EX-10.5(a)



 Exhibit 10.5A 

ARDELYX, INC. 
 2008
STOCK INCENTIVE PLAN 
 1. Purposes of the Plan. The purposes of this Plan are to attract and retain the best available
personnel, to provide additional incentives to Employees, Directors and Consultants and to promote the success of the Company’s business. 

2. Definitions. The following definitions shall apply as used herein and in the individual Award Agreements except as defined otherwise
in an individual Award Agreement. In the event a term is separately defined in an individual Award Agreement, such definition shall supersede the definition contained in this Section 2. 

(a) “Administrator” means the Board or any of the Committees appointed to administer the Plan. 

(b) “Affiliate” and “Associate” shall have the respective meanings ascribed to such terms in Rule 12b-2
promulgated under the Exchange Act. 
 (c) “Applicable Laws” means the legal requirements relating to the Plan and the
Awards under applicable provisions of federal and state securities laws, the corporate laws of California and, to the extent other than California, the corporate law of the state of the Company’s incorporation, the Code, the rules of any
applicable stock exchange or national market system, and the rules of any non-U.S. jurisdiction applicable to Awards granted to residents therein. 

(d) “Assumed” means that pursuant to a Corporate Transaction either (i) the Award is expressly affirmed by the Company
or (ii) the contractual obligations represented by the Award are expressly assumed (and not simply by operation of law) by the successor entity or its Parent in connection with the Corporate Transaction with appropriate adjustments to the
number and type of securities of the successor entity or its Parent subject to the Award and the exercise or purchase price thereof which at least preserves the compensation element of the Award existing at the time of the Corporate Transaction as
determined in accordance with the instruments evidencing the agreement to assume the Award. 
 (e) “Award” means the grant
of an Option, SAR, Dividend Equivalent Right, Restricted Stock, Restricted Stock Unit or other right or benefit under the Plan. 
 (f)
“Award Agreement” means the written agreement evidencing the grant of an Award executed by the Company and the Grantee, including any amendments thereto. 

(g) “Board” means the Board of Directors of the Company. 

(h) “Cause” means, with respect to the termination by the Company or a Related Entity of the Grantee’s Continuous
Service, that such termination is for “Cause” as such term (or word of like import) is expressly defined in a then-effective written agreement between the Grantee and the Company or such Related Entity, or in the absence of such
then-effective written agreement and definition, is based on, in the determination of the Administrator, the 

  
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Grantee’s: (i) performance of any act or failure to perform any act in bad faith and to the detriment of the Company or a Related Entity; (ii) dishonesty, intentional misconduct or
material breach of any agreement with the Company or a Related Entity; or (iii) commission of a crime involving dishonesty, breach of trust, or physical or emotional harm to any person; provided, however, that with regard to any agreement that
defines “Cause” on the occurrence of or in connection with a Corporate Transaction or a Change in Control, such definition of “Cause” shall not apply until a Corporate Transaction or a Change in Control actually occurs. 

(i) Change in Control” means a change in ownership or control of the Company after the Registration Date effected through either
of the following transactions: 
 (i) the direct or indirect acquisition by any person or related group of persons (other than an
acquisition from or by the Company or by a Company-sponsored employee benefit plan or by a person that directly or indirectly controls, is controlled by, or is under common control with, the Company) of beneficial ownership (within the meaning of
Rule 13d-3 of the Exchange Act) of securities possessing more than fifty percent (50%) of the total combined voting power of the Company’s outstanding securities pursuant to a tender or exchange offer made directly to the Company’s
stockholders which a majority of the Continuing Directors who are not Affiliates or Associates of the offeror do not recommend such stockholders accept, or 

(ii) a change in the composition of the Board over a period of twelve (12) months or less such that a majority of the Board members
(rounded up to the next whole number) ceases, by reason of one or more contested elections for Board membership, to be comprised of individuals who are Continuing Directors. 

(j) “Code” means the Internal Revenue Code of 1986, as amended. 

(k) “Committee” means any committee composed of members of the Board appointed by the Board to administer the Plan. 

(l) “Common Stock” means the common stock of the Company. 

(m) “Company” means Ardelyx, Inc., a Delaware corporation, or any successor entity that adopts the Plan in connection with a
Corporate Transaction. 
 (n) “Consultant” means any person (other than an Employee or a Director, solely with respect to
rendering services in such person’s capacity as a Director) who is engaged by the Company or any Related Entity to render consulting or advisory services to the Company or such Related Entity. 

(o) “Continuing Directors” means members of the Board who either (i) have been Board members continuously for a period
of at least twelve (12) months or (ii) have been Board members for less than twelve (12) months and were elected or nominated for election as Board members by at least a majority of the Board members described in clause (i) who
were still in office at the time such election or nomination was approved by the Board. 

  
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 (p) “Continuous Service” means that the provision of services to the Company or
a Related Entity in any capacity of Employee, Director or Consultant is not interrupted or terminated. In jurisdictions requiring notice in advance of an effective termination as an Employee, Director or Consultant, Continuous Service shall be
deemed terminated upon the actual cessation of providing services to the Company or a Related Entity notwithstanding any required notice period that must be fulfilled before a termination as an Employee, Director or Consultant can be effective under
Applicable Laws. A Grantee’s Continuous Service shall be deemed to have terminated either upon an actual termination of Continuous Service or upon the entity for which the Grantee provides services ceasing to be a Related Entity. Continuous
Service shall not be considered interrupted in the case of (i) any approved leave of absence, (ii) transfers among the Company, any Related Entity, or any successor, in any capacity of Employee, Director or Consultant, or (iii) any
change in status as long as the individual remains in the service of the Company or a Related Entity in any capacity of Employee, Director or Consultant (except as otherwise provided in the Award Agreement). An approved leave of absence shall
include sick leave, military leave, or any other authorized personal leave. For purposes of each Incentive Stock Option granted under the Plan, if such leave exceeds three (3) months, and reemployment upon expiration of such leave is not
guaranteed by statute or contract, then the Incentive Stock Option shall be treated as a Non-Qualified Stock Option on the day three (3) months and one (1) day following the expiration of such three (3) month period. 

(q) “Corporate Transaction” means any of the following transactions, provided, however, that the Administrator shall
determine under parts (iv) and (v) whether multiple transactions are related, and its determination shall be final, binding and conclusive: 

(i) a merger or consolidation in which the Company is not the surviving entity, except for a transaction the principal purpose of which is to
change the state in which the Company is incorporated; 
 (ii) the sale, transfer or other disposition of all or substantially all of the
assets of the Company; 
 (iii) the complete liquidation or dissolution of the Company; 

(iv) any reverse merger or series of related transactions culminating in a reverse merger (including, but not limited to, a tender offer
followed by a reverse merger) in which the Company is the surviving entity but (A) the shares of Common Stock outstanding immediately prior to such merger are converted or exchanged by virtue of the merger into other property, whether in the
form of securities, cash or otherwise, or (B) in which securities possessing more than fifty percent (50%) of the total combined voting power of the Company’s outstanding securities are transferred to a person or persons different
from those who held such securities immediately prior to such merger or the initial transaction culminating in such merger, but excluding any such transaction or series of related transactions that the Administrator determines shall not be a
Corporate Transaction; or 
 (v) acquisition in a single or series of related transactions by any person or related group of persons (other
than the Company or by a Company-sponsored employee benefit plan) of beneficial ownership (within the meaning of Rule 13d-3 of the 

  
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Exchange Act) of securities possessing more than fifty percent (50%) of the total combined voting power of the Company’s outstanding securities but excluding any such transaction or
series of related transactions that the Administrator determines shall not be a Corporate Transaction. 
 (r) “Covered
Employee” means an Employee who is a “covered employee” under Section 162(m)(3) of the Code. 
 (s)
“Director” means a member of the Board or the board of directors of any Related Entity. 
 (t)
“Disability” means as defined under the long-term disability policy of the Company or the Related Entity to which the Grantee provides services regardless of whether the Grantee is covered by such policy. If the Company or the
Related Entity to which the Grantee provides service does not have a long-term disability plan in place, “Disability” means that a Grantee is unable to carry out the responsibilities and functions of the position held by the Grantee by
reason of any medically determinable physical or mental impairment for a period of not less than ninety (90) consecutive days. A Grantee will not be considered to have incurred a Disability unless he or she furnishes proof of such impairment
sufficient to satisfy the Administrator in its discretion. 
 (u) “Dividend Equivalent Right” means a right entitling the
Grantee to compensation measured by dividends paid with respect to Common Stock. 
 (v) “Employee” means any person,
including an Officer or Director, who is in the employ of the Company or any Related Entity, subject to the control and direction of the Company or any Related Entity as to both the work to be performed and the manner and method of performance. The
payment of a director’s fee by the Company or a Related Entity shall not be sufficient to constitute “employment” by the Company. 

(w) “Exchange Act” means the Securities Exchange Act of 1934, as amended. 

(x) “Fair Market Value” means, as of any date, the value of Common Stock determined as follows: 

(i) If the Common Stock is listed on one or more established stock exchanges or national market systems, including without limitation The
NASDAQ Global Select Market, The NASDAQ Global Market or The NASDAQ Capital Market of The NASDAQ Stock Market LLC, its Fair Market Value shall be the closing sales price for such stock (or the closing bid, if no sales were reported) as quoted on the
principal exchange or system on which the Common Stock is listed (as determined by the Administrator) on the date of determination (or, if no closing sales price or closing bid was reported on that date, as applicable, on the last trading date such
closing sales price or closing bid was reported), as reported in The Wall Street Journal or such other source as the Administrator deems reliable; 

(ii) If the Common Stock is regularly quoted on an automated quotation system (including the OTC Bulletin Board) or by a recognized
securities dealer, its Fair Market Value shall be the closing sales price for such stock as quoted on such system or by 

  
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such securities dealer on the date of determination, but if selling prices are not reported, the Fair Market Value of a share of Common Stock shall be the mean between the high bid and low asked
prices for the Common Stock on the date of determination (or, if no such prices were reported on that date, on the last date such prices were reported), as reported in The Wall Street Journal or such other source as the Administrator deems reliable;
or 
 (iii) In the absence of an established market for the Common Stock of the type described in (i) and (ii), above, the Fair Market
Value thereof shall be determined by the Administrator in good faith and in a manner consistent with Applicable Laws. 
 (y)
“Grantee” means an Employee, Director or Consultant who receives an Award under the Plan. 
 (z) “Immediate
Family” means any child, stepchild, grandchild, parent, stepparent, grandparent, spouse, former spouse, sibling, niece, nephew, mother-in-law, father-in- law, son-in law, daughter-in-law, brother-in-law, or sister-in-law, including adoptive
relationships, any person sharing the Grantee’s household (other than a tenant or employee), a trust in which these persons (or the Grantee) have more than fifty percent (50%) of the beneficial interest, a foundation in which these persons
(or the Grantee) control the management of assets, and any other entity in which these persons (or the Grantee) own more than fifty percent (50%) of the voting interests. 

(aa) “Incentive Stock Option” means an Option intended to qualify as an incentive stock option within the meaning of
Section 422 of the Code. 
 (bb) “Non-Qualified Stock Option” means an Option not intended to qualify as an Incentive
Stock Option. 
 (cc) “Officer” means a person who is an officer of the Company or a Related Entity within the meaning of
Section 16 of the Exchange Act and the rules and regulations promulgated thereunder. 
 (dd) “Option” means an option
to purchase Shares pursuant to an Award Agreement granted under the Plan. 
 (ee) “Parent” means a “parent
corporation”, whether now or hereafter existing, as defined in Section 424(e) of the Code. 
 (ff) “Performance-Based
Compensation” means compensation qualifying as “performance-based compensation” under Section 162(m) of the Code. 

(gg) “Plan” means this 2008 Stock Incentive Plan. 

(hh) “Post-Termination Exercise Period” means the period specified in the Award Agreement of not less than thirty
(30) days commencing on the date of termination (other than termination by the Company or any Related Entity for Cause) of the Grantee’s Continuous Service, or such longer period as may be applicable upon death or Disability. 

  
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 (ii) “Registration Date” means the first to occur of (i) the closing of the
first sale to the general public pursuant to a registration statement filed with and declared effective by the Securities and Exchange Commission under the Securities Act of 1933, as amended, of (A) the Common Stock or (B) the same class
of securities of a successor corporation (or its Parent) issued pursuant to a Corporate Transaction in exchange for or in substitution of the Common Stock; and (ii) in the event of a Corporate Transaction, the date of the consummation of the
Corporate Transaction if the same class of securities of the successor corporation (or its Parent) issuable in such Corporate Transaction shall have been sold to the general public pursuant to a registration statement filed with and declared
effective by the Securities and Exchange Commission under the Securities Act of 1933, as amended, on or prior to the date of consummation of such Corporate Transaction. 

(jj) “Related Entity” means any Parent or Subsidiary of the Company. 

(kk) “Replaced” means that pursuant to a Corporate Transaction the Award is replaced with a comparable stock award or a cash
incentive program of the Company, the successor entity (if applicable) or Parent of either of them which preserves the compensation element of such Award existing at the time of the Corporate Transaction and provides for subsequent payout in
accordance with the same (or a more favorable) vesting schedule applicable to such Award. The determination of Award comparability shall be made by the Administrator and its determination shall be final, binding and conclusive. 

(ll) “Restricted Stock” means Shares issued under the Plan to the Grantee for such consideration, if any, and subject to such
restrictions on transfer, rights of first refusal, repurchase provisions, forfeiture provisions, and other terms and conditions as established by the Administrator. 

(mm) “Restricted Stock Units” means an Award which may be earned in whole or in part upon the passage of time or the
attainment of performance criteria established by the Administrator and which may be settled for cash, Shares or other securities or a combination of cash, Shares or other securities as established by the Administrator. 

(nn) “Rule 16b-3” means Rule 16b-3 promulgated under the Exchange Act or any successor thereto. 

(oo) “SAR” means a stock appreciation right entitling the Grantee to Shares or cash compensation, as established by the
Administrator, measured by appreciation in the value of Common Stock. 
 (pp) “Share” means a share of the Common Stock.

 (qq) “Subsidiary” means a “subsidiary corporation”, whether now or hereafter existing, as defined in
Section 424(f) of the Code. 
 3. Stock Subject to the Plan. 

(a) Subject to the provisions of Section 10 below, the maximum aggregate number of Shares which may be issued pursuant to all Awards
(including Incentive Stock Options) is six hundred and seventy thousand (670,000) Shares. The Shares may be authorized, but unissued, or reacquired Common Stock. 

  
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 (b) Any Shares covered by an Award (or portion of an Award) which is forfeited, canceled or
expires (whether voluntarily or involuntarily) shall be deemed not to have been issued for purposes of determining the maximum aggregate number of Shares which may be issued under the Plan. Shares that actually have been issued under the Plan
pursuant to an Award shall not be returned to the Plan and shall not become available for future issuance under the Plan, except that if unvested Shares are forfeited or repurchased by the Company, such Shares shall become available for future grant
under the Plan. To the extent not prohibited by the listing requirements of The NASDAQ Stock Market LLC (or other established stock exchange or national market system on which the Common Stock is traded) and Applicable Law, any Shares covered by an
Award which are surrendered (i) in payment of the Award exercise or purchase price or (ii) in satisfaction of tax withholding obligations incident to the exercise of an Award shall be deemed not to have been issued for purposes of
determining the maximum number of Shares which may be issued pursuant to all Awards under the Plan, unless otherwise determined by the Administrator. 

4. Administration of the Plan. 

(a) Plan Administrator. 

(i) Administration with Respect to Directors and Officers. Prior to the Registration Date, with respect to grants of Awards to
Directors or Employees who are also Officers or Directors of the Company, the Plan shall be administered by (A) the Board or (B) a Committee designated by the Board, which Committee shall be constituted in such a manner as to satisfy the
Applicable Laws. On or after the Registration Date, with respect to grants of Awards to Directors or Employees who are also Officers or Directors of the Company, the Plan shall be administered by (A) the Board or (B) a Committee designated
by the Board, which Committee shall be constituted in such a manner as to satisfy the Applicable Laws and to permit such grants and related transactions under the Plan to be exempt from Section 16(b) of the Exchange Act in accordance with Rule
16b-3. Once appointed, such Committee shall continue to serve in its designated capacity until otherwise directed by the Board. 
 (ii)
Administration With Respect to Consultants and Other Employees. With respect to grants of Awards to Employees or Consultants who are neither Directors nor Officers of the Company, the Plan shall be administered by (A) the Board or
(B) a Committee designated by the Board, which Committee shall be constituted in such a manner as to satisfy the Applicable Laws. Once appointed, such Committee shall continue to serve in its designated capacity until otherwise directed by the
Board. 
 (iii) Administration With Respect to Covered Employees. Notwithstanding the foregoing, as of and after the date that the
exemption for the Plan under Section 162(m) of the Code expires, as set forth in Section 20 below, grants of Awards to any Covered Employee intended to qualify as Performance-Based Compensation shall be made only by a Committee (or
subcommittee of a Committee) which is comprised solely of two or more Directors eligible to serve on a committee making Awards qualifying as Performance-Based 

  
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Compensation. In the case of such Awards granted to Covered Employees, references to the “Administrator” or to a “Committee” shall be deemed to be references to such Committee
or subcommittee. 
 (b) Multiple Administrative Bodies. The Plan may be administered by different bodies with respect to Directors,
Officers, Consultants, and Employees who are neither Directors nor Officers. 
 (c) Powers of the Administrator. Subject to
Applicable Laws and the provisions of the Plan (including any other powers given to the Administrator hereunder), and except as otherwise provided by the Board, the Administrator shall have the authority, in its discretion: 

(i) to select the Employees, Directors and Consultants to whom Awards may be granted from time to time hereunder; 

(ii) to determine whether and to what extent Awards are granted hereunder; 

(iii) to determine the number of Shares or the amount of other consideration to be covered by each Award granted hereunder; 

(iv) to approve forms of Award Agreements for use under the Plan; 

(v) to determine the terms and conditions of any Award granted hereunder; 

(vi) to establish additional terms, conditions, rules or procedures to accommodate the rules or laws of applicable non-U.S. jurisdictions and
to afford Grantees favorable treatment under such rules or laws; provided, however, that no Award shall be granted under any such additional terms, conditions, rules or procedures with terms or conditions which are inconsistent with the provisions
of the Plan; 
 (vii) to amend the terms of any outstanding Award granted under the Plan, provided that any amendment that would adversely
affect the Grantee’s rights under an outstanding Award shall not be made without the Grantee’s written consent; provided, however, that an amendment or modification that may cause an Incentive Stock Option to become a Non- Qualified Stock
Option shall not be treated as adversely affecting the rights of the Grantee; 
 (viii) to construe and interpret the terms of the Plan and
Awards, including without limitation, any notice of award or Award Agreement, granted pursuant to the Plan; and 
 (ix) to take such other
action, not inconsistent with the terms of the Plan, as the Administrator deems appropriate. 
 The express grant in the Plan of any
specific power to the Administrator shall not be construed as limiting any power or authority of the Administrator; provided that the 

  
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Administrator may not exercise any right or power reserved to the Board. Any decision made, or action taken, by the Administrator or in connection with the administration of this Plan shall be
final, conclusive and binding on all persons having an interest in the Plan. 
 (d) Indemnification. In addition to such other rights
of indemnification as they may have as members of the Board or as Officers or Employees of the Company or a Related Entity, members of the Board and any Officers or Employees of the Company or a Related Entity to whom authority to act for the Board,
the Administrator or the Company is delegated shall be defended and indemnified by the Company to the extent permitted by law on an after-tax basis against all reasonable expenses, including attorneys’ fees, actually and necessarily incurred in
connection with the defense of any claim, investigation, action, suit or proceeding, or in connection with any appeal therein, to which they or any of them may be a party by reason of any action taken or failure to act under or in connection with
the Plan, or any Award granted hereunder, and against all amounts paid by them in settlement thereof (provided such settlement is approved by the Company) or paid by them in satisfaction of a judgment in any such claim, investigation, action, suit
or proceeding, except in relation to matters as to which it shall be adjudged in such claim, investigation, action, suit or proceeding that such person is liable for gross negligence, bad faith or intentional misconduct; provided, however, that
within thirty (30) days after the institution of such claim, investigation, action, suit or proceeding, such person shall offer to the Company, in writing, the opportunity at the Company’s expense to defend the same. 

5. Eligibility. Awards other than Incentive Stock Options may be granted to Employees, Directors and Consultants. Incentive Stock
Options may be granted only to Employees of the Company or a Parent or a Subsidiary of the Company. An Employee, Director or Consultant who has been granted an Award may, if otherwise eligible, be granted additional Awards. Awards may be granted to
such Employees, Directors or Consultants who are residing in non-U.S. jurisdictions as the Administrator may determine from time to time. 

6. Terms and Conditions of Awards. 

(a) Types of Awards. The Administrator is authorized under the Plan to award any type of arrangement to an Employee, Director or
Consultant that is not inconsistent with the provisions of the Plan and that by its terms involves or might involve the issuance of (i) Shares, (ii) cash or (iii) an Option, a SAR, or similar right with a fixed or variable price
related to the Fair Market Value of the Shares and with an exercise or conversion privilege related to the passage of time, the occurrence of one or more events, or the satisfaction of performance criteria or other conditions. Such awards include,
without limitation, Options, SARs, sales or bonuses of Restricted Stock, Restricted Stock Units or Dividend Equivalent Rights, and an Award may consist of one such security or benefit, or two (2) or more of them in any combination or
alternative. 
 (b) Designation of Award. Each Award shall be designated in the Award Agreement. In the case of an Option, the Option
shall be designated as either an Incentive Stock Option or a Non-Qualified Stock Option. However, notwithstanding such designation, an Option will qualify as an Incentive Stock Option under the Code only to the extent the $100,000 dollar limitation
of Section 422(d) of the Code is not exceeded. The $100,000 limitation of Section 

  
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422(d) of the Code is calculated based on the aggregate Fair Market Value of the Shares subject to Options designated as Incentive Stock Options which become exercisable for the first time by a
Grantee during any calendar year (under all plans of the Company or any Parent or Subsidiary of the Company). For purposes of this calculation, Incentive Stock Options shall be taken into account in the order in which they were granted, and the Fair
Market Value of the Shares shall be determined as of the grant date of the relevant Option. In the event that the Code or the regulations promulgated thereunder are amended after the date the Plan becomes effective to provide for a different limit
on the Fair Market Value of Shares permitted to be subject to Incentive Stock Options, then such different limit will be automatically incorporated herein and will apply to any Options granted after the effective date of such amendment. 

(c) Conditions of Award. Subject to the terms of the Plan, the Administrator shall determine the provisions, terms, and conditions of
each Award including, but not limited to, the Award vesting schedule, repurchase provisions, rights of first refusal, forfeiture provisions, form of payment (cash, Shares, or other consideration) upon settlement of the Award, payment contingencies,
and satisfaction of any performance criteria. The performance criteria established by the Administrator may be based on any one of, or combination of, increase in share price, earnings per share, total stockholder return, return on equity, return on
assets, return on investment, net operating income, cash flow, revenue, economic value added, personal management objectives, or other measure of performance selected by the Administrator. Partial achievement of the specified criteria may result in
a payment or vesting corresponding to the degree of achievement as specified in the Award Agreement. In addition, the performance criteria shall be calculated in accordance with generally accepted accounting principles, but excluding the effect
(whether positive or negative) of any change in accounting standards and any extraordinary, unusual or nonrecurring item, as determined by the Administrator, occurring after the establishment of the performance criteria applicable to the Award
intended to be performance-based compensation. Each such adjustment, if any, shall be made solely for the purpose of providing a consistent basis from period to period for the calculation of performance criteria in order to prevent the dilution or
enlargement of the Grantee’s rights with respect to an Award intended to be performance-based compensation. 
 (d) Acquisitions and
Other Transactions. The Administrator may issue Awards under the Plan in settlement, assumption or substitution for, outstanding awards or obligations to grant future awards in connection with the Company or a Related Entity acquiring another
entity, an interest in another entity or an additional interest in a Related Entity whether by merger, stock purchase, asset purchase or other form of transaction. 

(e) Deferral of Award Payment. The Administrator may establish one or more programs under the Plan to permit selected Grantees the
opportunity to elect to defer receipt of consideration upon exercise of an Award, satisfaction of performance criteria, or other event that absent the election would entitle the Grantee to payment or receipt of Shares or other consideration under an
Award. The Administrator may establish the election procedures, the timing of such elections, the mechanisms for payments of, and accrual of interest or other earnings, if any, on amounts, Shares or other consideration so deferred, and such other
terms, conditions, rules and procedures that the Administrator deems advisable for the administration of any such deferral program. 

  
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 (f) Separate Programs. The Administrator may establish one or more separate programs under
the Plan for the purpose of issuing particular forms of Awards to one or more classes of Grantees on such terms and conditions as determined by the Administrator from time to time. 

(g) Individual Limitations on Awards. 

(i) Individual Option and SAR Limit. Following the date that the exemption from application of Section 162(m) of the Code
described in Section 20 (or any exemption having similar effect) ceases to apply to Awards, the maximum number of Shares with respect to which Options and SARs may be granted to any Grantee in any calendar year shall be three hundred fifty
thousand (350,000) of the Shares. In connection with a Grantee’s commencement of Continuous Service, a Grantee may be granted Options and SARs for up to an additional one hundred thousand (100,000) Shares which shall not count against
the limit set forth in the previous sentence. The foregoing limitations shall be adjusted proportionately in connection with any change in the Company’s capitalization pursuant to Section 10, below. To the extent required by
Section 162(m) of the Code or the regulations thereunder, in applying the foregoing limitations with respect to a Grantee, if any Option or SAR is canceled, the canceled Option or SAR shall continue to count against the maximum number of Shares
with respect to which Options and SARs may be granted to the Grantee. For this purpose, the repricing of an Option (or in the case of a SAR, the base amount on which the stock appreciation is calculated is reduced to reflect a reduction in the Fair
Market Value of the Common Stock) shall be treated as the cancellation of the existing Option or SAR and the grant of a new Option or SAR. 

(ii) Individual Limit for Restricted Stock and Restricted Stock Units. Following the date that the exemption from application of
Section 162(m) of the Code described in Section 20 (or any exemption having similar effect) ceases to apply to Awards, for awards of Restricted Stock and Restricted Stock Units that are intended to be Performance-Based Compensation, the
maximum number of Shares with respect to which such Awards may be granted to any Grantee in any calendar year shall be three hundred fifty thousand (350,000) Shares. The foregoing limitation shall be adjusted proportionately in connection with
any change in the Company’s capitalization pursuant to Section 10, below. 
 (h) Early Exercise. The Award Agreement may,
but need not, include a provision whereby the Grantee may elect at any time while an Employee, Director or Consultant to exercise any part or all of the Award prior to full vesting of the Award. Any unvested Shares received pursuant to such exercise
may be subject to a repurchase right in favor of the Company or a Related Entity or to any other restriction the Administrator determines to be appropriate. 

(i) Term of Award. The term of each Award shall be the term stated in the Award Agreement, provided, however, that the term shall be no
more than ten (10) years from the date of grant thereof. However, in the case of an Incentive Stock Option granted to a Grantee who, at the time the Option is granted, owns stock representing more than ten percent (10%) of the voting power
of all classes of stock of the Company or any Parent or Subsidiary of the Company, the term of the Incentive Stock Option shall be five (5) years from the date of grant thereof or such shorter term as may be provided in the Award Agreement.
Notwithstanding the foregoing, the specified term of any Award shall not include any period for which the Grantee has elected to defer the receipt of the Shares or cash issuable pursuant to the Award. 

  
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 (j) Transferability of Awards. Incentive Stock Options may not be sold, pledged, assigned,
hypothecated, transferred, or disposed of in any manner other than by will or by the laws of descent or distribution and may be exercised, during the lifetime of the Grantee, only by the Grantee. Other Awards shall be transferable (i) by will
and by the laws of descent and distribution and (ii) during the lifetime of the Grantee, to the extent and in the manner authorized by the Administrator by gift or pursuant to a domestic relations order to members of the Grantee’s
Immediate Family. Notwithstanding the foregoing, the Grantee may designate one or more beneficiaries of the Grantee’s Award in the event of the Grantee’s death on a beneficiary designation form provided by the Administrator. 

(k) Time of Granting Awards. The date of grant of an Award shall for all purposes be the date on which the Administrator makes the
determination to grant such Award, or such other later date as is determined by the Administrator. 
 7. Award Exercise or Purchase
Price, Consideration and Taxes. 
 (a) Exercise or Purchase Price. The exercise or purchase price, if any, for an Award shall be
as follows: 
 (i) In the case of an Incentive Stock Option: 

(A) granted to an Employee who, at the time of the grant of such Incentive Stock Option owns stock representing more than ten percent
(10%) of the voting power of all classes of stock of the Company or any Parent or Subsidiary of the Company, the per Share exercise price shall be not less than one hundred ten percent (110%) of the Fair Market Value per Share on the date
of grant; or 
 (B) granted to any Employee other than an Employee described in the preceding paragraph, the per Share exercise price shall
be not less than one hundred percent (100%) of the Fair Market Value per Share on the date of grant. 
 (ii) In the case of a
Non-Qualified Stock Option, the per Share exercise price shall be not less than one hundred percent (100%) of the Fair Market Value per Share on the date of grant. 

(iii) In the case of SARs, the base appreciation amount shall not be less than one hundred percent (100%) of the Fair Market Value per
Share on the date of grant. 
 (iv) In the case of Awards intended to qualify as Performance-Based Compensation, the exercise or purchase
price, if any, shall be not less than one hundred percent (100%) of the Fair Market Value per Share on the date of grant. 
 (v) In
the case of the sale of Shares, the per Share purchase price, if any, shall be such price as is determined by the Administrator. 

  
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 (vi) In the case of other Awards, such price as is determined by the Administrator. 

(vii) Notwithstanding the foregoing provisions of this Section 7(a), in the case of an Award issued pursuant to Section 6(d),
above, the exercise or purchase price for the Award shall be determined in accordance with the provisions of the relevant instrument evidencing the agreement to issue such Award. 

(b) Consideration. Subject to Applicable Laws, the consideration to be paid for the Shares to be issued upon exercise or purchase of an
Award including the method of payment, shall be determined by the Administrator. In addition to any other types of consideration the Administrator may determine, the Administrator is authorized to accept as consideration for Shares issued under the
Plan the following, provided that the portion of the consideration equal to the par value of the Shares must be paid in cash or other legal consideration permitted by the Delaware General Corporation Law: 

(i) cash; 
 (ii) check; 

(iii) delivery of Grantee’s promissory note with such recourse, interest, security, and redemption provisions as the Administrator
determines as appropriate (but only to the extent that the acceptance or terms of the promissory note would not violate an Applicable Law); 

(iv) surrender of Shares or delivery of a properly executed form of attestation of ownership of Shares as the Administrator may require which
have a Fair Market Value on the date of surrender or attestation equal to the aggregate exercise price of the Shares as to which said Award shall be exercised; 

(v) with respect to Options, if the exercise occurs on or after the Registration Date, payment through a broker-dealer sale and remittance
procedure pursuant to which the Grantee (A) shall provide written instructions to a Company designated brokerage firm to effect the immediate sale of some or all of the purchased Shares and remit to the Company sufficient funds to cover the
aggregate exercise price payable for the purchased Shares and (B) shall provide written directives to the Company to deliver the certificates for the purchased Shares directly to such brokerage firm in order to complete the sale transaction;

 (vi) with respect to Options, payment through a “net exercise” such that, without the payment of any funds, the Grantee may
exercise the Option and receive the net number of Shares equal to (i) the number of Shares as to which the Option is being exercised, multiplied by (ii) a fraction, the numerator of which is the Fair Market Value per Share (on such date as
is determined by the Administrator) less the Exercise Price per Share, and the denominator of which is such Fair Market Value per Share (the number of net Shares to be received shall be rounded down to the nearest whole number of Shares); or 

(vii) any combination of the foregoing methods of payment. 

  
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 The Administrator may at any time or from time to time, by adoption of or by amendment to the standard forms of
Award Agreement described in Section 4(c)(iv), or by other means, grant Awards which do not permit all of the foregoing forms of consideration to be used in payment for the Shares or which otherwise restrict one or more forms of consideration.

 (c) Taxes. No Shares shall be delivered under the Plan to any Grantee or other person until such Grantee or other person has made
arrangements acceptable to the Administrator for the satisfaction of any non-U.S., federal, state, or local income and employment tax withholding obligations, including, without limitation, obligations incident to the receipt of Shares. Upon
exercise or vesting of an Award the Company shall withhold or collect from the Grantee an amount sufficient to satisfy such tax obligations, including, but not limited to, by surrender of the whole number of Shares covered by the Award sufficient to
satisfy the minimum applicable tax withholding obligations incident to the exercise or vesting of an Award (reduced to the lowest whole number of Shares if such number of Shares withheld would result in withholding a fractional Share with any
remaining tax withholding settled in cash). 
 8. Exercise of Award. 

(a) Procedure for Exercise; Rights as a Stockholder. 

(i) Any Award granted hereunder shall be exercisable at such times and under such conditions as determined by the Administrator under the
terms of the Plan and specified in the Award Agreement. 
 (ii) An Award shall be deemed to be exercised when written notice of such
exercise has been given to the Company in accordance with the terms of the Award by the person entitled to exercise the Award and full payment for the Shares with respect to which the Award is exercised has been made, including, to the extent
selected, use of the broker-dealer sale and remittance procedure to pay the purchase price as provided in Section 7(b)(v). 
 (b)
Exercise of Award Following Termination of Continuous Service. In the event of termination of a Grantee’s Continuous Service for any reason other than Disability or death (but not in the event of a Grantee’s change of status from
Employee to Consultant or from Consultant to Employee), such Grantee may, but only during the Post-Termination Exercise Period (but in no event later than the expiration date of the term of such Award as set forth in the Award Agreement), exercise
the portion of the Grantee’s Award that was vested at the date of such termination or such other portion of the Grantee’s Award as may be determined by the Administrator. The Grantee’s Award Agreement may provide that upon the
termination of the Grantee’s Continuous Service for Cause, the Grantee’s right to exercise the Award shall terminate concurrently with the termination of Grantee’s Continuous Service. In the event of a Grantee’s change of status
from Employee to Consultant, an Employee’s Incentive Stock Option shall convert automatically to a Non-Qualified Stock Option on the day three (3) months and one day following such change of status. To the extent that the Grantee’s
Award was unvested at the date of termination, or if the Grantee does not exercise the vested portion of the Grantee’s Award within the Post-Termination Exercise Period, the Award shall terminate. 

  
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 (c) Disability of Grantee. In the event of termination of a Grantee’s Continuous
Service as a result of his or her Disability, such Grantee may, but only within twelve (12) months from the date of such termination (or such longer period as specified in the Award Agreement but in no event later than the expiration date of
the term of such Award as set forth in the Award Agreement), exercise the portion of the Grantee’s Award that was vested at the date of such termination; provided, however, that if such Disability is not a “disability” as such term is
defined in Section 22(e)(3) of the Code, in the case of an Incentive Stock Option such Incentive Stock Option shall automatically convert to a Non-Qualified Stock Option on the day three (3) months and one day following such termination.
To the extent that the Grantee’s Award was unvested at the date of termination, or if Grantee does not exercise the vested portion of the Grantee’s Award within the time specified herein, the Award shall terminate. 

(d) Death of Grantee. In the event of a termination of the Grantee’s Continuous Service as a result of his or her death, or in the
event of the death of the Grantee during the Post-Termination Exercise Period or during the twelve (12) month period following the Grantee’s termination of Continuous Service as a result of his or her Disability, the Grantee’s estate
or a person who acquired the right to exercise the Award by bequest or inheritance may exercise the portion of the Grantee’s Award that was vested as of the date of termination, within twelve (12) months from the date of death (or such
longer period as specified in the Award Agreement but in no event later than the expiration of the term of such Award as set forth in the Award Agreement). To the extent that, at the time of death, the Grantee’s Award was unvested, or if the
Grantee’s estate or a person who acquired the right to exercise the Award by bequest or inheritance does not exercise the vested portion of the Grantee’s Award within the time specified herein, the Award shall terminate. 

(e) Extension if Exercise Prevented by Law. Notwithstanding the foregoing, if the exercise of an Award within the applicable time
periods set forth in this Section 8 is prevented by the provisions of Section 9 below, the Award shall remain exercisable until one (1) month after the date the Grantee is notified by the Company that the Award is exercisable, but in
any event no later than the expiration of the term of such Award as set forth in the Award Agreement. 
 9. Conditions Upon Issuance of
Shares. 
 (a) If at any time the Administrator determines that the delivery of Shares pursuant to the exercise, vesting or any other
provision of an Award is or may be unlawful under Applicable Laws, the vesting or right to exercise an Award or to otherwise receive Shares pursuant to the terms of an Award shall be suspended until the Administrator determines that such delivery is
lawful and shall be further subject to the approval of counsel for the Company with respect to such compliance. The Company shall have no obligation to effect any registration or qualification of the Shares under federal or state laws. 

(b) As a condition to the exercise of an Award, the Company may require the person exercising such Award to represent and warrant at the time
of any such exercise that the Shares are being purchased only for investment and without any present intention to sell or distribute such Shares if, in the opinion of counsel for the Company, such a representation is required by any Applicable Laws.


  
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 10. Adjustments Upon Changes in Capitalization. Subject to any required action by the
stockholders of the Company and Section 11 hereof, the number of Shares covered by each outstanding Award, and the number of Shares which have been authorized for issuance under the Plan but as to which no Awards have yet been granted or which
have been returned to the Plan, the exercise or purchase price of each such outstanding Award, the maximum number of Shares with respect to which Awards may be granted to any Grantee in any calendar year, as well as any other terms that the
Administrator determines require adjustment shall be proportionately adjusted for (i) any increase or decrease in the number of issued Shares resulting from a stock split, reverse stock split, stock dividend, combination or reclassification of
the Shares, or similar transaction affecting the Shares, (ii) any other increase or decrease in the number of issued Shares effected without receipt of consideration by the Company, or (iii) any other transaction with respect to Common
Stock including a corporate merger, consolidation, acquisition of property or stock, separation (including a spin-off or other distribution of stock or property), reorganization, liquidation (whether partial or complete) or any similar transaction;
provided, however that conversion of any convertible securities of the Company shall not be deemed to have been “effected without receipt of consideration.” In connection with the foregoing adjustments, the Administrator may, in its
discretion, prohibit the exercise of Awards or other issuance of Shares, cash or other consideration pursuant to Awards during certain periods of time. Except as the Administrator determines, no issuance by the Company of shares of any class, or
securities convertible into shares of any class, shall affect, and no adjustment by reason hereof shall be made with respect to, the number or price of Shares subject to an Award. 

11. Corporate Transactions and Changes in Control. 

(a) Termination of Award to Extent Not Assumed in Corporate Transaction. In the event of a Corporate Transaction, outstanding Awards
may be Assumed or Replaced, and to the extent that outstanding Awards under the Plan are not Assumed or Replaced, such Awards shall terminate effective upon the consummation of a Corporate Transaction. 

(a) Acceleration of Award Upon Corporate Transaction or Change in Control. Except as provided otherwise in an individual Award
Agreement, in the event of any Corporate Transaction or Change in Control, there will not be any acceleration of vesting or exercisability of any Award. 

12. Repurchase Rights. If the provisions of an Award Agreement grant to the Company the right to repurchase Shares upon termination of
the Grantee’s Continuous Service, the Award Agreement shall (or may, with respect to Awards granted or issued to Officers, Directors or Consultants) provide that: 

(a) the right to repurchase must be exercised, if at all, within six (6) months of the termination of the Grantee’s Continuous
Service (or in the case of Shares issued upon exercise of Awards after the date of termination of the Grantee’s Continuous Service, within six (6) months after the date of the Award exercise); 

(b) the consideration payable for the Shares upon exercise of such repurchase right shall be made in cash or by cancellation of purchase money
indebtedness within the six (6) month periods specified in Section 12(a); 

  
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 (c) the amount of such consideration shall be equal to the original purchase price paid by
Grantee for each such Share or the Fair Market Value of the Shares to be repurchased on the date of termination of Grantee’s Continuous Service; and 

(d) the right to repurchase Shares, other than a right to repurchase under which Shares may be repurchased at the original purchase price,
shall terminate on the Registration Date. 
 13. Effective Date and Term of Plan. The Plan shall become effective upon the earlier to
occur of its adoption by the Board or its approval by the stockholders of the Company. It shall continue in effect for a term of ten (10) years unless sooner terminated. Subject to Section 18 below, and Applicable Laws, Awards may be
granted under the Plan upon its becoming effective. 
 14. Amendment, Suspension or Termination of the Plan. 

(a) The Board may at any time amend, suspend or terminate the Plan. To the extent necessary to comply with Applicable Laws, the Company shall
obtain stockholder approval of any Plan amendment in such a manner and to such a degree as required. 
 (b) No Award may be granted during
any suspension of the Plan or after termination of the Plan. 
 (c) No suspension or termination of the Plan (including termination of the
Plan under Section 13, above) shall adversely affect any rights under Awards already granted to a Grantee. 
 15. Reservation of
Shares. 
 (a) The Company, during the term of the Plan, will at all times reserve and keep available such number of Shares as shall be
sufficient to satisfy the requirements of the Plan. 
 (b) The inability of the Company to obtain authority from any regulatory body having
jurisdiction, which authority is deemed by the Company’s counsel to be necessary to the lawful issuance and sale of any Shares hereunder, shall relieve the Company of any liability in respect of the failure to issue or sell such Shares as to
which such requisite authority shall not have been obtained. 
 16. No Effect on Terms of Employment/Consulting Relationship. The
Plan shall not confer upon any Grantee any right with respect to the Grantee’s Continuous Service, nor shall it interfere in any way with his or her right or the right of the Company or a Related Entity to terminate the Grantee’s
Continuous Service at any time, with or without Cause, and with or without notice. The ability of the Company or any Related Entity to terminate the employment of a Grantee who is employed at will is in no way affected by its determination that the
Grantee’s Continuous Service has been terminated for Cause for the purposes of this Plan. 

  
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 17. No Effect on Retirement and Other Benefit Plans. Except as specifically provided in a
retirement or other benefit plan of the Company or a Related Entity, Awards shall not be deemed compensation for purposes of computing benefits or contributions under any retirement plan of the Company or a Related Entity, and shall not affect any
benefits under any other benefit plan of any kind or any benefit plan subsequently instituted under which the availability or amount of benefits is related to level of compensation. The Plan is not a “Retirement Plan” or “Welfare
Plan” under the Employee Retirement Income Security Act of 1974, as amended. 
 18. Stockholder Approval. Continuance of the
Plan shall be subject to approval by the stockholders of the Company within twelve (12) months before or after the date the Plan is adopted. Such stockholder approval shall be obtained in the degree and manner required under Applicable Laws.
Any Award exercised before stockholder approval is obtained shall be rescinded if stockholder approval is not obtained within the time prescribed, and Shares issued on the exercise of any such Award shall not be counted in determining whether
stockholder approval is obtained. 
 19. Information to Grantees. To the extent required by Applicable Law, the Company shall provide
to each Grantee, during the period for which such Grantee has one or more Awards outstanding, copies of financial statements at least annually. The Company shall not be required to provide such information to persons whose duties in connection with
the Company assure them access to equivalent information. 
 20. Effect of Section 162(m) of the Code. Section 162(m) of
the Code does not apply to the Plan prior to the Registration Date or such earlier time that the Company first becomes subject to the reporting obligations of Section 12 of the Exchange Act. Following the Registration Date or such earlier time
that the Company first becomes subject to the reporting obligations of Section 12 of the Exchange Act, the Plan, and all Awards (except Awards of Restricted Stock that vest over time) issued thereunder, are intended to be exempt from the
application of Section 162(m) of the Code, which restricts under certain circumstances the Federal income tax deduction for compensation paid by a public company to named executives in excess of $1 million per year. The exemption is based on
Treasury Regulation Section 1.162-27(f), in the form existing on the effective date of the Plan, with the understanding that such regulation generally exempts from the application of Section 162(m) of the Code compensation paid pursuant to
a plan that existed before a company becomes publicly held. Under such Treasury Regulation, this exemption is available to the Plan for the duration of the period that lasts until the earliest of (i) the expiration of the Plan, (ii) the
material modification of the Plan, (iii) the exhaustion of the maximum number of shares of Common Stock available for Awards under the Plan, as set forth in Section 3(a), (iv) the first meeting of stockholders at which directors are
to be elected that occurs after the close of the third calendar year following the calendar year in which the Company first becomes subject to the reporting obligations of Section 12 of the Exchange Act, or (v) such other date required by
Section 162(m) of the Code and the rules and regulations promulgated thereunder. To the extent that the Administrator determines as of the date of grant of an Award that (i) the Award is intended to qualify as Performance-Based
Compensation and (ii) the exemption described above is no longer available with respect to such Award, such Award shall not be effective until any stockholder approval required under Section 162(m) of the Code has been obtained. 

  
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 21. Unfunded Obligation. Grantees shall have the status of general unsecured creditors of
the Company. Any amounts payable to Grantees pursuant to the Plan shall be unfunded and unsecured obligations for all purposes, including, without limitation, Title I of the Employee Retirement Income Security Act of 1974, as amended. Neither the
Company nor any Related Entity shall be required to segregate any monies from its general funds, or to create any trusts, or establish any special accounts with respect to such obligations. The Company shall retain at all times beneficial ownership
of any investments, including trust investments, which the Company may make to fulfill its payment obligations hereunder. Any investments or the creation or maintenance of any trust or any Grantee account shall not create or constitute a trust or
fiduciary relationship between the Administrator, the Company or any Related Entity and a Grantee, or otherwise create any vested or beneficial interest in any Grantee or the Grantee’s creditors in any assets of the Company or a Related Entity.
The Grantees shall have no claim against the Company or any Related Entity for any changes in the value of any assets that may be invested or reinvested by the Company with respect to the Plan. 

22. Construction. Captions and titles contained herein are for convenience only and shall not affect the meaning or interpretation of
any provision of the Plan. Except when otherwise indicated by the context, the singular shall include the plural and the plural shall include the singular. Use of the term “or” is not intended to be exclusive, unless the context clearly
requires otherwise. 
 23. Nonexclusivity of the Plan. Neither the adoption of the Plan by the Board, the submission of the Plan to
the stockholders of the Company for approval, nor any provision of the Plan will be construed as creating any limitations on the power of the Board to adopt such additional compensation arrangements as it may deem desirable, including, without
limitation, the granting of Awards otherwise than under the Plan, and such arrangements may be either generally applicable or applicable only in specific cases. 

  
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 AMENDMENT 

TO THE ARDELYX, INC. 

2008 STOCK INCENTIVE PLAN 

JUNE 22, 2011 
 Pursuant
to the authority reserved to the Board of Directors (the “Board”) of Ardelyx, Inc., a Delaware corporation (the “Company”), under Section 14 of the Company’s 2008 Stock Incentive Plan (the
“Plan”), the Board hereby amends the Plan as follows. 
 1. Section 3(a) of the Plan is hereby deleted in its entirety
and replaced with the following: 
 “3. Stock Subject to the Plan 

(a) Subject to the provisions of Section 10 below, the maximum aggregate number of Shares which may be issued pursuant to
all Awards (including Incentive Stock Options) is eighteen million fifty one thousand two hundred six (18,051,206) Shares. The Shares may be authorized, but unissued, or reacquired Common Stock” 

2. Except as amended hereby, the Plan shall continue in full force and effect and is hereby ratified and confirmed. 

I hereby certify that the foregoing Amendment to the Plan was duly adopted by the Company’s Board effective as of June 22, 2011.

 I hereby further certify that the foregoing Amendment to the Plan was duly adopted by the Company’s Stockholders effective as of
June 22, 2011. 
 * * * * * * * * * * 







 Executed as of the date first written above. 

 

	
	 /s/ Alan C. Mendelson

	Alan C. Mendelson, Secretary


 SIGNATURE PAGE TO AMENDMENT TO THE ARDELYX, INC. 2008 STOCK INCENTIVE PLAN