0001628280-23-006041 | 10-K | XBRL Viewer

Borrowings

12 Months Ended

Dec. 31, 2022

BORROWINGS

Solar Capital and Western Alliance Bank Loan Agreement

In May 2018, we entered into a loan and security agreement ("2018 Loan Agreement"), with Solar Capital Ltd. and Western Alliance Bank ("Lenders”). The 2018 Loan Agreement provided for a $50.0 million term loan facility with a maturity date of November 1, 2022 ("2018 Term Loan”). The full amount of the 2018 Term Loan was funded on May 16, 2018. We received net proceeds from the loan of approximately $49.3 million, after deducting the closing fee, legal expenses and issuance costs. In October 2020, we and the Lenders entered into an amendment to the 2018 Loan Agreement (“2020 Amendment”) to extend the date through which we were permitted to make interest-only payments on the 2018 Term Loan by twelve months to December 1, 2021 subject to the repayment terms noted below.

Borrowings under the 2018 Term Loan bore interest at a floating per annum rate equal to 7.45% plus the one-month London Inter-bank Offered Rate ("LIBOR"). We were permitted to make interest-only payments on the 2018 Term Loan through June 1, 2020, or until we achieved our primary endpoint in the Phase 3 study of tenapanor for the treatment of hyperphosphatemia in end-stage renal disease patients on dialysis prior to June 1, 2020, in which case we would have been permitted to make interest-only payments on the 2018 Term Loan through December 1, 2020. In December 2019, we reported positive topline results for PHREEDOM, a long-term Phase 3 study evaluating the efficacy and safety of tenapanor as monotherapy for the treatment of hyperphosphatemia in adult patients with CKD on dialysis. The Lenders were in agreement that these positive data from the Phase 3 PHREEDOM study achieve the “Phase 3 Endpoint” required by the 2018 Term Loan to extend the interest only period by six months to December 1, 2020. Subsequent to the 2020 Amendment, the interest only period was extended an additional twelve months to December 1, 2021. Accordingly, beginning on December 1, 2021 through the maturity date, we would have been required to make monthly payments of interest plus repayment of the 2018 Term Loan in consecutive equal monthly installments of principal. If however, either the FDA did not approve our NDA for tenapanor for control of serum phosphorus in adult patients with CKD on dialysis on or before May 31, 2021 or the FDA issued a Complete Response Letter ("CRL") for tenapanor for the control of serum phosphorus in adult patients with CKD on dialysis, then we would begin principal payments on the earlier of June 1, 2021 or the first day of the month immediately following the date that the FDA issued a CRL to us.

In May and July 2021, we and the Lenders entered into additional amendments to the 2018 Loan Agreement (“the 2021 Amendments”) which together extended the period of time that we were permitted to make interest-only payments on the 2018 Term Loan to December 1, 2021; provided that if we had not received FDA approval for our NDA for tenapanor for the control of serum phosphorus in adult patients with CDK on dialysis on or before October 25, 2021, the interest-only period would expire and principal repayments would be required to begin on November 1, 2021. If principal repayments were required to begin prior to December 1, 2021 under the 2021 Amendments, then the first such repayment was required to include all payments that would have been due if monthly principal repayment had begun on June 1, 2021. Accordingly, during November 2021, in compliance with the terms of our 2018 Loan Agreement, we began to repay principal on the 2018 Term 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.

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 provides for a senior secured loan facility, with $27.5 million (“Term A Loan”) funded on the Closing Date and an additional $22.5 million that we may borrow on or prior to July 25, 2023; provided that (i) we have received approval by the FDA for our NDA for XPHOZAH by December 31, 2022, and (ii) we have achieved certain product revenue milestone targets described in the 2022 Loan Agreement (“Term B Loan”, and collectively, the Term A Loan and the Term B Loan, the “2022 Loan”). On February 9, 2023, we entered into an amendment to the 2022 Loan Agreement with SLR Investment Corp. that extends the date by which we must receive approval by the FDA for our NDA for the control of serum phosphorus in adult patients with CKD on dialysis in order to borrow the additional $22.5 million from December 31, 2022 to November 30, 2023 and extended the period during which we are permitted to make interest only payments until March 31,

2025 if we receive approval by the FDA for our NDA for XPHOZAH on or prior to November 30, 2023 or achieve a defined net product revenue threshold for 2023. The 2022 Term A Loan funds were used to repay the 2018 Loan with the 2018 Lenders. The 2022 Loan has a maturity date of March 1, 2027.

Borrowings under the 2022 Loan bear interest at a floating per annum rate equal to 7.95% plus the greater of (i) one tenth percent (0.10%) and (ii) the one-month rate published by the Intercontinental Exchange Benchmark Administration Ltd or its successor. We are permitted to make interest-only payments on the 2022 Loan through March 31, 2024 or if certain conditions described above are achieved, through March 31, 2025. Accordingly, beginning on April 1, 2024 or April 1, 2025, we will be required to make monthly payments of interest plus repay the 2022 Loan in consecutive equal monthly installments of principal over 36 months or 24 months, respectively. We were obligated to pay $0.2 million, upon the closing of the Term A Loan, and we are obligated to pay $0.1 million on the earliest of (i) the funding date of the Term B Loan, (ii) July 25, 2023, and (iii) the prepayment, refinancing, substitution, or replacement of the Term A Loan on or prior to July 25, 2023. We are obligated to pay a final fee equal to 4.95% of the aggregate original principal amount of the 2022 Loan funded upon the earliest to occur of the maturity date, the acceleration of the 2022 Loan, and the prepayment, refinancing, substitution, or replacement of the 2022 Loan. We may voluntarily prepay the outstanding 2022 Loan balance, subject to a prepayment premium of (i) 3% of the outstanding principal amount of the 2022 Loan if prepaid prior to or on the first anniversary of the Closing Date, (ii) 2% of the outstanding principal amount of the 2022 Loan if prepaid after the first anniversary of the Closing Date through and including the second anniversary of the Closing Date, or (iii) 1% of the outstanding principal amount of the 2022 Loan if prepaid after the second anniversary of the Closing Date and prior to the maturity date. The 2022 Loan is secured by substantially all of our assets, except for our intellectual property and certain other customary exclusions. Additionally, in connection with the 2022 Loan, we entered into an agreement, whereby we agreed to pay an exit fee in the amount of 2% of the 2022 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, tested monthly at the end of each month. 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 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 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 2022 Loan balance.

In addition, the 2022 Loan Agreement 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 2022 Term Loan, 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 Loan balance as a current liability as of December 31, 2022 due to the determination of the existence of substantial doubt about our ability to continue operating as a going concern discussed in Note 2. Summary of Significant Accounting Policies: Liquidity and our assessment that the material adverse change clause under the 2022 Loan Agreement is not within our control. The lenders have not invoked the material adverse change clause as of the date of issuance of these financial statements.

As discussed in Note 21. Subsequent Events, on February 9, 2023, we entered into a second amendment (“Second Amendment”) to our Loan Agreement with the Lenders. The Second Amendment extends the interest-only term of the loan by twelve months to March 31, 2025 provided that we either (i) receive approval from the FDA for our NDA for the control of serum phosphorus in adult patients with CKD on dialysis on or prior to November 30, 2023 or (ii) achieve certain product revenue milestone targets as described in the Second Amendment for the year ending December 31, 2023. The Second Amendment also extends the period under which we may draw the Term B Loan from July 25, 2023 to December 20, 2023, and amends the milestone that we must achieve in order to draw the Term B Loan by extending the time period for the receipt of approval by the FDA of the NDA for the control of serum phosphorus in adult patients with CKD on dialysis until November 30, 2023. In addition, the Second Amendment replaces the floating per annum interest rate with 7.95% plus the greater of (a) one percent (1.00%) per annum and (b)(i) 0.022% plus (ii) 1-month CME Term SOFR reference rate as published by the CME Term SOFR Administrator on the CME Term SOFR Administrator’s Website.

As of December 31, 2022, our future payment obligations related to the 2022 Loan, excluding interest payments and the 2022 final fee, were as follows (in thousands) and may be condensed to the 24 months ending March 1, 2027 if certain conditions noted above to extend the interest-only period are achieved:


2023	$	—
2024	7,639
2025	9,167
2026	9,167
2027	2,888
Thereafter	—
Total repayment obligations	28,861
Less: Unamortized discount and debt issuance costs	(1,110)
Less: Unaccreted value of final fee	(1,040)
Long-term debt	26,711
Less: Current portion of long-term debt	(26,711)
Long-term debt, net of current portion	$	—

- 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

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+ Details

Geographic Information and Concentrations

12 Months Ended

Dec. 31, 2022

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 or the domicile of our collaboration partners. A summary of our revenue by geographic areas for the years ended December 31, 2022, 2021 and 2020, is as follows (in thousands):


	Year Ended December 31,
	2022		2021		2020
United States (1)	$	15,600	$	—	$	—
International:
Asia Pacific (2)	36,527		10,084		6,765
North America (3)	31		13		806
Total revenue	$	52,158	$	10,097	$	7,571

(1)Revenues from the United States are comprised of amounts earned from sales of IBSRELA.

(2)Revenues from Asia Pacific are primarily comprised of amounts earned in accordance with the 2017 KKC Agreement and the 2019 KKC 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, 2022, 2021 and 2020 were as follows:


	Year Ended December 31,
	2022		2021		2020
KKC	70.0	%	100	%	89	%
Knight	0.1	%	—	%	11	%

AmerisourceBergen Drug Corporation	11.1	%	—	%	—	%

Historically, we have not experienced credit losses from our accounts receivable. We have not recorded a reserve for credit losses as of December 31, 2022 and 2021.

Deferred Royalty Obligation Related To The Sale Of Future Royalties	12 Months Ended
	Dec. 31, 2022
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 KKC based upon KKC'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 are eligible to receive a $5.0 million payment following KKC's receipt of regulatory approval to market tenapanor for hyperphosphatemia in Japan, and another $5.0 million payment in the event net sales by KKC in Japan exceed a certain annual target level by the end of 2025. 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 KKC Agreement, to create or incur any liens with respect to the Royalty Interest Payments, the 2017 KKC Agreement or certain patents, or to sell, license or transfer certain patents in the field and territory described in the 2017 KKC 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 KKC 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 KKC 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. We received the $10.0 million upfront payment from HCR during June 2022 and recorded it as a deferred royalty obligation related to the sale of future royalties ("deferred royalty obligation") on our balance sheet. Due to our ongoing manufacturing obligations under the 2017 KKC Agreement, we account for the proceeds as imputed debt and therefore will recognize royalties received 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 KKC. 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 KKC, 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 KKC under the 2017 KKC 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 KKC are made in Japanese yen, and other events or circumstances that could result in reduced royalty payments from KKC, 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 KKC 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, 2022, our effective interest rate used to amortize the liability is 34.4%. During the twelve months ended December 31, 2022, we recognized approximately $1.7 million of non-cash interest expense for the amortization of the deferred royalty obligation. As of December 31, 2022, we have received no royalty payments from KKC and, therefore, the deferred royalty obligation has not begun to be reduced.

Commitments and Contingencies (Details)			4 Months Ended
Commitments and Contingencies (Details)	Aug. 12, 2022 claim defendant	Jul. 19, 2022 claim	Mar. 29, 2022 claim defendant	Dec. 31, 2022 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

Fair Value Measurements

12 Months Ended

Dec. 31, 2022

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, 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 liabilities for exit fees	$	1,656	$	—	$	—	$	1,656
Total	$	1,656	$	—	$	—	$	1,656


	December 31, 2021
	Total Fair Value		Level 1		Level 2		Level 3
Assets:
Money market funds	$	71,175	$	71,175	$	—	$	—
Commercial paper	31,935		—		31,935		—
Corporate bonds	7,022		—		7,022		—
Asset-backed securities	5,304		—		5,304		—


Total	$	115,436	$	71,175	$	44,261	$	—

Liabilities:
Derivative liability for exit fee	$	698	$	—	$	—	$	698
Total	$	698	$	—	$	—	$	698

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 notes, 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, 2022 and 2021, 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, 2022 and 2021.

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, 2022 and 2021. 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, 2022 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

Leases - Additional Lease Information (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Facilities - right-of-use assets and lease liabilities
Right-of-use assets	$ 9,295	$ 12,752
Current portion of lease liabilities	3,894	3,492
Operating lease liability, net of current portion	5,855	9,748
Total operating lease liabilities	$ 9,749	$ 13,240
Additional details
Weighted-average remaining life (years)	2 years 4 months 24 days	3 years 4 months 24 days
Weighted-average discount rate	6.80%	6.90%

Net Loss Per Share - Computation of Net Loss Per Common Share (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Numerator:
Net loss	$ (67,207)	$ (158,165)	$ (94,313)
Denominator:
Weighted average common shares outstanding - basic (in shares)	158,690,083	104,205,645	89,582,138
Weighted average common shares outstanding - diluted (in shares)	158,690,083	104,205,645	89,582,138
Net loss per share - basic (in dollars per share)	$ (0.42)	$ (1.52)	$ (1.05)
Net loss per share - diluted (in dollars per share)	$ (0.42)	$ (1.52)	$ (1.05)

- 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
-Publisher FASB
-Name Accounting Standards Codification
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Product Revenue, Net

12 Months Ended

Dec. 31, 2022

Revenue from Contract with Customer [Abstract]

Product Revenue, Net

PRODUCT REVENUE, NET

We received approval from the FDA in September 2019 to market IBSRELA in the U.S. We began selling IBSRELA in the U.S. in March 2022. We recorded net revenue for IBSRELA of $15.6 million during the twelve months ended December 31, 2022.

Sales to AmerisourceBergen Drug Corporation, Cardinal Health, and McKesson Corporation made up 26.8%, 23.1%, and 21.6%, respectively, of our gross product revenue during the twelve months ended December 31, 2022.

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	$	—	$	—	$	—	$	—
Activity related to 2022 sales	825		2,721		2,502		6,048
Credits/deductions issued	(683)		(1,277)		(1,244)		(3,204)
Balance as of December 31, 2022	$	142	$	1,444	$	1,258	$	2,844

There were no product sales or gross-to-net accruals during the twelve months ended December 31, 2021 or 2020.

- 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.

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-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (d)
-URI https://asc.fasb.org/extlink&oid=126920106&loc=SL49130554-203045

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 15
-URI https://asc.fasb.org/extlink&oid=126920106&loc=SL49130558-203045

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (c)
-URI https://asc.fasb.org/extlink&oid=126920106&loc=SL49130554-203045

+ Details

Collaboration and Licensing Agreements - Deferred Revenue (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Deferred revenue - current
Beginning balance	$ 0
Ending balance	4,211	$ 0
Deferred revenue - non-current
Beginning balance	4,727
Ending balance	9,025	4,727
2019 KKC Agreement
Deferred revenue - current
Beginning balance	0	4,177
Increases due to cash received, excluding amounts recognized as revenue during the period		0
Increases due to amounts reclassified from non-current, to be recognized in the next twelve months		0
Increases to amounts invoiced, for which cash has not yet been received		0
Decreases due to revenue recognized in the period for which cash has been received		(4,177)
Ending balance	0	0
Deferred revenue - non-current
Beginning balance	4,727
Increases due to cash received during the period	7,794
Increases to amounts invoiced, for which cash has not yet been received	465
Increase due to unbilled prepayments recorded during the period	0
Decreases due to amounts reclassified as current, to be recognized in the next twelve months	(3,961)
Ending balance	9,025	4,727
2017 KKC Agreement
Deferred revenue - current
Beginning balance	0
Increases due to cash received, excluding amounts recognized as revenue during the period	42
Increases due to amounts reclassified from non-current, to be recognized in the next twelve months	3,961
Increases to amounts invoiced, for which cash has not yet been received	208
Decreases due to revenue recognized in the period for which cash has been received	0
Ending balance	4,211	0
Deferred revenue - non-current
Beginning balance	$ 4,727	0
Increases due to cash received during the period		3,242
Increases to amounts invoiced, for which cash has not yet been received		0
Increase due to unbilled prepayments recorded during the period		1,485
Decreases due to amounts reclassified as current, to be recognized in the next twelve months		0
Ending balance		$ 4,727

Net Loss Per Share

12 Months Ended

Dec. 31, 2022

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, less shares subject to repurchase, 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, 2022, 2021 and 2020, 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,
	2022		2021		2020
Numerator:
Net loss	$	(67,207)	$	(158,165)	$	(94,313)
Denominator:
Weighted average common shares outstanding - basic and diluted	158,690		104,206		89,582
Net loss per share - basic and diluted	$	(0.42)	$	(1.52)	$	(1.05)

For the years ended December 31, 2022, 2021 and 2020, 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,
	2022	2021	2020
Options to purchase common stock	13,522	11,871	9,247
Restricted stock units	2,694	1,602	26
ESPP shares issuable	166	207	94
Warrants to purchase common stock	—	—	932
Total	16,382	13,680	10,299

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, 2022, 2021 and 2020, was approximately 0.6 million, 1.1 million and 2.1 million, respectively.

Summary of Significant Accounting Policies - Narrative (Details) - USD ($)	1 Months Ended	12 Months Ended
	Jun. 30, 2015	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Summary of significant accounting policies
Impairment loss of long-lived assets		$ 0	$ 0	$ 0
Minimum
Summary of significant accounting policies
Estimated useful lives		3 years
Payment terms		30 days
Maximum
Summary of significant accounting policies
Estimated useful lives		5 years
Payment terms		60 days
AstraZeneca
Summary of significant accounting policies
Aggregate cost of revenue recognized		$ 15,300,000
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	$ 75,000,000

Restructuring	12 Months Ended
Restructuring	Dec. 31, 2022
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 new drug application (“NDA”) for XPHOZAH and following the conclusion of an End of Review Type A meeting with the 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. Impacted employees were eligible to receive severance benefits and additional Company funded COBRA premiums, contingent upon an impacted employee’s execution (and non-revocation) of a separation agreement, which included a general release of claims against us. In connection with restructuring, we incurred restructuring charges of $6.2 million, which were recorded during the twelve months 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. Most of the cash payments related to the reduction in workforce were disbursed during the twelve months ended December 31, 2021. We reported the remaining estimated restructuring liability of zero and $0.5 million as accrued compensation and benefits in our balance sheet as of December 31, 2022 and 2021, respectively. In addition, in October, 2021, our Board approved, and management has implemented a retention program consisting of cash payments and grants of RSUs to our employees, including our executives, not impacted by the reduction in force.

STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Deficit	Accumulated Other Comprehensive (Loss) Income
Balance (in shares) at Dec. 31, 2019		88,817,741
Balance at Dec. 31, 2019	$ 186,655	$ 9	$ 647,078	$ (460,452)	$ 20
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock under employee stock purchase plan (in shares)		169,931
Issuance of common stock under employee stock purchase plan	834		834
Issuance of common stock for services (in shares)		42,403
Issuance of common stock for services	310		310
Issuance of common stock upon exercise of options (in shares)		445,942
Issuance of common stock upon exercise of options	1,020		1,020
Issuance of common stock upon vesting of restricted stock units (in shares)		866,528
Issuance of common stock in at the market offering (in shares)		3,257,430
Issuance of common stock in at the market offering	21,047		21,047
Stock-based compensation	10,583		10,583
Unrealized losses on available-for-sale securities	(24)				(24)
Net loss	(94,313)			(94,313)
Balance (in shares) at Dec. 31, 2020		93,599,975
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 losses on available-for-sale securities	(2)				(2)
Net loss	(158,165)			(158,165)
Balance (in shares) at Dec. 31, 2021		130,182,535
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)	14,000	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 losses on available-for-sale securities	(48)				(48)
Net loss	(67,207)			(67,207)
Balance (in shares) at Dec. 31, 2022		198,575,016
Balance at Dec. 31, 2022	$ 98,329	$ 20	$ 878,500	$ (780,137)	$ (54)

Restructuring (Details) - USD ($) $ in Millions	12 Months Ended
Restructuring (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Restructuring Cost and Reserve [Line Items]
Restructuring charges		$ 6.2
Estimated restructuring liability	$ 0.0	$ 0.5
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

Equity Incentive Plans - Unrecognized Stock-Based Compensation (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2022 USD ($)
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized Compensation Expense	$ 9,434
Average Remaining Vesting Period (Years)	2 years 6 months 18 days
RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized Compensation Expense	$ 2,937
Average Remaining Vesting Period (Years)	2 years 11 months 12 days
ESPP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized Compensation Expense	$ 22
Average Remaining Vesting Period (Years)	2 months 12 days

Accrued Expenses and Other Current Liabilities

12 Months Ended

Dec. 31, 2022

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,
	2022		2021
Accrued payments due to AstraZeneca	$	3,385	$	69
Accrued gross to net revenue liabilities	1,991		—
Accrued contract manufacturing expenses	1,657		2,485
Derivative liability for exit fees	1,656		698
Accrued non-clinical research and development expenses	1,188		265
Accrued professional and consulting services	808		597
Accrued sales and marketing expenses	587		256
Accrued clinical expenses	223		2,522

Other	885		474
Total accrued expenses and other current liabilities	$	12,380	$	7,366

Summary of Significant Accounting Policies - Accounts Receivable (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Accounts receivable	$ 7,733	$ 502
Collaborators
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Accounts receivable	700	$ 500
Commercial customers
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Accounts receivable	$ 7,000

Equity Incentive Plans - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands		1 Months Ended					6 Months Ended	12 Months Ended
	Jun. 18, 2014	Dec. 31, 2022	Jan. 31, 2022	Jan. 31, 2021	Sep. 30, 2020	Jul. 31, 2018	Jun. 30, 2014	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Nov. 30, 2016
Equity Incentive Plans
Common stock closing price (in dollars per share)		$ 2.85						$ 2.85
Intrinsic value of options exercised								$ 30	$ 1,700	$ 2,700
Weighted-average grant-date estimated fair value of options granted (in dollars per share)								$ 0.63	$ 3.92	$ 4.82
Issuance of common stock for services								$ 390	$ 190	$ 310
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
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)											1,000,000
Share of common stock subject to issued inducement grants		2,100,000						2,100,000
ESPP
Equity Incentive Plans
Common stock reserved for future issuance (in shares)	200,000
Potential increase in shares reserved as a percentage of shares outstanding	1.00%
Dividend yield								0.00%	0.00%	0.00%
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
PRSUs
Equity Incentive Plans
Number of shares granted						900,000				30,000
Number of shares vested					900,000
RSUs
Equity Incentive Plans
Estimated fair value of RSUs vested								$ 2,600	$ 800	$ 0
Number of shares granted								2,195,000
Number of shares vested								3,956,000
Board of directors
Equity Incentive Plans
Issuance of common stock for services (in shares)								700,000	26,000	42,000
Issuance of common stock for services								$ 400	$ 200	$ 300

Product Revenue, Net (Tables)

12 Months Ended

Dec. 31, 2022

Revenue from Contract with Customer [Abstract]

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	$	—	$	—	$	—	$	—
Activity related to 2022 sales	825		2,721		2,502		6,048
Credits/deductions issued	(683)		(1,277)		(1,244)		(3,204)
Balance as of December 31, 2022	$	142	$	1,444	$	1,258	$	2,844

Leases (Tables)

12 Months Ended

Dec. 31, 2022

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	2022			2021
Right-of-use assets	$	9,295		$	12,752

Current portion of lease liabilities	3,894			3,492
Operating lease liability, net of current portion	5,855			9,748
Total	$	9,749		$	13,240

Weighted-average remaining life (years)	2.4			3.4
Weighted-average discount rate	6.8		%	6.9		%

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,
	2022		2021		2020
Operating lease expense	$	4,257	$	3,671	$	2,608
Cash paid for operating lease	$	4,292	$	3,438	$	3,065

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, 2022 (in thousands):


Ending December 31,
2023	$	4,440
2024	4,589
2025	1,321
2026	252
Thereafter	—
Total undiscounted operating lease payments	10,602
Imputed interest expenses	(853)
Total operating lease liabilities	9,749
Less: Current portion of operating lease liability	(3,894)
Operating lease liability, net of current portion	$	5,855

Geographic Information and Concentrations - Revenue by Geographical Area (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	$ 52,158	$ 10,097	$ 7,571
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	15,600	0	0
Asia Pacific
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	36,527	10,084	6,765
North America
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	$ 31	$ 13	$ 806

- 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
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 30
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e8906-108599

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 40
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e9031-108599

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 41
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e9038-108599

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e8933-108599

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e8933-108599

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=126920106&loc=SL49130543-203045

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 22
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e8736-108599

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 22
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e8736-108599

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 42
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e9054-108599

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 5
-URI https://asc.fasb.org/extlink&oid=126920106&loc=SL49130545-203045

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 924
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 11.L)
-URI https://asc.fasb.org/extlink&oid=6472922&loc=d3e499488-122856

+ Details

Property and Equipment, Net (Tables)

12 Months Ended

Dec. 31, 2022

Property, Plant and Equipment [Abstract]

Schedule of Property and Equipment

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


	December 31,
	2022		2021
Laboratory equipment	$	46	$	7,474
Office equipment and furniture	2,089		2,034
Leasehold improvements	8,745		8,745
Property and equipment, gross	10,880		18,253
Less: accumulated depreciation	(9,657)		(15,891)
Total property and equipment, net	$	1,223	$	2,362

Leases

12 Months Ended

Dec. 31, 2022

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 have recorded a right-of-use operating lease asset 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.

We have recorded a right-of-use operating lease asset located in Waltham, Massachusetts under a lease agreement entered into in October 2018. The office space consisted of 3,520 square feet with the lease terminating in September 2021. We did not renew the lease at our original Waltham, Massachusetts facility. During April 2021 and May 2021, we recorded right-of-use operating lease assets for a new facility in Waltham, Massachusetts under a lease agreement entered into during December 2020 with lease commencement dates during April and May 2021. The office space consists of 12,864 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 since currently 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.

We have recorded a right-of-use operating lease asset 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 since currently 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	2022			2021
Right-of-use assets	$	9,295		$	12,752

Current portion of lease liabilities	3,894			3,492
Operating lease liability, net of current portion	5,855			9,748
Total	$	9,749		$	13,240

Weighted-average remaining life (years)	2.4			3.4
Weighted-average discount rate	6.8		%	6.9		%

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


	Year Ended December 31,
	2022		2021		2020
Operating lease expense	$	4,257	$	3,671	$	2,608
Cash paid for operating lease	$	4,292	$	3,438	$	3,065

The following table summarizes our undiscounted cash payment obligations for our operating lease liabilities as of December 31, 2022 (in thousands):


Ending December 31,
2023	$	4,440
2024	4,589
2025	1,321
2026	252
Thereafter	—
Total undiscounted operating lease payments	10,602
Imputed interest expenses	(853)
Total operating lease liabilities	9,749
Less: Current portion of operating lease liability	(3,894)
Operating lease liability, net of current portion	$	5,855

Cash, Cash Equivalents and Short-Term Investments

12 Months Ended

Dec. 31, 2022

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, 2022 and 2021 are summarized below (in thousands):


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


	December 31, 2021
			Gross Unrealized
	Amortized Cost		Gains		Losses		Fair Value
Cash and cash equivalents:
Cash	$	1,253	$	—	$	—	$	1,253
Money market funds	71,175		—		—		71,175
Commercial Paper	—		—		—		—
Corporate bonds	—		—		—		—
Total cash and cash equivalents	72,428		—		—		72,428
Short-term investments
Commercial paper	$	31,936	$	1	$	(2)	$	31,935
Corporate bonds	7,025		—		(3)		7,022

Asset backed securities	5,306		—		(2)		5,304
Total short-term investments	44,267		1		(7)		44,261


Total cash equivalents and investments	$	116,695	$	1	$	(7)	$	116,689

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 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, 2022 and 2021 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, 2022 and 2021 were not material. We determined that none of our available-for-sale securities were other-than-temporarily impaired as of December 31, 2022 and 2021, 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.

Derivative Liabilities

12 Months Ended

Dec. 31, 2022

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) FDA approval of XPHOZAH and (ii) 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 will expire on May 16, 2028. We concluded that the 2018 Exit Fee is a freestanding derivative which should be accounted for at fair value on a recurring basis. The estimated fair value of the 2018 Exit Fee is recorded as a derivative liability and included in accrued expense and other current liabilities on the accompanying balance sheets. As of December 31, 2022 and 2021, the estimated fair value of the 2018 Exit Fee was $1.2 million and $0.7 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 derivative instrument include: (i) our estimates of both the probability and timing of a potential $1.5 million payment to Solar Capital Ltd. and Western Alliance Bank as a result of the FDA approvals, and (ii) a discount rate which was derived from our estimated cost of debt, adjusted with current LIBOR. Generally, increases or decreases in the probability of occurrence would result in a directionally similar impact in the fair value measurement of the derivative instrument and it is estimated that a 10% increase (decrease), not to exceed 100%, in the probability of occurrence would result in a fair value fluctuation of no more than $0.1 million.

2022 Exit Fee

In February 2022, in connection with entering into the 2022 Loan Agreement, we entered into an agreement, whereby we agreed to pay an exit fee in the amount of 2% of the 2022 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. Notwithstanding the prepayment or termination of the 2022 Loan, 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, 2022, the estimated fair value of the 2022 Exit Fee is $0.4 million.

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 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 is dependent upon (a) approval by the FDA for our NDA for the control of serum phosphorus in adult patients with CKD on dialysis by December 31, 2022, and (b) achievement of certain product revenue milestone targets. 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 were as follows for the years ended December 31, 2022, 2021 and 2020 (in thousands):


	2022		2021		2020
Balance at January 1,	$	698	$	1,376	$	969
2022 Exit Fee addition at fair value	375		—		—
Changes in estimated fair value:
2018 Exit Fee	510		(678)		407
2022 Exit Fee	73		—		—
Fair value of exit fee derivative liabilities at December 31,	$	1,656	$	698	$	1,376

Borrowings - Future Payment Obligations (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Future payment obligations
2023	$ 0
2024	7,639
2025	9,167
2026	9,167
2027	2,888
Thereafter	0
Total repayment obligations	28,861
Less: Unamortized discount and debt issuance costs	(1,110)
Less: Unaccreted value of final fee	(1,040)
Long-term debt	26,711
Less: Current portion of long-term debt	(26,711)	$ (32,264)
Long-term debt, net of current portion	$ 0

Collaboration and Licensing Agreements (Tables)

12 Months Ended

Dec. 31, 2022

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. The December 31, 2022 deferred revenue current and non-current balances are attributable entirely to prepayments for product supply under the 2017 KKC Agreement, while the December 31, 2021 current deferred revenue balance is attributable to the 2019 KKC Agreement and the December 31, 2021 non-current deferred revenue balance is attributable prepayments for product supply under the 2017 KKC Agreement (in thousands):


Deferred revenue - current	2022		2021
Balance at Balance at January 1,	$	—	$	4,177
Increases due to cash received, excluding amounts recognized as revenue during the period	42		—
Increases due to amounts reclassified from non-current, to be recognized in the next twelve months	3,961		—
Increases to amounts invoiced, for which cash has not yet been received	208		—

Decreases due to revenue recognized in the period for which cash has been received	—		(4,177)

Balance at December 31,	$	4,211	$	—


Deferred revenue - non-current	2022		2021
Balance at Balance at January 1,	$	4,727	$	—
Increases due to cash received during the period	7,794		3,242
Increases to amounts invoiced, for which cash has not yet been received	465		—
Increase due to unbilled prepayments recorded during the period	—		1,485
Decreases due to amounts reclassified as current, to be recognized in the next twelve months	(3,961)		—

Balance at December 31,	$	9,025	$	4,727

Income Taxes - Reconciliation of Effective Tax Rate (Details)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Income tax at the federal statutory rate	21.00%	21.00%	21.00%
State taxes, net of federal benefit	1.90%	0.40%	0.70%
Tax credits	1.50%	1.00%	1.30%
Executive compensation disallowed under IRC Sec 162(m)	(1.60%)	(1.10%)	(0.50%)
Stock based compensation	(2.30%)	(1.30%)	(0.10%)
Other	(0.80%)	0.00%	(0.10%)
Change in valuation allowance	(19.70%)	(20.00%)	(22.30%)
Income tax provision	0.00%	0.00%	0.00%

Income Taxes - Reconciliation of Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Reconciliation of Unrecognized Tax Benefits
Balance at beginning of year	$ 24,426	$ 23,624	$ 24,538
Additions based on tax positions related to current year	460	1,613	474
Subtractions related to lapse of statute of limitation	(811)	0	0
Subtractions based on tax positions related to prior year	0	(811)	(1,388)
Balance at end of year	$ 24,075	$ 24,426	$ 23,624

Income Taxes - Narrative (Details) $ in Millions	12 Months Ended
Income Taxes - Narrative (Details) $ in Millions	Dec. 31, 2022 USD ($)
Income Tax Disclosure [Line Items]
Increase in valuation allowance	$ 20.5
Federal
Income Tax Disclosure [Line Items]
Net operating loss carryforwards	433.6
Net operating loss carryforwards, indefinite	283.4
Federal \| Research and development tax credit
Income Tax Disclosure [Line Items]
Tax credit carryforwards	17.2
Foreign
Income Tax Disclosure [Line Items]
Tax credit carryforwards	1.2
State \| California
Income Tax Disclosure [Line Items]
Net operating loss carryforwards	89.8
State \| California \| Research and development tax credit
Income Tax Disclosure [Line Items]
Tax credit carryforwards	8.6
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	$ 19.0

Derivative Liabilities (Tables)

12 Months Ended

Dec. 31, 2022

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Schedule of Changes in Fair Value of Derivative Liabilities


	2022		2021		2020
Balance at January 1,	$	698	$	1,376	$	969
2022 Exit Fee addition at fair value	375		—		—
Changes in estimated fair value:
2018 Exit Fee	510		(678)		407
2022 Exit Fee	73		—		—
Fair value of exit fee derivative liabilities at December 31,	$	1,656	$	698	$	1,376

Equity Incentive Plans - Employee Stock Purchase Plan (Details) - ESPP $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2022 USD ($) $ / shares shares
Shares Available for Grant
Shares available for grant, beginning (shares)	899,000
Shares purchased (shares)	(308,000)
Shares available for grant, ending (shares)	591,000
Number of Shares Purchased
Purchased, beginning (shares)	1,048,000
Shares purchased (shares)	308,000
Purchased, ending (shares)	1,356,000
Purchase Price per Share (in dollars per share) \| $ / shares	$ 0.63
Gross Proceeds \| $	$ 195

Equity Incentive Plans - Valuation Assumptions for ESPP (Details) - ESPP	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (years)	6 months	6 months	6 months
Expected volatility	97.20%	123.00%	79.40%
Risk-free interest rate	1.90%	0.70%	0.50%
Dividend yield	0.00%	0.00%	0.00%

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

12 Months Ended

Dec. 31, 2022

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, 2022 and 2021 are summarized below (in thousands):


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


	December 31, 2021
			Gross Unrealized
	Amortized Cost		Gains		Losses		Fair Value
Cash and cash equivalents:
Cash	$	1,253	$	—	$	—	$	1,253
Money market funds	71,175		—		—		71,175
Commercial Paper	—		—		—		—
Corporate bonds	—		—		—		—
Total cash and cash equivalents	72,428		—		—		72,428
Short-term investments
Commercial paper	$	31,936	$	1	$	(2)	$	31,935
Corporate bonds	7,025		—		(3)		7,022

Asset backed securities	5,306		—		(2)		5,304
Total short-term investments	44,267		1		(7)		44,261


Total cash equivalents and investments	$	116,695	$	1	$	(7)	$	116,689

Property and Equipment, Net - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Property, Plant and Equipment [Abstract]
Depreciation and amortization expense	$ 700	$ 1,400	$ 1,800
Sale of property, plant and equipment	500
Proceeds from sale of property and equipment	1,798	$ 0	$ 0
Gain on disposition of property plant equipment	$ 1,300

Product Revenue, Net - Narrative (Details) - USD ($)	12 Months Ended
Product Revenue, Net - Narrative (Details) - USD ($)	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Disaggregation of Revenue [Line Items]
Revenue	$ 52,158,000	$ 10,097,000	$ 7,571,000
Contract with customer product sales gross to net accruals		0	0
Gross product revenue \| Customer \| AmerisourceBergen Drug Corporation
Disaggregation of Revenue [Line Items]
Concentration risk (percent)	26.80%
Gross product revenue \| Customer \| Cardinal Health
Disaggregation of Revenue [Line Items]
Concentration risk (percent)	23.10%
Gross product revenue \| Customer \| McKesson Corporation
Disaggregation of Revenue [Line Items]
Concentration risk (percent)	21.60%
IBSRELA
Disaggregation of Revenue [Line Items]
Revenue	$ 15,600,000
Product sales, net
Disaggregation of Revenue [Line Items]
Revenue	$ 15,600,000	$ 0	$ 0

Inventory

12 Months Ended

Dec. 31, 2022

Inventory Disclosure [Abstract]

Inventory

INVENTORY

We began capitalizing inventory during the fourth quarter of 2021, at which time our intent to commercialize IBSRELA was established and we commenced preparation for the commercial launch of IBSRELA. Inventory as of December 31, 2021 was not material. Inventory as of December 31, 2022 consisted of the following (in thousands):


	December 31, 2022
Raw materials	$	22,299
Work in process	5,324
Finished goods	723
Total	$	28,346
Reported as:
Inventory	$	3,282
Inventory, non-current	25,064
Total	$	28,346

Prepaid commercial manufacturing of $13.6 million and $9.4 million as of December 31, 2022 and 2021, respectively, consisted of prepayments to third party contract manufacturing organizations for the manufacture of IBSRELA for production orders which we expect work to commence within the next 12 months.

STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Operating activities
Net loss	$ (67,207)	$ (158,165)	$ (94,313)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization expense	1,144	2,807	2,541
Non-cash lease expense	3,457	3,085	2,147
Stock-based compensation	10,750	12,039	10,583
Change in derivative liabilities	583	(678)	407
Debt refinancing costs	102	0	0
Gain on sale of equipment	(1,260)	0	0
Non-cash interest expense	1,962	283	413
Changes in operating assets and liabilities:
Unbilled revenue	0	0	750
Accounts receivable	(7,231)	(502)	0
Inventory	(28,346)	0	0
Prepaid commercial manufacturing	(4,161)	(9,406)	0
Prepaid expenses and other assets	2,299	502	(4,653)
Accounts payable	6,582	(1,349)	3,439
Accrued compensation and benefits	2,126	(250)	1,219
Operating lease liabilities	(3,491)	(2,853)	(2,604)
Accrued and other liabilities	4,138	1,386	(1,000)
Deferred revenue	8,509	550	(364)
Net cash used in operating activities	(70,044)	(152,551)	(81,435)
Investing activities
Proceeds from maturities and redemptions of investments	67,000	125,550	119,734
Purchases of investments	(50,328)	(72,735)	(150,852)
Proceeds from sale of property and equipment	1,798	0	0
Purchases of property and equipment	(55)	(1,867)	(324)
Net cash provided by (used in) investing activities	18,415	50,948	(31,442)
Financing activities
Proceeds from 2022 Loan, net of issuance costs	26,971	0	0
Payments for 2018 Loan, net of costs	(33,038)	(19,444)	(125)
Proceeds from the sale of future royalties, net of issuance costs	9,581	0	0
Proceeds from issuance of common stock in at the market offering, net of issuance costs	71,625	101,146	21,047
Proceeds from issuance of common stock under equity incentive and stock purchase plans	202	1,403	1,854
Payments for taxes related to net share settlement of equity awards	0	(106)	0
Net cash provided by financing activities	75,341	82,999	22,776
Net increase (decrease) in cash and cash equivalents	23,712	(18,604)	(90,101)
Cash and cash equivalents at beginning of period	72,428	91,032	181,133
Cash and cash equivalents at end of period	96,140	72,428	91,032
Supplementary disclosure of cash flow information:
Cash paid for interest	2,901	3,469	4,200
Cash paid for income taxes	6	4	1
Supplementary disclosure of non-cash activities:
Right-of-use assets obtained in exchange for lease obligations	0	1,604	450
Issuance of common stock for services	390	190	310
Issuance of derivative in connection with issuance of loan payable	$ 375	$ 0	$ 0

Equity Incentive Plans (Tables)

12 Months Ended

Dec. 31, 2022

Share-Based Payment Arrangement [Abstract]

Schedule of Stock Option Activity

A summary of our stock option activity and related information during the twelve months ended December 31, 2022 is as follows (in thousands, except per share dollar amounts and years):


	Shares Available for Grant	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, 2021	4,974	10,417	$	7.00
Options authorized	10,207	—	$	—
Options granted	(5,392)	5,392	$	0.96
Options exercised	—	(14)	$	0.99
Options canceled	1,832	(1,832)	$	5.80
Issuance of common stock for services	(712)	—	$	—

Balance at December 31, 2022	10,909	13,963	$	4.83	7.3	$	10,156
Vested and expected to vest at December 31, 2022		13,963	$	4.83	7.3	$	10,156
Exercisable at December 31, 2022		8,283	$	6.32	6.3	$	2,727

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,
	2022		2021		2020
Expected term (years)	4.9		5.0		6.0
Expected volatility	92.1	%	77.0	%	83.0	%
Risk-free interest rate	2.2	%	4.7	%	1.1	%
Dividend yield	—	%	—	%	—	%

Schedule of Restricted Stock Units Activity

A summary of our RSUs activity and related information for the twelve months ended December 31, 2022 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, 2021	3,529	$	2.04
Granted	2,195	$	0.89
Vested	(3,956)	$	1.34
Forfeited	(362)	$	2.23
Non-vested restricted stock units at December 31, 2022	1,406	$	2.17

Schedule of Employee Stock Purchase Plan Activity

A summary of our ESPP activity during the twelve months ended December 31, 2022 is as follows (in thousands, except per share dollar amounts):


	Shares Available for Grant	Number of Shares Purchased	Average Purchase Price per Share		Gross Proceeds
Balance at December 31, 2021	899	1,048
Shares purchased	(308)	308	$	0.63	$	195
Balance at December 31, 2022	591	1,356

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,
	2022		2021		2020
Expected term (years)	0.5		0.5		0.5
Expected volatility	97.2	%	123.0	%	79.4	%
Risk-free interest rate	1.9	%	0.7	%	0.5	%
Dividend yield	—	%	—	%	—	%

Schedule of Stock-Based Compensation Recognized

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


	Year Ended December 31,
	2022		2021		2020
Selling, general and administrative	$	7,525	$	7,923	$	6,522
Research and development	3,225		4,116		4,061
Total	$	10,750	$	12,039	$	10,583

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, 2022 is as follows (dollars in thousands):


	December 31, 2022
	Unrecognized Compensation Expense		Average Remaining Vesting Period (Years)
Stock options grant	$	9,434	2.55
RSU grants	$	2,937	2.95
ESPP	$	22	0.2

BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Current assets:
Cash and cash equivalents	$ 96,140	$ 72,428
Short-term investments	27,769	44,261
Accounts receivable	7,733	502
Inventory	3,282	0
Prepaid commercial manufacturing	13,567	9,406
Prepaid expenses and other current assets	5,112	7,052
Total current assets	153,603	133,649
Property and equipment, net	1,223	2,362
Inventory, non-current	25,064	0
Right-of-use assets	9,295	12,752
Other assets	881	1,150
Total assets	190,066	149,913
Current liabilities:
Accounts payable	10,859	4,277
Accrued compensation and benefits	7,548	5,422
Current portion of operating lease liability	3,894	3,492
Current portion of long-term debt	26,711	32,264
Deferred revenue	4,211	0
Accrued expenses and other current liabilities	12,380	7,366
Total current liabilities	65,603	52,821
Operating lease liability, net of current portion	5,855	9,748
Deferred revenue, non-current	9,025	4,727
Deferred royalty obligation related to the sale of future royalties	11,254	0
Total liabilities	91,737	67,296
Commitments and contingencies
Stockholders’ equity:
Preferred stock, $0.0001 par value; 5,000,000 shares authorized; no shares issued and outstanding as of December 31, 2022 and December 31, 2021, respectively.	0	0
Common stock, $0.0001 par value; 300,000,000 shares authorized; 198,575,016 and 130,182,535 shares issued and outstanding as of December 31, 2022 and December 31, 2021, respectively.	20	13
Additional paid-in capital	878,500	795,540
Accumulated deficit	(780,137)	(712,930)
Accumulated other comprehensive loss	(54)	(6)
Total stockholders’ equity	98,329	82,617
Total liabilities and stockholders’ equity	$ 190,066	$ 149,913

Property and Equipment, Net

12 Months Ended

Dec. 31, 2022

Property, Plant and Equipment [Abstract]

Property and Equipment, Net

PROPERTY AND EQUIPMENT, NET

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


	December 31,
	2022		2021
Laboratory equipment	$	46	$	7,474
Office equipment and furniture	2,089		2,034
Leasehold improvements	8,745		8,745
Property and equipment, gross	10,880		18,253
Less: accumulated depreciation	(9,657)		(15,891)
Total property and equipment, net	$	1,223	$	2,362

We recognized depreciation expense in the amount of $0.7 million, $1.4 million, and $1.8 million for the years ended December 31, 2022, 2021 and 2020, 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.

Geographic Information and Concentrations (Tables)

12 Months Ended

Dec. 31, 2022

Risks and Uncertainties [Abstract]

Schedule of Revenue by Geographic Areas

A summary of our revenue by geographic areas for the years ended December 31, 2022, 2021 and 2020, is as follows (in thousands):


	Year Ended December 31,
	2022		2021		2020
United States (1)	$	15,600	$	—	$	—
International:
Asia Pacific (2)	36,527		10,084		6,765
North America (3)	31		13		806
Total revenue	$	52,158	$	10,097	$	7,571

(1)Revenues from the United States are comprised of amounts earned from sales of IBSRELA.

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

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

Schedule of Customers and Collaboration Partnerships

Revenues from Customers and collaboration partnerships accounting for more than 10% of total revenues during the years ended December 31, 2022, 2021 and 2020 were as follows:


	Year Ended December 31,
	2022		2021		2020
KKC	70.0	%	100	%	89	%
Knight	0.1	%	—	%	11	%

AmerisourceBergen Drug Corporation	11.1	%	—	%	—	%

Summary of Significant Accounting Policies	12 Months Ended
Summary of Significant Accounting Policies	Dec. 31, 2022
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, 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, 2022, we had cash and short-term investments of approximately $123.9 million. We have incurred operating losses since inception in 2007 and our accumulated deficit as of December 31, 2022 is $780.1 million. Our current level of cash and short-term investments alone is not sufficient to meet our plans for the next twelve months following the issuance of these financial statements on March 2, 2023. These factors raise substantial doubt regarding our ability to continue as a going concern for a period of one year from the issuance of these financial statements. We plan to address our operating cash flow requirements with our current cash and short-term investments, cash generated from product sales of IBSRELA, and if approved, cash generated from sales of XPHOZAH, our potential receipt of anticipated milestones payments from our collaboration partners, our potential receipt of anticipated payments from our Japanese collaboration partner under the second amendment to our License Agreement, with additional financing sources and through the implementation of cash preservation activities to reduce or defer discretionary spending. There are no assurances that our efforts to meet our operating cash flow requirements will be successful. If our current cash and short-term investments as well as our plans to meet our operating cash flow requirements are not sufficient to fund necessary expenditures and meet our obligations for at least the next twelve months following the issuance of these financial statements, our liquidity, financial condition and business prospects will be materially affected. These financial statements have been prepared on a going concern basis and do not include any adjustments to the amounts and classification of assets and liabilities that may be necessary in the event that we can no longer continue as a going concern. 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 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 its 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 value 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. For the years ending December 31, 2022, 2021 and 2020 we have recognized no impairment losses. 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 is reported net of allowances for returns, chargebacks and contractual off-invoice and prompt-pay discounts offered to our customers. Our estimate of the allowance for doubtful accounts is based on an evaluation of the aging of our receivables. Trade receivable balances are written off against the allowance when it is probable that the receivable will not be collected. To date, we have determined that an allowance for doubtful accounts is not required. 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. As of December 31, 2021 our accounts receivable balance was comprised of $0.5 million from our collaborators. 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. Inventory is stated at the lower of cost or estimated net realizable value with cost determined under the first-in first-out 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 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, 2022, 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 U.S. Food and Drug Administration (“FDA”) in September 2019 to market IBSRELA in the U.S.. We began selling IBSRELA in the U.S. in March 2022. We distribute IBSRELA principally through major wholesalers, specialty pharmacies and group purchasing organizations ("GPOs") (collectively, our "Customers"). Our Customers subsequently sell IBSRELA 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 programs, 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 product launch. 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. 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 estimated utilization by types of contracted purchasers. 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 and 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. 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 it 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, it 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 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 our control or the control of 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 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 accounts receivable or 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 Revenue Cost of revenue consists of the cost of commercial goods sold to our Customers and international partners under product supply agreements as well as royalty expense 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 units recognized as revenue during the twelve months ended December 31, 2022 were expensed prior to the fourth quarter of 2021, at which time our intent to commercialize IBSRELA was established and we commenced preparation for the commercial launch of IBSRELA. Cost of revenue includes payments due to AstraZeneca, which under the terms of a termination agreement entered into in 2015 ("AZ 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 as a result of the development and commercialization of tenapanor or certain other NHE3 inhibitors. 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 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 $15.3 million as cost of revenue under the AZ Termination Agreement. 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 Research and Development Expenses We are required to estimate our accrued expenses at the end of each reporting period. 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 costs. The majority of our service providers submit invoices 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. Examples of estimated accrued research and development expenses include fees paid to: •contract research organizations ("CROs") in connection with clinical studies; •investigative sites in connection with clinical studies; •vendors related to product manufacturing, development and distribution of clinical supplies; and •vendors in connection with preclinical development activities. We record expenses related to clinical studies and manufacturing development activities based on our estimates of the services received and efforts expended pursuant to contracts with multiple CROs and manufacturing vendors that conduct and manage these activities on our behalf. The financial terms of these agreements are subject to negotiation, vary from contract to contract, and may result in uneven payment flows. There may be instances in which payments made to our vendors will exceed the level of services provided and result in a prepayment of the expense. Payments under some of these contracts depend on factors such as the successful enrollment of subjects and the completion of clinical trial milestones. In accruing service fees, we estimate the time period over which services will be performed, enrollment of subjects, number of sites activated and the level of effort to be expended in each period. If the actual timing of the performance of services or the level of effort varies from our estimate, we will adjust the accrued or prepaid expense balance accordingly. 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 The net proceeds we receive from the sale of certain future royalties are recorded as deferred royalty obligation related to the sale of future royalties on our balance sheets. As we earn royalties and remit those royalties pursuant to the agreement, the balance of the deferred royalty obligation will be effectively repaid over the life of agreement and non-cash interest expense related to the sale of future royalties is recorded using the effective interest method. To determine the amortization of our deferred royalty obligation, we are required to estimate the total amount of future royalty payments we expect to earn. There are a number of factors that could materially affect the amount and timing of royalty payments, most of which are not within our control. We periodically assess the amount of royalty payments we expect to receive which are subject to the agreement 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. 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. Restructuring We recognize restructuring charges related to reorganization plans that have been committed to by management when liabilities have been incurred. In connection with these activities, we record restructuring charges at fair value for, (a) contractual employee termination benefits when obligations are associated to services already rendered, rights to such benefits have vested, and payment of benefits is probable and can be reasonably estimated, (b) one-time employee termination benefits when management has committed to a plan of termination, the plan identifies the employees and their expected termination dates, the details of termination benefits are complete, it is unlikely changes to the plan will be made or the plan will be withdrawn and communication to such employees has occurred, and (c) contract termination costs when a contract is terminated before the end of its term. One-time employee termination benefits are recognized in their entirety when communication has occurred and future services are not required. If future services are required, the costs are recorded ratably over the remaining period of service. Contract termination costs to be incurred over the remaining contract term without economic benefit are recorded in their entirety when the contract is canceled. 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 We adopted Accounting Standards Update 2016-13, Financial Instruments - Credit Losses: Measurement of Credit Losses on Financial Instruments ("ASU 2016-13"), as of December 1, 2021 under the modified retrospective approach. ASU 2016-13 requires an entity to measure and recognize expected credit losses for certain financial instruments, including trade receivables, as an allowance that reflects the entity's current estimate of credit losses expected to be incurred. For available-for-sale debt securities with unrealized credit losses, the standard requires allowances to be recorded through net income instead of directly reducing the amortized cost of the investment under the previous other-than-temporary impairment model. The adoption of this standard did not have a material impact on our financial statements or a significant impact on our internal controls. Recent Accounting Pronouncements Not Yet Adopted There were various accounting standards and interpretations issued recently, none of which are expected to a have a material impact on our financial position, operations or cash flows.

Fair Value Measurements - Narrative (Details) - USD ($)	Dec. 31, 2022	Dec. 31, 2021
Fair Value Disclosures [Abstract]
Allowance for credit loss on available-for-sale debt securities	$ 0	$ 0

Cover - USD ($)	12 Months Ended
Cover - USD ($)	Dec. 31, 2022	Feb. 28, 2023	Jun. 30, 2022
Cover [Abstract]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2022
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	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	false
Entity Shell Company	false
Entity Public Float			$ 89,227,062
Entity Common Stock, Shares Outstanding		206,492,664
Entity Central Index Key	0001437402
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	FY
Amendment Flag	false
Documents Incorporated by Reference	Portions of the Registrant’s Definitive Proxy Statement for its 2023 Annual Meeting of Stockholders, which will be filed with the Commission within 120 days of December 31, 2022, the close of the Registrant’s 2022 fiscal year, are incorporated by reference into Part III of this Report.

Collaboration and Licensing Agreements - Narrative (Details) $ in Millions, ¥ in Billions	1 Months Ended					12 Months Ended				50 Months Ended	91 Months Ended
	Nov. 30, 2019 USD ($) segment item	Mar. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Nov. 30, 2017 USD ($)	Jun. 30, 2015 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2022 CAD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2022 JPY (¥)	Oct. 31, 2022 USD ($)	Apr. 30, 2022 USD ($) payment_tranche
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Total revenues						$ 52,158,000		$ 10,097,000	$ 7,571,000
Deferred revenue						4,211,000		0		$ 0	$ 4,211,000
Cost of revenue						4,117,000		1,000,000	145,000
Licensing revenue
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Total revenues						35,031,000		5,013,000	706,000
Product supply revenue
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Total revenues						1,527,000		907,000	1,501,000
2019 KKC Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Total revenues						0		4,200,000
Deferred revenue						0		0	$ 4,177,000	0	0
2017 KKC Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Deferred revenue						4,211,000		0		0	4,211,000
2017 KKC Agreement \| Licensing revenue
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Total revenues						35,000,000		5,000,000		$ 20,000,000
2017 KKC Agreement \| Product supply revenue
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Total revenues						1,500,000		900,000
Fosun Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Total revenues						0		0
Knight Agreement \| Licensing revenue
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Total revenues						31,000		13,000
Knight Agreement \| Product supply revenue
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Total revenues						0		0
Kyowa Kirin Co. Ltd \| 2019 KKC Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Upfront license fees	$ 10,000,000
First installment of upfront license fees	$ 5,000,000
Term of payment of license fee, first installment	30 days
Second installment of upfront license fees	$ 5,000,000
Term of agreement	2 years
Number of amendments \| segment	3
Kyowa Kirin Co. Ltd \| 2019 KKC Agreement \| Minimum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Number of separate collaborative agreements \| item	1
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
Potential commercialization milestones						64,600,000					64,600,000	¥ 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													$ 35,000,000
Fosun Pharma \| Fosun Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Upfront payment received			$ 12,000,000
Potential development and commercialization milestones						$ 110,000,000
Threshold percentage of net sales for tiered royalties						20.00%	20.00%
Knight \| Knight Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Upfront payment received		$ 2,300,000
Potential development and commercialization milestones						$ 16,300,000	$ 22.2
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
Cost of revenue						$ 3,600,000		$ 1,000,000			$ 15,300,000

STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Revenues:
Total revenues	$ 52,158,000	$ 10,097,000	$ 7,571,000
Operating expenses:
Cost of revenue	4,117,000	1,000,000	145,000
Research and development	35,201,000	91,140,000	65,053,000
Selling, general and administrative	76,599,000	72,303,000	33,153,000
Total operating expenses	115,917,000	164,443,000	98,351,000
Loss from operations	(63,759,000)	(154,346,000)	(90,780,000)
Interest expense	(3,400,000)	(4,502,000)	(5,099,000)
Non-cash interest expense related to the sale of future royalties	(1,673,000)	0	0
Other income, net	1,633,000	687,000	1,568,000
Loss before provision for income taxes	(67,199,000)	(158,161,000)	(94,311,000)
Provision for income taxes	8,000	4,000	2,000
Net loss	$ (67,207,000)	$ (158,165,000)	$ (94,313,000)
Net loss per share of common stock - basic (in dollars per share)	$ (0.42)	$ (1.52)	$ (1.05)
Net loss per share of common stock - diluted (in dollars per share)	$ (0.42)	$ (1.52)	$ (1.05)
Shares used in computing net loss per share - basic	158,690,083	104,205,645	89,582,138
Shares used in computing net loss per share - diluted	158,690,083	104,205,645	89,582,138
Comprehensive loss:
Net loss	$ (67,207,000)	$ (158,165,000)	$ (94,313,000)
Unrealized losses on available-for-sale securities	(48,000)	(2,000)	(24,000)
Comprehensive loss	(67,255,000)	(158,167,000)	(94,337,000)
Product sales, net
Revenues:
Total revenues	15,600,000	0	0
Product supply revenue
Revenues:
Total revenues	1,527,000	907,000	1,501,000
Licensing revenue
Revenues:
Total revenues	35,031,000	5,013,000	706,000
Collaborative development revenue
Revenues:
Total revenues	$ 0	$ 4,177,000	$ 5,364,000

Summary of Significant Accounting Policies - Liquidity (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Accounting Policies [Abstract]
Cash and short-term investments	$ 123,909	$ 116,689
Accumulated deficit	$ (780,137)	$ (712,930)

Income Taxes

12 Months Ended

Dec. 31, 2022

Income Tax Disclosure [Abstract]

Income Taxes

INCOME TAXES

The components of our provision for income taxes for the years ended December 31, 2022, 2021 and 2020, are as follows (in thousands):


	Year Ended December 31,
	2022		2021		2020
Current:
State	$	8	$	4	$	2
Foreign	—		—		—
Total current	8		4		2
Deferred:
Federal	—		—		—
Total deferred	—		—		—
Provision for income taxes	$	8	$	4	$	2

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


	Year Ended December 31,
	2022		2021		2020
Income tax at the federal statutory rate	21.0	%	21.0	%	21.0	%
State taxes, net of federal benefit	1.9		0.4		0.7
Tax credits	1.5		1.0		1.3
Executive compensation disallowed under IRC Sec 162(m)	(1.6)		(1.1)		(0.5)
Stock based compensation	(2.3)		(1.3)		(0.1)
Other	(0.8)		—		(0.1)
Change in valuation allowance	(19.7)		(20.0)		(22.3)
Income tax provision	—	%	—	%	—	%

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, 2022 and 2021 (in thousands):


	December 31,
	2022		2021
Deferred tax assets:
Amortization and depreciation	$	64,111	$	61,098
Net operating loss carryforwards	86,547		74,989
Tax credits	14,411		13,827
Stock-based compensation	5,244		4,054

Other	7,486		3,867
Gross deferred tax assets	177,799		157,835
Valuation allowance	(175,670)		(155,141)
Deferred tax assets net of valuation allowance	2,129		2,694
Deferred tax liabilities:
Right-of-use asset	(2,129)		(2,689)

Other	—		(5)
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, 2022. 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, 2022, December 31, 2021 and December 31, 2020, a full valuation allowance has been recorded against our net deferred tax asset. The valuation allowance increased by $20.5 million in 2022 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, 2022, we had net operating loss carryforwards for federal income tax purposes of approximately $433.6 million, of which approximately $283.4 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 $17.2 million that expire beginning in 2027, if not utilized, and foreign tax credit carryforwards of approximately $1.2 million that expire in 2027, if not utilized.

In addition, we had net operating loss carryforwards for California income tax purposes of approximately $89.8 million that expire beginning of 2030, if not utilized, and state research and development tax credit carryforwards of approximately $8.6 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 $19.0 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,
	2022		2021		2020
Balance at beginning of year	$	24,426	$	23,624	$	24,538
Additions based on tax positions related to current year	460		1,613		474
Subtractions related to lapse of statute of limitation	(811)		—		—
Subtractions based on tax positions related to prior year	—		(811)		(1,388)
Balance at end of year	$	24,075	$	24,426	$	23,624

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, 2022, 2021 and 2020, 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
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 21
-URI https://asc.fasb.org/extlink&oid=121826272&loc=d3e32857-109319

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SAB Topic 11.C)
-URI https://asc.fasb.org/extlink&oid=122134291&loc=d3e330215-122817

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 17
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=121826272&loc=d3e32809-109319

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB TOPIC 6.I.5.Q1)
-URI https://asc.fasb.org/extlink&oid=122134291&loc=d3e330036-122817

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 14
-URI https://asc.fasb.org/extlink&oid=121826272&loc=d3e32705-109319

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 270
-Section 50
-Paragraph 1
-URI https://asc.fasb.org/extlink&oid=6424409&loc=d3e44925-109338

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-URI https://asc.fasb.org/topic&trid=2144680

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=6424122&loc=d3e41874-109331

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(h)(2))
-URI https://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

+ Details

Product Revenue, Net - Gross-to-Net Sales Accruals (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2022 USD ($)
Gross-to-net sales accruals and reserves
Beginning balance	$ 0
Activity related to 2022 sales	6,048
Credits/deductions issued	(3,204)
Ending balance	2,844
Discounts and Chargebacks
Gross-to-net sales accruals and reserves
Beginning balance	0
Activity related to 2022 sales	825
Credits/deductions issued	(683)
Ending balance	142
Rebates, Wholesaler and GPO Fees
Gross-to-net sales accruals and reserves
Beginning balance	0
Activity related to 2022 sales	2,721
Credits/deductions issued	(1,277)
Ending balance	1,444
Copay and Returns
Gross-to-net sales accruals and reserves
Beginning balance	0
Activity related to 2022 sales	2,502
Credits/deductions issued	(1,244)
Ending balance	$ 1,258

Equity Incentive Plans - Stock Options (Details) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2022 USD ($) $ / shares shares
Number of Shares
Options issued and outstanding balance, beginning (shares)	10,417,000
Options granted (shares)	5,392,000
Options exercised (shares)	(14,000)
Options canceled (shares)	(1,832,000)
Options issued and outstanding balance, ending (shares)	13,963,000
Options vested and expected to vest (shares)	13,963,000
Options exercisable (shares)	8,283,000
Weighted-Average Exercise Price per Share
Options issued and outstanding balance, beginning (in dollars per share) \| $ / shares	$ 7.00
Options granted (in dollars per share) \| $ / shares	0.96
Options exercised (in dollars per share) \| $ / shares	0.99
Options canceled (in dollars per share) \| $ / shares	5.80
Options issued and outstanding balance, ending (in dollars per share) \| $ / shares	4.83
Options vested and expected to vest (in dollars per share) \| $ / shares	4.83
Options exercisable (in dollars per share) \| $ / shares	$ 6.32
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 3 months 18 days
Aggregate Intrinsic Value
Options issued and outstanding \| $	$ 10,156
Options vested and expected to vest \| $	10,156
Options exercisable \| $	$ 2,727
Stock options
Shares Available for Grant
Shares available for grant, beginning (shares)	4,974,000
Shares available for grant, effect of authorized (shares)	10,207,000
Shares available for grant, effect of granted (shares)	(5,392,000)
Shares available for grant, effect of canceled (shares)	1,832,000
Shares available for grant, effect of shares issued for services (shares)	(712,000)
Shares available for grant, ending (shares)	10,909,000

Borrowings - Narrative (Details) - USD ($)				1 Months Ended
Borrowings - Narrative (Details) - USD ($)	Feb. 23, 2022	Oct. 09, 2020	May 16, 2018	Oct. 31, 2020	Dec. 31, 2019	May 31, 2018	Dec. 31, 2022
Term Loans
Principal outstanding							$ 28,861,000
2022 Exit Fee
Term Loans
Exit fee (percent)	2.00%
Exit fee, net product revenue threshold	$ 100,000,000
Exit fee, term (in years)	10 years
Loan Agreement \| 2018 Term Loan
Term Loans
Term loan amount						$ 50,000,000
Net proceeds from loan						$ 49,300,000
Interest-only payment extension term (in months)		12 months		12 months	6 months
Principal outstanding			$ 25,000,000
Loan Agreement \| 2018 Term Loan \| LIBOR
Term Loans
Floating per annum rate (percent)			7.45%
Loan Agreement \| 2022 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%
Loan Agreement \| 2022 Term Loan \| LIBOR
Term Loans
Floating per annum rate (percent)	7.95%
Addition to floating per annum rate (percent)	0.10%
Loan Agreement \| 2022 Term Loan \| Prior to first anniversary of closing date
Term Loans
Prepayment premium (as a percent)	3.00%
Loan Agreement \| 2022 Term Loan \| After first anniversary through second anniversary of closing date
Term Loans
Prepayment premium (as a percent)	2.00%
Loan Agreement \| 2022 Term Loan \| After second anniversary to maturity date
Term Loans
Prepayment premium (as a percent)	1.00%
Loan Agreement \| Term Loan A
Term Loans
Net proceeds from loan	$ 27,500,000
Payment term	36 months
Closing fee	$ 200,000
Loan Agreement \| Term Loan B
Term Loans
Remaining funding based on milestone achievement	$ 22,500,000
Payment term	24 months
Future obligation upon loan funding or other events	$ 100,000

Subsequent Events (Details) - USD ($)		1 Months Ended
Subsequent Events (Details) - USD ($)	Feb. 09, 2023	Jan. 31, 2023	Jul. 31, 2020
Subsequent event \| Term B Loan \| Term loan
Subsequent Event [Line Items]
Floating per annum rate (percent)	7.95%
Addition to floating per annum rate (percent)	1.00%
Addition plus to floating per annum rate (percent)	0.022%
Subsequent event \| 2023 Open Market Sales Agreement
Subsequent Event [Line Items]
Offering sales commission (percent)		3.00%
Common stock
Subsequent Event [Line Items]
Maximum aggregate offering price			$ 250,000,000
Common stock \| Subsequent event
Subsequent Event [Line Items]
Maximum aggregate offering price		$ 250,000,000
Common stock \| Subsequent event \| 2023 Open Market Sales Agreement
Subsequent Event [Line Items]
Maximum aggregate offering price		$ 150,000,000

Income Taxes - Components of Provision for Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Current:
State	$ 8	$ 4	$ 2
Foreign	0	0	0
Total current	8	4	2
Deferred:
Federal	0	0	0
Total deferred	0	0	0
Provision for income taxes	$ 8	$ 4	$ 2

- Definition

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

+ References + Details

Derivative Liabilities - Changes in Fair Value (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
2018 Exit Fee
Change in Fair Value of Derivative Liability
Fair value of exit fee derivative liabilities, beginning	$ 700
Fair value of exit fee derivative liabilities, ending	1,200	$ 700
2022 Exit Fee
Change in Fair Value of Derivative Liability
Fair value of exit fee derivative liabilities, ending	400
Exit fee derivative liability
Change in Fair Value of Derivative Liability
Fair value of exit fee derivative liabilities, beginning	698	1,376	$ 969
2022 Exit Fee addition at fair value	375	0	0
Fair value of exit fee derivative liabilities, ending	1,656	698	1,376
Exit fee derivative liability \| 2018 Exit Fee
Change in Fair Value of Derivative Liability
Changes in estimated fair value:	510	(678)	407
Exit fee derivative liability \| 2022 Exit Fee
Change in Fair Value of Derivative Liability
Changes in estimated fair value:	$ 73	$ 0	$ 0

Deferred Royalty Obligation Related To The Sale Of Future Royalties (Details) - USD ($)	1 Months Ended	12 Months Ended
	Jun. 30, 2022	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Amortization of the deferred royalty obligation		$ 1,673,000	$ 0	$ 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
Transaction costs		$ 400,000
Amortization, effective interest rate, percent		34.40%

Organization and Basis of Presentation (Details)	12 Months Ended
Organization and Basis of Presentation (Details)	Dec. 31, 2022 segment
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of operating segments	1

Borrowings (Tables)

12 Months Ended

Dec. 31, 2022

Debt Disclosure [Abstract]

Schedule of Future Debt Payment Obligations


2023	$	—
2024	7,639
2025	9,167
2026	9,167
2027	2,888
Thereafter	—
Total repayment obligations	28,861
Less: Unamortized discount and debt issuance costs	(1,110)
Less: Unaccreted value of final fee	(1,040)
Long-term debt	26,711
Less: Current portion of long-term debt	(26,711)
Long-term debt, net of current portion	$	—

Collaboration and Licensing Agreements

12 Months Ended

Dec. 31, 2022

Collaboration and Licensing Agreements [Abstract]

Collaboration and Licensing Agreements

COLLABORATION AND LICENSING AGREEMENTS

Kyowa Kirin Co., Ltd. ("KKC")

2019 KKC Agreement

In November 2019, we entered into a research collaboration and option agreement with KKC ("2019 KKC Agreement”), to undergo research to identify two preclinical study-ready compounds for designation as development compounds, with one compound inhibiting the first undisclosed target (“Program 1”) and a second inhibiting the second undisclosed target (“Program

2”). Pursuant to the 2019 KKC Agreement, upon completion of the research and designation by the research steering committee of one or more development candidates (“DCs”), KKC has the right to execute one or more separate collaborative agreements relating to the development and commercialization of one or both DCs in certain specified territories.

Under the terms of the 2019 KKC Agreement, KKC paid us a non-refundable, non-creditable upfront fee of $10.0 million, in two installments as follows: the first installment of $5.0 million within 30 days of November 11, 2019 ("Effective Date"), and the second installment of $5.0 million on the first anniversary of the Effective Date. The original term of the 2019 KKC Agreement commenced on the Effective Date and was to end on the earliest of: (i) two years following the Effective Date, (ii) the nomination of a program DC for both programs, (iii) the nomination of one program DC and the decision by the parties to cease research for the other program, or (iv) the decision by the parties to cease research for both programs. We entered into three amendments to the 2019 KKC Agreement, which have resulted in the extension of the original term. Under the third amendment to the 2019 KKC Agreement entered into on June 28, 2022, the 2019 KKC Agreement ended on February 28, 2023.

We assessed the 2019 KKC Agreement in accordance with ASC 606 and concluded that the contract’s counterparty, KKC, is a customer. We also considered the modification guidance prescribed in ASC 606 and concluded that the 2019 KKC Agreement should be accounted for as a separate contract from the 2017 KKC Agreement, as defined and discussed below.

We identified various promises in the 2019 KKC Agreement, including the grant of an initial research license, the Program 1 research, the Program 2 research, the right to obtain certain development and commercialization rights with Program 1 in certain territories and the right to obtain development and commercialization rights with Program 2 in certain territories, and participation in a joint steering committee (“JSC”) and determined that KKC could not benefit from either of the research programs without the research license and participation in the JSC. As such, the combined license, research programs and participation in the JSC were deemed to be the highest level of goods and services that can be deemed distinct for each of the Program 1 research and Program 2 research. We concluded that the options to obtain additional development and commercialization rights that are exercisable by KKC under certain circumstances are not performance obligations of the contract at inception because the option fees reflect the standalone selling price of the options, and therefore, the options are not considered to be material rights.

At the outset of the 2019 KKC Agreement, we determined that the initial transaction price was $10.0 million and that revenue associated with the combined performance obligations should be recognized as services are provided using the input method. Since transfer of control occurs over time, in management’s judgment this input method is the best measure of progress towards satisfying the performance obligations and reflects a faithful depiction of the transfer of goods and services. Revenue was recognized over the Program 1 and Program 2 research periods which concluded in 2021.

During the years ended December 31, 2022 and 2021, we recognized zero and $4.2 million, respectively, as revenue under the 2019 KKC Agreement in the statement of operations and comprehensive loss. The transaction price had been fully allocated to revenue as of December 31, 2021 and there was no associated deferred revenue presented on the balance sheet as of December 31, 2022 or 2021. As of December 31, 2022 and 2021, we had no material future obligations under the 2019 KKC Agreement.

2017 KKC Agreement

In November 2017, we entered into an exclusive license agreement with KKC (“2017 KKC Agreement”), under which we granted KKC 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 KKC Agreement, KKC 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 KKC’s use in development and commercialization throughout the term of the 2017 KKC Agreement, provided that KKC may exercise an option to manufacture the tenapanor drug substance under certain conditions. In October 2022, we entered into a Commercial Supply Agreement with KKC to further define the obligations of the parties with respect to the commercial supply of tenapanor drug substance (“2022 KKC Supply Agreement”). As detailed below under the heading “Deferred revenue’ we have received advanced payments from KKC for the manufacturing of tenapanor drug substance that will be used to satisfy KKC 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, KKC, is a customer. Under the terms of the 2017 KKC Agreement, we received $30.0 million in up-front 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 the material performance obligations at the inception of the 2017 KKC Agreement and, as such, each of the performance obligations is distinct.

Under the terms of the 2017 KKC Agreement, KKC paid us an up-front license fee of $30.0 million,. We may be entitled to receive up to $55.0 million in total development and regulatory milestones, of which $20.0 million has been received and recognized as revenue as of December 31, 2022. We may also be eligible to receive approximately ¥8.5 billion for commercialization milestones, or approximately $64.6 million at the currency exchange rate on December 31, 2022, 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 KKC 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, 2022 and 2021.

In April 2022, we entered into a second amendment to the 2017 KKC Agreement ("2022 Amendment"). Under the terms of the 2022 Amendment, we and KKC have agreed to a reduction in the royalty rate payable to us by KKC 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 KKC 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, KKC agreed to pay us up to an additional $40.0 million payable in two tranches, with the first payment due following KKC's filing with the Japanese Ministry of Health, Labour and Welfare of its application for marketing approval for tenapanor and the second payment due following KKC’s receipt of regulatory approval to market tenapanor for hyperphosphatemia in Japan.

In October 2022, we announced that KKC submitted an NDA to the Japanese Ministry of Health, Labour and Welfare for tenapanor for the improvement of hyperphosphatemia in adult patients with CKD on dialysis, which resulted in payment to us from KKC 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 loss. The remaining variable consideration related to the reduction in the royalty rate was fully constrained at December 31, 2022. For the year ended December 31, 2021, $5.0 million of licensing revenue was recorded upon the initiation of phase 3 clinical studies by KKC in Japan to evaluate tenapanor for hyperphosphatemia.

For the years ended December 31, 2022 and 2021, $1.5 million and $0.9 million, respectively, of product supply revenue was recorded for manufacturing supply of tenapanor and other materials to KKC for product development and clinical trials in Japan, in accordance with our agreement with the 2017 KKC Agreement.

For the years ended December 31, 2022 and 2021, $35.0 million and $5.0 million, respectively, of licensing revenue was recorded. The 2022 licensing revenue was earned upon KKC's submission of an NDA to the Japanese Ministry of Health, Labour and Welfare for tenapanor for the improvement of hyperphosphatemia in adult patients with CKD on dialysis. The 2021 licensing revenue was recorded upon the initiation of Phase 3 clinical studies by KKC in Japan to evaluate tenapanor for hyperphosphatemia.

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 up-front 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 additional development and commercialization milestones of up to $110.0 million, 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, 2022 and 2021.

We recorded no revenue related to the Fosun Agreement during the years ended December 31, 2022 and 2021.

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 CAD22.2, or approximately $16.3 million at the currency exchange rate on December 31, 2022. 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 were fully constrained at December 31, 2022 and 2021.

For the years ended December 31, 2022 and 2021, $31 thousand and $13 thousand of licensing revenue was recorded, respectively, related to the Knight Agreement. For the years ended December 31, 2022 and 2021, no product supply revenue was recorded, respectively, related to the Knight Agreement.

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 another NHE3 inhibitor, up to a maximum of $75.0 million in aggregate for (i) and (ii). For the years ended December 31, 2022 and 2021, we recognized $3.6 million and $1.0 million, respectively, as cost of revenue related to the AstraZeneca Termination Agreement. To date in aggregate, we have recognized $15.3 million of the $75.0 million aggregate maximum related to the AstraZeneca Termination Agreement.

Deferred Revenue


Deferred revenue - current	2022		2021
Balance at Balance at January 1,	$	—	$	4,177
Increases due to cash received, excluding amounts recognized as revenue during the period	42		—
Increases due to amounts reclassified from non-current, to be recognized in the next twelve months	3,961		—
Increases to amounts invoiced, for which cash has not yet been received	208		—

Decreases due to revenue recognized in the period for which cash has been received	—		(4,177)

Balance at December 31,	$	4,211	$	—


Deferred revenue - non-current	2022		2021
Balance at Balance at January 1,	$	4,727	$	—
Increases due to cash received during the period	7,794		3,242
Increases to amounts invoiced, for which cash has not yet been received	465		—
Increase due to unbilled prepayments recorded during the period	—		1,485
Decreases due to amounts reclassified as current, to be recognized in the next twelve months	(3,961)		—

Balance at December 31,	$	9,025	$	4,727

Derivative Liabilities - Narrative (Details) - USD ($) $ in Millions	Feb. 23, 2022	Dec. 31, 2022	Dec. 31, 2021	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		$ 1.2	$ 0.7
2018 Exit Fee \| Level 3
Derivative [Line Items]
Fair value analysis, percentage change in probability of occurrence		10.00%
Fair value analysis, effect on fair value based on 10% change in probability of occurrence		$ 0.1
2022 Exit Fee
Derivative [Line Items]
Estimated fair value		$ 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%

Income Taxes - Components of Deferred Tax Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Deferred tax assets:
Amortization and depreciation	$ 64,111	$ 61,098
Net operating loss carryforwards	86,547	74,989
Tax credits	14,411	13,827
Stock-based compensation	5,244	4,054
Other	7,486	3,867
Gross deferred tax assets	177,799	157,835
Valuation allowance	(175,670)	(155,141)
Deferred tax assets net of valuation allowance	2,129	2,694
Deferred tax liabilities:
Right-of-use asset	(2,129)	(2,689)
Other	0	(5)
Net deferred tax assets	$ 0	$ 0

Equity Incentive Plans - Restricted Stock Units (Details) - RSUs	12 Months Ended
	Dec. 31, 2022 $ / shares shares
Number of RSUs
Nonvested balance, beginning (shares) \| shares	3,529,000
Granted (shares) \| shares	2,195,000
Vested (shares) \| shares	(3,956,000)
Forfeited (shares) \| shares	(362,000)
Nonvested balance, ending (shares) \| shares	1,406,000
Weighted-Average Grant Date Fair Value Per Share
Nonvested balance, beginning (in dollars per share) \| $ / shares	$ 2.04
Granted (in dollars per share) \| $ / shares	0.89
Vested (in dollars per share) \| $ / shares	1.34
Forfeited (in dollars per share) \| $ / shares	2.23
Nonvested balance, ending (in dollars per share) \| $ / shares	$ 2.17

Geographic Information and Concentrations - Concentration Risk (Details) - Revenue - Collaboration partnership concentration risk	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
KKC
Concentration Risk [Line Items]
Concentration risk (percent)	70.00%	100.00%	89.00%
Knight
Concentration Risk [Line Items]
Concentration risk (percent)	0.10%	0.00%	11.00%
AmerisourceBergen Drug Corporation
Concentration Risk [Line Items]
Concentration risk (percent)	11.10%	0.00%	0.00%

Summary of Significant Accounting Policies (Policies)	12 Months Ended
Summary of Significant Accounting Policies (Policies)	Dec. 31, 2022
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, 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 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 its 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 value 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. For the years ending December 31, 2022, 2021 and 2020 we have recognized no impairment losses.
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 ReceivableAccounts receivable is reported net of allowances for returns, chargebacks and contractual off-invoice and prompt-pay discounts offered to our customers. Our estimate of the allowance for doubtful accounts is based on an evaluation of the aging of our receivables. Trade receivable balances are written off against the allowance when it is probable that the receivable will not be collected. 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. Inventory is stated at the lower of cost or estimated net realizable value with cost determined under the first-in first-out 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 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, 2022, 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 U.S. Food and Drug Administration (“FDA”) in September 2019 to market IBSRELA in the U.S.. We began selling IBSRELA in the U.S. in March 2022. We distribute IBSRELA principally through major wholesalers, specialty pharmacies and group purchasing organizations ("GPOs") (collectively, our "Customers"). Our Customers subsequently sell IBSRELA 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 programs, 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 product launch. 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. 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 estimated utilization by types of contracted purchasers. 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 and 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. 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 it 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, it 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 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 our control or the control of 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 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 accounts receivable or 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 Revenue	Cost of Revenue Cost of revenue consists of the cost of commercial goods sold to our Customers and international partners under product supply agreements as well as royalty expense 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 units recognized as revenue during the twelve months ended December 31, 2022 were expensed prior to the fourth quarter of 2021, at which time our intent to commercialize IBSRELA was established and we commenced preparation for the commercial launch of IBSRELA. Cost of revenue includes payments due to AstraZeneca, which under the terms of a termination agreement entered into in 2015 ("AZ 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 as a result of the development and commercialization of tenapanor or certain other NHE3 inhibitors. 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 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 $15.3 million as cost of revenue under the AZ Termination Agreement.
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 Research and Development Expenses	Accrued Research and Development Expenses We are required to estimate our accrued expenses at the end of each reporting period. 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 costs. The majority of our service providers submit invoices 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. Examples of estimated accrued research and development expenses include fees paid to: •contract research organizations ("CROs") in connection with clinical studies; •investigative sites in connection with clinical studies; •vendors related to product manufacturing, development and distribution of clinical supplies; and •vendors in connection with preclinical development activities. We record expenses related to clinical studies and manufacturing development activities based on our estimates of the services received and efforts expended pursuant to contracts with multiple CROs and manufacturing vendors that conduct and manage these activities on our behalf. The financial terms of these agreements are subject to negotiation, vary from contract to contract, and may result in uneven payment flows. There may be instances in which payments made to our vendors will exceed the level of services provided and result in a prepayment of the expense. Payments under some of these contracts depend on factors such as the successful enrollment of subjects and the completion of clinical trial milestones. In accruing service fees, we estimate the time period over which services will be performed, enrollment of subjects, number of sites activated and the level of effort to be expended in each period. If the actual timing of the performance of services or the level of effort varies from our estimate, we will adjust the accrued or prepaid expense balance accordingly.
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 The net proceeds we receive from the sale of certain future royalties are recorded as deferred royalty obligation related to the sale of future royalties on our balance sheets. As we earn royalties and remit those royalties pursuant to the agreement, the balance of the deferred royalty obligation will be effectively repaid over the life of agreement and non-cash interest expense related to the sale of future royalties is recorded using the effective interest method. To determine the amortization of our deferred royalty obligation, we are required to estimate the total amount of future royalty payments we expect to earn. There are a number of factors that could materially affect the amount and timing of royalty payments, most of which are not within our control. We periodically assess the amount of royalty payments we expect to receive which are subject to the agreement 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.
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.
Restructuring	Restructuring We recognize restructuring charges related to reorganization plans that have been committed to by management when liabilities have been incurred. In connection with these activities, we record restructuring charges at fair value for, (a) contractual employee termination benefits when obligations are associated to services already rendered, rights to such benefits have vested, and payment of benefits is probable and can be reasonably estimated, (b) one-time employee termination benefits when management has committed to a plan of termination, the plan identifies the employees and their expected termination dates, the details of termination benefits are complete, it is unlikely changes to the plan will be made or the plan will be withdrawn and communication to such employees has occurred, and (c) contract termination costs when a contract is terminated before the end of its term. One-time employee termination benefits are recognized in their entirety when communication has occurred and future services are not required. If future services are required, the costs are recorded ratably over the remaining period of service. Contract termination costs to be incurred over the remaining contract term without economic benefit are recorded in their entirety when the contract is canceled.
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 We adopted Accounting Standards Update 2016-13, Financial Instruments - Credit Losses: Measurement of Credit Losses on Financial Instruments ("ASU 2016-13"), as of December 1, 2021 under the modified retrospective approach. ASU 2016-13 requires an entity to measure and recognize expected credit losses for certain financial instruments, including trade receivables, as an allowance that reflects the entity's current estimate of credit losses expected to be incurred. For available-for-sale debt securities with unrealized credit losses, the standard requires allowances to be recorded through net income instead of directly reducing the amortized cost of the investment under the previous other-than-temporary impairment model. The adoption of this standard did not have a material impact on our financial statements or a significant impact on our internal controls. Recent Accounting Pronouncements Not Yet Adopted There were various accounting standards and interpretations issued recently, none of which are expected to a have a material impact on our financial position, operations or cash flows.

Accrued Expenses and Other Current Liabilities (Tables)

12 Months Ended

Dec. 31, 2022

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,
	2022		2021
Accrued payments due to AstraZeneca	$	3,385	$	69
Accrued gross to net revenue liabilities	1,991		—
Accrued contract manufacturing expenses	1,657		2,485
Derivative liability for exit fees	1,656		698
Accrued non-clinical research and development expenses	1,188		265
Accrued professional and consulting services	808		597
Accrued sales and marketing expenses	587		256
Accrued clinical expenses	223		2,522

Other	885		474
Total accrued expenses and other current liabilities	$	12,380	$	7,366

Inventory - Narrative (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Inventory Disclosure [Abstract]
Prepaid commercial manufacturing	$ 13,567	$ 9,406

Organization and Basis of Presentation	12 Months Ended
Organization and Basis of Presentation	Dec. 31, 2022
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 targeted, 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 is in development for the control of serum phosphorus in adult patients with chronic kidney disease (“CKD”) on dialysis under the brand name XPHOZAH. 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.

Net Loss Per Share - Anti-Dilutive Securities and Potential Common Shares (Details) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities not included in computation of diluted net loss per share	16,382	13,680	10,299
Potential common shares that would have been included if not for anti-dilutive effect of securities	600	1,100	2,100
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	13,522	11,871	9,247
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	2,694	1,602	26
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	166	207	94
Warrants 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	0	0	932

Equity Incentive Plans - Valuation Assumptions for Stock Options (Details) - Stock options	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (years)	4 years 10 months 24 days	5 years	6 years
Expected volatility	92.10%	77.00%	83.00%
Risk-free interest rate	2.20%	4.70%	1.10%
Dividend yield	0.00%	0.00%	0.00%

Subsequent Events	12 Months Ended
Subsequent Events	Dec. 31, 2022
Subsequent Events [Abstract]
Subsequent Events	SUBSEQUENT EVENTS 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 LLC ("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. On February 9, 2023, we entered into a second amendment (“Second Amendment”) to our Loan Agreement with the Lenders. The Second Amendment extends the interest-only term of the loan by twelve months to March 31, 2025 provided that we either (i) receive approval from the FDA for our NDA for the control of serum phosphorus in adult patients with CKD on dialysis on or prior to November 30, 2023 or (ii) achieve certain product revenue milestone targets as described in the Second Amendment for the year ending December 31, 2023. The Second Amendment also extends the period under which we may draw the Term B Loan from July 25, 2023 to December 20, 2023, and amends the milestone that we must achieve in order to draw the Term B Loan by extending the time period for the receipt of approval by the FDA of the NDA for the control of serum phosphorus in adult patients with CKD on dialysis until November 30, 2023. In addition, the Second Amendment replaces the floating per annum interest rate with 7.95% plus the greater of (a) one percent (1.00%) per annum and (b)(i) 0.022% plus (ii) 1-month CME Term SOFR reference rate as published by the CME Term SOFR Administrator on the CME Term SOFR Administrator’s Website.

Property and Equipment, Net - Balances (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 10,880	$ 18,253
Less: accumulated depreciation	(9,657)	(15,891)
Total property and equipment, net	1,223	2,362
Laboratory equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	46	7,474
Office equipment and furniture
Property, Plant and Equipment [Line Items]
Property and equipment, gross	2,089	2,034
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 8,745	$ 8,745

Cash, Cash Equivalents and Short-Term Investments - Narrative (Details) - investment	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Available-for-Sale Debt Securities
Short-term securities, contractual maturities, maximum	1 year	1 year
Investment in continuous unrealized loss position for more than one year	0	0

Inventory (Tables)

12 Months Ended

Dec. 31, 2022

Inventory Disclosure [Abstract]

Schedule of Current Inventory

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


	December 31, 2022
Raw materials	$	22,299
Work in process	5,324
Finished goods	723
Total	$	28,346
Reported as:
Inventory	$	3,282
Inventory, non-current	25,064
Total	$	28,346

Schedule of Noncurrent Inventory

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


	December 31, 2022
Raw materials	$	22,299
Work in process	5,324
Finished goods	723
Total	$	28,346
Reported as:
Inventory	$	3,282
Inventory, non-current	25,064
Total	$	28,346

Stockholders' Equity (Details) - USD ($) $ / shares in Units, shares in Millions		1 Months Ended	3 Months Ended	12 Months Ended			17 Months Ended
	Jan. 12, 2023	Jan. 31, 2023	Dec. 31, 2022	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2022	Aug. 31, 2021	Jul. 31, 2020
Subsidiary, Sale of Stock [Line Items]
Proceeds from issuance of common stock				$ 71,625,000	$ 101,146,000	$ 21,047,000
Common stock
Subsidiary, Sale of Stock [Line Items]
Maximum aggregate offering price									$ 250,000,000
Common stock \| Subsequent event
Subsidiary, Sale of Stock [Line Items]
Maximum aggregate offering price		$ 250,000,000
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					$ 100,000,000
2020 Open Market Sales Agreement \| Common stock
Subsidiary, Sale of Stock [Line Items]
Maximum aggregate offering price									$ 100,000,000
2021 Open Market Sales Agreement
Subsidiary, Sale of Stock [Line Items]
Offering sales commission (percent)							3.00%
Common stock sold and issued (in shares)			64.1
Proceeds from issuance of common stock				$ 73,100,000
Weighted-average share price (in dollars per share)				$ 1.14			$ 1.23
Total of shares sold			79.8	79.8			79.8
Total of gross proceeds			$ 98,100,000	$ 98,100,000			$ 98,100,000
2021 Open Market Sales Agreement \| Subsequent event
Subsidiary, Sale of Stock [Line Items]
Common stock sold and issued (in shares)	7.7
Proceeds from issuance of common stock	$ 20,000,000
Weighted-average share price (in dollars per share)	$ 2.60
2021 Open Market Sales Agreement \| Common stock
Subsidiary, Sale of Stock [Line Items]
Maximum aggregate offering price								$ 150,000,000
2023 Open Market Sales Agreement \| Subsequent event
Subsidiary, Sale of Stock [Line Items]
Offering sales commission (percent)		3.00%
2023 Open Market Sales Agreement \| Common stock \| Subsequent event
Subsidiary, Sale of Stock [Line Items]
Maximum aggregate offering price		$ 150,000,000

Stockholders' Equity	12 Months Ended
Stockholders' Equity	Dec. 31, 2022
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. 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. During the twelve months ended December 31, 2022, we sold 64.1 million shares and received gross proceeds of $73.1 million at a weighted average sales price of approximately $1.14 per share under the 2021 Open Market Sales Agreement. As of December 31, 2022 we sold a total of 79.8 million shares and received gross proceeds of $98.1 million at a weighted average sales price of approximately $1.23 per share under the 2021 Open Market Sales Agreement. During the period January 1, 2023 to January 12, 2023, we received additional gross proceeds of $20.0 million for the sale of an additional 7.7 million shares which were sold at a weighted average sales price of approximately $2.60 per share under the 2021 Open Market Sales Agreement. There have been no other sales under the 2021 Open Market Sales Agreement after December 31, 2022. 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 LLC ("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. There have been no sales of our common stock under the 2023 Open Market Sales Agreement.

- Definition

The entire disclosure for shareholders' equity comprised of portions attributable to the parent entity and noncontrolling interest, including other comprehensive income. Includes, but is not limited to, balances of common stock, preferred stock, additional paid-in capital, other capital and retained earnings, accumulated balance for each classification of other comprehensive income and amount of comprehensive income.

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+ Details

Audit Information	12 Months Ended
Audit Information	Dec. 31, 2022
Audit Information [Abstract]
Auditor Name	Ernst & Young LLP
Auditor Location	San Mateo, California
Auditor Firm ID	42

Leases - Lease Costs (Details) - USD ($) $ in Thousands	12 Months Ended
Leases - Lease Costs (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Lease costs
Operating lease expense	$ 4,257	$ 3,671	$ 2,608
Cash paid for operating lease	$ 4,292	$ 3,438	$ 3,065

Equity Incentive Plans - Stock-Based Compensation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation	$ 10,750	$ 12,039	$ 10,583
Selling, general and administrative
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation	7,525	7,923	6,522
Research and development
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation	$ 3,225	$ 4,116	$ 4,061

Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2022

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, 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 liabilities for exit fees	$	1,656	$	—	$	—	$	1,656
Total	$	1,656	$	—	$	—	$	1,656


	December 31, 2021
	Total Fair Value		Level 1		Level 2		Level 3
Assets:
Money market funds	$	71,175	$	71,175	$	—	$	—
Commercial paper	31,935		—		31,935		—
Corporate bonds	7,022		—		7,022		—
Asset-backed securities	5,304		—		5,304		—


Total	$	115,436	$	71,175	$	44,261	$	—

Liabilities:
Derivative liability for exit fee	$	698	$	—	$	—	$	698
Total	$	698	$	—	$	—	$	698

Leases - Narrative (Details) $ in Thousands	1 Months Ended	2 Months Ended	12 Months Ended
Leases - Narrative (Details) $ in Thousands	Nov. 30, 2020 USD ($) ft² renewal_option	May 31, 2021 USD ($) ft² renewal_option	Dec. 31, 2022 USD ($) ft² lease_agreement	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Oct. 31, 2018 ft²
Lessee, Lease, Description [Line Items]
Number of lease agreements \| lease_agreement			3
Right-of-use assets obtained in exchange for lease obligations \| $			$ 0	$ 1,604	$ 450
Fremont facility
Lessee, Lease, Description [Line Items]
Office space area (sq ft)			72,500
Original Waltham facility
Lessee, Lease, Description [Line Items]
Office space area (sq ft)						3,520
Waltham facility
Lessee, Lease, Description [Line Items]
Office space area (sq ft)		12,864
Number of options to extend \| renewal_option		1
Term of lease extension		5 years
Right-of-use assets obtained in exchange for lease obligations \| $		$ 1,600
Milwaukee facility
Lessee, Lease, Description [Line Items]
Office space area (sq ft)	4,768
Number of options to extend \| renewal_option	1
Term of lease extension	5 years
Right-of-use assets obtained in exchange for lease obligations \| $	$ 400
Existence of option to extend	true

Cash, Cash Equivalents and Short-Term Investments - Securities Classified as Cash and Short-Term Investments (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Cash and cash equivalents:
Cash and cash equivalents	$ 96,140	$ 72,428
Short-term investments:
Short-term investments, Cost	27,823	44,267
Short-term investments, Gross Unrealized Gains	6	1
Short-term investments, Gross Unrealized Losses	(60)	(7)
Short-term investments, Fair Value	27,769	44,261
Total cash equivalents and investments, Cost	123,963	116,695
Total cash equivalents and investments, Gross Unrealized Gains	6	1
Total cash equivalents and investments, Gross Unrealized Losses	(60)	(7)
Total cash equivalents and investments, Fair Value	123,909	116,689
Commercial paper
Short-term investments:
Short-term investments, Cost	25,336	31,936
Short-term investments, Gross Unrealized Gains	6	1
Short-term investments, Gross Unrealized Losses	(51)	(2)
Short-term investments, Fair Value	25,291	31,935
Corporate bonds
Short-term investments:
Short-term investments, Cost	1,000	7,025
Short-term investments, Gross Unrealized Gains	0	0
Short-term investments, Gross Unrealized Losses	(1)	(3)
Short-term investments, Fair Value	999	7,022
U.S. government-sponsored agency bonds
Short-term investments:
Short-term investments, Cost	1,487
Short-term investments, Gross Unrealized Gains	0
Short-term investments, Gross Unrealized Losses	(8)
Short-term investments, Fair Value	1,479
Asset backed securities
Short-term investments:
Short-term investments, Cost		5,306
Short-term investments, Gross Unrealized Gains		0
Short-term investments, Gross Unrealized Losses		(2)
Short-term investments, Fair Value		5,304
Cash
Cash and cash equivalents:
Cash and cash equivalents	11,827	1,253
Money market funds
Cash and cash equivalents:
Cash and cash equivalents	$ 84,313	71,175
Commercial paper
Cash and cash equivalents:
Cash and cash equivalents		0
Corporate bonds
Cash and cash equivalents:
Cash and cash equivalents		$ 0

Equity Incentive Plans

12 Months Ended

Dec. 31, 2022

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.

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 and December 2022, 0.5 million, 2.0 million and 3.0 million shares, respectively, were added to the Inducement Plan. As of December 31, 2022, 2.1 million shares of our common stock were subject to inducement grants that were issued pursuant to the Inducement Plan.

Stock Options

A summary of our stock option activity and related information during the twelve months ended December 31, 2022 is as follows (in thousands, except per share dollar amounts and years):


	Shares Available for Grant	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, 2021	4,974	10,417	$	7.00
Options authorized	10,207	—	$	—
Options granted	(5,392)	5,392	$	0.96
Options exercised	—	(14)	$	0.99
Options canceled	1,832	(1,832)	$	5.80
Issuance of common stock for services	(712)	—	$	—

Balance at December 31, 2022	10,909	13,963	$	4.83	7.3	$	10,156
Vested and expected to vest at December 31, 2022		13,963	$	4.83	7.3	$	10,156
Exercisable at December 31, 2022		8,283	$	6.32	6.3	$	2,727

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, 2022, based on our common stock closing price of $2.85 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, 2022, 2021 and 2020, was $30 thousand, $1.7 million, and $2.7 million, respectively.

The weighted-average grant-date estimated fair value of options granted during the years ended December 31, 2022, 2021 and 2020 was $0.63, $3.92 and $4.82 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,
	2022		2021		2020
Expected term (years)	4.9		5.0		6.0
Expected volatility	92.1	%	77.0	%	83.0	%
Risk-free interest rate	2.2	%	4.7	%	1.1	%
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 does 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 twelve months ended December 31, 2022 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, 2021	3,529	$	2.04
Granted	2,195	$	0.89
Vested	(3,956)	$	1.34
Forfeited	(362)	$	2.23
Non-vested restricted stock units at December 31, 2022	1,406	$	2.17

The total estimated fair value of RSUs vested during the years ended December 31, 2022, 2021 and 2020 was $2.6 million, $0.8 million and zero, respectively.

In July 2018, we granted 0.9 million PRSUs to our employees that vested upon the achievement of certain performance conditions, subject to the employees’ continued service relationship with us through the achievement date. During 2020, we granted an additional 30 thousand PRSUs subject to the same performance conditions. All 0.9 million of these PRSUs vested in September 2020.

Issuance of Common Stock for Services

During the years ended December 31, 2022, 2021 and 2020, we issued approximately 0.7 million, 26 thousand and 42 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, 2022, 2021 and 2020 were valued at $0.4 million, $0.2 million and $0.3 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.

A summary of our ESPP activity during the twelve months ended December 31, 2022 is as follows (in thousands, except per share dollar amounts):


	Shares Available for Grant	Number of Shares Purchased	Average Purchase Price per Share		Gross Proceeds
Balance at December 31, 2021	899	1,048
Shares purchased	(308)	308	$	0.63	$	195
Balance at December 31, 2022	591	1,356

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,
	2022		2021		2020
Expected term (years)	0.5		0.5		0.5
Expected volatility	97.2	%	123.0	%	79.4	%
Risk-free interest rate	1.9	%	0.7	%	0.5	%
Dividend yield	—	%	—	%	—	%

Stock-based Compensation Expense


	Year Ended December 31,
	2022		2021		2020
Selling, general and administrative	$	7,525	$	7,923	$	6,522
Research and development	3,225		4,116		4,061
Total	$	10,750	$	12,039	$	10,583

A summary of our total unrecognized stock-based compensation expense, net of estimated forfeitures, as of December 31, 2022 is as follows (dollars in thousands):


	December 31, 2022
	Unrecognized Compensation Expense		Average Remaining Vesting Period (Years)
Stock options grant	$	9,434	2.55
RSU grants	$	2,937	2.95
ESPP	$	22	0.2

Net Loss Per Share (Tables)

12 Months Ended

Dec. 31, 2022

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,
	2022		2021		2020
Numerator:
Net loss	$	(67,207)	$	(158,165)	$	(94,313)
Denominator:
Weighted average common shares outstanding - basic and diluted	158,690		104,206		89,582
Net loss per share - basic and diluted	$	(0.42)	$	(1.52)	$	(1.05)

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


	Year Ended December 31,
	2022	2021	2020
Options to purchase common stock	13,522	11,871	9,247
Restricted stock units	2,694	1,602	26
ESPP shares issuable	166	207	94
Warrants to purchase common stock	—	—	932
Total	16,382	13,680	10,299

Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Payables and Accruals [Abstract]
Accrued payments due to AstraZeneca	$ 3,385	$ 69
Accrued gross to net revenue liabilities	1,991	0
Accrued contract manufacturing expenses	1,657	2,485
Derivative liability for exit fees	1,656	698
Accrued non-clinical research and development expenses	1,188	265
Accrued professional and consulting services	808	597
Accrued sales and marketing expenses	587	256
Accrued clinical expenses	223	2,522
Other	885	474
Total accrued expenses and other current liabilities	$ 12,380	$ 7,366

Commitments and Contingencies	12 Months Ended
Commitments and Contingencies	Dec. 31, 2022
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 to represent all persons who purchased or otherwise acquired Ardelyx securities between August 6, 2020, and July 19, 2021. 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 compliant and defendants filed an opposition to the motion for leave to further amend the complaint. A hearing on the motion for leave to further amend the complaint is scheduled for mid-May 2023. 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, 2022, 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, 2022.

BALANCE SHEETS (Parenthetical) - $ / shares	Dec. 31, 2022	Dec. 31, 2021
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)	300,000,000	300,000,000
Common stock, shares issued (in shares)	198,575,016	130,182,535
Common stock, shares outstanding (in shares)	198,575,016	130,182,535

Leases - Undiscounted Cash Payment Obligations (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Undiscounted cash payment obligations
2023	$ 4,440
2024	4,589
2025	1,321
2026	252
Thereafter	0
Total undiscounted operating lease payments	10,602
Imputed interest expenses	(853)
Total operating lease liabilities	9,749	$ 13,240
Less: Current portion of operating lease liability	(3,894)	(3,492)
Operating lease liability, net of current portion	$ 5,855	$ 9,748

Fair Value Measurements - Financial Assets and Liabilities Measured on a Recurring Basis (Details) - Recurring - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Assets:
Assets, fair value	$ 112,082	$ 115,436
Liabilities:
Liabilities, fair value	1,656	698
Money market funds
Assets:
Assets, fair value	84,313	71,175
Commercial paper
Assets:
Assets, fair value	25,291	31,935
U.S. government-sponsored agency bonds
Assets:
Assets, fair value	1,479
Corporate bonds
Assets:
Assets, fair value	999	7,022
Asset backed securities
Assets:
Assets, fair value		5,304
Derivative liabilities for exit fees
Liabilities:
Liabilities, fair value	1,656	698
Level 1
Assets:
Assets, fair value	84,313	71,175
Liabilities:
Liabilities, fair value	0	0
Level 1 \| Money market funds
Assets:
Assets, fair value	84,313	71,175
Level 1 \| Commercial paper
Assets:
Assets, fair value	0	0
Level 1 \| U.S. government-sponsored agency bonds
Assets:
Assets, fair value	0
Level 1 \| Corporate bonds
Assets:
Assets, fair value	0	0
Level 1 \| Asset backed securities
Assets:
Assets, fair value		0
Level 1 \| Derivative liabilities for exit fees
Liabilities:
Liabilities, fair value	0	0
Level 2
Assets:
Assets, fair value	27,769	44,261
Liabilities:
Liabilities, fair value	0	0
Level 2 \| Money market funds
Assets:
Assets, fair value	0	0
Level 2 \| Commercial paper
Assets:
Assets, fair value	25,291	31,935
Level 2 \| U.S. government-sponsored agency bonds
Assets:
Assets, fair value	1,479
Level 2 \| Corporate bonds
Assets:
Assets, fair value	999	7,022
Level 2 \| Asset backed securities
Assets:
Assets, fair value		5,304
Level 2 \| Derivative liabilities for exit fees
Liabilities:
Liabilities, fair value	0	0
Level 3
Assets:
Assets, fair value	0	0
Liabilities:
Liabilities, fair value	1,656	698
Level 3 \| Money market funds
Assets:
Assets, fair value	0	0
Level 3 \| Commercial paper
Assets:
Assets, fair value	0	0
Level 3 \| U.S. government-sponsored agency bonds
Assets:
Assets, fair value	0
Level 3 \| Corporate bonds
Assets:
Assets, fair value	0	0
Level 3 \| Asset backed securities
Assets:
Assets, fair value		0
Level 3 \| Derivative liabilities for exit fees
Liabilities:
Liabilities, fair value	$ 1,656	$ 698

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2022

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, 2022, 2021 and 2020, are as follows (in thousands):


	Year Ended December 31,
	2022		2021		2020
Current:
State	$	8	$	4	$	2
Foreign	—		—		—
Total current	8		4		2
Deferred:
Federal	—		—		—
Total deferred	—		—		—
Provision for income taxes	$	8	$	4	$	2

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,
	2022		2021		2020
Income tax at the federal statutory rate	21.0	%	21.0	%	21.0	%
State taxes, net of federal benefit	1.9		0.4		0.7
Tax credits	1.5		1.0		1.3
Executive compensation disallowed under IRC Sec 162(m)	(1.6)		(1.1)		(0.5)
Stock based compensation	(2.3)		(1.3)		(0.1)
Other	(0.8)		—		(0.1)
Change in valuation allowance	(19.7)		(20.0)		(22.3)
Income tax provision	—	%	—	%	—	%

Schedule of Components of Deferred Tax Assets

Significant components of our deferred tax assets are as follows as of December 31, 2022 and 2021 (in thousands):


	December 31,
	2022		2021
Deferred tax assets:
Amortization and depreciation	$	64,111	$	61,098
Net operating loss carryforwards	86,547		74,989
Tax credits	14,411		13,827
Stock-based compensation	5,244		4,054

Other	7,486		3,867
Gross deferred tax assets	177,799		157,835
Valuation allowance	(175,670)		(155,141)
Deferred tax assets net of valuation allowance	2,129		2,694
Deferred tax liabilities:
Right-of-use asset	(2,129)		(2,689)

Other	—		(5)
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,
	2022		2021		2020
Balance at beginning of year	$	24,426	$	23,624	$	24,538
Additions based on tax positions related to current year	460		1,613		474
Subtractions related to lapse of statute of limitation	(811)		—		—
Subtractions based on tax positions related to prior year	—		(811)		(1,388)
Balance at end of year	$	24,075	$	24,426	$	23,624

Inventory - Schedule (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Inventory Disclosure [Abstract]
Raw materials	$ 22,299
Work in process	5,324
Finished goods	723
Inventory	3,282	$ 0
Inventory, non-current	25,064	$ 0
Total	$ 28,346