Document:

EX-10.5(b)

 Exhibit 10.5B 

ARDELYX, INC. 2008 STOCK INCENTIVE PLAN 

NOTICE OF STOCK OPTION AWARD 
  

			
	Grantee’s Name and Address:	 	  

		
		 	  

		
		 	  

 You (the “Grantee”) have been granted an option to purchase shares of Common Stock, subject to the
terms and conditions of this Notice of Stock Option Award (the “Notice”), the Ardelyx, Inc. 2008 Stock Incentive Plan, as amended from time to time (the “Plan”) and the Stock Option Award Agreement (the “Option
Agreement”) attached hereto, as follows. Unless otherwise defined herein, the terms defined in the Plan shall have the same defined meanings in this Notice. 
  

					
	Award Number	 	  

		
	Date of Award	 	  

		
	Vesting Commencement Date	 	  

			
	Exercise Price per Share	 	$	 	  

		
	Total Number of Shares Subject to the Option (the “Shares”)	 	  

			
	Total Exercise Price	 	$	 	  

		
	Type of Option:	 	             Incentive Stock Option
		
		 	             Non-Qualified Stock Option
		
	Expiration Date:	 	  

		
	Post-Termination Exercise Period:	 	Three (3) Months

 Vesting Schedule: 

Subject to the Grantee’s Continuous Service and other limitations set forth in this Notice, the Plan and the Option Agreement, the Option
may be exercised, in whole or in part, in accordance with the following schedule: 
 25% of the Shares subject to the Option shall vest on
the first anniversary of the Vesting Commencement Date, and 1/48 of the Shares subject to the Option shall vest on each monthly anniversary of the Vesting Commencement Date thereafter. 

During any authorized leave of absence, the vesting of the Option as provided in this schedule shall be suspended after the leave of absence
exceeds a period of three (3) months. Vesting of the Option shall resume upon the Grantee’s termination of the leave of absence and return to service to the Company or a Related Entity. The Vesting Schedule of the Option shall be extended
by the length of the suspension. 

  
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 In the event of termination of the Grantee’s Continuous Service for Cause, the
Grantee’s right to exercise the Option shall terminate concurrently with the termination of the Grantee’s Continuous Service, except as otherwise determined by the Administrator. 

IN WITNESS WHEREOF, the Company and the Grantee have executed this Notice and agree that the Option is to be governed by the terms and
conditions of this Notice, the Plan, and the Option Agreement. 
  

			
	 Ardelyx, Inc.
 a Delaware
corporation

		
	By:	 	  

	Title:	 	  

 THE GRANTEE ACKNOWLEDGES AND AGREES THAT THE SHARES SUBJECT TO THE OPTION SHALL VEST, IF AT ALL, ONLY DURING THE PERIOD
OF THE GRANTEE’S CONTINUOUS SERVICE (NOT THROUGH THE ACT OF BEING HIRED, BEING GRANTED THE OPTION OR ACQUIRING SHARES HEREUNDER). THE GRANTEE FURTHER ACKNOWLEDGES AND AGREES THAT NOTHING IN THIS NOTICE, THE OPTION AGREEMENT, OR THE PLAN SHALL
CONFER UPON THE GRANTEE ANY RIGHT WITH RESPECT TO FUTURE AWARDS OR CONTINUATION OF THE GRANTEE’S CONTINUOUS SERVICE, NOR SHALL IT INTERFERE IN ANY WAY WITH THE GRANTEE’S RIGHT OR THE RIGHT OF THE COMPANY OR RELATED ENTITY TO WHICH THE
GRANTEE PROVIDES SERVICES TO TERMINATE THE GRANTEE’S CONTINUOUS SERVICE, WITH OR WITHOUT CAUSE, AND WITH OR WITHOUT NOTICE. THE GRANTEE ACKNOWLEDGES THAT UNLESS THE GRANTEE HAS A WRITTEN EMPLOYMENT AGREEMENT WITH THE COMPANY TO THE CONTRARY,
THE GRANTEE’S STATUS IS AT WILL. 
 The Grantee acknowledges receipt of a copy of the Plan and the Option Agreement, and represents
that he or she is familiar with the terms and provisions thereof, and hereby accepts the Option subject to all of the terms and provisions hereof and thereof. The Grantee has reviewed this Notice, the Plan, and the Option Agreement in their
entirety, has had an opportunity to obtain the advice of counsel prior to executing this Notice, and fully understands all provisions of this Notice, the Plan and the Option Agreement. The Grantee hereby agrees that all questions of interpretation
and administration relating to this Notice, the Plan and the Option Agreement shall be resolved by the Administrator in accordance with Section 18 of the Option Agreement. The Grantee further agrees to the venue selection in accordance with
Section 19 of the Option Agreement. The Grantee further agrees to notify the Company upon any change in the residence address indicated in this Notice. 
  

											
	Dated:	 	  
	 		 	Signed:	 	  
	 	Grantee

  
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 Award
Number:                     

ARDELYX, INC. 2008 STOCK INCENTIVE PLAN 

STOCK OPTION AWARD AGREEMENT 

1. Grant of Option. Ardelyx, Inc., a Delaware corporation (the “Company”), hereby grants to the Grantee (the
“Grantee”) named in the Notice of Stock Option Award (the “Notice”), an option (the “Option”) to purchase the Total Number of Shares of Common Stock subject to the Option (the “Shares”) set forth in the
Notice, at the Exercise Price per Share set forth in the Notice (the “Exercise Price”) subject to the terms and provisions of the Notice, this Stock Option Award Agreement (the “Option Agreement”) and the Company’s 2008
Stock Incentive Plan, as amended from time to time (the “Plan”), which are incorporated herein by reference. Unless otherwise defined herein, the terms defined in the Plan shall have the same defined meanings in this Option Agreement. 

If designated in the Notice as an Incentive Stock Option, the Option is intended to qualify as an Incentive Stock Option as defined in
Section 422 of the Code. However, notwithstanding such designation, the 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 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 the 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 subject to such options shall be determined as of the grant date of the relevant option. 
 2. Exercise of Option. 

(a) Right to Exercise. The Option shall be exercisable during its term in accordance with the Vesting Schedule set out in the Notice
and with the applicable provisions of the Plan and this Option Agreement. The Option shall be subject to the provisions of Section 11 of the Plan relating to the exercisability or termination of the Option in the event of a Corporate
Transaction or Change in Control. The Grantee shall be subject to reasonable limitations on the number of requested exercises during any monthly or weekly period as determined by the Administrator. In no event shall the Company issue fractional
Shares. 
 (b) Method of Exercise. The Option shall be exercisable by delivery of an exercise notice (a form of which is attached as
Exhibit A) or by such other procedure as specified from time to time by the Administrator which shall state the election to exercise the Option, the whole number of Shares in respect of which the Option is being exercised, and such other provisions
as may be required by the Administrator. The exercise notice shall be delivered in person, by certified mail, or by such other method (including electronic transmission) as determined from time to time by the Administrator to the Company accompanied
by payment of the Exercise Price. The Option shall be deemed to be exercised upon receipt by the Company of 

  
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such notice accompanied by the Exercise Price, which, to the extent selected, shall be deemed to be satisfied by use of the broker-dealer sale and remittance procedure to pay the Exercise Price
provided in Section 4(d) below. 
 (c) Taxes. No Shares will be delivered to the Grantee or other person pursuant to the
exercise of the Option until the Grantee or other person has made arrangements acceptable to the Administrator for the satisfaction of applicable income tax and employment tax withholding obligations, including, without limitation, such other tax
obligations of the Grantee incident to the receipt of Shares. Upon exercise of the Option, the Company or the Grantee’s employer may offset or withhold (from any amount owed by the Company or the Grantee’s employer to the Grantee) or
collect from the Grantee or other person an amount sufficient to satisfy such tax withholding obligations. Furthermore, in the event of any determination that the Company has failed to withhold a sum sufficient to pay all withholding taxes due in
connection with the Option, the Grantee agrees to pay the Company the amount of such deficiency in cash within five (5) days after receiving a written demand from the Company to do so, whether or not the Grantee is an employee of the Company at
that time. 
 3. Grantee’s Representations. The Grantee understands that neither the Option nor the Shares exercisable pursuant
to the Option have been registered under the Securities Act of 1933, as amended or any United States securities laws. In the event the Shares purchasable pursuant to the exercise of the Option have not been registered under the Securities Act of
1933, as amended, at the time the Option is exercised, the Grantee shall, if requested by the Company, concurrently with the exercise of all or any portion of the Option, deliver to the Company his or her Investment Representation Statement in the
form attached hereto as Exhibit B. 
 4. Method of Payment. Payment of the Exercise Price shall be made by any of the following, or a
combination thereof, at the election of the Grantee; provided, however, that such exercise method does not then violate any Applicable Law and, provided further, that the portion of the Exercise Price equal to the par value of the Shares must be
paid in cash or other legal consideration permitted by the Delaware General Corporation Law. 
 (a) cash; 

(b) check; 
 (c) if the exercise
occurs on or after the Registration Date, 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 the Option is being exercised; or 
 (i) if the exercise occurs on or after the
Registration Date, payment through a broker-dealer sale and remittance procedure pursuant to which the Grantee (i) 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 (ii) 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. 

  
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 5. Restrictions on Exercise. The Option may not be exercised if the issuance of the Shares
subject to the Option upon such exercise would constitute a violation of any Applicable Laws. In addition, the Option may not be exercised until such time as the Plan has been approved by the stockholders of the Company. If the exercise of the
Option within the applicable time periods set forth in Section 6, 7 and 8 of this Option Agreement is prevented by the provisions of this Section 5, the Option shall remain exercisable until one (1) month after the date the Grantee is
notified by the Company that the Option is exercisable, but in any event no later than the Expiration Date set forth in the Notice. 
 6.
Termination or Change of Continuous Service. In the event the Grantee’s Continuous Service terminates, other than for Cause, the Grantee may, but only during the Post-Termination Exercise Period, exercise the portion of the Option that
was vested at the date of such termination (the “Termination Date”). The Post-Termination Exercise Period shall commence on the Termination Date. In the event of termination of the Grantee’s Continuous Service for Cause, the
Grantee’s right to exercise the Option shall, except as otherwise determined by the Administrator, terminate concurrently with the termination of the Grantee’s Continuous Service (also the “Termination Date”). In no event,
however, shall the Option be exercised later than the Expiration Date set forth in the Notice. In the event of the Grantee’s change in status from Employee, Director or Consultant to any other status of Employee, Director or Consultant, the
Option shall remain in effect and the Option shall continue to vest in accordance with the Vesting Schedule set forth in the Notice consistent with any minimum vesting requirements set forth in the Plan; provided, however, with respect to any
Incentive Stock Option that shall remain in effect after a change in status from Employee to Director or Consultant, such Incentive Stock Option shall cease to be treated as an Incentive Stock Option and shall be treated as a Non-Qualified Stock
Option on the day three (3) months and one (1) day following such change in status. Except as provided in Sections 7 and 8 below, to the extent that the Option was unvested on the Termination Date, or if the Grantee does not
exercise the vested portion of the Option within the Post-Termination Exercise Period, the Option shall terminate. 
 7. Disability of
Grantee. In the event the Grantee’s Continuous Service terminates as a result of his or her Disability, the Grantee may, but only within twelve (12) months commencing on the Termination Date (but in no event later than the Expiration
Date), exercise the portion of the Option that was vested on the Termination Date; provided, however, that if such Disability is not a “disability” as such term is defined in Section 22(e)(3) of the Code and the Option is an Incentive
Stock Option, such Incentive Stock Option shall cease to be treated as an Incentive Stock Option and shall be treated as a Non-Qualified Stock Option on the day three (3) months and one (1) day following the Termination Date. To the extent
that the Option was unvested on the Termination Date, or if the Grantee does not exercise the vested portion of the Option within the time specified herein, the Option shall terminate. Section 22(e)(3) of the Code provides that an individual is
permanently and totally disabled if he or she is unable to engage in any substantial gainful activity by reason of any medically determinable physical or mental impairment which can be expected to result in death or which has lasted or can be
expected to last for a continuous period of not less than twelve (12) months. 

  
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 8. Death of Grantee. In the event of the termination of the Grantee’s Continuous
Service as a result of his or her death, or in the event of the Grantee’s death 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 person who acquired the right to exercise the Option pursuant to Section 9 may exercise the portion of the Option that was vested at the date of termination within twelve (12) months commencing on the date of
death (but in no event later than the Expiration Date). To the extent that the Option was unvested on the date of death, or if the vested portion of the Option is not exercised within the time specified herein, the Option shall terminate. 

9. Transferability of Option. The Option, if an Incentive Stock Option, may not be transferred in any manner other than by will or by
the laws of descent and distribution and may be exercised during the lifetime of the Grantee only by the Grantee. The Option, if a Non-Qualified Stock Option, may not be transferred in any manner other than by will or by the laws of descent and
distribution; provided, however, that a Non-Qualified Stock Option may be transferred during the lifetime of the Grantee by gift or pursuant to a domestic relations order to members of the Grantee’s Immediate Family to the extent and in the
manner determined by the Administrator. Notwithstanding the foregoing, the Grantee may designate one or more beneficiaries of the Grantee’s Incentive Stock Option or Non-Qualified Stock Option in the event of the Grantee’s death on a
beneficiary designation form provided by the Administrator. Following the death of the Grantee, the Option, to the extent provided in Section 8, may be exercised (a) by the person or persons designated under the deceased Grantee’s
beneficiary designation or (b) in the absence of an effectively designated beneficiary, by the Grantee’s legal representative or by any person empowered to do so under the deceased Grantee’s will or under the then applicable laws of
descent and distribution. The terms of the Option shall be binding upon the executors, administrators, heirs, successors and transferees of the Grantee. 

10. Term of Option. The Option must be exercised no later than the Expiration Date set forth in the Notice or such earlier date as
otherwise provided herein. After the Expiration Date or such earlier date, the Option shall be of no further force or effect and may not be exercised. 

11. Company’s Right of First Refusal. The Grantee acknowledges and agrees that the Shares are subject to a right of first refusal
(“Right of First Refusal”) as set forth in Article 10 of the Bylaws of the Company, which Right of First Refusal is incorporated herein by reference irrespective of whether the Bylaws are amended at some future date to remove the Right of
First Refusal therefrom, and that, except in compliance with such Right of First Refusal, neither the Grantee nor a transferee (either being sometimes referred to herein as the “Holder”) shall sell, hypothecate, encumber or otherwise
transfer any Shares or any right or interest therein. 
 12. Stop-Transfer Notices. In order to ensure compliance with the
restrictions on transfer set forth in this Option Agreement, the Notice or the Plan, the Company may issue appropriate “stop transfer” instructions to its transfer agent, if any, and, if the Company transfers its own securities, it may
make appropriate notations to the same effect in its own records. 
 13. Refusal to Transfer. The Company shall not be required
(i) to transfer on its books any Shares that have been sold or otherwise transferred in violation of any of the 

  
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provisions of this Option Agreement or (ii) to treat as owner of such Shares or to accord the right to vote or pay dividends to any purchaser or other transferee to whom such Shares shall
have been so transferred. 
 14. Tax Consequences. 

(a) The Grantee may incur tax liability as a result of the Grantee’s purchase or disposition of the Shares. THE GRANTEE SHOULD CONSULT A
TAX ADVISER BEFORE EXERCISING THE OPTION OR DISPOSING OF THE SHARES. 
 (b) Notwithstanding the Company’s good faith determination of
the Fair Market Value of the Company’s Common Stock for purposes of determining the Exercise Price Per Share of the Option as set forth in the Notice, the taxing authorities may assert that the Fair Market Value of the Common Stock on the Date
of Award was greater than the Exercise Price Per Share. If designated in the Notice as an Incentive Stock Option, the Option may fail to qualify as an Incentive Stock Option if the Exercise Price Per Share of the Option is less than the Fair Market
Value of the Common Stock on the Date of Award. In addition, under Section 409A of the Code, if the Exercise Price Per Share of the Option is less than the Fair Market Value of the Common Stock on the Date of Award, the Option may be treated as
a form of deferred compensation and the Grantee may be subject to an acceleration of income recognition, an additional 20% tax, plus interest and possible penalties. In addition, the Company makes no representation that the Option will comply with
Section 409A of the Code and makes no undertaking to prevent Section 409A of the Code from applying to the Option or to mitigate its effects on any deferrals or payments made in respect of the Option. The Grantee is encouraged to consult a
tax adviser regarding the potential impact of Section 409A of the Code. 
 15. Lock-Up Agreement. 

(a) Agreement. The Grantee, if requested by the Company and the lead underwriter of any public offering of the Common Stock (the
“Lead Underwriter”), hereby irrevocably agrees not to sell, contract to sell, grant any option to purchase, transfer the economic risk of ownership in, make any short sale of, pledge or otherwise transfer or dispose of any interest in any
Common Stock or any securities convertible into or exchangeable or exercisable for or any other rights to purchase or acquire Common Stock (except Common Stock included in such public offering or acquired on the public market after such offering)
during the 180-day period following the effective date of a registration statement of the Company filed under the Securities Act of 1933, as amended, or such shorter or longer period of time as the Lead Underwriter shall specify. The Grantee further
agrees to sign such documents as may be requested by the Lead Underwriter to effect the foregoing and agrees that the Company may impose stop-transfer instructions with respect to such Common Stock subject to the lock-up period until the end of such
period. The Company and the Grantee acknowledge that each Lead Underwriter of a public offering of the Company’s stock, during the period of such offering and for the lock-up period thereafter, is an intended beneficiary of this
Section 15. 
 (b) No Amendment Without Consent of Underwriter. During the period from identification of a Lead Underwriter in
connection with any public offering of the Company’s Common Stock until the earlier of (i) the expiration of the lock-up period specified in 

  
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Section 15(a) in connection with such offering or (ii) the abandonment of such offering by the Company and the Lead Underwriter, the provisions of this Section 15 may not be
amended or waived except with the consent of the Lead Underwriter. 
 16. Entire Agreement: Governing Law. The Notice, the Plan and
this Option Agreement constitute the entire agreement of the parties with respect to the subject matter hereof and supersede in their entirety all prior undertakings and agreements of the Company and the Grantee with respect to the subject matter
hereof, and may not be modified adversely to the Grantee’s interest except by means of a writing signed by the Company and the Grantee. Nothing in the Notice, the Plan and this Option Agreement (except as expressly provided therein) is intended
to confer any rights or remedies on any persons other than the parties. The Notice, the Plan and this Option Agreement are to be construed in accordance with and governed by the internal laws of the State of California without giving effect to any
choice of law rule that would cause the application of the laws of any jurisdiction other than the internal laws of the State of California to the rights and duties of the parties. Should any provision of the Notice, the Plan or this Option
Agreement be determined to be illegal or unenforceable, such provision shall be enforced to the fullest extent allowed by law and the other provisions shall nevertheless remain effective and shall remain enforceable. 

17. Construction. The captions used in the Notice and this Option Agreement are inserted for convenience and shall not be deemed a part
of the Option for construction or interpretation. 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. 
 18. Administration and Interpretation. Any question or dispute regarding the
administration or interpretation of the Notice, the Plan or this Option Agreement shall be submitted by the Grantee or by the Company to the Administrator. The resolution of such question or dispute by the Administrator shall be final and binding on
all persons. 
 19. Venue. The Company, the Grantee, and the Grantee’s assignees pursuant to Section 9 (the
“parties”) agree that any suit, action, or proceeding arising out of or relating to the Notice, the Plan or this Option Agreement shall be brought in the United States District Court for the Northern District of California (or should such
court lack jurisdiction to hear such action, suit or proceeding, in a California state court in the County of Santa Clara) and that the parties shall submit to the jurisdiction of such court. The parties irrevocably waive, to the fullest extent
permitted by law, any objection the party may have to the laying of venue for any such suit, action or proceeding brought in such court. If any one or more provisions of this Section 19 shall for any reason be held invalid or unenforceable, it
is the specific intent of the parties that such provisions shall be modified to the minimum extent necessary to make it or its application valid and enforceable. 

20. Notices. Any notice required or permitted hereunder shall be given in writing and shall be deemed effectively given upon personal
delivery, upon deposit for delivery by an internationally recognized express mail courier service or upon deposit in the United States mail by certified mail (if the parties are within the United States), with postage and fees prepaid, addressed to
the other party at its address as shown in these instruments, or to such other address as such party may designate in writing from time to time to the other party. 

  
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 21. Confidentiality. The Company shall provide to the Grantee, during the period the
Option is outstanding, copies of financial statements of the Company at least annually. The Grantee understands and agrees that such financial statements are confidential and shall not be disclosed by the Grantee, to any entity or person, for any
reason, at any time, without the prior written consent of the Company, unless required by law. If disclosure of such financial statements is required by law, whether through subpoena, request for production, deposition, or otherwise, the Grantee
promptly shall provide written notice to Company, including copies of the subpoena, request for production, deposition, or otherwise, within five (5) business days of their receipt by the Grantee and prior to any disclosure so as to provide
Company an opportunity to move to quash or otherwise to oppose the disclosure. Notwithstanding the foregoing, the Grantee may disclose the terms of such financial statements to his or her spouse or domestic partner, and for legitimate business
reasons, to legal, financial, and tax advisors. 
 END OF AGREEMENT 

  
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 EXHIBIT A 

ARDELYX, INC. 2008 STOCK INCENTIVE PLAN 

EXERCISE NOTICE 
 Ardelyx, Inc. 

                          
       

                          
       
 Attention: Secretary 

1. Effective as of today,
                    , the undersigned (the “Grantee”) hereby elects to exercise the Grantee’s option to purchase
                 shares of the Common Stock (the “Shares”) of Ardelyx, Inc., (the “Company”) under and pursuant to the Company’s 2008 Stock
Incentive Plan, as amended from time to time (the “Plan”) and the [ ] Incentive [ ] Non-Qualified Stock Option Award Agreement (the “Option Agreement”) and Notice of Stock Option Award (the “Notice”)
dated             ,         . Unless otherwise defined herein, the terms defined in the Plan shall have the same defined meanings in this Exercise
Notice. 
 2. Representations of the Grantee. The Grantee acknowledges that the Grantee has received, read and understood the Notice,
the Plan and the Option Agreement and agrees to abide by and be bound by their terms and conditions. 
 3. Rights as Stockholder.
Until the stock certificate evidencing such Shares is issued (as evidenced by the appropriate entry on the books of the Company or of a duly authorized transfer agent of the Company), no right to vote or receive dividends or any other rights as a
stockholder shall exist with respect to the Shares, notwithstanding the exercise of the Option. The Company shall issue (or cause to be issued) such stock certificate promptly after the Option is exercised. No adjustment will be made for a dividend
or other right for which the record date is prior to the date the stock certificate is issued, except as provided in Section 10 of the Plan. 

The Grantee shall enjoy rights as a stockholder until such time as the Grantee disposes of the Shares or the Company and/or its assignee(s)
exercises the Right of First Refusal (as such term is defined in the Option Agreement). Upon such exercise, the Grantee shall have no further rights as a holder of the Shares so purchased except the right to receive payment for the Shares so
purchased in accordance with the provisions of the Option Agreement, and the Grantee shall forthwith cause the certificate(s) evidencing the Shares so purchased to be surrendered to the Company for transfer or cancellation. 

4. Delivery of Payment. The Grantee herewith delivers to the Company the full Exercise Price for the Shares, which, to the extent
selected, shall be deemed to be satisfied by use of the broker-dealer sale and remittance procedure to pay the Exercise Price provided in Section 4(d) of the Option Agreement. 

5. Tax Consultation. The Grantee understands that the Grantee may suffer adverse tax consequences as a result of the Grantee’s
purchase or disposition of the Shares. The Grantee represents that the Grantee has consulted with any tax consultants the Grantee deems advisable in connection with the purchase or disposition of the Shares and that the Grantee is not relying on the
Company for any tax advice. 

  
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 6. Taxes. The Grantee agrees to satisfy all applicable federal, state and local income and
employment tax withholding obligations and herewith delivers to the Company the full amount of such obligations or has made arrangements acceptable to the Company to satisfy such obligations. In the case of an Incentive Stock Option, the Grantee
also agrees, as partial consideration for the designation of the Option as an Incentive Stock Option, to notify the Company in writing within thirty (30) days of any disposition of any shares acquired by exercise of the Option if such
disposition occurs within two (2) years from the Date of Award or within one (1) year from the date the Shares were transferred to the Grantee. 

7. Restrictive Legends. The Grantee understands and agrees that the Company shall cause the legends set forth below or legends
substantially equivalent thereto, to be placed upon any certificate(s) evidencing ownership of the Shares together with any other legends that may be required by the Company or by state or federal securities laws: 

THE SECURITIES REPRESENTED HEREBY HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933 (THE “ACT”) OR ANY STATE SECURITIES LAWS
AND MAY NOT BE OFFERED, SOLD OR OTHERWISE TRANSFERRED, PLEDGED OR HYPOTHECATED UNLESS AND UNTIL REGISTERED UNDER THE ACT OR, IN THE OPINION OF COUNSEL SATISFACTORY TO THE ISSUER OF THESE SECURITIES, SUCH OFFER, SALE OR TRANSFER, PLEDGE OR
HYPOTHECATION IS IN COMPLIANCE THEREWITH. 
 THE SHARES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO A RIGHT OF FIRST REFUSAL IN FAVOR OF
THE COMPANY AS SET FORTH IN THE BYLAWS OF THE COMPANY. 
 8. Successors and Assigns. The Company may assign any of its rights under
this Exercise Notice to single or multiple assignees, and this agreement shall inure to the benefit of the successors and assigns of the Company. Subject to the restrictions on transfer herein set forth, this Exercise Notice shall be binding upon
the Grantee and his or her heirs, executors, administrators, successors and assigns. 
 9. Construction. The captions used in this
Exercise Notice are inserted for convenience and shall not be deemed a part of this agreement for construction or interpretation. 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. 
 10.
Administration and Interpretation. The Grantee hereby agrees that any question or dispute regarding the administration or interpretation of this Exercise Notice shall be submitted by the Grantee or by the Company to the Administrator. The
resolution of such question or dispute by the Administrator shall be final and binding on all persons. 

  
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 11. Governing Law; Severability. This Exercise Notice is to be construed in accordance
with and governed by the internal laws of the State of California without giving effect to any choice of law rule that would cause the application of the laws of any jurisdiction other than the internal laws of the State of California to the
rights and duties of the parties. Should any provision of this Exercise Notice be determined by a court of law to be illegal or unenforceable, such provision shall be enforced to the fullest extent allowed by law and the other provisions shall
nevertheless remain effective and shall remain enforceable. 
 12. Notices. Any notice required or permitted hereunder shall be given
in writing and shall be deemed effectively given upon personal delivery, upon deposit for delivery by an internationally recognized express mail courier service or upon deposit in the United States mail by certified mail (if the parties are within
the United States), with postage and fees prepaid, addressed to the other party at its address as shown below beneath its signature, or to such other address as such party may designate in writing from time to time to the other party. 

13. Further Instruments. The parties agree to execute such further instruments and to take such further action as may be reasonably
necessary to carry out the purposes and intent of this agreement. 
 14. Entire Agreement. The Notice, the Plan and the Option
Agreement are incorporated herein by reference and together with this Exercise Notice constitute the entire agreement of the parties with respect to the subject matter hereof and supersede in their entirety all prior undertakings and agreements of
the Company and the Grantee with respect to the subject matter hereof, and may not be modified adversely to the Grantee’s interest except by means of a writing signed by the Company and the Grantee. Nothing in the Notice, the Plan, the Option
Agreement and this Exercise Notice (except as expressly provided therein) is intended to confer any rights or remedies on any persons other than the parties. 
  

							
	Submitted by:	 		 	Accepted by:
			
	GRANTEE:	 		 	ARDELYX, INC.
				
		 		 	By:	 	  

				
	  
	 		 	Title:	 	  

	(Signature)	 		 		 	
				
	Address:	 		 	Address:	 	
			
	  
	 		 	  

	  
	 		 	  

  
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 EXHIBIT B 

ARDELYX, INC. 2008 STOCK INCENTIVE PLAN 

INVESTMENT REPRESENTATION STATEMENT 
  

					
	GRANTEE:	  	  
	  	
			
	COMPANY:	  	ARDELYX, INC.	  	
			
	SECURITY:	  	COMMON STOCK	  	
			
	AMOUNT:	  	  
	  	
			
	DATE:	  	  
	  	

 In connection with the purchase of the above-listed Securities, the undersigned
Grantee represents to the Company the following: 
 (a) Grantee is aware of the Company’s business affairs and financial condition and
has acquired sufficient information about the Company to reach an informed and knowledgeable decision to acquire the Securities. Grantee is acquiring these Securities for investment for Grantee’s own account only and not with a view to, or for
resale in connection with, any “distribution” thereof within the meaning of the Securities Act of 1933, as amended (the “Securities Act”). 

(b) Grantee acknowledges and understands that the Securities constitute “restricted securities” under the Securities Act and have
not been registered under the Securities Act in reliance upon a specific exemption therefrom, which exemption depends upon among other things, the bona fide nature of Grantee’s investment intent as expressed herein. Grantee further understands
that the Securities must be held indefinitely unless they are subsequently registered under the Securities Act or an exemption from such registration is available. Grantee further acknowledges and understands that the Company is under no obligation
to register the Securities. Grantee understands that the certificate evidencing the Securities will be imprinted with a legend which prohibits the transfer of the Securities unless they are registered or such registration is not required in the
opinion of counsel satisfactory to the Company. 
 (c) Grantee is familiar with the provisions of Rule 701 and Rule 144, each
promulgated under the Securities Act, which, in substance, permit limited public resale of “restricted securities” acquired, directly or indirectly from the issuer thereof, in a non-public offering
subject to the satisfaction of certain conditions. Rule 701 provides that if the issuer qualifies under Rule 701 at the time of the grant of the Option to the Grantee, the exercise will be exempt from registration under the Securities Act.
In the event the Company becomes subject to the reporting requirements of Section 13 or 15(d) of the Securities Exchange Act of 1934, ninety (90) days thereafter (or such longer period as any market
stand-off agreement may require) the Securities exempt under Rule 701 may be resold, subject to the satisfaction of certain of the conditions specified by Rule 144, including: (1) the resale
being made through a broker in an unsolicited “broker’s transaction” or in transactions directly with a market maker (as said term is defined under the Securities Exchange Act of 1934); and, in the case of an affiliate, (2) the
availability of certain public information about the Company, (3) the amount of Securities being sold during any three month period not exceeding the limitations specified in Rule 144(e), and (4) the timely filing of a Form 144, if
applicable. 

  
 1 

 In the event that the Company does not qualify under Rule 701 at the time of sale of the
Securities, then the Securities may be resold in certain limited circumstances subject to the provisions of Rule 144, which requires the resale to occur not less than six (6) months after the later of the date the Securities were sold by
the Company or the date the Securities were sold by an affiliate of the Company, within the meaning of Rule 144; and, in the case of acquisition of the Securities by an affiliate, or by a non-affiliate who subsequently holds the Securities less
than one (1) year, the satisfaction of the conditions set forth in sections (1), (2), (3) and (4) of the paragraph immediately above. 

(d) Grantee further understands that in the event all of the applicable requirements of Rule 701 or 144 are not satisfied, registration
under the Securities Act, compliance with Regulation A, or some other registration exemption will be required; and that, notwithstanding the fact that Rules 144 and 701 are not exclusive, the Staff of the Securities and Exchange Commission has
expressed its opinion that persons proposing to sell private placement securities other than in a registered offering and otherwise than pursuant to Rules 144 or 701 will have a substantial burden of proof in establishing that an exemption from
registration is available for such offers or sales, and that such persons and their respective brokers who participate in such transactions do so at their own risk. Grantee understands that no assurances can be given that any such other registration
exemption will be available in such event. 
 (e) Grantee represents that Grantee is a resident of the state of
                                        . 

 

			
	Signature of Grantee:
	
	  

	Date:	 	  

  
 2EX-10.5(c)

 Exhibit 10.5C 

ARDELYX, INC. 2008 STOCK INCENTIVE PLAN 

NOTICE OF RESTRICTED STOCK PURCHASE AWARD 
  

							
		 	Grantee’s Name and Address:	 	  
	 	
				
		 		 	  
	 	
				
		 		 	  
	 	

 You (the “Grantee”) have been granted the right to purchase shares of Common Stock of the Company,
subject to the terms and conditions of this Notice of Restricted Stock Purchase Award (the “Notice”), the Ardelyx, Inc. 2008 Stock Incentive Plan, as amended from time to time (the “Plan”) and the Restricted Stock Purchase Award
Agreement (the “Agreement”) attached hereto, as follows. Unless otherwise defined herein, the terms defined in the Plan shall have the same defined meanings in this Notice. 

 

							
		 	Award Number	 	  
	 	
				
		 	Date of Award	 	  
	 	
				
		 	Vesting Commencement Date	 	  
	 	
				
		 	Purchase Price per Share	 	  
	 	
				
		 	Total Number of Shares of Common Stock Awarded	 	  
	 	
				
		 	Total Purchase Price	 	  
	 	

 Vesting Schedule: 

Subject to the Grantee’s Continuous Service and other limitations set forth in this Notice, the Agreement and the Plan, the Shares will
“vest” in accordance with the following schedule: 
 25% of the Total Number of Shares of Common Stock Awarded shall vest on the
first anniversary of the Vesting Commencement Date, and 1/48 of the Total Number of Shares of Common Stock Awarded shall vest on each monthly anniversary of the Vesting Commencement Date thereafter. 

During any authorized leave of absence, the vesting of the Shares shall be suspended after the leave of absence exceeds a period of three
(3) months. Vesting of the Shares shall resume upon the Grantee’s termination of the leave of absence and return to Continuous Service. The Vesting Schedule of the Shares shall be extended by the length of the suspension. 

In the event of the Grantee’s change in status from Employee, Director or Consultant to any other status of Employee, Director or
Consultant, the Shares shall continue to vest in accordance with the Vesting Schedule. 
 Vesting shall cease upon the date of termination
of the Grantee’s Continuous Service for any reason, including death or Disability. For purposes of this Notice and the Agreement, the term “vest” shall mean, with respect to any Shares, that such Shares are no longer subject to

  
 1 

 
repurchase at the Purchase Price per Share; provided, however, that such Shares shall remain subject to other restrictions on transfer set forth in the Agreement or the Plan. Shares that have not
vested are deemed “Restricted Shares.” If the Grantee would become vested in a fraction of a Restricted Share, such Restricted Share shall not vest until the Grantee becomes vested in the entire Share. Notwithstanding the foregoing, the
Shares subject to this Notice will be subject to the provisions of the Agreement and Section 11 of the Plan relating to the release of repurchase and forfeiture provisions in the event of a Corporate Transaction or Change of Control. 

IN WITNESS WHEREOF, the Company and the Grantee have executed this Notice and agree that the Award is to be governed by the terms and
conditions of this Notice, the Plan, and the Agreement. 
  

			
	 Ardelyx, Inc.,
 a Delaware
corporation

		
	By:	 	  

		
	Title:	 	  

 THE GRANTEE ACKNOWLEDGES AND AGREES THAT THE SHARES SHALL VEST, IF AT ALL, ONLY DURING THE PERIOD OF THE GRANTEE’S
CONTINUOUS SERVICE (NOT THROUGH THE ACT OF BEING HIRED, BEING GRANTED THIS AWARD OR ACQUIRING SHARES HEREUNDER). THE GRANTEE FURTHER ACKNOWLEDGES AND AGREES THAT NOTHING IN THIS NOTICE, THE AGREEMENT, NOR IN THE PLAN, SHALL CONFER UPON THE GRANTEE
ANY RIGHT WITH RESPECT TO CONTINUATION OF THE GRANTEE’S CONTINUOUS SERVICE, NOR SHALL IT INTERFERE IN ANY WAY WITH THE GRANTEE’S RIGHT OR THE COMPANY’S RIGHT TO TERMINATE THE GRANTEE’S CONTINUOUS SERVICE AT ANY TIME, WITH OR
WITHOUT CAUSE, AND WITH OR WITHOUT NOTICE. THE GRANTEE ACKNOWLEDGES THAT UNLESS THE GRANTEE HAS A WRITTEN EMPLOYMENT AGREEMENT WITH THE COMPANY TO THE CONTRARY, THE GRANTEE’S STATUS IS AT WILL. 

The Grantee acknowledges receipt of a copy of the Plan and the Agreement and represents that he or she is familiar with the terms and
provisions thereof, and hereby accepts the Award subject to all of the terms and provisions hereof and thereof. The Grantee has reviewed this Notice, the Agreement and the Plan in their entirety, has had an opportunity to obtain the advice of
counsel prior to executing this Notice and fully understands all provisions of this Notice, the Agreement and the Plan. The Grantee hereby agrees that all questions of interpretation and administration relating to this Notice, the Plan and the
Agreement shall be resolved by the Administrator in accordance with Section 17 of the Agreement. The Grantee further agrees to the venue selection in accordance with Section 18 of the Agreement. The Grantee further agrees to notify the
Company upon any change in the residence address indicated in this Notice. 
  

									
	Dated:	 	  
	 		 	Signed:	 	  

  
 2 

 Award
Number:                     

ARDELYX, INC. 2008 STOCK INCENTIVE PLAN 

RESTRICTED STOCK PURCHASE AWARD AGREEMENT 

1. Purchase of Shares. Ardelyx, Inc., a Delaware corporation (the “Company”), hereby issues and sells to the Grantee (the
“Grantee”) named in the Notice of Restricted Stock Purchase Award (the “Notice”), the Total Number of Shares of Common Stock Awarded set forth in the Notice (the “Shares”) for a Purchase Price per Share set forth in the
Notice (the “Total Purchase Price”), subject to the Notice, this Restricted Stock Purchase Award Agreement (the “Agreement”) and the terms and provisions of the Company’s 2008 Stock Incentive Plan, as amended from time to
time (the “Plan”), which is incorporated herein by reference. Payment for the Shares in the amount of the Total Purchase Price set forth in the Notice shall be made to the Company upon execution of the Notice. Unless otherwise defined
herein, the terms defined in the Plan shall have the same defined meanings in this Agreement. All Shares sold hereunder will be deemed issued to the Grantee as fully paid and nonassessable shares, and the Grantee will have the right to vote the
Shares at meetings of the Company’s shareholders. The Company shall pay any applicable stock transfer taxes imposed upon the issuance of the Shares to the Grantee hereunder. 

2. Method of Payment. Payment of the Total Purchase Price shall be by any of the following, or a combination thereof, at the election
of the Grantee; provided, however, that such payment method does not then violate an Applicable Law and, provided further, that the portion of the Total Purchase Price equal to the par value of the Shares must be paid in cash or other legal
consideration permitted by the Delaware General Corporation Law: 
 (a) cash; or 

(b) check. 
 3. Transfer
Restrictions. The Shares sold to the Grantee hereunder may not be sold, transferred by gift, pledged, hypothecated, or otherwise transferred or disposed of by the Grantee prior to the date when the Shares become vested pursuant to the Vesting
Schedule set forth in the Notice. Any attempt to transfer Restricted Shares in violation of this Section 3 will be null and void and will be disregarded. After the Shares vest, the Shares will be subject to the Company’s Right of First
Refusal as set forth in Section 8 below. 
 4. Escrow of Stock. For purposes of facilitating the enforcement of the provisions
of this Agreement, the Grantee agrees, immediately upon receipt of the certificate(s) for the Restricted Shares, to deliver such certificate(s), together with an Assignment Separate from Certificate in the form attached hereto as
Exhibit A, executed in blank by the Grantee with respect to each such stock certificate, to the Secretary or Assistant Secretary of the Company, or their designee, to hold in escrow for so long as such Restricted Shares have not vested
pursuant to the Vesting Schedule set forth in the Notice or continue to remain subject to the Company’s 

  
 1 

 
Right of First Refusal or Repurchase Right, with the authority to take all such actions and to effectuate all such transfers and/or releases as may be necessary or appropriate to accomplish the
objectives of this Agreement in accordance with the terms hereof. The Grantee hereby acknowledges that the appointment of the Secretary or Assistant Secretary of the Company (or their designee) as the escrow holder hereunder with the stated
authorities is a material inducement to the Company to make this Agreement and that such appointment is coupled with an interest and is accordingly irrevocable. The Grantee agrees that the Restricted Shares may be held electronically in a book entry
system maintained by the Company’s transfer agent or other third-party and that all the terms and conditions of this Section 4 applicable to certificated Restricted Shares will apply with the same force and effect to such electronic method
for holding the Restricted Shares. The Grantee agrees that such escrow holder shall not be liable to any party hereto (or to any other party) for any actions or omissions unless such escrow holder is grossly negligent relative thereto. The escrow
holder may rely upon any letter, notice or other document executed by any signature purported to be genuine and may resign at any time. Upon the vesting of all Restricted Shares and termination of the Company’s Right of First Refusal and
Repurchase Right, the escrow holder will, without further order or instruction, transmit to the Grantee the certificate evidencing such Shares, subject, however, to satisfaction of any withholding obligations provided in Section 6 below. 

5. Distributions. Except as set forth in Section 9(e), the Company shall disburse to the Grantee all regular cash dividends with
respect to the Shares and Additional Securities (whether vested or not), less any applicable withholding obligations. 
 6.
Section 83(b) Election and Withholding of Taxes. The Grantee shall provide the Administrator with a copy of any timely election made pursuant to Section 83(b) of the Internal Revenue Code or similar provision of state law
(collectively, an “83(b) Election”), a form of which is attached hereto as Exhibit B. If the Grantee makes a timely 83(b) Election, the Grantee shall immediately pay the Company the amount necessary to satisfy any applicable
foreign, federal, state, and local income and employment tax withholding obligations. If the Grantee does not make a timely 83(b) Election, the Grantee shall, as Restricted Shares shall vest or at the time withholding is otherwise required by any
Applicable Law, pay the Company the amount necessary to satisfy any applicable foreign, federal, state, and local income and employment tax withholding obligations. The Grantee hereby represents that he or she understands (a) the contents and
requirements of the 83(b) Election, (b) the application of Section 83(b) to the receipt of the Shares by the Grantee pursuant to this Agreement, (c) the nature of the election to be made by the Grantee under Section 83(b), and
(d) the effect and requirements of the 83(b) Election under relevant state and local tax laws. The Grantee further represents that he or she intends to file an election pursuant to Section 83(b) with the Internal Revenue Service within
thirty (30) days following the date of this Agreement, and submit a copy of such election to the Company and with his or her federal tax return for the calendar year in which the date of this Agreement falls. 

7. Additional Securities. Any securities or cash received (other than a regular cash dividend) as the result of ownership of the
Restricted Shares (the “Additional Securities”), including, but not by way of limitation, warrants, options and securities received as a stock dividend or stock split, or as a result of a recapitalization or reorganization or other similar
change in the Company’s capital structure, shall be retained in escrow in the same manner and 

  
 2 

 
subject to the same conditions and restrictions as the Restricted Shares with respect to which they were issued, including, without limitation, the Vesting Schedule set forth in the Notice, the
Right of First Refusal and the Repurchase Right. The Grantee shall be entitled to direct the Company to exercise any warrant or option received as Additional Securities upon supplying the funds necessary to do so, in which event the securities so
purchased shall constitute Additional Securities, but the Grantee may not direct the Company to sell any such warrant or option. If Additional Securities consist of a convertible security, the Grantee may exercise any conversion right, and any
securities so acquired shall constitute Additional Securities. Appropriate adjustments to reflect the distribution of Additional Securities shall be made to the price per share to be paid upon the exercise of the Repurchase Right in order to reflect
the effect of any such transaction upon the Company’s capital structure. In the event of any change in certificates evidencing the Shares or the Additional Securities by reason of any recapitalization, reorganization or other transaction that
results in the creation of Additional Securities, the escrow holder is authorized to deliver to the issuer the certificates evidencing the Shares or the Additional Securities in exchange for the certificates of the replacement securities. 

8. Company’s Right of First Refusal. The Grantee acknowledges and agrees that the Shares are subject to a right of first refusal
(“Right of First Refusal”) as set forth in Article 10 of the Bylaws of the Company, which Right of First Refusal is incorporated herein by reference irrespective of whether the Bylaws are amended at some future date to remove the Right of
First Refusal therefrom, and that, except in compliance with such Right of First Refusal, neither the Grantee nor a transferee (either being sometimes referred to herein as the “Holder”) shall sell, hypothecate, encumber or otherwise
transfer any Shares or any right or interest therein. 
 9. Company’s Repurchase Right. 

(a) Grant of Repurchase Right. The Company is hereby granted the right (the “Repurchase Right”), exercisable at any time
during the six (6) month period (the “Share Repurchase Period”) following the date the Grantee’s Continuous Service terminates for any reason, with or without cause (including death or disability) (the “Termination
Date”) to repurchase all or any portion of the Restricted Shares. 
 (b) Exercise of the Repurchase Right. The Repurchase Right
shall be exercisable by written notice delivered to each Holder of the Shares prior to the expiration of the Share Repurchase Period. The notice shall indicate the number of Shares to be repurchased and the date on which the repurchase is to be
effected, such date to be not later than the last day of the Share Repurchase Period. On the date on which the repurchase is to be effected, the Company and/or its assigns shall pay to the Holder of the Shares in cash or cash equivalents (including
the cancellation of any purchase-money indebtedness) for Restricted Shares being repurchased an amount equal to the Purchase Price per Share previously paid by the Grantee to the Company for such Shares. Upon such payment to the Holder of the Shares
or into escrow for the benefit of the Holder of the Shares, the Company and/or its assigns shall become the legal and beneficial owner of the Shares being repurchased and all rights and interest thereon or related thereto, and the Company shall have
the right to transfer to its own name or its assigns the number of Shares being repurchased, without further action by the Holder of the Shares. 

  
 3 

 (c) Assignment. Whenever the Company shall have the right to purchase Shares under this
Repurchase Right, the Company may designate and assign one or more employees, officers, directors or shareholders of the Company or other persons or organizations, to exercise all or a part of the Company’s Repurchase Right. 

(d) Termination of the Repurchase Right. The Repurchase Right shall terminate with respect to any Shares for which it is not timely
exercised. 
 (e) Additional Securities. In the event of any transaction described in Sections10 or 11 of the Plan, the Repurchase
Right shall apply to the new, substituted or additional capital stock or other property (including cash paid other than as a regular cash dividend) received in exchange for the Shares in consummation of any such transaction and such stock or
property shall be deemed Additional Securities for purposes of this Agreement, but only to the extent the Shares are at the time covered by such Repurchase Right. Appropriate adjustments shall be made to the price per share payable upon exercise of
the Repurchase Right to reflect the effect of any such transaction. 
 10. Stop-Transfer Notices. In order to ensure compliance with
the restrictions on transfer set forth in this Agreement, the Notice or the Plan, the Company may issue appropriate “stop transfer” instructions to its transfer agent, if any, and, if the Company transfers its own securities, it may make
appropriate notations to the same effect in its own records. 
 11. Refusal to Transfer. The Company shall not be required
(i) to transfer on its books any Shares that have been sold or otherwise transferred in violation of any of the provisions of this Agreement or (ii) to treat as owner of such Shares or to accord the right to vote or pay dividends to any
purchaser or other transferee to whom such Shares shall have been so transferred. 
 12. Restrictive Legends. The Grantee understands
and agrees that the Company shall cause the legends set forth below or legends substantially equivalent thereto, to be placed upon any certificate(s) evidencing ownership of the Shares together with any other legends that may be required by the
Company or by state or federal securities laws: 
 THE SECURITIES REPRESENTED HEREBY HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF
1933 (THE “ACT”) AND MAY NOT BE OFFERED, SOLD OR OTHERWISE TRANSFERRED, PLEDGED OR HYPOTHECATED UNLESS AND UNTIL REGISTERED UNDER THE ACT OR, IN THE OPINION OF COUNSEL SATISFACTORY TO THE ISSUER OF THESE SECURITIES, SUCH OFFER, SALE OR
TRANSFER, PLEDGE OR HYPOTHECATION IS IN COMPLIANCE THEREWITH. 
 THE SHARES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO CERTAIN
RESTRICTIONS ON TRANSFER AND A REPURCHASE RIGHT HELD BY THE ISSUER OR ITS ASSIGNEE(S) AS SET FORTH IN THE RESTRICTED 

  
 4 

 
STOCK PURCHASE AGREEMENT BETWEEN THE ISSUER AND THE ORIGINAL HOLDER OF THESE SHARES, A COPY OF WHICH MAY BE OBTAINED AT THE PRINCIPAL OFFICE OF THE ISSUER. SUCH TRANSFER RESTRICTIONS AND
REPURCHASE RIGHT ARE BINDING ON TRANSFEREES OF THESE SHARES. 
 THE SHARES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO A RIGHT OF FIRST
REFUSAL IN FAVOR OF THE COMPANY AS SET FORTH IN THE BYLAWS OF THE COMPANY 
 13. Lock-Up Agreement. 

(a) Agreement. The Grantee, if requested by the Company and the lead underwriter of any public offering of the Common Stock (the
“Lead Underwriter”), hereby irrevocably agrees not to sell, contract to sell, grant any option to purchase, transfer the economic risk of ownership in, make any short sale of, pledge or otherwise transfer or dispose of any interest in any
Common Stock or any securities convertible into or exchangeable or exercisable for or any other rights to purchase or acquire Common Stock (except Common Stock included in such public offering or acquired on the public market after such offering)
during the 180-day period following the effective date of a registration statement of the Company filed under the Securities Act of 1933, as amended, or such shorter or longer period of time as the Lead
Underwriter shall specify. The Grantee further agrees to sign such documents as may be requested by the Lead Underwriter to effect the foregoing and agrees that the Company may impose stop-transfer instructions with respect to such Common Stock
subject until the end of such period. The Company and the Grantee acknowledge that each Lead Underwriter of a public offering of the Company’s stock, during the period of such offering and for the lock-up period thereafter, is an intended
beneficiary of this Section 13. 
 (b) No Amendment Without Consent of Underwriter. During the period from identification as a
Lead Underwriter in connection with any public offering of the Company’s Common Stock until the earlier of (i) the expiration of the lock-up period specified in Section 13(a) in connection with such offering or (ii) the
abandonment of such offering by the Company and the Lead Underwriter, the provisions of this Section 13 may not be amended or waived except with the consent of the Lead Underwriter. 

14. Grantee’s Representations. In the event the Shares purchasable pursuant to this Agreement have not been registered under the
Securities Act of 1933, as amended, at the time of purchase, the Grantee shall, if required by the Company, concurrently with the purchase of the Shares, deliver to the Company his or her Investment Representation Statement in the form attached
hereto as Exhibit C. 
 15. Entire Agreement: Governing Law. The Notice, the Plan and this Agreement constitute the
entire agreement of the parties with respect to the subject matter hereof and supersede in their entirety all prior undertakings and agreements of the Company and the Grantee with respect to the subject matter hereof, and may not be modified
adversely to the Grantee’s 

  
 5 

 
interest except by means of a writing signed by the Company and the Grantee. These agreements are to be construed in accordance with and governed by the internal laws of the State of California
without giving effect to any choice of law rule that would cause the application of the laws of any jurisdiction other than the internal laws of the State of California to the rights and duties of the parties. Should any provision of the Notice or
this Agreement be determined to be illegal or unenforceable, the other provisions shall nevertheless remain effective and shall remain enforceable. 

16. Construction. The captions used in the Notice and this Agreement are inserted for convenience and shall not be deemed a part of the
Agreement for construction or interpretation. 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. 
 17. Administration and Interpretation. Any question or dispute regarding the administration or
interpretation of the Notice, the Plan or this Agreement shall be submitted by the Grantee or by the Company to the Administrator. The resolution of such question or dispute by the Administrator shall be final and binding on all persons. 

18. Venue. The Company, the Grantee, and the Grantee’s assignees pursuant to Section 3 (the “parties”) agree that
any suit, action, or proceeding arising out of or relating to the Notice, the Plan or this Agreement shall be brought in the United States District Court for the Northern District of California (or should such court lack jurisdiction to hear such
action, suit or proceeding, in a California state court in the County of Santa Clara) and that the parties shall submit to the jurisdiction of such court. The parties irrevocably waive, to the fullest extent permitted by law, any objection the party
may have to the laying of venue for any such suit, action or proceeding brought in such court. If any one or more provisions of this Section 18 shall for any reason be held invalid or unenforceable, it is the specific intent of the parties that
such provisions shall be modified to the minimum extent necessary to make it or its application valid and enforceable. 
 19.
Notices. Any notice required or permitted hereunder shall be given in writing and shall be deemed effectively given upon personal delivery, upon deposit for delivery by an internationally recognized express mail courier service or upon
deposit in the United States mail by certified mail (if the parties are within the United States), with postage and fees prepaid, addressed to the other party at its address as shown in these instruments, or to such other address as such party may
designate in writing from time to time to the other party. 
 20. Spousal Consent. Grantee shall cause his or her spouse to execute a
Consent of Spouse in the form attached hereto as Exhibit D concurrently with the execution of this Agreement or, if later, at the time Grantee becomes married. 

  
 6 

 EXHIBIT A 

STOCK ASSIGNMENT SEPARATE FROM CERTIFICATE 

[Please sign this document but do not date it. The date and information of the transferee will be completed if and when the shares are assigned.] 

FOR VALUE RECEIVED,
                                         hereby
sells, assigns and transfers unto
                                        ,
                     (            ) shares of the Common Stock of Ardelyx, Inc., a
Delaware corporation (the “Company”), standing in his or her name on the books of, the Company represented by Certificate No.      herewith, and does hereby irrevocably constitute and appoint the Secretary of the
Company attorney to transfer the said stock in the books of the Company with full power of substitution. 
  

									
	DATED:	 	  
	 		 		 	
					
		 		 		 		 	  

  
 1 

 EXHIBIT B 

ELECTION UNDER SECTION 83(b) 

OF THE INTERNAL REVENUE CODE OF 1986 

The undersigned taxpayer hereby elects, pursuant to the Internal Revenue Code, to include in gross income for 20     the
amount of any compensation taxable in connection with the taxpayer’s receipt of the property described below: 
 1. The name, address,
taxpayer identification number and taxable year of the undersigned are: 
 TAXPAYER’S NAME: 

TAXPAYER’S SOCIAL SECURITY NO.: 

SPOUSE’S SOCIAL SECURITY NO.: 

TAXABLE YEAR: Calendar Year 20     

ADDRESS: 
 2. The property which
is the subject of this election is                  shares of common stock of Ardelyx, Inc. 

3. The property was transferred to the undersigned on             ,
20    . 
 4. The property is subject to the following restrictions: The property is subject to a repurchase right
pursuant to which the issuer has the right to acquire the property at the original purchase price if for any reason taxpayer’s employment or service with the issuer is terminated. The issuer’s repurchase right lapses in a series of
periodic installments. 
 5. The fair market value of the property at the time of transfer (determined without regard to any restriction
other than a restriction which by its terms will never lapse) is: $         per share x                  shares =
$        . 
 6. The undersigned paid $         per share
x                  shares for the property transferred or a total of $        . 

The undersigned has submitted a copy of this statement to the person for whom the services were performed in connection with the
undersigned’s receipt of the above-described property. The undersigned taxpayer is the person performing the services in connection with the transfer of said property. 

The undersigned will file this election with the Internal Revenue Service office to which he or she files his or her annual income tax return
not later than 30 days after the date of transfer of the property. A copy of the election also will be furnished to the person for whom the services 

  
 1 

 
were performed. Additionally, the undersigned will include a copy of the election with his or her income tax return for the taxable year in which the property is transferred. The undersigned
understands that this election will also be effective as an election under California law. 
  

							
	Dated:	 	  
	 		 	  

		 		 		 	Taxpayer

  
 2 

 EXHIBIT C 

ARDELYX, INC. 2008 STOCK INCENTIVE PLAN 

INVESTMENT REPRESENTATION STATEMENT 
  

							
	GRANTEE	 	:	    	  
	    	
				
	COMPANY	 	:	    	ARDELYX, INC.	    	
				
	SECURITY	 	:	    	COMMON STOCK	    	
				
	AMOUNT	 	:	    	  
	    	
				
	DATE	 	:	    	  
	    	

 In connection with the purchase of the above-listed Securities, the undersigned
Grantee represents to the Company the following: 
 (a) The Grantee is aware of the Company’s business affairs and financial condition
and has acquired sufficient information about the Company to reach an informed and knowledgeable decision to acquire the Securities. The Grantee is acquiring these Securities for investment for the Grantee’s own account only and not with a view
to, or for resale in connection with, any “distribution” thereof within the meaning of the Securities Act of 1933, as amended (the “Securities Act”). 

(b) The Grantee acknowledges and understands that the Securities constitute “restricted securities” under the Securities Act and
have not been registered under the Securities Act in reliance upon a specific exemption therefrom, which exemption depends upon among other things, the bona fide nature of the Grantee’s investment intent as expressed herein. In this connection,
the Grantee understands that, in the view of the Securities and Exchange Commission, the statutory basis for such exemption may be unavailable if the Grantee’s representation was predicated solely upon a present intention to hold these
Securities for the minimum capital gains period specified under tax statutes, for a deferred sale, for or until an increase or decrease in the market price of the Securities, or for a period of one year or any other fixed period in the future. The
Grantee further understands that the Securities must be held indefinitely unless they are subsequently registered under the Securities Act or an exemption from such registration is available. The Grantee further acknowledges and understands that the
Company is under no obligation to register the Securities. The Grantee understands that the certificate evidencing the Securities will be imprinted with a legend which prohibits the transfer of the Securities unless they are registered or such
registration is not required in the opinion of counsel satisfactory to the Company. 
 (c) The Grantee is familiar with the provisions of
Rule 701 and Rule 144, each promulgated under the Securities Act, which, in substance, permit limited public resale of “restricted securities” acquired, directly or indirectly from the issuer thereof, in a non-public offering subject to the satisfaction of certain conditions. Rule 701 provides that if the issuer 

  
 1 

 
qualifies under Rule 701 at the time of the sale of the Shares to the Grantee, the sale will be exempt from registration under the Securities Act. In the event the Company becomes subject to
the reporting requirements of Section 13 or 15(d) of the Securities Exchange Act of 1934, ninety (90) days thereafter (or such longer period as any market stand-off agreement may require) the
Securities exempt under Rule 701 may be resold, subject to the satisfaction of certain of the conditions specified by Rule 144, including: (1) the resale being made through a broker in an unsolicited “broker’s
transaction” or in transactions directly with a market maker (as said term is defined under the Securities Exchange Act of 1934); and, in the case of an affiliate, (2) the availability of certain public information about the Company,
(3) the amount of Securities being sold during any three month period not exceeding the limitations specified in Rule 144(e), and (4) the timely filing of a Form 144, if applicable. 

In the event that the Company does not qualify under Rule 701 at the time of sale of the Securities, then the Securities may be resold in
certain limited circumstances subject to the provisions of Rule 144, which requires the resale to occur not less than six (6) months after the later of the date the Securities were sold by the Company or the date the Securities were sold
by an affiliate of the Company, within the meaning of Rule 144; and, in the case of acquisition of the Securities by an affiliate, or by a non-affiliate who subsequently holds the Securities less than one (1) year, the satisfaction of the
conditions set forth in sections (1), (2), (3) and (4) of the paragraph immediately above. 
 (d) The Grantee further understands
that in the event all of the applicable requirements of Rule 701 or 144 are not satisfied, registration under the Securities Act, compliance with Regulation A, or some other registration exemption will be required; and that,
notwithstanding the fact that Rules 144 and 701 are not exclusive, the Staff of the Securities and Exchange Commission has expressed its opinion that persons proposing to sell private placement securities other than in a registered offering and
otherwise than pursuant to Rules 144 or 701 will have a substantial burden of proof in establishing that an exemption from registration is available for such offers or sales, and that such persons and their respective brokers who participate in
such transactions do so at their own risk. The Grantee understands that no assurances can be given that any such other registration exemption will be available in such event. 

(e) The Grantee represents that the Grantee is a resident of the state of
                                        . 

 

			
	Signature of the Grantee:
	
	  

		
	Date:	 	  

  
 2 

 EXHIBIT D 

CONSENT OF SPOUSE 
 I,
                                        , spouse
of                                         , have
read and approved the foregoing Agreement. In consideration of the right of my spouse to purchase shares of Ardelyx, Inc. as set forth in the Agreement, I hereby appoint my spouse as my attorney-in-fact in respect to the exercise of any rights under
the Agreement insofar as I may have any rights under the community property laws of the State of California or similar laws relating to marital property in effect in the state of our residence as of the date of the signing of the foregoing
Agreement. 
  

							
	Dated:	 	  
	 		 	  

  
 1

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