0 million for milestone payments and payments under the 2022 Amendment. We received these payments in October 2023 and recorded them as licensing revenue on our statement of operations and comprehensive income (loss) when earned during the three months ended September 30, 2023.

During the years ended December 31, 2023, 2022, and 2021, we recognized $30.0 million, $35.0 million, and $5.0 million of licensing revenue pursuant to the 2017 Kyowa Kirin Agreement, as amended.

During the years ended December 31, 2023, 2022, and 2021, we recognized $6.1 million, $1.5 million, and $0.9 million respectively, of product supply revenue pursuant to the 2017 Kyowa Kirin Agreement.

Shanghai Fosun Pharmaceutical Industrial Development Co. Ltd. (Fosun Pharma)

In December 2017, we entered into an exclusive license agreement with Fosun Pharma (Fosun Agreement) for the development, commercialization and distribution of tenapanor in China for both hyperphosphatemia and IBS-C. We assessed these arrangements in accordance with ASC 606 and concluded that the contract counterparty, Fosun Pharma, is a customer. Under the terms of the Fosun Agreement, we received $12.0 million in upfront license fees which was recognized as revenue when the agreement was executed. Based on our assessment, we determined that the license and the manufacturing supply services represented the material performance obligations at the inception of the agreement and, as such, each of the performance obligations are distinct.

We may be entitled to receive development and commercialization milestones of up to $113.0 million, of which $8.0 million has been recognized as revenue and $5.0 million has been received as of December 31, 2023 and $3.0 million was received in January 2024, as well as reimbursement of cost plus a reasonable overhead for the supply of product and tiered royalties on net sales ranging from the mid-teens to 20%. The variable consideration related to the remaining development milestone payments was fully constrained at December 31, 2023.

In July 2023, we announced that an NDA for tenapanor had been accepted for review by China’s Center for Drug Evaluation of the National Medical Products Administration (NMPA) for the control of serum phosphorus in adult patients with CKD on hemodialysis. This acceptance triggered a $2.0 million milestone payment to us under the terms of the Fosun Agreement. We received this payment during the third quarter of 2023 and recorded it as licensing revenue on our statement of operations and comprehensive loss when earned during the three months ended September 30, 2023. In October 2023, we announced that the U.S. FDA has approved XPHOZAH to reduce serum phosphorus in adults with CKD on dialysis as add-on therapy in patients who have an inadequate response to phosphate binders or who are intolerant of any dose of phosphate binder therapy. This triggered an additional $3.0 million milestone payment to us under the terms of the Fosun Agreement, which was received during the first quarter of 2024. Also, in October 2023, we announced that Fosun Pharma received approval from the Hong Kong Department of Health for the marketing application for tenapanor for the treatment of irritable bowel syndrome with constipation (IBS-C).

During the year ended December 31, 2023, we recognized $5.0 million of licensing revenue pursuant to the Fosun Agreement. During the years ended December 31, 2022, and 2021, we did not recognize a material amount of revenue pursuant to the Fosun Agreement.

Knight Therapeutics, Inc. (Knight)

In March 2018, we entered into an exclusive license agreement with Knight Therapeutics, Inc., (Knight Agreement) for the development, commercialization and distribution of tenapanor in Canada for hyperphosphatemia and IBS-C. We assessed this arrangement in accordance with ASC 606 and concluded that the contract counterparty, Knight, is a customer. Based on our assessment, we determined that the license and the manufacturing supply services were the material performance obligations at the inception of the agreement and, as such, each of the performance obligations are distinct.

Under the terms of the Knight Agreement, we received a $2.3 million non-refundable, one-time upfront payment in March 2018 and may be eligible to receive additional development and commercialization milestone payments worth up to CAD 22.2 million, or approximately $16.7 million at the currency exchange rate on December 31, 2023, of which $0.7 million has been received and recognized as revenue as of December 31, 2023. We are also eligible to receive royalties ranging from the mid-single digits to the low twenties throughout the term of the agreement, and a transfer price for manufacturing services. The variable consideration related to the remaining development milestone payments was fully constrained at December 31, 2023.

During the years ended December 31, 2023, 2022, and 2021, we did not recognize a material amount of revenue pursuant to the Knight Agreement.

METiS Therapeutics Inc. (METiS)

In April 2023, we entered into an exclusive, worldwide license agreement with METiS Therapeutics Inc., (METiS Agreement) for the development and commercialization of a portfolio of TGR5 agonist compounds that were discovered and developed by Ardelyx for all therapeutic areas. We assessed this arrangement in accordance with ASC 606 and concluded that the contract counterparty, METiS, is a customer. Based on our assessment, we determined that the license was the material performance obligation at the inception of the agreement.

Under the terms of the METiS Agreement, we received a $0.8 million non-refundable, one-time upfront payment in April 2023 and may be eligible to receive additional development and commercialization milestone payments worth up to $243.0 million. We are also eligible to receive royalties ranging within the mid-single digits throughout the term of the agreement. The variable consideration related to the remaining development and commercialization milestone payments was fully constrained at December 31, 2023.

During the year ended December 31, 2023, we recognized $0.8 million of licensing revenue pursuant to the METiS Agreement upon delivery of the license.

AstraZeneca AB (AstraZeneca)

In June 2015, we entered into a termination agreement with AstraZeneca (AstraZeneca Termination Agreement) pursuant to which we have agreed to pay AstraZeneca (i) future royalties at a royalty rate of 10% of net sales of tenapanor or other NHE3 products by us or our licensees, and (ii) 20% of non-royalty revenue received from a new collaboration partner should we elect to license, or otherwise provide rights to develop and commercialize tenapanor or other NHE3 products, up to a maximum of $75.0 million in aggregate for (i) and (ii). As of December 31, 2023, to date in aggregate, we have recognized $27.6 million of the $75.0 million, which has been recorded as other cost of revenue on our statements of operations and comprehensive income (loss). During the years ended December 31, 2023, 2022, and 2021, we recognized $12.4 million and $3.6 million, and $1.0 million, respectively, as other cost of revenue related to the AstraZeneca Termination Agreement.

Deferred Revenue

The following tables present changes in our current and non-current deferred revenue balances during the reporting period, which are all attributable to the 2017 Kyowa Kirin Agreement (in thousands):


	2023				2022
	Current		Non-Current		Current		Non-Current
Balance at January 1,	$	4,211	$	9,025	$	—	$	4,727
Amounts invoiced as prepayments for product supply	1,547		5,629		250		8,259
Decrease for revenue recognized for product supply	(4,586)		—		—		—
Reclassify amounts to be recognized in the next twelve months	6,010		(6,010)		3,961		(3,961)
Balance at December 31,	$	7,182	$	8,644	$	4,211	$	9,025

Equity Incentive Plans - Stock Options (Details) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2023 USD ($) $ / shares shares
Number of Shares
Options issued and outstanding balance, beginning (shares) \| shares	13,963,000
Options granted (shares) \| shares	8,914,000
Options exercised (shares) \| shares	(226,000)
Options canceled (shares) \| shares	(483,000)
Options issued and outstanding balance, ending (shares) \| shares	22,168,000
Options vested and expected to vest (shares) \| shares	22,168,000
Options exercisable (shares) \| shares	12,199,000
Weighted-Average Exercise Price per Share
Options issued and outstanding balance, beginning (in dollars per share) \| $ / shares	$ 4.83
Options granted (in dollars per share) \| $ / shares	3.14
Options exercised (in dollars per share) \| $ / shares	1.61
Options canceled (in dollars per share) \| $ / shares	3.83
Options issued and outstanding balance, ending (in dollars per share) \| $ / shares	4.20
Options vested and expected to vest (in dollars per share) \| $ / shares	4.20
Options exercisable (in dollars per share) \| $ / shares	$ 5.30
Weighted Average Remaining Contractual Term (in Years)
Options issued and outstanding (in years)	7 years 3 months 18 days
Options vest and expected to vest (in years)	7 years 3 months 18 days
Options exercisable (in years)	6 years 1 month 6 days
Aggregate Intrinsic Value
Options issued and outstanding \| $	$ 58,606
Options vested and expected to vest \| $	58,606
Options exercisable \| $	$ 25,116

Geographic Information and Concentrations

12 Months Ended

Dec. 31, 2023

Risks and Uncertainties [Abstract]

Geographic Information and Concentrations

GEOGRAPHIC INFORMATION AND CONCENTRATIONS

Revenues are attributed to geographical areas based on the location at which we earned revenue for product sales of IBSRELA and XPHOZAH or the domicile of our collaboration partners. A summary of our revenue by geographic areas for the years ended December 31, 2023, 2022 and 2021, is as follows (in thousands):


	Year Ended December 31,
	2023		2022		2021
United States (1)	$	83,276	$	15,600	$	—
International:
Asia Pacific (2)	41,121		36,527		10,084
North America (3)	59		31		13
Total revenue	$	124,456	$	52,158	$	10,097

(1)Revenues from the United States are primarily comprised of amounts earned from sales of IBSRELA and XPHOZAH, as well as the upfront license fee from the METiS Agreement.

(2)Revenues from Asia Pacific are primarily comprised of amounts earned in accordance with the 2017 Kyowa Kirin Agreement, the 2019 Kyowa Kirin Agreement and the Fosun Agreement.

(3)Revenues from North America are comprised of amounts earned from Canada in accordance with the Knight Agreement.

Revenues from Customers and collaboration partnerships accounting for more than 10% of total revenues during the years ended December 31, 2023, 2022 and 2021 were as follows:


	Year Ended December 31,
	2023		2022		2021
Kyowa Kirin	29.0	%	70.0	%	100.0	%
Bioridge Phama	24.0	%	3.2	%	—	%
Cardinal	19.8	%	9.6	%	—	%


AmerisourceBergen Drug Corporation	19.1	%	11.1	%	—	%
McKesson	15.7	%	8.9	%	—	%

Revenue - Gross-to-Net Sales Accruals (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Gross-to-net sales accruals and reserves
Beginning balance	$ 2,844	$ 0
Provisions	31,335	6,048
Credits/payments	(25,551)	(3,204)
Ending balance	8,628	2,844
Discounts and Chargebacks
Gross-to-net sales accruals and reserves
Beginning balance	142	0
Provisions	5,341	825
Credits/payments	(5,005)	(683)
Ending balance	478	142
Rebates, Wholesaler and GPO Fees
Gross-to-net sales accruals and reserves
Beginning balance	1,444	0
Provisions	15,365	2,721
Credits/payments	(12,575)	(1,277)
Ending balance	4,234	1,444
Copay and Returns
Gross-to-net sales accruals and reserves
Beginning balance	1,258	0
Provisions	10,629	2,502
Credits/payments	(7,971)	(1,244)
Ending balance	$ 3,916	$ 1,258

Derivative Liabilities (Tables)

12 Months Ended

Dec. 31, 2023

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Schedule of Changes in Fair Value of Derivative Liabilities


	2023		2022
Balance at January 1,	$	1,656	$	698
2022 Exit Fee addition at fair value	—		375
Changes in estimated fair value:
2018 Exit Fee	292		510
2022 Exit Fee	227		73
2018 Exit Fee payment	$	(1,500)	$	—
Fair value of exit fee derivative liabilities at December 31,	$	675	$	1,656

Net Loss Per Share (Tables)

12 Months Ended

Dec. 31, 2023

Earnings Per Share [Abstract]

Schedule of Computation of Net Loss Per Common Share

The following table sets forth the computation of net loss per common share (in thousands, except per share dollar amounts):


	Year Ended December 31,
	2023		2022		2021
Numerator:
Net loss	$	(66,067)	$	(67,207)	$	(158,165)
Denominator:
Weighted average common shares outstanding - basic and diluted	219,331		158,690		104,206
Net loss per share - basic and diluted	$	(0.30)	$	(0.42)	$	(1.52)

Schedule of Anti-Dilutive Securities Not Considered in Diluted Net Loss Per Common Share Calculation


	Year Ended December 31,
	2023	2022	2021
Options to purchase common stock	20,877	13,522	11,871
Restricted stock units	3,086	2,694	1,602
ESPP shares issuable	249	166	207

Total	24,212	16,382	13,680

Leases (Tables)

12 Months Ended

Dec. 31, 2023

Leases [Abstract]

Summary of Additional Details of the Leases

The following table provides additional details of our facility leases presented in our balance sheets (dollars in thousands):


	December 31,
Facilities	2023			2022
Right-of-use assets	$	5,589		$	9,295

Current portion of lease liabilities	4,435			3,894
Operating lease liability, net of current portion	1,725			5,855
Total lease liabilities	$	6,160		$	9,749

Weighted-average remaining life (years)	1.6			2.4
Weighted-average discount rate	6.8		%	6.8		%

Summary of Lease Costs

The lease costs, which are included in operating expenses in our statements of operations, were as follows (in thousands):


	Year Ended December 31,
	2023		2022		2021
Operating lease expense	$	3,857	$	4,257	$	3,671
Cash paid for operating lease	$	4,481	$	4,292	$	3,438

Summary of Undiscounted Cash Payment Obligations for Operating Lease Liabilities

The following table summarizes our undiscounted cash payment obligations for our operating lease liabilities as of December 31, 2023 (in thousands):


Ending December 31,
2024	$	4,715
2025	1,450
2026	329

Thereafter	—
Total undiscounted operating lease payments	6,494
Imputed interest expenses	(334)
Total operating lease liabilities	6,160
Less: Current portion of operating lease liability	(4,435)
Operating lease liability, net of current portion	$	1,725

Equity Incentive Plans - Restricted Stock Units (Details) - RSUs	12 Months Ended
	Dec. 31, 2023 $ / shares shares
Number of RSUs
Nonvested balance, beginning (shares) \| shares	1,406,000
Granted (shares) \| shares	3,269,000
Vested (shares) \| shares	(942,000)
Forfeited (shares) \| shares	(87,000)
Nonvested balance, ending (shares) \| shares	3,646,000
Weighted-Average Grant Date Fair Value Per Share
Nonvested balance, beginning (in dollars per share) \| $ / shares	$ 2.17
Granted (in dollars per share) \| $ / shares	3.39
Vested (in dollars per share) \| $ / shares	2.76
Forfeited (in dollars per share) \| $ / shares	3.05
Nonvested balance, ending (in dollars per share) \| $ / shares	$ 3.09

Income Taxes - Reconciliation of Effective Tax Rate (Details)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Income tax at the federal statutory rate	21.00%	21.00%	21.00%
State taxes, net of federal benefit	3.40%	1.90%	0.40%
Tax credits	1.70%	1.50%	1.00%
Stock based compensation	0.10%	(2.30%)	(1.30%)
Foreign withholding tax	(0.80%)	0.00%	0.00%
Executive compensation disallowed under IRC Sec 162(m)	(1.90%)	(1.60%)	(1.10%)
Other	0.00%	(0.80%)	0.00%
Change in valuation allowance	(24.30%)	(19.70%)	(20.00%)
Income tax provision	(0.80%)	0.00%	0.00%

Derivative Liabilities - Changes in Fair Value (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
2018 Exit Fee
Change in Fair Value of Derivative Liability
Fair value of exit fee derivative liabilities, beginning	$ 1,200
Fair value of exit fee derivative liabilities, ending	0	$ 1,200
2022 Exit Fee
Change in Fair Value of Derivative Liability
Fair value of exit fee derivative liabilities, beginning	400
Fair value of exit fee derivative liabilities, ending	700	400
Exit fee derivative liability
Change in Fair Value of Derivative Liability
Fair value of exit fee derivative liabilities, beginning	1,656	698
2022 Exit Fee addition at fair value	0	375
Fair value of exit fee derivative liabilities, ending	675	1,656
Exit fee derivative liability \| 2018 Exit Fee
Change in Fair Value of Derivative Liability
Changes in estimated fair value:	292	510
2018 Exit Fee payment	(1,500)	0
Exit fee derivative liability \| 2022 Exit Fee
Change in Fair Value of Derivative Liability
Changes in estimated fair value:	$ 227	$ 73

Inventory

12 Months Ended

Dec. 31, 2023

Inventory Disclosure [Abstract]

Inventory

INVENTORY

Inventory as of December 31, 2023 and 2022 consisted of the following (in thousands):


	December 31, 2023		December 31, 2022
Raw materials	$	22,920	$	22,299
Work in process	24,582		5,324
Finished goods	1,985		723
Total	$	49,487	$	28,346
Reported as:
Inventory	$	12,448	$	3,282
Inventory, non-current	37,039		25,064
Total	$	49,487	$	28,346

In addition to inventory, we had prepaid commercial manufacturing of $23.2 million and $13.6 million as of December 31, 2023 and 2022, respectively, which consisted of prepayments to third party contract manufacturing organizations, including prepayments of $4.2 million and zero as of December 31, 2023 and 2022, respectively, that are expected to be converted into inventory after 12 months.

Geographic Information and Concentrations - Concentration Risk (Details) - Revenue - Collaboration partnership concentration risk	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Kyowa Kirin
Concentration Risk [Line Items]
Concentration risk (percent)	29.00%	70.00%	100.00%
Bioridge Phama
Concentration Risk [Line Items]
Concentration risk (percent)	24.00%	3.20%	0.00%
Cardinal
Concentration Risk [Line Items]
Concentration risk (percent)	19.80%	9.60%	0.00%
AmerisourceBergen Drug Corporation
Concentration Risk [Line Items]
Concentration risk (percent)	19.10%	11.10%	0.00%
McKesson
Concentration Risk [Line Items]
Concentration risk (percent)	15.70%	8.90%	0.00%

Equity Incentive Plans

12 Months Ended

Dec. 31, 2023

Share-Based Payment Arrangement [Abstract]

Equity Incentive Plans

EQUITY INCENTIVE PLANS

2008 Plan

We granted options under our 2008 Stock Incentive Plan (2008 Plan) until June 2014 when it was terminated as to future awards, although it continues to govern the terms of options that remain outstanding under the 2008 Plan. The 2008 Plan provided for the granting of incentive and non-qualified stock options, and stock purchase rights to employees, directors and consultants at the discretion of the board of directors. Stock options granted generally vested over a period of four years from the date of grant. In connection with the board of directors and stockholders’ approval of the 2014 Plan, all remaining shares available for future award under the 2008 Plan were transferred to 2014 Plan, as discussed below, and the 2008 Plan was terminated.

2014 Plan

The 2014 Equity Incentive Award Plan (2014 Plan) became effective on June 18, 2014. Under the 2014 Plan, 1.4 million shares of common stock were initially reserved for issuance pursuant to a variety of stock-based compensation awards, including stock options, stock appreciation rights (SARs), restricted stock awards, service-based restricted stock unit (RSU) awards, performance-based restricted stock unit (PRSU) awards, deferred stock awards, deferred stock unit awards, dividend equivalent awards, stock payment awards and performance awards. In addition, 35 thousand shares that had been available for future awards under the 2008 Plan as of June 18, 2014, were added to the initial reserve available under the 2014 Plan, bringing the total reserve upon the effective date of the 2014 Plan to 1.5 million shares. The number of shares initially reserved for issuance or transfer pursuant to awards under the 2014 Plan will be increased by (i) the number of shares represented by awards outstanding under 2008 Plan on June 18, 2014, that are either forfeited or lapse unexercised or that are repurchased for the original purchase price thereof, up to a maximum of 1.2 million shares, and (ii) if approved by the administrator of the 2014 Plan, an annual increase on the first day of each fiscal year ending in 2024 equal to the lesser of (A) four percent (4.0%) of the shares of stock outstanding (on an as converted basis) on the last day of the immediately preceding fiscal year and (B) such smaller number of shares of stock as determined by our board of directors; provided, however, that no more than 10.7 million shares of stock may be issued upon the exercise of incentive stock options. As of December 31, 2023, approximately 2.5 million shares of our common stock were available for future issuance under the 2014 Plan.

2016 Plan

In November 2016, our board of directors approved the 2016 Employment Commencement Incentive Plan (Inducement Plan) under which 1.0 million shares were reserved. In January 2021, January 2022, December 2022 and January 2024, 0.5 million, 2.0 million, 3.0 million and 5.8 million shares, respectively, were added to the Inducement Plan. As of December 31, 2023, 6.0 million shares of our common stock were subject to inducement grants that were issued pursuant to the Inducement Plan. As of December 31, 2023, approximately 0.9 million shares of our common stock were available for future issuance under the 2016 Plan.

Stock Options

A summary of our stock option activity and related information during the year ended December 31, 2023 is as follows (in thousands, except per share dollar amounts and years):


		Options Issued and Outstanding				Weighted Average Remaining Contractual Term (in Years)	Aggregate Intrinsic Value
	Number of Shares		Weighted-Average Exercise Price per Share
Balance at December 31, 2022		13,963		$	4.83

Options granted		8,914		$	3.14
Options exercised		(226)		$	1.61
Options canceled		(483)		$	3.83


Balance at December 31, 2023		22,168		$	4.20	7.3	$	58,606
Vested and expected to vest at December 31, 2023		22,168		$	4.20	7.3	$	58,606
Exercisable at December 31, 2023		12,199		$	5.30	6.1	$	25,116

The aggregate intrinsic value represents the difference between the total pre-tax value (i.e., the difference between our stock price and the exercise price) of stock options outstanding as of December 31, 2023, based on our common stock closing price of $6.20 per share, which would have been received by the option holders if all their in-the-money options had been exercised as of that date.

The intrinsic value of options exercised during the years ended December 31, 2023, 2022 and 2021, was $1.1 million, $30 thousand, and $1.7 million, respectively.

The weighted-average grant-date estimated fair value of options granted during the years ended December 31, 2023, 2022 and 2021 was $2.36, $0.63 and $3.92 per share, respectively. The estimated grant date fair value of employee stock options was calculated using the Black-Scholes option-pricing model, based on the following weighted-average assumptions:


	Year Ended December 31,
	2023		2022		2021
Expected term (years)	5.1		4.9		5.0
Expected volatility	97.6	%	92.1	%	77.0	%
Risk-free interest rate	3.8	%	2.2	%	4.7	%
Dividend yield	—	%	—	%	—	%

Expected Term—We have limited historical information to develop reasonable expectations about future exercise patterns and post-vesting employment termination behavior for its stock-option grants. As such, the expected term was initially estimated using the simplified method whereby the expected term equals the arithmetic average of the vesting term and the original contractual term of the option. Beginning in 2021, we estimate the expected term of our options based upon historical exercises and post-vesting termination behavior, which has not resulted in a material difference as compared to using the simplified method.

Expected Volatility—Since January 1, 2017, we use the historic volatility of our own stock over the retrospective period corresponding to the expected remaining term of the options, or the period since our shares were first quoted on The Nasdaq Global Market, if that is shorter, to compute our expected stock price volatility.

Risk-Free Interest Rate—The risk-free interest rate assumption is based on the zero-coupon U.S. treasury instruments on the date of grant with a maturity date consistent with the expected term of our stock option grants.

Dividend Yield—To date, we have not declared or paid any cash dividends and do not have any plans to do so in the future. Therefore, we use an expected dividend yield of zero.

Restricted Stock Units

A summary of our RSUs activity and related information for the year ended December 31, 2023 is as follows (in thousands, except per share dollar amounts):


	Number of RSUs	Weighted-Average Grant Date Fair Value Per Share
Non-vested restricted stock units at December 31, 2022	1,406	$	2.17
Granted	3,269	$	3.39
Vested	(942)	$	2.76
Forfeited	(87)	$	3.05
Non-vested restricted stock units at December 31, 2023	3,646	$	3.09

The total estimated fair value of RSUs vested during the years ended December 31, 2023, 2022 and 2021 was $3.5 million, $2.6 million and $0.8 million, respectively.

Issuance of Common Stock for Services

During the years ended December 31, 2023, 2022 and 2021, we issued approximately 0.1 million, 0.7 million and 26 thousand shares, respectively, of common stock to members of the board of directors who elected to receive stock in lieu of

their cash fees under our Non-Employee Director Compensation Program. The shares issued during the years ended December 31, 2023, 2022 and 2021 were valued at $0.3 million, $0.4 million and $0.2 million for each year, respectively, based on the fair value of the common stock on the date of grant.

Employee Stock Purchase Plan

We adopted the 2014 Employee Stock Purchase Plan (ESPP) and initially reserved approximately 0.2 million shares of common stock as of its effective date of June 18, 2014. If approved by the administrator of the ESPP, on the first day of each calendar year, ending in 2024, the number of shares in the reserve will increase by an amount equal to the lesser of (i) one percent (1.0%) of the shares of common stock outstanding on the last day of the immediately preceding fiscal year and (ii) such number of shares of common stock as determined by the board of directors; provided, however, no more than 2.2 million shares of our common stock may be issued under the ESPP.

During the years ended December 31, 2023, 2022 and 2021, we issued approximately 436 thousand, 308 thousand and 387 thousand shares, respectively, at an average share price of $1.85, $0.63 and $2.12, respectively, pursuant to the ESPP. As of December 31, 2023, approximately 1.1 million shares of our common stock were available for future issuance under the ESPP.

The following table illustrates the weighted-average assumptions for the Black-Scholes option-pricing model used in determining the fair value of ESPP purchase rights granted to our employees:


	Year Ended December 31,
	2023		2022		2021
Expected term (years)	0.5		0.5		0.5
Expected volatility	86.0	%	97.2	%	123.0	%
Risk-free interest rate	5.3	%	1.9	%	0.7	%
Dividend yield	—	%	—	%	—	%

Stock-based Compensation Expense

Stock-based compensation expense recognized for stock options, RSUs, and our ESPP are recorded as operating expenses in our statements of operations and comprehensive loss, as follows (in thousands):


	Year Ended December 31,
	2023		2022		2021
Selling, general and administrative	$	9,952	$	7,525	$	7,923
Research and development	3,578		3,225		4,116
Total	$	13,530	$	10,750	$	12,039

A summary of our total unrecognized stock-based compensation expense, net of estimated forfeitures, as of December 31, 2023 is as follows (dollars in thousands):


	December 31, 2023
	Unrecognized Compensation Expense		Average Remaining Vesting Period (Years)
Stock option grants	$	19,960	2.75
RSU grants	$	10,579	3.03
ESPP	$	154	0.2

Property and Equipment, Net

12 Months Ended

Dec. 31, 2023

Property, Plant and Equipment [Abstract]

Property and Equipment, Net

PROPERTY AND EQUIPMENT, NET

Property and equipment consist of the following (in thousands):


	December 31,
	2023		2022
Laboratory equipment	$	46	$	46
Office equipment and furniture	2,433		2,089
Leasehold improvements	8,731		8,745
Property and equipment, gross	11,210		10,880
Less: accumulated depreciation	(10,201)		(9,657)
Total property and equipment, net	$	1,009	$	1,223

We recognized depreciation expense in the amount of $0.6 million, $0.7 million, and $1.4 million for the years ended December 31, 2023, 2022 and 2021, respectively.

During the year ended December 31, 2022, following the elimination of our internal research organization in the fourth quarter of 2021, we sold laboratory equipment with total net carrying value of $0.5 million and received cash proceeds of $1.8 million, resulting in a gain of $1.3 million which has been reported within other income, net on our statement of operations and comprehensive loss.

Commitments and Contingencies (Details)			4 Months Ended
Commitments and Contingencies (Details)	Jul. 19, 2022 claim	Aug. 12, 2021 claim defendant	Mar. 29, 2022 claim defendant	Dec. 31, 2023 USD ($)
Contingencies [Line Items]
Contingent liabilities \| $				$ 0
Strezsak v. Ardelyx, Inc.
Contingencies [Line Items]
Number of lawsuits \| claim	2	2
Number of defendants \| defendant		2
Go v. Raab
Contingencies [Line Items]
Number of lawsuits \| claim			2
Number of defendants \| defendant			2

Equity Incentive Plans - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands		1 Months Ended				6 Months Ended	12 Months Ended
	Jun. 18, 2014	Jan. 31, 2024	Dec. 31, 2022	Jan. 31, 2022	Jan. 31, 2021	Jun. 30, 2015	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Nov. 30, 2016
Equity Incentive Plans
Common stock closing price (in dollars per share)							$ 6.20
Intrinsic value of options exercised							$ 1,100	$ 30	$ 1,700
Weighted-average grant-date estimated fair value of options granted (in dollars per share)							$ 2.36	$ 0.63	$ 3.92
Issuance of common stock for services							$ 337	$ 390	$ 190
2014 Plan
Equity Incentive Plans
Number of shares initially authorized (in shares)	1,400,000
Number of shares added to initial reserve	35,000
Common stock reserved for future issuance (in shares)	1,500,000						2,500,000
Potential increase to shares reserved for inclusion of forfeited or unexercised options from prior plan	1,200,000
Potential increase in shares reserved as a percentage of shares outstanding	4.00%
Maximum shares to be issued upon exercise of incentive stock options	10,700,000
Inducement Plan
Equity Incentive Plans
Number of shares added to initial reserve			3,000,000	2,000,000	500,000
Common stock reserved for future issuance (in shares)							900,000			1,000,000
Share of common stock subject to issued inducement grants							6,000,000
Inducement Plan \| Subsequent event
Equity Incentive Plans
Number of shares added to initial reserve		5,800,000
ESPP
Equity Incentive Plans
Common stock reserved for future issuance (in shares)	200,000						1,100,000
Potential increase in shares reserved as a percentage of shares outstanding	1.00%
Weighted-average grant-date estimated fair value of options granted (in dollars per share)							$ 1.85	$ 0.63	$ 2.12
Dividend yield							0.00%	0.00%	0.00%
Issuance of common stock for services (in shares)							436,000	308,000	387,000
Maximum shares to be issued under ESPP	2,200,000
Stock options
Equity Incentive Plans
Dividend yield							0.00%	0.00%	0.00%
Stock options \| 2008 Plan
Equity Incentive Plans
Vesting period (in years)						4 years
RSUs
Equity Incentive Plans
Estimated fair value of RSUs vested							$ 3,500	$ 2,600	$ 800
Number of shares granted							3,269,000
Number of shares vested							942,000
Board of directors
Equity Incentive Plans
Issuance of common stock for services (in shares)							100,000	700,000	26,000
Issuance of common stock for services							$ 300	$ 400	$ 200

Equity Incentive Plans - Unrecognized Stock-Based Compensation (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2023 USD ($)
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized Compensation Expense	$ 19,960
Average Remaining Vesting Period (Years)	2 years 9 months
RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized Compensation Expense	$ 10,579
Average Remaining Vesting Period (Years)	3 years 10 days
ESPP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized Compensation Expense	$ 154
Average Remaining Vesting Period (Years)	2 months 12 days

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

+ Details

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2023

Income Tax Disclosure [Abstract]

Schedule of Components of Provision for Income Taxes

The components of our provision for income taxes for the years ended December 31, 2023, 2022 and 2021, are as follows (in thousands):


	Year Ended December 31,
	2023		2022		2021
Current:
State	$	47	$	8	$	4
Foreign	500		—		—
Total current	547		8		4
Deferred:
Federal	—		—		—
Total deferred	—		—		—
Provision for income taxes	$	547	$	8	$	4

Schedule of Reconciliation of Effective Tax Rate

A reconciliation of the statutory federal income tax rate to our effective tax rate is as follows:


	Year Ended December 31,
	2023		2022		2021
Income tax at the federal statutory rate	21.0	%	21.0	%	21.0	%
State taxes, net of federal benefit	3.4		1.9		0.4
Tax credits	1.7		1.5		1.0
Stock based compensation	0.1		(2.3)		(1.3)
Foreign withholding tax	(0.8)		—		—
Executive compensation disallowed under IRC Sec 162(m)	(1.9)		(1.6)		(1.1)
Other	—		(0.8)		—
Change in valuation allowance	(24.3)		(19.7)		(20.0)
Income tax provision	(0.8)	%	—	%	—	%

Schedule of Components of Deferred Tax Assets

Significant components of our deferred tax assets are as follows as of December 31, 2023 and 2022 (in thousands):


	December 31,
	2023		2022
Deferred tax assets:
Amortization and depreciation	$	64,919	$	64,111
Net operating loss carryforwards	98,702		86,547
Tax credits	15,375		14,411
Stock-based compensation	6,946		5,244
Deferred royalty obligation	4,907		2,577
Other	6,707		4,909
Gross deferred tax assets	197,556		177,799
Valuation allowance	(196,197)		(175,670)
Deferred tax assets net of valuation allowance	1,359		2,129
Deferred tax liabilities:
Right-of-use asset	(1,359)		(2,129)

Other	—		—
Net deferred tax assets	$	—	$	—

Schedule of Reconciliation of Unrecognized Tax Benefits

A reconciliation of the beginning and ending amount of unrecognized tax benefits is as follows (in thousands):


	December 31,
	2023		2022		2021
Balance at beginning of year	$	24,075	$	24,426	$	23,624
Additions based on tax positions related to current year	262		460		1,613
Additions based on tax positions related to prior year	99		—		—
Subtractions based on tax positions related to prior year	(811)		(811)		(811)
Balance at end of year	$	23,625	$	24,075	$	24,426

Cash, Cash Equivalents and Short-Term Investments

12 Months Ended

Dec. 31, 2023

Cash and Cash Equivalents [Abstract]

Cash, Cash Equivalents and Short-Term Investments

CASH, CASH EQUIVALENTS AND SHORT-TERM INVESTMENTS

Securities classified as cash, cash equivalents and short-term investments as of December 31, 2023 and 2022 are summarized below (in thousands):


	December 31, 2023
			Gross Unrealized
	Amortized Cost		Gains		Losses		Fair Value
Cash and cash equivalents:
Cash	$	2,829	$	—	$	—	$	2,829
Money market funds	18,641		—		—		18,641


Total cash and cash equivalents	21,470		—		—		21,470
Short-term investments:
U.S. government-sponsored agency bonds	$	101,892	$	235	$	(34)	$	102,093
Commercial paper	$	49,630	$	41	$	(17)	$	49,654
Asset-backed securities	8,628		2		(5)		8,625

U.S. treasury securities	2,455		2		—		2,457
Total short-term investments	162,605		280		(56)		162,829


Total cash, cash equivalents and investments	$	184,075	$	280	$	(56)	$	184,299


	December 31, 2022
			Gross Unrealized
	Amortized Cost		Gains		Losses		Fair Value
Cash and cash equivalents:
Cash	$	11,827	$	—	$	—	$	11,827
Money market funds	84,313		—		—		84,313


Total cash and cash equivalents	96,140		—		—		96,140
Short-term investments
Commercial paper	$	25,336	$	6	$	(51)	$	25,291
Corporate bonds	1,000		—		(1)		999
U.S. government-sponsored agency bonds	1,487		—		(8)		1,479

Total short-term investments	27,823		6		(60)		27,769


Total cash, cash equivalents and investments	$	123,963	$	6	$	(60)	$	123,909

Cash equivalents consist of money market funds with original maturities of three months or less at the time of purchase, and the carrying amount is a reasonable approximation of fair value. We invest our cash in high quality securities of financial and commercial institutions. These securities are carried at fair value, which is based on readily available market information, with unrealized gains and losses included in accumulated other comprehensive income (loss) within stockholders’ equity on our balance sheets. We use the specific identification method to determine the amount of realized gains or losses on sales of marketable securities. Realized gains or losses have been insignificant and are included in other income, net, in the statement of operations and comprehensive loss.

All of the short-term available-for sale securities held as of December 31, 2023 and 2022 had contractual maturities of less than one year. Our available-for-sale securities are subject to a periodic impairment review. We consider a debt security to be impaired when its fair value is less than its carrying cost, in which case we would further review the investment to determine whether it is other-than-temporarily impaired. When we evaluate an investment for other-than-temporary impairment, we review factors such as the length of time and extent to which fair value has been below cost basis, the financial condition of the issuer and any changes thereto, intent to sell, and whether it is more likely than not we will be required to sell the investment before the recovery of its cost basis. If an investment is other-than-temporarily impaired or subject to credit losses, we write it down through the statement of operations and comprehensive loss to its fair value and establish that value as a new cost basis for the investment. Our unrealized losses as of December 31, 2023 and 2022 were not material. We determined that none of our available-for-sale securities were other-than-temporarily impaired as of December 31, 2023 and 2022, and no investment was in a continuous unrealized loss position for more than one year. As such, we believe that it is more likely than not that the investments will be held until maturity or a forecasted recovery of fair value.

Fair Value Measurements - Financial Assets and Liabilities Measured on a Recurring Basis (Details) - Recurring - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Assets:
Assets, fair value	$ 181,470	$ 112,082
Liabilities:
Liabilities, fair value	675	1,656
Money market funds
Assets:
Assets, fair value	18,641	84,313
U.S. government-sponsored agency bonds
Assets:
Assets, fair value	102,093	1,479
Commercial paper
Assets:
Assets, fair value	49,654	25,291
Asset-backed securities
Assets:
Assets, fair value	8,625
U.S. treasury securities
Assets:
Assets, fair value	2,457
Corporate bonds
Assets:
Assets, fair value		999
Derivative liabilities for exit fee
Liabilities:
Liabilities, fair value	675	1,656
Level 1
Assets:
Assets, fair value	18,641	84,313
Liabilities:
Liabilities, fair value	0	0
Level 1 \| Money market funds
Assets:
Assets, fair value	18,641	84,313
Level 1 \| U.S. government-sponsored agency bonds
Assets:
Assets, fair value	0	0
Level 1 \| Commercial paper
Assets:
Assets, fair value	0	0
Level 1 \| Asset-backed securities
Assets:
Assets, fair value	0
Level 1 \| U.S. treasury securities
Assets:
Assets, fair value	0
Level 1 \| Corporate bonds
Assets:
Assets, fair value		0
Level 1 \| Derivative liabilities for exit fee
Liabilities:
Liabilities, fair value	0	0
Level 2
Assets:
Assets, fair value	162,829	27,769
Liabilities:
Liabilities, fair value	0	0
Level 2 \| Money market funds
Assets:
Assets, fair value	0	0
Level 2 \| U.S. government-sponsored agency bonds
Assets:
Assets, fair value	102,093	1,479
Level 2 \| Commercial paper
Assets:
Assets, fair value	49,654	25,291
Level 2 \| Asset-backed securities
Assets:
Assets, fair value	8,625
Level 2 \| U.S. treasury securities
Assets:
Assets, fair value	2,457
Level 2 \| Corporate bonds
Assets:
Assets, fair value		999
Level 2 \| Derivative liabilities for exit fee
Liabilities:
Liabilities, fair value	0	0
Level 3
Assets:
Assets, fair value	0	0
Liabilities:
Liabilities, fair value	675	1,656
Level 3 \| Money market funds
Assets:
Assets, fair value	0	0
Level 3 \| U.S. government-sponsored agency bonds
Assets:
Assets, fair value	0	0
Level 3 \| Commercial paper
Assets:
Assets, fair value	0	0
Level 3 \| Asset-backed securities
Assets:
Assets, fair value	0
Level 3 \| U.S. treasury securities
Assets:
Assets, fair value	0
Level 3 \| Corporate bonds
Assets:
Assets, fair value		0
Level 3 \| Derivative liabilities for exit fee
Liabilities:
Liabilities, fair value	$ 675	$ 1,656

Inventory (Tables)

12 Months Ended

Dec. 31, 2023

Inventory Disclosure [Abstract]

Schedule of Current Inventory

Inventory as of December 31, 2023 and 2022 consisted of the following (in thousands):


	December 31, 2023		December 31, 2022
Raw materials	$	22,920	$	22,299
Work in process	24,582		5,324
Finished goods	1,985		723
Total	$	49,487	$	28,346
Reported as:
Inventory	$	12,448	$	3,282
Inventory, non-current	37,039		25,064
Total	$	49,487	$	28,346

Schedule of Noncurrent Inventory

Inventory as of December 31, 2023 and 2022 consisted of the following (in thousands):


	December 31, 2023		December 31, 2022
Raw materials	$	22,920	$	22,299
Work in process	24,582		5,324
Finished goods	1,985		723
Total	$	49,487	$	28,346
Reported as:
Inventory	$	12,448	$	3,282
Inventory, non-current	37,039		25,064
Total	$	49,487	$	28,346

Collaboration and Licensing Agreements - Deferred Revenue (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Current
Beginning balance	$ 4,211
Ending balance	7,182	$ 4,211
Non-Current
Beginning balance	9,025
Ending balance	8,644	9,025
2017 KKC Agreement
Current
Beginning balance	4,211	0
Amounts invoiced as prepayments for product supply	1,547	250
Decrease for revenue recognized for product supply	(4,586)	0
Reclassify amounts to be recognized in the next twelve months	6,010	3,961
Ending balance	7,182	4,211
Non-Current
Beginning balance	9,025	4,727
Amounts invoiced as prepayments for product supply	5,629	8,259
Decrease for revenue recognized for product supply	0	0
Reclassify amounts to be recognized in the next twelve months	(6,010)	(3,961)
Ending balance	$ 8,644	$ 9,025

Income Taxes - Reconciliation of Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Reconciliation of Unrecognized Tax Benefits
Balance at beginning of year	$ 24,075	$ 24,426	$ 23,624
Additions based on tax positions related to current year	262	460	1,613
Additions based on tax positions related to prior year	99	0	0
Subtractions based on tax positions related to prior year	(811)	(811)	(811)
Balance at end of year	$ 23,625	$ 24,075	$ 24,426

Stockholders' Equity	12 Months Ended
Stockholders' Equity	Dec. 31, 2023
Stockholders' Equity Note [Abstract]
Stockholders' Equity	STOCKHOLDERS’ EQUITY In July 2020, we filed a Form S-3 registration statement, which became effective in August 2020 (2020 Registration Statement), containing (i) a base prospectus for the offering, issuance and sale by us of up to a maximum aggregate offering price of $250.0 million of our common stock, preferred stock, debt securities, warrants and/or units, from time to time in one or more offerings; and (ii) a prospectus supplement for the offering, issuance and sale by us of up to a maximum aggregate offering price of $100.0 million of our common stock that may be issued and sold, from time to time, under a sales agreement with Jefferies LLC (Jefferies), deemed to be “at-the-market offerings” (2020 Open Market Sales Agreement). Pursuant to the 2020 Open Market Sales Agreement, Jefferies, as sales agent, received a commission of up to 3.0% of the gross sales price for shares of common stock sold under the 2020 Open Market Sales Agreement. As of December 31, 2021, we had sold 23.3 million shares and received the maximum gross proceeds of $100.0 million pursuant to the 2020 Open Market Sales Agreement at a weighted average share prices of $4.30 per share. In August 2021, we filed an additional prospectus supplement under the 2020 Registration Statement for the offering, issuance and sale by us of up to a maximum aggregate offering price of $150.0 million of our common stock that may be issued and sold, from time to time, under an additional sales agreement we entered into with Jefferies (2021 Open Market Sales Agreement), pursuant to which we may, from time to time, sell up to $150.0 million in shares of our common stock through Jefferies. We are required to sell shares under the 2021 Open Market Sales Agreement. Pursuant to the 2021 Open Market Sales Agreement, Jefferies, as our sales agent, receives a commission of up to 3.0% of the gross sales price for shares of common stock sold under the 2021 Open Market Sales Agreement. As of March 2023, we had received the maximum gross proceeds of $150.0 million under the 2021 Open Market Sales Agreement at a weighted average share price of approximately $1.57 per share, which included 15.5 million shares of our common stock for which we received gross proceeds of $51.9 million at a weighted average share price of approximately $3.35 during the quarter ended March 31, 2023. In January 2023, we filed a Form S-3 registration statement, which became effective in January 2023 (2023 Registration Statement), containing (i) a base prospectus for the offering, issuance and sale by us of up to a maximum aggregate offering price of $250.0 million of our common stock, preferred stock, debt securities, warrants and/or units, from time to time in one or more offerings; and (ii) a prospectus supplement for the offering, issuance and sale by us of up to a maximum aggregate offering price of $150.0 million of our common stock that may be issued and sold, from time to time, under a sales agreement with Jefferies, deemed to be “at-the-market offerings” (2023 Open Market Sales Agreement). Pursuant to the 2023 Open Market Sales Agreement, Jefferies, as sales agent, may receive a commission of up to 3.0% of the gross sales price for shares of common stock sold under the 2023 Open Market Sales Agreement. During the year ended December 31, 2023, we sold 16.8 million shares of our common stock and received gross proceeds of $70.0 million at a weighted average sales price of approximately $4.17 per share under the 2023 Open Market Sales Agreement.

- Definition

The entire disclosure for equity.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-13

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (h)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-13

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 14
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-14

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 235
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481062/946-235-50-2

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 235
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481062/946-235-50-2

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 505
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481004/946-505-50-6

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 40
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480237/815-40-50-6

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480008/505-10-S99-1

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(e)(1))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480678/235-10-S99-1

Reference 10: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 505
-Name Accounting Standards Codification
-Publisher FASB
-URI https://asc.fasb.org//505/tableOfContent

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-13

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (g)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-13

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (i)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-13

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 14
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-14

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 14
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-14

Reference 16: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 16
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-16

Reference 17: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 18
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-18

Reference 18: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 18
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-18

Reference 19: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 18
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-18

+ Details

Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2023

Fair Value Disclosures [Abstract]

Schedule of Fair Value of Financial Assets and Liabilities Measured on a Recurring Basis

The following table sets forth the fair value of our financial assets and liabilities that are measured or disclosed on a recurring basis by level within the fair value hierarchy (in thousands):


	December 31, 2023
	Total Fair Value		Level 1		Level 2		Level 3
Assets:
Money market funds	$	18,641	$	18,641	$	—	$	—
U.S. government-sponsored agency bonds	102,093		—		102,093		—
Commercial paper	49,654		—		49,654		—
Asset-backed securities	8,625		—		8,625		—
U.S. treasury securities	2,457		—		2,457		—

Total	$	181,470	$	18,641	$	162,829	$	—

Liabilities:
Derivative liabilities for exit fee	$	675	$	—	$	—	$	675
Total	$	675	$	—	$	—	$	675


	December 31, 2022
	Total Fair Value		Level 1		Level 2		Level 3
Assets:
Money market funds	$	84,313	$	84,313	$	—	$	—
Commercial paper	25,291		—		25,291		—
U.S. government-sponsored agency bonds	1,479		—		1,479		—
Corporate bonds	999		—		999		—


Total	$	112,082	$	84,313	$	27,769	$	—

Liabilities:
Derivative liability for exit fees	$	1,656	$	—	$	—	$	1,656
Total	$	1,656	$	—	$	—	$	1,656