SCHEDULE 13G

Amendment No. 2
ARDELYX INC
COMMON STOCK
Cusip #039697107
Check the appropriate box to designate the rule pursuant to which this 
Schedule is filed:
[x]       Rule 13d-1(b)
[ ]       Rule 13d-1(c)
[ ]       Rule 13d-1(d)
Cusip #039697107
Item 1:                 Reporting Person - FMR LLC
Item 2:                 (a)     [ ]
(b)     [ ]
Item 4:                 Delaware
Item 5:                 0
Item 6:                 0
Item 7:                 3,303,912
Item 8:                 0
Item 9:                 3,303,912
Item 11:                12.728%
Item 12:                HC
Cusip #039697107
Item 1:                 Reporting Person - Abigail P. Johnson
Item 2:                 (a)     [ ]
(b)     [ ]
Item 4:                 United States of America
Item 5:                 0
Item 6:                 0
Item 7:                 3,303,912
Item 8:                 0
Item 9:                 3,303,912
Item 11:                12.728%
Item 12:                IN
Cusip #039697107
Item 1:                 Reporting Person - Select Biotechnology Portfolio
Item 2:                 (a)     [ ]
(b)     [ ]
Item 4:                 Massachusetts
Item 5:                 2,420,748
Item 6:                 0
Item 7:                 0
Item 8:                 0
Item 9:                 2,420,748
Item 11:                9.326%
Item 12:                IV

Item 1(a).              Name of Issuer:

ARDELYX INC

Item 1(b).              Address of Issuer's Principal Executive Offices:

34175 ARDENWOOD BLVD.
Fremont, CA 94555
USA

Item 2(a).               Name of Person Filing:

FMR LLC

Item 2(b).               Address or Principal Business Office or, if None, 
Residence:

245 Summer Street, Boston, Massachusetts 02210

Item 2(c).               Citizenship:

Not applicable

Item 2(d).               Title of Class of Securities:

COMMON STOCK

Item 2(e).               CUSIP Number:

039697107

Item 3.                 This statement is filed pursuant to Rule 13d-1(b) or 13d-2(b) 
or (c) and the
person filing, FMR LLC, is a parent holding company in accordance with
Section 240.13d-1(b)(1)(ii)(G).   (Note:  See Exhibit A).

Item 4.                 Ownership

(a)    Amount Beneficially Owned:       3,303,912

(b)    Percent of Class:        12.728%

(c)    Number of shares as to which such person has:

(i)    sole power to vote or to direct the vote:         0

(ii)    shared power to vote or to direct the vote:      0

(iii)    sole power to dispose or to direct the 
disposition of:         3,303,912

(iv)    shared power to dispose or to direct the 
disposition of:         0

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.

Various persons have the right to receive or the power to direct the 
receipt of dividends from, or the proceeds from the sale of, the COMMON 
STOCK of ARDELYX INC. No one other person's interest in the COMMON STOCK of 
ARDELYX INC is more than five percent of the total outstanding COMMON 
STOCK.

Item 7.                 Identification and Classification of the Subsidiary Which 
Acquired the Security Being Reported on By the Parent Holding Company.

See attached Exhibit A.

Item 8.                 Identification and Classification of Members of the Group.

Not applicable.

Item 9.                 Notice of Dissolution of Group.

Not applicable.

Item 10.                Certifications.

By signing below I certify that, to the best of my knowledge and belief, 
the securities referred to above were acquired and are held in the ordinary 
course of business and 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.

February 12, 2016
Date

/s/ Marc R. Bryant
Signature

Marc R. Bryant
Duly authorized under Power of Attorney effective as of September 23, 
2015, by and on behalf of FMR LLC and its direct and indirect subsidiaries*

* This power of attorney is incorporated herein by reference to Exhibit 24 
to the Form 4 filed by FMR LLC on November 25, 2015, accession number: 
0000315066-15-003312

Exhibit A

Pursuant to the instructions in Item 7 of Schedule 13G, 
the following table lists the identity and Item 3 classification, if 
applicable, of each relevant entity that beneficially owns shares of the 
security class being reported on this Schedule 13G.

Entity  ITEM 3 Classification
FMR CO., INC *  IA

* Entity beneficially owns 5% or greater of the outstanding shares of the 
security class being reported on this Schedule 13G.

Abigail P. Johnson is a Director, the Vice Chairman, the 
Chief Executive Officer and the President of FMR LLC.

Members of the Johnson family, including Abigail P. 
Johnson, are the predominant owners, directly or through trusts, of Series 
B voting common shares of FMR LLC, representing 49% of the voting power of 
FMR LLC. The Johnson family group and all other Series B shareholders have 
entered into a shareholders' voting agreement under which all Series B 
voting common shares will be voted in accordance with the majority vote of 
Series B voting common shares. Accordingly, through their ownership of 
voting common shares and the execution of the shareholders' voting 
agreement, members of the Johnson family may be deemed, under the 
Investment Company Act of 1940, to form a controlling group with respect to 
FMR LLC.

Neither FMR LLC nor Abigail P. Johnson has the sole power 
to vote or direct the voting of the shares owned directly by the various 
investment companies registered under the Investment Company Act ("Fidelity 
Funds") advised by Fidelity Management & Research Company ("FMR Co"), a 
wholly owned subsidiary of FMR LLC, which power resides with the Fidelity 
Funds' Boards of Trustees. Fidelity Management & Research Company carries 
out the voting of the shares under written guidelines established by the 
Fidelity Funds' Boards of Trustees.

This filing reflects the securities beneficially owned, or 
that may be deemed to be beneficially owned, by FMR LLC, certain of its 
subsidiaries and affiliates, and other companies (collectively, the "FMR 
Reporters"). This filing does not reflect securities, if any, beneficially 
owned by certain other companies whose beneficial ownership of securities 
is disaggregated from that of the FMR Reporters in accordance with 
Securities and Exchange Commission Release No. 34-39538 (January 12, 1998).

RULE 13d-1(k)(1) AGREEMENT

The undersigned persons, on February 12, 2016, agree and 
consent to the joint filing on their behalf of this Schedule 13G in 
connection with their beneficial ownership of the COMMON STOCK of ARDELYX 
INC at December 31, 2015.

FMR LLC

By /s/ Marc R. Bryant
Marc R. Bryant
Duly authorized under Power of Attorney effective as of September 23, 
2015, by and on behalf of FMR LLC and its direct and indirect subsidiaries*

Abigail P. Johnson

By /s/ Marc R. Bryant
Marc R. Bryant
Duly authorized under Power of Attorney effective as of October 12, 
2015, by and on behalf of Abigail P. Johnson*

Select Biotechnology Portfolio

By /s/ Marc R. Bryant
Marc R. Bryant
Secretary

* This power of attorney is incorporated herein by reference to Exhibit 24 
to the Form 4 filed by FMR LLC on November 25, 2015, accession number: 
0000315066-15-003312