UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549
 
SCHEDULE 13G
Under the Securities Exchange Act of 1934
 
(Amendment No. __)*
ARDELYX, INC. 
 
 (Name of Issuer)
 
Common Stock, par value $0.0001 per share
 
(Title of Class of Securities)
 
039697107
 
(CUSIP Number)
 
July 18, 2016
 
(Date of Event Which Requires Filing of this Statement)
 
Check the appropriate box to designate the rule pursuant to which this Schedule is filed:
 
 	¨	Rule 13d-1(b)	
 	x	Rule 13d-1(c)	
 	¨	Rule 13d-1(d)	
 
*The remainder of this cover page shall be filled out for a reporting person’s initial filing on this form with respect to the subject class of securities, and for any subsequent amendment containing information which would alter the disclosures provided in a prior cover page.
 
The information required in the remainder of this cover page shall not be deemed to be “filed” for the purpose of Section 18 of the Securities Exchange Act of 1934 (“ Act ”) or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

 
 
CUSIP No. 039697107	13G	 	

 	1.	Names of Reporting Persons.
I.R.S. Identification Nos. of above persons (entities only).
 
RA Capital Management, LLC           	

 	2.	Check the Appropriate Box if a Member of a Group (See Instructions)	
 	 	(a)	¨	
 	 	(b)	¨	

 	3.	SEC Use Only	

 	4.	Citizenship or Place of Organization Massachusetts	

Number of
Shares
Beneficially
Owned by
Each Reporting
Person With	5.	Sole Voting Power	0	 	
 	 	 	 	
 	6.	Shared Voting Power	3,625,943	 	 	 	
 	 	 	 	 	 	
 	7.	Sole Dispositive Power	0	 	 	 	 	 	
 	 	 	 	 	 	 	 	
 	8.	Shared Dispositive Power	3,625,943	 	 	 	 	 	 	
 
 	9.	Aggregate Amount Beneficially Owned by Each Reporting Person
 
3,625,943 	
 	10.	Check if the Aggregate Amount in Row (9) Excludes                         ¨
Certain Shares (See Instructions) 	
 	11.	Percent of Class Represented by Amount in Row (9)
 
7.7%1 	
 	12.	Type of Reporting Person (See Instructions)
 
IA	

1 The reporting person is the beneficial owner of 3,457,718 shares of Common Stock, as well as warrants to acquire 168,225 shares of Common Stock, which together would constitute approximately 7.7% of the issuer’s Common Stock if the warrants were exercised in full, following the issuance of 168,225 shares of Common Stock in respect of the fully-exercised warrants. The percentage calculation assumes that there are currently 47,230,378 outstanding shares of the Issuer, based on the Issuer’s 10-Q as filed with the Securities and Exchange Commission (“SEC”) on May 9, 2016 and the Issuer’s 8-K as filed with the SEC on July 20, 2016.

 
 
CUSIP No. 039697107	13G	 	

 	1.	Names of Reporting Persons.
I.R.S. Identification Nos. of above persons (entities only).
 
Peter Kolchinsky           	

 	2.	Check the Appropriate Box if a Member of a Group (See Instructions)	
 	 	(a)	¨	
 	 	(b)	¨	

 	3.	SEC Use Only	
 	4.	Citizenship or Place of Organization United States	

Number of
Shares
Beneficially
Owned by
Each Reporting
Person With	5.	Sole Voting Power	0	 	
 	 	 	 	
 	6.	Shared Voting Power	3,625,943	 	 	 	
 	 	 	 	 	 	
 	7.	Sole Dispositive Power	0	 	 	 	 	 	
 	 	 	 	 	 	 	 	
 	8.	Shared Dispositive Power	3,625,943	 	 	 	 	 	 	
 
 	9.	Aggregate Amount Beneficially Owned by Each Reporting Person
 
3,625,943 	
 	10.	Check if the Aggregate Amount in Row (9) Excludes                         ¨
Certain Shares (See Instructions) 	
 	11.	Percent of Class Represented by Amount in Row (9)
 
7.7%2 	
 	12.	Type of Reporting Person (See Instructions)
 
IN 	

2 The reporting person is the beneficial owner of 3,457,718 shares of Common Stock, as well as warrants to acquire 168,225 shares of Common Stock, which together would constitute approximately 7.7% of the issuer’s Common Stock if the warrants were exercised in full, following the issuance of 168,225 shares of Common Stock in respect of the fully-exercised warrants. The percentage calculation assumes that there are currently 47,230,378 outstanding shares of the Issuer, based on the Issuer’s 10-Q as filed with the SEC on May 9, 2016 and the Issuer’s 8-K as filed with the SEC on July 20, 2016.

 
 
CUSIP No. 039697107	13G	 	

 	1.	Names of Reporting Persons.
I.R.S. Identification Nos. of above persons (entities only).
 
RA Capital Healthcare Fund, L.P.           	

 	2.	Check the Appropriate Box if a Member of a Group (See Instructions)	
 	 	(a)	¨	
 	 	(b)	¨	

 	3.	SEC Use Only	
 	4.	Citizenship or Place of Organization Delaware	

Number of
Shares
Beneficially
Owned by
Each Reporting
Person With	5.	Sole Voting Power	0  	 	
 	 	 	 	
 	6.	Shared Voting Power	2,451,968	 	 	 	
 	 	 	 	 	 	
 	7.	Sole Dispositive Power	0	 	 	 	 	 	
 	 	 	 	 	 	 	 	
 	8.	Shared Dispositive Power	2,451,968	 	 	 	 	 	 	
 
 	9.	Aggregate Amount Beneficially Owned by Each Reporting Person
 
2,451,968 	
 	10.	Check if the Aggregate Amount in Row (9) Excludes                         ¨
Certain Shares (See Instructions)	
 	11.	Percent of Class Represented by Amount in Row (9)
 
5.2%3	
 	12.	Type of Reporting Person (See Instructions)
 
PN (Limited Partnership)	

3 The reporting person is the beneficial owner of 2,314,024 shares of Common Stock, as well as warrants to acquire 137,944 shares of Common Stock, which together would constitute approximately 7.7% of the issuer’s Common Stock if the warrants were exercised in full, following the issuance of 137,944 shares of Common Stock in respect of the fully-exercised warrants. The percentage calculation assumes that there are currently 47,230,378 outstanding shares of the Issuer, based on the Issuer’s 10-Q as filed with the SEC on May 9, 2016 and the Issuer’s 8-K as filed with the SEC on July 20, 2016.

 
 
Item 1.
 
(a)           Name of Issuer: ARDELYX, INC. (the “Issuer”).
 
(b)           Address of the Issuer’s Principal Executive Offices: 34175 Ardenwood Blvd., Suite 200, Fremont, CA 94555.
 
Item 2.
 
(a)           Name of Person Filing: This joint statement on Schedule 13G is being filed by Peter Kolchinsky, RA Capital Management, LLC (“Capital”), and RA Capital Healthcare Fund, L.P. (the “Fund”). Mr. Kolchinsky, Capital and the Fund are collectively referred to herein as the “Reporting Persons.”  Capital is the general partner of the Fund and serves as investment adviser for a separately managed account (the “Account”). Mr. Kolchinsky is the manager of Capital. As the investment adviser to the Fund and the Account, Capital may be deemed a beneficial owner, for purposes of Section 13(d) of the Securities Exchange Act of 1934 (the “Act”), of any securities of the Issuer owned by the Fund or the Account. As the manager of Capital, Mr. Kolchinsky may be deemed a beneficial owner, for purposes of Section 13(d) of the Act, of any securities of the Issuer beneficially owned by Capital. Capital is a registered investment adviser within the meaning of Rule 13d-1(b)(1)(ii)(E) and Rule 16a-1(a)(v), and Mr. Kolchinsky is a parent or control person of Capital within the meaning of Rule 13d-1(b)(1)(ii)(G) and Rule 16a-1(a)(1)(vii). Capital and Mr. Kolchinsky disclaim beneficial ownership of the securities reported in this Schedule 13G Statement (the “Statement”) other than for the purpose of determining their obligations under Section 13(d) of the Act, and neither the filing of the Statement nor the filing of this Amendment shall not be deemed an admission that either Capital or Mr. Kolchinsky is or was the beneficial owner of such securities for any other purpose .
 
(b)           Address of Principal Business Office: The principal business office of the Reporting Persons is c/o RA Capital Management, LLC, 20 Park Plaza, Suite 1200, Boston, MA 02116.
 
(c)           Citizenship: Capital is a Massachusetts limited liability company. The Fund is a Delaware limited partnership. Mr. Kolchinsky is a United States citizen.
 
(d)           Title and Class of Securities: Common stock (“Common Stock”) of the Issuer.
 
(e)           CUSIP Number: 039697107
 
Item 3.           If this statement is filed pursuant to §§240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a:
 
Not applicable.
 
Item 4.           Ownership:
 
(a)	Amount Beneficially Owned:
See the response(s) to Item 9 on the attached cover page(s).	
 	 	
(b)	Percent of Class:
See the response(s) to Item 11 on the attached cover page(s).	

 
 
(c)	Number of shares as to which such person has:	
 	 	
 	(i)	sole power to vote or to direct the vote:
See the response(s) to Item 5 on the attached cover page(s).	
 	 	 	
 	(ii)	shared power to vote or to direct the vote
See the response(s) to Item 6 on the attached cover page(s).	
 	 	 	
 	(iii)	sole power to dispose or to direct the disposition of
See the response(s) to Item 7 on the attached cover page(s).	
 	 	 	
 	(iv)	shared power to dispose or to direct the disposition of
See the response(s) to Item 8 on the attached cover page(s).	
 
Item 5.           Ownership of Five Percent or Less of a Class:
 
Not applicable.
 
Item 6.           Ownership of More than Five Percent on Behalf of Another Person:
 
Not applicable.
 
Item 7.           Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on By the Parent Holding Company or Control Person:
 
Not applicable.
 
Item 8.           Identification and Classification of Members of the Group:
 
Not applicable.
 
Item 9.           Notice of Dissolution of Group:
 
Not applicable.
 
Item 10.         Certification:
 
By signing below I hereby certify that, to the best of my knowledge and belief, the securities referred to above were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect.

 
 
SIGNATURE
 
After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.
 
 	Date: July 28, 2016	
 	 	
 	RA CAPITAL MANAGEMENT, LLC	
 	 	 	
 	By:	/s/ Peter Kolchinsky	
 	Peter Kolchinsky
Authorized Signatory	
 	 	
 	PETER KOLCHINSKY	
 	 	
 	/s/ Peter Kolchinsky	
 	 	
 	RA CAPITAL HEALTHCARE FUND, L.P.	
 	 	
 	By: RA Capital Management, LLC	
 	Its: General Partner	
 	 	 	
 	By:	/s/ Peter Kolchinsky	
 	Peter Kolchinsky
Authorized Signatory	

 

Exhibit 1
 
JOINT FILING AGREEMENT
 
This Joint Filing Agreement, dated as of July 28, 2016, is by and among RA Capital Management, LLC, Peter Kolchinsky, and RA Capital Healthcare Fund, L.P. (the foregoing are collectively referred to herein as the “Filers”).
 
Each of the Filers may be required to file with the United States Securities and Exchange Commission a statement on Schedule 13G and/or 13D with respect to Common Stock, par value $0.0001 per share of ARDELYX, INC. beneficially owned by them from time to time.
 
Pursuant to and in accordance with Rule 13(d)(1)(k) promulgated under the Securities Exchange Act of 1934, as amended, the Filers hereby agree to file a single statement on Schedule 13G and/or 13D (and any amendments thereto) on behalf of each of such parties, and hereby further agree to file this Joint Filing Agreement as an exhibit to such statement, as required by such rule.
 
This Joint Filing Agreement may be terminated by any of the Filers upon one week’s prior written notice or such lesser period of notice as the Filers may mutually agree.
 
Executed and delivered as of the date first above written.
 
 	RA CAPITAL MANAGEMENT, LLC	
 	 	 	
 	By:	/s/ Peter Kolchinsky	
 	Peter Kolchinsky
Authorized Signatory	
 	 	
 	PETER KOLCHINSKY	
 	 	
 	/s/ Peter Kolchinsky	
 	 	
 	RA CAPITAL HEALTHCARE FUND, L.P.	
 	 	
 	By: RA Capital Management, LLC	
 	Its: General Partner	
 	 	 	
 	By:	/s/ Peter Kolchinsky	
 	Peter Kolchinsky
Authorized Signatory