EX-10.3





 Exhibit 10.3 

SIERRA ONCOLOGY, INC. 

2018 EQUITY INDUCEMENT PLAN 

ADOPTED BY THE COMPENSATION COMMITTEE OF THE BOARD OF DIRECTORS: 

SEPTEMBER 2018 
 AMENDED
BY THE BOARD OF DIRECTORS: JUNE 2020 
 1.    PURPOSE. The purpose of this Plan is to provide
incentives to attract, retain and motivate eligible persons whose present and potential contributions are important to the success of the Company, and any Parents and Subsidiaries that exist now or in the future, by offering them an
opportunity to participate in the Company’s future performance through the grant of Awards. Capitalized terms not defined elsewhere in the text are defined in Section 21. 

2.    SHARES SUBJECT TO THE PLAN. 

2.1    Number of Shares Available. Subject to Section 2.4 and any other applicable provisions hereof,
the total number of Shares reserved and available for grant and issuance pursuant to this Plan is 537,500. 

2.2    Lapsed, Returned Awards. Shares subject to Awards, and Shares issued under the Plan under any Award,
will again be available for grant and issuance in connection with subsequent Awards under this Plan to the extent such Shares: (a) are subject to issuance upon exercise of an Option granted under this Plan but which cease to be subject to the
Option for any reason other than exercise of the Option; (b) are subject to Awards granted under this Plan that are forfeited or are repurchased by the Company at the original issue price or (c) are subject to Awards granted under this
Plan that otherwise terminate without such Shares being issued. To the extent an Award under the Plan is paid out in cash rather than Shares, such cash payment will not result in reducing the number of Shares available for issuance under the Plan.
Shares used to pay the exercise price of an Award or withheld to satisfy the tax withholding obligations related to an Award will become available for future grant or sale under the Plan. 

2.3    Minimum Share Reserve. At all times the Company shall reserve and keep available a sufficient number
of Shares as shall be required to satisfy the requirements of all outstanding Awards granted under this Plan. 

2.4    Adjustment of Shares. If the number of outstanding Shares is changed by a stock dividend,
extraordinary dividends or distributions (whether in cash, shares or other property, other than a regular cash dividend) recapitalization, stock split, reverse stock split, subdivision, combination, reclassification,
spin-off or similar change in the capital structure of the Company, without consideration, then (a) the number of Shares reserved for issuance and future grant under the Plan set forth in
Section 2.1, (b) the Exercise Prices of and number of Shares subject to outstanding Options and (c) the number of Shares subject to other outstanding Awards, shall be proportionately adjusted, subject to any required action by the Board or
the stockholders of the Company and in compliance with applicable securities laws; provided that fractions of a Share will not be issued. 

3.    ELIGIBILITY. Awards may be granted only to a person who, at the time of granting of the Award
by the Committee: (a) has been hired as an Employee by the Company or any Subsidiary and such Award is a material inducement to such person being hired; (b) has been rehired as an Employee following a bona fide period of interruption
of employment with the Company or any Subsidiary; or (c) has become an Employee of the Company or any Subsidiary in connection with a merger or acquisition. 












 4.    ADMINISTRATION. 

4.1    Committee Composition; Authority. This Plan will be administered by the Committee or by the Board
acting as the Committee. Subject to the general purposes, terms and conditions of this Plan, and to the direction of the Board, the Committee will have full power to implement and carry out this Plan. Notwithstanding the foregoing, the grant of any
Award will not be effective unless: (i) if the grant is made by the Board, then it must be approved by a majority of the Outside Directors on the Board; and (ii) if the grant is made by the Committee, then the Committee must be comprised
solely of Outside Directors (except as otherwise permitted under applicable rules). The Committee will have the authority to: 

(a)    construe and interpret this Plan, any Award Agreement and any other agreement or document executed pursuant to this
Plan; 
 (b)    prescribe, amend and rescind rules and regulations relating to this Plan or any Award; 

(c)    select persons to receive Awards; 

(d)    determine the form and terms and conditions, not inconsistent with the terms of the Plan, of any Award granted
hereunder. Such terms and conditions include, but are not limited to, the exercise price, the time or times when Awards may vest and be exercised (which may be based on performance criteria) or settled, any vesting acceleration or waiver of
forfeiture restrictions, the method to satisfy tax withholding obligations or any other tax liability legally due and any restriction or limitation regarding any Award or the Shares relating thereto, based in each case on such factors as the
Committee will determine; 
 (e)    determine the number of Shares or other consideration subject to Awards; 

(f)    determine the Fair Market Value in good faith and interpret the applicable provisions of this Plan and the
definition of Fair Market Value in connection with circumstances that impact the Fair Market Value, if necessary; 

(g)    determine whether Awards will be granted singly, in combination with, in tandem with, or as alternatives to, other
Awards under this Plan or any other incentive or compensation plan of the Company or any Parent or Subsidiary of the Company; 

(h)    grant waivers of Plan or Award conditions; 

(i)    determine the vesting, exercisability and payment of Awards; 

(j)    correct any defect, supply any omission or reconcile any inconsistency in this Plan, any Award or any Award
Agreement; 
 (k)    determine whether an Award has been earned; 

(l)    reduce or waive any criteria with respect to Performance Factors; 

  
 2 













 (m)    adjust Performance Factors to take into account changes in law
and accounting or tax rules as the Committee deems necessary or appropriate to reflect the impact of extraordinary or unusual items, events or circumstances to avoid windfalls or hardships; 

(n)    adopt terms and conditions, rules and/or procedures (including the adoption of any subplan under this Plan)
relating to the operation and administration of the Plan to accommodate requirements of local law and procedures outside of the United States; and 

(o)    make all other determinations necessary or advisable for the administration of this Plan. 

4.2    Committee Interpretation and Discretion. Any determination made by the Committee with respect to any
Award shall be made in its sole discretion at the time of grant of the Award or, unless in contravention of any express term of the Plan or Award, at any later time, and such determination shall be final and binding on the Company and all persons
having an interest in any Award under the Plan. Any dispute regarding the interpretation of the Plan or any Award Agreement shall be submitted by the Employee or Company to the Committee for review. The resolution of such a dispute by the Committee
shall be final and binding on the Company and the Employee. The Committee may delegate to one or more executive officers the authority to review and resolve disputes with respect to Awards held by Employees who are not Insiders, and such resolution
shall be final and binding on the Company and the Employee. 
 4.3    Section 16 of the Exchange Act.
Awards granted to Employees who are subject to Section 16 of the Exchange Act must be approved by two or more “non-employee directors” (as defined in the regulations promulgated under
Section 16 of the Exchange Act). 
 4.4    Documentation. The Award Agreement for a given Award, the
Plan and any other documents may be delivered to, and accepted by, an Employee or any other person in any manner (including electronic distribution or posting) that meets applicable legal requirements. 

4.5    Foreign Award Recipients. Notwithstanding any provision of the Plan to the contrary, in order to
comply with the laws and practices in other countries in which the Company and its Subsidiaries operate or have employees eligible for Awards, the Committee, in its sole discretion, shall have the power and authority to: (a) determine which
Subsidiaries and Affiliates shall be covered by the Plan; (b) determine which Employees outside the United States are eligible to participate in the Plan; (c) modify the terms and conditions of any Award granted to individuals outside the
United States or foreign nationals to comply with applicable foreign laws, policies, customs and practices; (d) establish subplans and modify exercise procedures and other terms and procedures, to the extent the Committee determines such
actions to be necessary or advisable (and such subplans and/or modifications shall be attached to this Plan as appendices); provided, however, that no such subplans and/or modifications shall increase the share limitations contained in the Plan; and
(e) take any action, before or after an Award is made, that the Committee determines to be necessary or advisable to obtain approval or comply with any local governmental regulatory exemptions or approvals. Notwithstanding the foregoing, the
Committee may not take any actions hereunder, and no Awards shall be granted, that would violate the Exchange Act or any other applicable United States securities law, the Code, or any other applicable United States governing statute or law. 

5.    OPTIONS. An Option is the right but not the obligation to purchase a Share, subject to certain
conditions, if applicable. The Committee may grant Options to eligible Employees and will determine the number of Shares subject to the Option, the Exercise Price of the Option, the period during which the Option may vest and be exercised, and
all other terms and conditions of the Option, subject to the following terms of this section. 

  
 3 













 5.1    Option Grant. Each Option granted under this Plan
will be a Nonqualified Stock Option (“NSO”). An Option may be, but need not be, awarded upon satisfaction of such Performance Factors during any Performance Period as are set out in advance in the Employee’s individual
Award Agreement. If the Option is being earned upon the satisfaction of Performance Factors, then the Committee will: (a) determine the nature, length and starting date of any Performance Period for each Option; and (b) select from among
the Performance Factors to be used to measure the performance, if any. Performance Periods may overlap and Employees may participate simultaneously with respect to Options that are subject to different performance goals and other criteria. 

5.2    Date of Grant. The date of grant of an Option will be the date on which the Committee makes the
determination to grant such Option, or a specified future date. The Award Agreement and a copy of this Plan will be delivered to the Employee within a reasonable time after the granting of the Option. 

5.3    Exercise Period. Options may be vested and exercisable within the times or upon the conditions as set
forth in the Award Agreement governing such Option; provided, however, that no Option will be exercisable after the expiration of ten (10) years from the date the Option is granted. The Committee also may provide for Options to become
vested or exercisable at one time or from time to time, periodically or otherwise, in such number of Shares or percentage of Shares as the Committee determines. 

5.4    Exercise Price. The Exercise Price of an Option will be determined by the Committee when the Option
is granted; provided that: the Exercise Price of an Option will be not less than one hundred percent (100%) of the Fair Market Value of the Shares on the date of grant. Payment for the Shares purchased may be made in accordance with Section 7
and the Award Agreement and in accordance with any procedures established by the Company. 
 5.5    Method of
Exercise. Any Option granted hereunder will be vested and exercisable according to the terms of the Plan and at such times and under such conditions as determined by the Committee and set forth in the Award Agreement. An Option may not be
exercised for a fraction of a Share. An Option will be deemed exercised when the Company receives: (a) notice of exercise (in such form as the Committee may specify from time to time) from the person entitled to exercise the Option (and/or via
electronic execution through the authorized third party administrator), and (b) full payment for the Shares with respect to which the Option is exercised (together with applicable withholding taxes). Full payment may consist of any
consideration and method of payment authorized by the Committee and permitted by the Award Agreement and the Plan. Shares issued upon exercise of an Option will be issued in the name of the Employee. Until the Shares are 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 will exist with respect to the Shares, notwithstanding the exercise of
the Option. The Company will issue (or cause to be issued) such Shares 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 Shares are issued, except as
provided in Section 2.4 of the Plan. Exercising an Option in any manner will decrease the number of Shares thereafter available, both for purposes of the Plan and for sale under the Option, by the number of Shares as to which the Option is
exercised. 
 5.6    Termination of Service. If the Employee’s Service terminates for any reason
except for Cause or the Employee’s death or Disability, then the Employee may exercise such Employee’s Options (only to the extent that such Options are exercisable by the Employee on the date Employee’s Service terminates) during the
period ending no later than three (3) months after the date Employee’s Service terminates (or such shorter or longer time period as may be determined by the Committee), but in any event no later than the expiration date of the Options.


  
 4 













 (a)    Death. If the Employee’s Service terminates because
of the Employee’s death (or the Employee dies within three (3) months after Employee’s Service terminates other than for Cause or because of the Employee’s Disability), then the Employee’s Options may be exercised only to
the extent that such Options would have been exercisable by the Employee on the date Employee’s Service terminates and must be exercised by the Employee’s legal representative, or authorized assignee, no later than twelve (12) months
after the date Employee’s Service terminates (or such shorter time period or longer time period as may be determined by the Committee), but in any event no later than the expiration date of the Options. 

(b)    Disability. If the Employee’s Service terminates because of the Employee’s Disability, then the
Employee’s Options may be exercised only to the extent that such Options would have been exercisable by the Employee on the date Employee’s Service terminates and must be exercised by the Employee (or the Employee’s legal
representative or authorized assignee) no later than twelve (12) months after the date Employee’s Service terminates (or such shorter or longer time period as may be determined by the Committee, but in any event no later than the
expiration date of the Options. 
 (c)    Cause. If the Employee is terminated for Cause, then Employee’s
Options shall expire on such Employee’s date of termination of Service, or at such later time and on such conditions as are determined by the Committee, but in any event no later than the expiration date of the Options. Unless otherwise
provided in the Award Agreement or other agreement between the Company and Employee, Cause shall have the meaning set forth in this Plan. 

5.7    Limitations on Exercise. The Committee may specify a minimum number of Shares that may be purchased
on any exercise of an Option, provided that such minimum number will not prevent any Employee from exercising the Option for the full number of Shares for which it is then exercisable. 

5.8    Modification, Extension or Renewal. The Committee may modify, extend or renew outstanding Options and
authorize the grant of new Options in substitution therefor, provided that any such action may not, without the written consent of an Employee, impair any of such Employee’s rights under any Option previously granted. 

6.    RESTRICTED STOCK UNITS. A Restricted Stock Unit (“RSU”) is an award to an
eligible Employee covering a number of Shares that may be settled in cash, or by issuance of those Shares. All RSUs shall be made pursuant to an Award Agreement. 

6.1    Terms of RSUs. The Committee will determine the terms of an RSU including, without limitation:
(a) the number of Shares subject to the RSU; (b) the time or times during which the RSU may be settled; (c) the consideration to be distributed on settlement; and (d) the effect of the Employee’s termination of Service on
each RSU. An RSU may be awarded upon satisfaction of such performance goals based on Performance Factors during any Performance Period as are set out in advance in the Employee’s Award Agreement. If the RSU is being earned upon satisfaction of
Performance Factors, then the Committee will: (x) determine the nature, length and starting date of any Performance Period for the RSU; (y) select from among the Performance Factors to be used to measure the performance, if any; and
(z) determine the number of Shares deemed subject to the RSU. Performance Periods may overlap and participants may participate simultaneously with respect to RSUs that are subject to different Performance Periods and different performance goals
and other criteria. 
 6.2    Form and Timing of Settlement. Payment of earned RSUs shall be made as soon
as practicable after the date(s) determined by the Committee and set forth in the Award Agreement. The 

  
 5 













 
Committee, in its sole discretion, may settle earned RSUs in cash, Shares, or a combination of both. The Committee may also permit a Employee to defer payment under an RSU to a date or dates
after the RSU is earned provided that the terms of the RSU and any deferral satisfy the requirements of Section 409A of the Code. 

6.3     Termination of Service. Except as may be set forth in the Employee’s Award Agreement,
vesting ceases on such date Employee’s Service terminates (unless determined otherwise by the Committee). 
 7.
    PAYMENT FOR SHARE PURCHASES. Payment from an Employee for Shares purchased pursuant to this Plan may be made in cash or by check or, where expressly approved for the Employee by the Committee
and where permitted by law (and to the extent not otherwise set forth in the applicable Award Agreement): 
 (a)    by
cancellation of indebtedness of the Company to the Employee; 
 (b)    by surrender of shares of the Company held by the
Employee that have a Fair Market Value on the date of surrender equal to the aggregate exercise price of the Shares as to which said Award will be exercised or settled; 

(c)    by waiver of compensation due or accrued to the Employee for services rendered or to be rendered to the Company or
a Parent or Subsidiary of the Company; 
 (d)    by consideration received by the Company pursuant to a broker-assisted
or other form of cashless exercise program implemented by the Company in connection with the Plan; 
 (e)    by any
combination of the foregoing; or 
 (f)    by any other method of payment as is permitted by applicable law. 

8.    WITHHOLDING TAXES. 

8.1    Withholding Generally. Whenever Shares are to be issued in satisfaction of Awards granted under this
Plan or the applicable tax event occurs, the Company may require the Employee to remit to the Company, or to the Parent or Subsidiary employing the Employee, an amount sufficient to satisfy applicable U.S. federal, state, local and international
withholding tax requirements or any other tax or social insurance liability legally due from the Employee prior to the delivery of Shares pursuant to exercise or settlement of any Award. Whenever payments in satisfaction of Awards granted under this
Plan are to be made in cash, such payment will be net of an amount sufficient to satisfy applicable U.S. federal, state, local and international withholding tax or social insurance requirements or any other tax liability legally due from the
Employee. The Fair Market Value of the Shares will be determined as of the date that the taxes are required to be withheld and such Shares will be valued based on the value of the actual trade or, if there is none, the Fair Market Value of the
Shares as of the previous trading day. 
 8.2    Stock Withholding. The Committee, in its sole discretion
and pursuant to such procedures as it may specify from time to time and to limitations of local law, may require or permit an Employee to satisfy such tax withholding obligation or any other tax liability legally due from the Employee, in whole or
in part by (without limitation) (a) paying cash, (b) electing to have the Company withhold otherwise deliverable cash or Shares having a Fair Market Value equal to up to the maximum statutory amount permitted to be withheld,
(c) delivering to the Company already-owned Shares having a Fair Market Value equal to up to the maximum statutory amount permitted to be withheld or (d) withholding from the proceeds of the sale of otherwise deliverable Shares acquired
pursuant to an Award either through a voluntary sale or through a mandatory sale arranged by the Company. 

  
 6 













 9.    TRANSFERABILITY. Unless determined otherwise by the
Committee, an Award 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. If the Committee makes an Award transferable, including, without
limitation, by instrument to an inter vivos or testamentary trust in which the Awards are to be passed to beneficiaries upon the death of the trustor (settlor) or by gift or by domestic relations order to a Permitted Transferee, such Award will
contain such additional terms and conditions as the Committee deems appropriate. All Awards shall be exercisable: (a) during the Employee’s lifetime only by (i) the Employee, or (ii) the Employee’s guardian or legal
representative; (b) after the Employee’s death, by the legal representative of the Employee’s heirs or legatees; and (c) by a Permitted Transferee 

10.    PRIVILEGES OF STOCK OWNERSHIP; RESTRICTIONS ON SHARES. 

10.1    Voting and Dividends. No Employee will have any of the rights of a stockholder with respect to any
Shares until the Shares are issued to the Employee, except for any Dividend Equivalent Rights permitted by an applicable Award Agreement. Any Dividend Equivalent Rights shall be subject to the same vesting or performance conditions as the underlying
Award. In addition, the Committee may provide that any Dividend Equivalent Rights permitted by an applicable Award Agreement shall be deemed to have been reinvested in additional Shares or otherwise reinvested. After Shares are issued to the
Employee, the Employee will be a stockholder and have all the rights of a stockholder with respect to such Shares, including the right to vote and receive all dividends or other distributions made or paid with respect to such Shares; provided, that
if such Shares are Unvested Shares, then any new, additional or different securities the Employee may become entitled to receive with respect to such Shares by virtue of a stock dividend, stock split or any other change in the corporate or capital
structure of the Company will be subject to the same restrictions as the Unvested Shares; provided, further, that the Employee will have no right to retain such stock dividends or stock distributions with respect to Shares that are repurchased at
the Employee’s Exercise Price, pursuant to Section 10.2. 
 10.2    Restrictions on Shares. At
the discretion of the Committee, the Company may reserve to itself and/or its assignee(s) a right to repurchase (a “Right of Repurchase”) a portion of any or all Unvested Shares held by an Employee following such
Employee’s termination of Service at any time within ninety (90) days (or such longer or shorter time determined by the Committee) after the later of the date Employee’s Service terminates and the date the Employee purchases Shares
under this Plan, for cash and/or cancellation of purchase money indebtedness, at the Employee’s Exercise Price. 

11.    CERTIFICATES. All Shares or other securities (whether or not certificated) delivered under
this Plan will be subject to such stock transfer orders, legends and other restrictions as the Committee may deem necessary or advisable, including restrictions under any applicable U.S. federal, state or foreign securities law, or any rules,
regulations and other requirements of the SEC or any stock exchange or automated quotation system upon which the Shares may be listed or quoted and any non-U.S. exchange controls or securities law restrictions
to which the Shares are subject. 
 12.    ESCROW; PLEDGE OF SHARES. To enforce any restrictions on
an Employee’s Shares, the Committee may require the Employee to deposit all certificates representing Shares, together with stock powers or other instruments of transfer approved by the Committee, appropriately endorsed in blank, with
the Company or an agent designated by the Company to hold in escrow until such restrictions have lapsed or terminated, and the Committee may cause a legend or legends referencing such restrictions to be placed on the certificates. Any Employee who
is permitted to execute a promissory note as partial or full consideration for the purchase of Shares under this Plan will be required to pledge and deposit with the 

  
 7 













 
Company all or part of the Shares so purchased as collateral to secure the payment of the Employee’s obligation to the Company under the promissory note; provided, however, that the
Committee may require or accept other or additional forms of collateral to secure the payment of such obligation and, in any event, the Company will have full recourse against the Employee under the promissory note notwithstanding any pledge of the
Employee’s Shares or other collateral. In connection with any pledge of the Shares, the Employee will be required to execute and deliver a written pledge agreement in such form as the Committee will from time to time approve. The Shares
purchased with the promissory note may be released from the pledge on a pro rata basis as the promissory note is paid. 

13.    SECURITIES LAW AND OTHER REGULATORY COMPLIANCE. An Award will not be effective unless
such Award is in compliance with all applicable U.S. and foreign federal and state securities and exchange control laws, rules and regulations of any governmental body, and the requirements of any stock exchange or automated quotation system upon
which the Shares may then be listed or quoted, as they are in effect on the date of grant of the Award and also on the date of exercise or other issuance. Notwithstanding any other provision in this Plan, the Company will have no obligation to issue
or deliver certificates for Shares under this Plan prior to: (a) obtaining any approvals from governmental agencies that the Company determines are necessary or advisable; and/or (b) completion of any registration or other qualification of
such Shares under any state or federal or foreign law or ruling of any governmental body that the Company determines to be necessary or advisable. The Company will be under no obligation to register the Shares with the SEC or to effect compliance
with the registration, qualification or listing requirements of any foreign or state securities laws, exchange control laws, stock exchange or automated quotation system, and the Company will have no liability for any inability or failure to do so.

 14.    NO OBLIGATION TO EMPLOY. The Employee’s participation in the Plan is voluntary.
Nothing in this Plan or any Award granted under this Plan will confer or be deemed to confer on any Employee any right to continue in the employ of, or to continue any other relationship with, the Company or any Parent, Subsidiary or Affiliate
or limit in any way the right of the Company or any Parent, Subsidiary or Affiliate to terminate Employee’s employment or other relationship at any time. 

15.    CORPORATE TRANSACTIONS. In the event of a Corporate Transaction any or all outstanding Awards may be
assumed or replaced by the successor corporation, which assumption or replacement shall be binding on all Employees. In the alternative, the successor corporation may substitute equivalent Awards or provide substantially similar consideration to
Employees as was provided to stockholders (after taking into account the existing provisions of the Awards). The successor corporation may also issue, in place of outstanding Shares of the Company held by the Employee, substantially similar shares,
cash or other property subject to repurchase restrictions no less favorable to the Employee. In the event such successor or acquiring corporation (if any) refuses to assume, convert, replace or substitute Awards, as provided above, pursuant to a
Corporate Transaction, then notwithstanding any other provision in this Plan to the contrary, such Awards shall have their vesting accelerate as to all shares subject to such Award (and any applicable rights of repurchase shall fully lapse)
immediately prior to the Corporate Transaction. In addition, in the event such successor or acquiring corporation (if any) refuses to assume, convert, replace or substitute Awards, as provided above, pursuant to a Corporate Transaction, the
Committee will (i) notify the Employee in writing or electronically that such Award will, if applicable, be exercisable for a period of time determined by the Committee in its sole discretion, and such Award will terminate upon the earlier of
the expiration of such period or immediately prior to the Corporate Transaction or (ii) provide that each Award shall be cancelled immediately upon the occurrence of the Corporate Transaction in exchange for a payment in cash or securities in
an amount equal to (A) the excess of the consideration paid per Share in the Corporate Transaction over the exercise price or purchase price (if any) per Share subject to the Award multiplied by (B) the number of Shares subject to the
Award. Awards need not be treated similarly in a Corporate Transaction 

  
 8 













 16.    TERM OF PLAN/GOVERNING LAW. Unless earlier
terminated as provided herein, this Plan will become effective on the Effective Date and will terminate on the later of ten (10) years from the date this Plan is adopted by the Committee or the date additional Shares are added to the
Plan by the Committee. This Plan and all Awards granted hereunder shall be governed by and construed in accordance with the laws of the State of Delaware (excluding its conflict of law rules). 

17.    AMENDMENT OR TERMINATION OF PLAN. The Board or Committee may at any time terminate or
amend this Plan in any respect, including, without limitation, amendment of any form of Award Agreement or instrument to be executed pursuant to this Plan; provided, however, that the Board or Committee will not, without the approval of the
stockholders of the Company, amend this Plan in any manner that requires such stockholder approval; provided further, that an Employee’s Award shall be governed by the version of this Plan then in effect at the time such Award was
granted. 
 18.    NONEXCLUSIVITY OF THE PLAN. Neither the adoption of this Plan by the Committee
nor any provision of this Plan will be construed as creating any limitations on the power of the Board or the Committee to adopt such additional compensation arrangements as it may deem desirable, including, without limitation, the granting
of stock awards and bonuses otherwise than under this Plan, and such arrangements may be either generally applicable or applicable only in specific cases. 

19.    INSIDER TRADING POLICY. Each Employee who receives an Award shall comply with any policy
adopted by the Company from time to time covering transactions in the Company’s securities by Employees, officers and/or directors of the Company. 

20.    ALL AWARDS SUBJECT TO COMPANY CLAWBACK OR RECOUPMENT POLICY. All Awards, subject to applicable law,
shall be subject to clawback or recoupment pursuant to any compensation clawback or recoupment policy adopted by the Board or required by law during the term of Employee’s employment or other service with the Company that is applicable to
executive officers, employees, directors or other service providers of the Company, and in addition to any other remedies available under such policy and applicable law, may require the cancellation of outstanding Awards and the recoupment of any
gains realized with respect to Awards. 
 21.    DEFINITIONS. As used in this Plan, and except as
elsewhere defined herein, the following terms will have the following meanings: 

21.1    “Affiliate” means (i) any entity that, directly or indirectly, is controlled
by, controls or is under common control with, the Company and (ii) any entity in which the Company has a significant equity interest, in either case as determined by the Committee, whether now or hereafter existing. 

21.2 “Award” means any award under this Plan, including any Option or Restricted Stock Unit. 

21.3    “Award Agreement” means, with respect to each Award, the written or electronic
agreement between the Company and the Employee setting forth the terms and conditions of the Award, and country-specific appendix thereto for grants to non-U.S. Employees, which shall be in substantially a
form (which need not be the same for each Employee) that the Committee (or in the case of Award agreements that are not used for Insiders, the Committee’s delegate(s)) has from time to time approved, and will comply with and be subject to the
terms and conditions of this Plan. 
 21.4    “Board” means the Board of Directors of the
Company. 

  
 9 













 21.5    “Cause” means
(a) Employee’s conviction (including a guilty plea or plea of nolo contendere) of any felony or any other crime involving fraud, dishonesty or moral turpitude; (b) Employee’s commission or attempted
commission of or participation in a fraud or act of dishonesty or misrepresentation against the Company that results (or could reasonably be expected to result) in material harm or injury to the business or reputation of the Company;
(c) Employee’s material violation of any contract or agreement between Employee and the Company, or of any Company policy, or of any statutory duty Employee owes to the Company; or (d) Employee’s conduct that constitutes gross
insubordination, incompetence or habitual neglect of duties and that results in (or could reasonably be expected to have resulted in) material harm to the business or reputation of the Company. The determination as to whether an Employee is being
terminated for Cause shall be made in good faith by the Company and shall be final and binding on the Employee. The foregoing definition does not in any way limit the Company’s ability to terminate an Employee’s employment or consulting
relationship at any time as provided in Section 14 above, and the term “Company” will be interpreted to include any Subsidiary or Parent, as appropriate. Notwithstanding the foregoing, the foregoing definition of “Cause”
may, in part or in whole, be modified or replaced in each individual employment agreement or Award Agreement with any Employee, provided that such document supersedes the definition provided in this Section 21.5. 

21.6    “Code” means the United States Internal Revenue Code of 1986, as amended, and the
regulations promulgated thereunder. 
 21.7    “Committee” means the Compensation
Committee of the Board. 
 21.8    “Common Stock” means the common stock of the Company.

 21.9    “Company” means Sierra Oncology, Inc., or any successor corporation. 

21.10    “Corporate Transaction” means the occurrence of any of the following events:
(a) any “Person” (as such term is used in Sections 13(d) and 14(d) of the Exchange Act) becomes the “beneficial owner” (as defined in Rule 13d-3 of the Exchange Act), directly or
indirectly, of securities of the Company representing more than fifty percent (50%) of the total voting power represented by the Company’s then-outstanding voting securities; provided, however, that for purposes of this subclause (a) the
acquisition of additional securities by any one Person who is considered to own more than fifty percent (50%) of the total voting power of the securities of the Company will not be considered a Corporate Transaction; (b) the consummation of the
sale or disposition by the Company of all or substantially all of the Company’s assets; (c) the consummation of a merger or consolidation of the Company with any other corporation, other than a merger or consolidation which would result in
the voting securities of the Company outstanding immediately prior thereto continuing to represent (either by remaining outstanding or by being converted into voting securities of the surviving entity or its parent) at least fifty percent (50%) of
the total voting power represented by the voting securities of the Company or such surviving entity or its parent outstanding immediately after such merger or consolidation; (d) any other transaction which qualifies as a “corporate
transaction” under Section 424(a) of the Code wherein the stockholders of the Company give up all of their equity interest in the Company (except for the acquisition, sale or transfer of all or substantially all of the outstanding shares
of the Company) or (e) a change in the effective control of the Company that occurs on the date that a majority of members of the Board are replaced during any twelve (12) month period by members of the Board whose appointment or election
is not endorsed by as majority of the members of the Board prior to the date of such appointment or election. For purpose of this subclause (e), if any Person is considered to be in effective control of the Company, the acquisition of additional
control of the Company by the same Person will not be considered a Corporate Transaction. For purposes of this definition, Persons will be considered to be acting as a group if they are owners of a corporation that enters into a merger,
consolidation, purchase or acquisition of stock, or similar business transaction with the Company. Notwithstanding the foregoing, to the extent that any amount constituting deferred compensation (as 


  
 10 













 
defined in Section 409A of the Code) would become payable under this Plan by reason of a Corporate Transaction, such amount shall become payable only if the event constituting a Corporate
Transaction would also qualify as a change in ownership or effective control of the Company or a change in the ownership of a substantial portion of the assets of the Company, each as defined within the meaning of Code Section 409A, as it has
been and may be amended from time to time, and any proposed or final Treasury Regulations and IRS guidance that has been promulgated or may be promulgated thereunder from time to time. 

21.11     “Director” means a member of the Board. 

21.12    “Disability” means in the case of incentive stock options, total and permanent
disability as defined in Section 22(e)(3) of the Code and in the case of other Awards, that the Employee is unable to engage in any substantial gainful activity by reason of any medically determinable physical or mental impairment that can be
expected to result in death or can be expected to last for a continuous period of not less than 12 months. 

21.13    “Dividend Equivalent Right” means the right of an Employee, granted at the
discretion of the Committee or as otherwise provided by the Plan or an Award Agreement, to receive a credit for the account of such Employee in an amount equal to the cash, stock or other property dividends in amounts equal equivalent to cash, stock
or other property dividends for each Share represented by an Award held by such Employee. 
 21.14
    “Effective Date” means September 20, 2018. 

21.15    “Employee” means any person, including Officers, providing services as an employee
to the Company or any Parent, Subsidiary or Affiliate. Neither service as a director nor payment of a director’s fee by the Company will be sufficient to constitute “employment” by the Company. 

21.16     “Exchange Act” means the United States Securities Exchange Act of 1934, as
amended. 
 21.17    “Exercise Price” means, with respect to an Option, the price at
which a holder may purchase the Shares issuable upon exercise of an Option. 
 21.18    “Fair Market
Value” means, as of any date, the value of a share of the Company’s Common Stock determined as follows: 
 (a)
    if such Common Stock is publicly traded and is then listed on a national securities exchange, its closing price on the date of determination on the principal national securities exchange on which the Common Stock is listed or
admitted to trading as reported in The Wall Street Journal or such other source as the Board or the Committee deems reliable; 
 (b)
    if such Common Stock is publicly traded but is neither listed nor admitted to trading on a national securities exchange, the average of the closing bid and asked prices on the date of determination as reported in The Wall
Street Journal or such other source as the Board or the Committee deems reliable; or 
 (c)     if none of the
foregoing is applicable, by the Board or the Committee in good faith. 

21.19    “Insider” means an officer or director of the Company or any other person whose
transactions in the Company’s Common Stock are subject to Section 16 of the Exchange Act. 

  
 11 













 21.20     “IRS” means the United States
Internal Revenue Service. 
 21.21     “Option” means an award of an option to purchase
Shares pursuant to Section 5. 
 21.22    “Outside Director” means a Director who is
not an Employee of the Company or any Parent or Subsidiary and who is an “independent” director under the rules of The Nasdaq Stock Market, as may be amended from time to time. 

21.23    “Parent” means any corporation (other than the Company) in an unbroken chain of
corporations ending with the Company if each of such corporations other than the Company owns stock possessing fifty percent (50%) or more of the total combined voting power of all classes of stock in one of the other corporations in such chain.

 21.24    “Performance Factors” means the factors selected by the Committee to
determine whether performance goals established by the Committee applicable to Awards have been satisfied. 

21.25    “Performance Period” means the period of service determined by the Committee
during which years of service or performance is to be measured for the Award. 
 21.26    “Permitted
Transferee” 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) of the Employee, any person sharing the Employee’s household (other than a tenant or employee), a trust in which these persons (or the Employee) have more
than 50% of the beneficial interest, a foundation in which these persons (or the Employee) control the management of assets, and any other entity in which these persons (or the Employee) own more than 50% of the voting interests. 

21.27     “Plan” means this Sierra Oncology, Inc. 2018 Equity Inducement Plan. 

21.28     “Restricted Stock Unit” means an Award granted pursuant to Section 6 of the
Plan. 
 21.29     “SEC” means the United States Securities and Exchange Commission. 

21.30     “Securities Act” means the United States Securities Act of 1933, as amended. 

21.31    “Service” shall mean service as an Employee to the Company or a Parent, Subsidiary
or Affiliate, subject to such further limitations as may be set forth in the Plan or the applicable Award Agreement. An Employee will not be deemed to have ceased to provide Service in the case of (a) sick leave, (b) military leave, or
(c) any other leave of absence approved by the Company; provided, that such leave is for a period of not more than 90 days (x) unless reemployment upon the expiration of such leave is guaranteed by contract or statute, or
(y) unless provided otherwise pursuant to formal policy adopted from time to time by the Company and issued and promulgated to employees in writing. In the case of any Employee on an approved leave of absence or a reduction in hours worked (for
illustrative purposes only, a change in schedule from that of full-time to part-time), the Committee may make such provisions regarding suspension of or modification of vesting of the Award while on leave from the employ of the Company or a Parent,
Subsidiary or Affiliate or during such change in working hours as it may deem appropriate, except that in no event may an Award be exercised after the expiration of the term set forth in the applicable Award Agreement. In the event of military
leave, if required by applicable laws, vesting shall continue for the longest period that vesting continues under any other statutory or Company approved leave of absence and, upon a Employee’s returning from military leave (under conditions
that would entitle him or her to protection upon such return under the Uniform Services Employment and Reemployment Rights 

  
 12 













 
Act), he or she shall be given vesting credit with respect to Awards to the same extent as would have applied had the Employee continued to provide services to the Company throughout the leave on
the same terms as he or she was providing services immediately prior to such leave. Except as set forth in this Section 28.39, an employee shall have terminated employment as of the date he or she ceases provide services (regardless of whether
the termination is in breach of local employment laws or is later found to be invalid) and employment shall not be extended by any notice period or garden leave mandated by local law, provided however, that a change in status from an
employee to a consultant or advisor shall not terminate the service provider’s Service, unless determined by the Committee, in its discretion. The Committee will have sole discretion to determine whether a Employee has ceased to provide
Services and the effective date on which the Employee ceased to provide Services. 
 21.32
    “Shares” means shares of Common Stock and the common stock of any successor entity. 

21.33    “Subsidiary” means any corporation (other than the Company) in an unbroken chain
of corporations beginning with the Company if each of the corporations other than the last corporation in the unbroken chain owns stock possessing fifty percent (50%) or more of the total combined voting power of all classes of stock in one of the
other corporations in such chain. 
 21.34     “Treasury Regulations” means regulations
promulgated by the United States Treasury Department. 
 21.35    “Unvested Shares” means
Shares that have not yet vested or are subject to a right of repurchase in favor of the Company (or any successor thereto). 

  
 13 













 SIERRA ONCOLOGY, INC. 

(the “Company”) 

2018 EQUITY INDUCEMENT PLAN 

(the “Plan”) 

ADDENDUM FOR CANADIAN PARTICIPANTS 
  

	A.	 The Company has adopted the Plan, to be effective on the Effective Date. 



 

	B.	 The Company desires to modify certain terms of the Plan in their application for Employees (as those terms are
defined in the Plan) who are resident in Canada for purposes of the Income Tax Act (Canada) or otherwise subject to Canadian personal income tax (the “Canadian Employees”). 



NOW THEREFORE, the Company does hereby amend certain terms and conditions of the Plan as they apply to the Canadian Employees,
as follows. 
  

	1.	 Defined Terms. In this Addendum, all defined terms shall have the respective meanings set
forth in the Plan, unless otherwise defined herein. 


  

	2.	 Effective Date. The effective date of this Addendum is the Effective Date. 



  

	3.	 Addendum. The Company hereby amends certain terms and conditions of the Plan
pursuant to which the Company may grant Options to any Canadian Eligible Person, if the participation by the Canadian Eligible Person in such distribution of securities is voluntary (as such term is interpreted pursuant to
Section 2.23(2) of NI 45-106) and is otherwise permitted under NI 45-106. 



 

	4.	 Options. 



 

	 	(a)	 Notwithstanding section 5.2 of the Plan, the grant date of an Option awarded to a Canadian Employee shall be,
in all cases, the date the Option is actually granted to the Canadian Employee, as evidenced by the Award Agreement. 


  

	 	(b)	 Notwithstanding section 5.1 of the Plan, satisfaction of Performance Factors, if any, will be treated as a
condition subsequent to the grant to a Canadian Employee of an Option giving rise to a risk of forfeiture of the Option and not a condition precedent to the grant of the Option. 



 

	 	(c)	 For purposes of section 5.9 of the Plan, Options granted to a Canadian Employee will not be modified or
altered, or new options granted in substitution therefor, if such modification, alteration or substitution has a material adverse affect on such Canadian Employee’s tax treatment of such Options, except with such Canadian Employee’s
consent. 



  
 A-1 














	5.	 Restricted Stock Units. 



Section 6.2 of the Plan shall be modified as it applies to Canadian Employees such that the Company agrees to issue only Shares in payment
of RSUs to a Canadian Employee and the Company cannot choose, at its option, to make such payment in cash or a combination of cash and Shares, and section 6.2 shall read as follows: 

“6.2. Form and Timing of Settlement to Canadian Employees. Payment of earned RSUs of a Canadian Employee shall be made as soon as
practicable after the date(s) determined by the Committee and set forth in the Award Agreement. Such earned RSUs shall be settled solely by the issuance of Shares. The Committee may permit a Canadian Employee to defer settlement and the issuance of
Shares in payment of an earned RSU to a date that is acceptable to the Committee, provided that, in the case of a Canadian Eligible Person that is an Employee, the terms of the Award Agreement, the RSUs and any deferral meet the conditions of
section 7 of the Income Tax Act (Canada).” 
  

	6.	 Payment for Share Purchases. 



Section 7(b) of the Plan shall be modified as at applies to Canadian Employees with respect to the consideration that may be paid by
Canadian Employees for Shares purchased pursuant to the Plan. In no circumstances shall a Canadian Employee be permitted to make, and the Committee shall not approve, a payment by the Canadian Employee by the surrender of any Shares that were
acquired at any time by the Canadian Employee on the exercise of any Option. 
  

	7.	 Withholding Taxes. 



 

	 	(a)	 Section 8.1 of the Plan shall be modified as it applies to Canadian Employees and shall read as follows:



 “8.1 Withholding for Canadian Employees. The Company or any Affiliate shall deduct and withhold any taxes
and other required source deductions which the Company or Affiliate, as the case may be, is required by law or regulation of any governmental authority whatsoever to deduct, withhold or remit in connection with the grant, exercise or settlement of
any Award. Without limiting the generality of the foregoing, whenever a settlement or payment is made by the issuance of Shares to a Canadian Employee in satisfaction of Awards granted under this Plan, the Company or Affiliate, as the case may be,
may, at its discretion (i) deduct and withhold those amounts it is required to remit from any cash remuneration or other amount payable to the Canadian Employee, whether or not such amount payable is related to the Plan, or the exercise or
settlement of any Awards; (ii) permit the Canadian Employee to make a cash payment to the Company or Affiliate, as the case may be, equal to the amount required to be remitted; or (iii) sell, on behalf of the Canadian Employee, that number
of Shares to be issued on the exercise or settlement such that the amount of the proceeds of such sale will be sufficient to satisfy any taxes or other source deductions required to be remitted for the account of the Canadian Employee. If the
Company or Affiliate, as the case may be, considers that the foregoing steps undertaken in connection with this section 13.1 result in inadequate withholding or a late remittance of taxes or other source deductions, then the delivery of Shares to be
issued on the exercise or settlement of Awards may be made conditional upon the Canadian Employee (or other person) reimbursing or compensating the Company or Affiliate or making arrangements satisfactory to the Company or Affiliate for the payment
in a timely manner of all taxes and other source deductions required to be remitted.” 
  

	 	(b)	 Section 8.2 of the Plan shall not apply to Canadian Employees. For greater certainty, the Committee shall
not approve funding by a Canadian Employee of withholding taxes or other source deductions by the withholding of Shares the Canadian Employee is otherwise entitled to receive or the surrender by the Canadian Employee of any Shares that were acquired
at any time by the Canadian Employee on the exercise of any Option. 



  
 A-2