Document:

Exhibit 10.2

 Exhibit 10.2 
 AMBIT BIOSCIENCES CORPORATION 

AMENDED AND RESTATED 2011 EQUITY INCENTIVE
PLAN 
 Adopted January 24, 2001 

Approved By Stockholders February 21, 2001 
 As Amended by the Board of Directors on June 6, 2001 
 Amendment
approved by the Stockholders 
 As Amended by the Board of Directors on October 31, 2001 

Amendment approved by the Stockholders 
 As Amended by the Board of Directors on August 12, 2004 
 Amendment
approved by the Stockholders 
 As Amended by the Board of Directors on March 10, 2005 

Amendment approved by the Stockholders 
 As Amended by the Board of Directors on January 31, 2006 
 Amendment
approved by the Stockholders 
 As Amended by the Board of Directors on October 24, 2007 

Amendment approved by the Stockholders 
 As Amended by the Board of Directors on November 5 and 6, 2008 

Amendment approved by the Stockholders 
 As Amended by the Board of Directors on August 19, 2010 
 Amendment
approved by the Stockholders 
 As Amended and Restated by the Board of Directors on January 25, 2011 

Amendment and Restatement approved by the Stockholders 
 Termination Date: January 24, 2021 
  

	1.	PURPOSES. 

(a) Eligible Stock Award Recipients. The persons eligible to receive Stock Awards are the Employees, Directors and
Consultants of the Company and its Affiliates. 
 (b) Available Stock Awards. The purpose of the Plan is to
provide a means by which eligible recipients of Stock Awards may be given an opportunity to benefit from increases in value of the Common Stock through the granting of the following Stock Awards: (i) Incentive Stock Options,
(ii) Nonstatutory Stock Options, (iii) stock bonuses and (iv) rights to acquire restricted stock. 
 (c)
General Purpose. The Company, by means of the Plan, seeks to retain the services of the group of persons eligible to receive Stock Awards, to secure and retain the services of new members of this group and to provide incentives for such
persons to exert maximum efforts for the success of the Company and its Affiliates. 

  
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	2.	DEFINITIONS. 

 (a) “Affiliate” means any parent corporation or subsidiary corporation of the Company, whether now or hereafter existing, as those terms are defined in Sections 424(e) and
(f), respectively, of the Code. 
 (b) “Board” means the Board of Directors of the Company.

 (c) “Cause” means, with respect to a Participant, the occurrence of any of the following:
(i) such Participant’s conviction of any felony or any crime involving fraud or dishonesty that has a material adverse effect on the Company; (ii) such Participant’s participation (whether by affirmative act or omission) in a
fraud, act of dishonesty or other act of misconduct against the Company and/or its Affiliates; (iii) conduct by such Participant which, based upon a good faith and reasonable factual investigation by the Company (or, if such Participant is an
Officer, by the Board), demonstrates such Participant’s gross unfitness to serve; (iv) such Participant’s violation of any statutory or fiduciary duty, or duty of loyalty, owed to the Company and/or its Affiliates; (v) such
Participant’s breach of any material term of any material contract between such Participant and the Company and/or its Affiliates; and (vi) such Participant’s repeated violation of any material Company policy. An occurrence of
“cause” as set forth in the preceding sentence shall be based upon a good faith determination by the Company (or, if such Participant is an Officer, by the Board). Notwithstanding the foregoing, such Participant’s Disability shall not
constitute Cause as set forth herein. The determination that a termination is for Cause shall be by the Committee in its sole and exclusive judgment and discretion. 
 (d) “Code” means the Internal Revenue Code of 1986, as amended. 
 (e) “Committee” means a committee of one or more members of the Board appointed by the Board in accordance with subsection 3(c). 

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

(g) “Company” means Ambit Biosciences Corporation, a Delaware corporation. 

(h) “Consultant” means any person, including an advisor, (i) engaged by the Company or an Affiliate
to render consulting or advisory services and who is compensated for such services or (ii) who is a member of the Board of Directors of an Affiliate. However, the term “Consultant” shall not include Directors who are not compensated
by the Company for their services as Directors, nor shall the payment of a director’s fee by the Company for services as a Director cause a Director to be deemed a Consultant for the purposes of this Plan. 

(i) “Continuous Service” means that the Participant’s service with the Company or an Affiliate,
whether as an Employee, Director or Consultant, is not interrupted or terminated. Neither a change in the capacity in which such Participant renders service to the Company or an Affiliate as an Employee, Consultant or Director, nor a change in the
entity for which the Participant renders such service, shall be deemed to interrupt or terminate such Participant’s 

  
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Continuous Service provided that there is no interruption or termination of the Participant’s Continuous Service. For example, a change in status from an Employee of the Company to a
Consultant of an Affiliate or a Director will not constitute an interruption of Continuous Service. The Board or the chief executive officer of the Company, in that party’s sole discretion, may determine whether Continuous Service shall be
considered interrupted in the case of any leave of absence approved by that party, including sick leave, military leave or any other personal leave. 
 (j) “Covered Employee” means the chief executive officer and the four (4) other highest compensated officers of the Company for whom total compensation is required to
be reported to stockholders under the Exchange Act, as determined for purposes of Section 162(m) of the Code. 
 (k)
“Director” means a member of the Board of Directors of the Company. 
 (l)
“Disability” means (i) before the Listing Date, the inability of a person, in the opinion of a qualified physician acceptable to the Company, to perform the major duties of that person’s position with the Company or
an Affiliate of the Company because of the sickness or injury of the person and (ii) after the Listing Date, the permanent and total disability of a person within the meaning of Section 22(e)(3) of the Code. 

(m) “Employee” means any person employed by the Company or an Affiliate. Service as a Director or payment
of a director’s fee by the Company or an Affiliate shall not be sufficient to constitute “employment” by the Company or an Affiliate. 
 (n) “Exchange Act” means the Securities Exchange Act of 1934, as amended. 
 (o) “Fair Market Value” means, as of any date, the value of the Common Stock determined as follows: 

(i) If the Common Stock is listed on any established stock exchange or traded on the Nasdaq National Market or the
Nasdaq SmallCap Market, the Fair Market Value of a share of Common Stock shall be the closing sales price for such stock (or the closing bid, if no sales were reported) as quoted on such exchange or market (or the exchange or market with the
greatest volume of trading in the Common Stock) on the last market trading day prior to the day of determination, as reported in The Wall Street Journal or such other source as the Board deems reliable. 

(ii) In the absence of such markets for the Common Stock, the Fair Market Value shall be determined in good faith
by the Board. 
 (iii) Prior to the Listing Date, the value of the Common Stock shall be determined by the
Board in compliance with Section 409A of the Code or, in the case of an Incentive Stock Option, in compliance with Section 422 of the Code. 

  
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 (p) “Incentive Stock Option” means an Option intended to
qualify as an incentive stock option within the meaning of Section 422 of the Code and the regulations promulgated thereunder. 
 (q) “Listing Date” means the first date upon which any security of the Company is listed (or approved for listing) upon notice of issuance on any securities exchange or
designated (or approved for designation) upon notice of issuance as a national market security on an interdealer quotation system if such securities exchange or interdealer quotation system has been certified in accordance with the provisions of
Section 25100(o) of the California Corporate Securities Law of 1968. 
 (r) “Non-Employee Director”
means a Director who either (i) is not a current Employee or Officer of the Company or its parent or a subsidiary, does not receive compensation (directly or indirectly) from the Company or its parent or a subsidiary for services
rendered as a consultant or in any capacity other than as a Director (except for an amount as to which disclosure would not be required under Item 404(a) of Regulation S-K promulgated pursuant to the Securities Act (“Regulation
S-K”)), does not possess an interest in any other transaction as to which disclosure would be required under Item 404(a) of Regulation S-K and is not engaged in a business relationship as to which disclosure would be required under
Item 404(b) of Regulation S-K; or (ii) is otherwise considered a “non-employee director” for purposes of Rule 16b-3. 
 (s) “Nonstatutory Stock Option” means an Option not intended to qualify as an Incentive Stock Option. 

(t) “Officer” means (i) before the Listing Date, any person designated by the Company as an officer
and (ii) on and after the Listing Date, a person who is an officer of the Company within the meaning of Section 16 of the Exchange Act and the rules and regulations promulgated thereunder. 

(u) “Option” means an Incentive Stock Option or a Nonstatutory Stock Option granted pursuant to the Plan.

 (v) “Option Agreement” means a written agreement between the Company and an Optionholder
evidencing the terms and conditions of an individual Option grant. Each Option Agreement shall be subject to the terms and conditions of the Plan. 
 (w) “Optionholder” means a person to whom an Option is granted pursuant to the Plan or, if applicable, such other person who holds an outstanding Option. 

(x) “Outside Director” means a Director who either (i) is not a current employee of the Company or an
“affiliated corporation” (within the meaning of Treasury Regulations promulgated under Section 162(m) of the Code), is not a former employee of the Company or an “affiliated corporation” receiving compensation for prior
services (other than benefits under a tax qualified pension plan), was not an officer of the Company or an “affiliated corporation” at any time and is not currently receiving direct or indirect remuneration from the Company or an

  
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“affiliated corporation” for services in any capacity other than as a Director or (ii) is otherwise considered an “outside director” for purposes of Section 162(m)
of the Code. 
 (y) “Participant” means a person to whom a Stock Award is granted pursuant to the
Plan or, if applicable, such other person who holds an outstanding Stock Award. 
 (z) “Plan”
means this Ambit Biosciences Corporation Amended and Restated 2011 Equity Incentive Plan. 
 (aa) “Rule
16b-3” means Rule 16b-3 promulgated under the Exchange Act or any successor to Rule 16b-3, as in effect from time to time. 
 (bb) “Securities Act” means the Securities Act of 1933, as amended. 
 (cc) “Stock Award” means any right granted under the Plan, including an Option, a stock bonus and a right to acquire restricted stock. 

(dd) “Stock Award Agreement” means a written agreement between the Company and a holder of a Stock Award
evidencing the terms and conditions of an individual Stock Award grant. Each Stock Award Agreement shall be subject to the terms and conditions of the Plan. 
 (ee) “Ten Percent Stockholder” means a person who owns (or is deemed to own pursuant to Section 424(d) of the Code) stock possessing more than ten percent (10%) of
the total combined voting power of all classes of stock of the Company or of any of its Affiliates. 
  

	3.	ADMINISTRATION. 

 (a) Administration by Board. The Board shall administer the Plan unless and until the Board delegates administration to a Committee, as provided in subsection 3(c). 

(b) Powers of Board. The Board shall have the power, subject to, and within the limitations of, the express provisions of
the Plan: 
 (i) To determine from time to time which of the persons eligible under the Plan shall be
granted Stock Awards; when and how each Stock Award shall be granted; what type or combination of types of Stock Award shall be granted; the provisions of each Stock Award granted (which need not be identical), including the time or times when a
person shall be permitted to receive Common Stock pursuant to a Stock Award; and the number of shares of Common Stock with respect to which a Stock Award shall be granted to each such person. 

(ii) To construe and interpret the Plan and Stock Awards granted under it, and to establish, amend and revoke rules
and regulations for its administration. The Board, in the exercise of this power, may correct any defect, omission or inconsistency in the Plan or in any Stock Award Agreement, in a manner and to the extent it shall deem necessary or expedient to
make the Plan fully effective. 
 (iii) To amend the Plan or a Stock Award as provided in Section 12.

  
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 (iv) Generally, to exercise such powers and to perform such acts as
the Board deems necessary or expedient to promote the best interests of the Company which are not in conflict with the provisions of the Plan. 
 (c) Delegation to Committee. 
 (i) General.
The Board may delegate administration of the Plan to a Committee or Committees of one (1) or more members of the Board, and the term “Committee” shall apply to any person or persons to whom such authority has been delegated. If
administration is delegated to a Committee, the Committee shall have, in connection with the administration of the Plan, the powers theretofore possessed by the Board, including the power to delegate to a subcommittee any of the administrative
powers the Committee is authorized to exercise (and references in this Plan to the Board shall thereafter be to the Committee or subcommittee), subject, however, to such resolutions, not inconsistent with the provisions of the Plan, as may be
adopted from time to time by the Board. The Board may abolish the Committee at any time and revest in the Board the administration of the Plan. 
 (ii) Committee Composition when Common Stock is Publicly Traded. At such time as the Common Stock is publicly traded, in the discretion of the Board, a Committee may consist solely of two or
more Outside Directors, in accordance with Section 162(m) of the Code, and/or solely of two or more Non-Employee Directors, in accordance with Rule 16b-3. Within the scope of such authority, the Board or the Committee may (1) delegate to a
committee of one or more members of the Board who are not Outside Directors the authority to grant Stock Awards to eligible persons who are either (a) not then Covered Employees and are not expected to be Covered Employees at the time of
recognition of income resulting from such Stock Award or (b) not persons with respect to whom the Company wishes to comply with Section 162(m) of the Code and/or) (2) delegate to a committee of one or more members of the Board who are
not Non-Employee Directors the authority to grant Stock Awards to eligible persons who are not then subject to Section 16 of the Exchange Act. 
 (d) Effect of Board’s Decision. All determinations, interpretations and constructions made by the Board in good faith shall not be subject to review by any person and shall be final,
binding and conclusive on all persons. 
  

	4.	SHARES SUBJECT TO THE PLAN. 

(a) Share Reserve. Subject to the provisions of Section 11 relating to adjustments upon changes in Common Stock, the
Common Stock that may be issued pursuant to Stock Awards shall not exceed in the aggregate 7,306,247 shares of Common Stock. 

(b) Reversion of Shares to the Share Reserve. If any Stock Award shall for any reason expire or otherwise terminate, in
whole or in part, without having been exercised in full, the shares of Common Stock not acquired under such Stock Award shall revert to and again become available for issuance under the Plan. 

  
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 (c) Source of Shares. The shares of Common Stock subject to the Plan may be
unissued shares or reacquired shares, bought on the market or otherwise. 
 (d) Incentive Stock Option Limit.
Notwithstanding anything to the contrary in this subsection 4(d), subject to the provisions of subsection 11(a) relating to Capitalization Adjustments, the aggregate maximum number of shares of Common Stock that may be issued
pursuant to the exercise of Incentive Stock Options shall be 14,612,494 shares of Common Stock. 
  

	5.	ELIGIBILITY. 

 (a) Eligibility for Specific Stock Awards. Incentive Stock Options may be granted only to employees of the Company or a “parent corporation” or “subsidiary corporation”
thereof (as such terms are defined in Sections 424(e) and (f) of the Code). Stock Awards other than Incentive Stock Options may be granted to Employees, Directors and Consultants; provided, however, Nonstatutory Stock Options may
not be granted to Employees, Directors and Consultants who are providing Continuous Service only to any “parent” of the Company, as such term is defined in Rule 405 promulgated under the Securities Act, unless the stock underlying
such Stock Awards is treated as “service recipient stock” under Section 409A of the Code because the Stock Awards are granted pursuant to a corporate transaction (such as a spin off transaction) or unless such Stock Awards comply with
the distribution requirements of Section 409A of the Code. 
 (b) Ten Percent Stockholders. A Ten Percent
Stockholder shall not be granted an Incentive Stock Option unless the exercise price of such Option is at least one hundred ten percent (110%) of the Fair Market Value of the Common Stock at the date of grant and the Option is not exercisable
after the expiration of five (5) years from the date of grant. 
 (c) Section 162(m) Limitation. Subject
to the provisions of Section 11 relating to adjustments upon changes in the shares of Common Stock, no Employee shall be eligible to be granted Options covering more than One Million Two Hundred Thousand (1,200,000) shares of Common Stock
during any calendar year. This subsection 5(c) shall not apply prior to the Listing Date and, following the Listing Date, this subsection 5(c) shall not apply until (i) the earliest of: (1) the first material modification of the Plan
(including any increase in the number of shares of Common Stock reserved for issuance under the Plan in accordance with Section 4); (2) the issuance of all of the shares of Common Stock reserved for issuance under the Plan; (3) the
expiration of the Plan; or (4) the first meeting of stockholders at which Directors are to be elected that occurs after the close of the third calendar year following the calendar year in which occurred the first registration of an equity
security under Section 12 of the Exchange Act; or (ii) such other date required by Section 162(m) of the Code and the rules and regulations promulgated thereunder. 

(d) Consultants. 
 (i) Prior to the Listing Date, a Consultant shall not be eligible for the grant of a Stock Award if, at the time of grant, either the offer or the sale of the Company’s securities to

  
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such Consultant is not exempt under Rule 701 of the Securities Act (“Rule 701”) because of the nature of the services that the Consultant is providing to the Company, or
because the Consultant is not a natural person, or as otherwise provided by Rule 701, unless the Company determines that such grant need not comply with the requirements of Rule 701 and will satisfy another exemption under the Securities Act as well
as comply with the securities laws of all other relevant jurisdictions. 
 (ii) From and after the Listing
Date, a Consultant shall not be eligible for the grant of a Stock Award if, at the time of grant, a Form S-8 Registration Statement under the Securities Act (“Form S-8”) is not available to register either the offer or the sale of the
Company’s securities to such Consultant because of the nature of the services that the Consultant is providing to the Company, or because the Consultant is not a natural person, or as otherwise provided by the rules governing the use of Form
S-8, unless the Company determines both (i) that such grant (A) shall be registered in another manner under the Securities Act (e.g., on a Form S-3 Registration Statement) or (B) does not require registration under the
Securities Act in order to comply with the requirements of the Securities Act, if applicable, and (ii) that such grant complies with the securities laws of all other relevant jurisdictions. 

(iii) Rule 701 and Form S-8 generally are available to consultants and advisors only if (i) they are natural
persons; (ii) they provide bona fide services to the issuer, its parents, its majority-owned subsidiaries or majority-owned subsidiaries of the issuer’s parent; and (iii) the services are not in connection with the offer or sale of
securities in a capital-raising transaction, and do not directly or indirectly promote or maintain a market for the issuer’s securities. 
  

	6.	OPTION PROVISIONS. 

 Each Option shall be in such form and shall contain such terms and conditions as the Board shall deem appropriate. All Options shall be separately designated Incentive Stock Options or Nonstatutory Stock
Options at the time of grant, and, if certificates are issued, a separate certificate or certificates will be issued for shares of Common Stock purchased on exercise of each type of Option. The provisions of separate Options need not be identical,
but each Option shall include (through incorporation of provisions hereof by reference in the Option or otherwise) the substance of each of the following provisions: 
 (a) Term. Subject to the provisions of subsection 5(b) regarding Incentive Stock Options granted to Ten Percent Stockholders, no Option granted prior to the Listing Date shall be exercisable
after the expiration of ten (10) years from the date it was granted, and no Incentive Stock Option granted on or after the Listing Date shall be exercisable after the expiration of ten (10) years from the date it was granted. 

(b) Exercise Price. Subject to the provisions of subsection 5(b) regarding Incentive Stock Options granted to Ten Percent
Stockholders, the exercise price of each Option shall be not less than one hundred percent (100%) of the Fair Market Value of the Common Stock subject to the Option on the date the Option is granted. Notwithstanding the foregoing, an Option may
be granted with an exercise price lower than that set forth in the preceding sentence if such Option is granted pursuant to an assumption or substitution for another option pursuant to a 

  
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Corporate Transaction and in a manner consistent with the provisions of Sections 409A and 424(a) of the Code (whether or not such Stock Awards are Incentive Stock Options). 

(c) Consideration. The purchase price of Common Stock acquired pursuant to an Option shall be paid, to the extent permitted
by applicable statutes and regulations, either (i) in cash at the time the Option is exercised or (ii) at the discretion of the Board at the time of the grant of the Option (or subsequently in the case of a Nonstatutory Stock Option)
(1) by delivery to the Company of other Common Stock, (2) according to a deferred payment or other similar arrangement with the Optionholder or (3) in any other form of legal consideration that may be acceptable to the Board. Unless
otherwise specifically provided in the Option, the purchase price of Common Stock acquired pursuant to an Option that is paid by delivery to the Company of other Common Stock acquired, directly or indirectly from the Company, shall be paid only by
shares of the Common Stock of the Company that have been held for more than six (6) months (or such longer or shorter period of time required to avoid a charge to earnings for financial accounting purposes). At any time that the Company is
incorporated in Delaware, payment of the Common Stock’s “par value,” as defined in the Delaware General Corporation Law, shall not be made by deferred payment. 
 In the case of any deferred payment arrangement, interest shall be compounded at least annually and shall be charged at the market rate of interest necessary to avoid a charge to earnings for financial
accounting purposes. 
 (d) Transferability of an Incentive Stock Option. An Incentive Stock Option shall not be
transferable except by will or by the laws of descent and distribution and shall be exercisable during the lifetime of the Optionholder only by the Optionholder. Notwithstanding the foregoing, the Optionholder may, by delivering written notice to
the Company, in a form satisfactory to the Company, designate a third party who, in the event of the death of the Optionholder, shall thereafter be entitled to exercise the Option. 

(e) Transferability of a Nonstatutory Stock Option. A Nonstatutory Stock Option granted prior to the Listing Date shall not
be transferable except by will or by the laws of descent and distribution and, to the extent provided in the Option Agreement, to such further extent as permitted by Section 260.140.41(e) of Title 10 of the California Code of Regulations at the
time of the grant of the Option, and shall be exercisable during the lifetime of the Optionholder only by the Optionholder. A Nonstatutory Stock Option granted on or after the Listing Date shall be transferable to the extent provided in the Option
Agreement. If the Nonstatutory Stock Option does not provide for transferability, then the Nonstatutory Stock Option shall not be transferable except by will or by the laws of descent and distribution and shall be exercisable during the lifetime of
the Optionholder only by the Optionholder. Notwithstanding the foregoing, the Optionholder may, by delivering written notice to the Company, in a form satisfactory to the Company, designate a third party who, in the event of the death of the
Optionholder, shall thereafter be entitled to exercise the Option. 
 (f) Vesting Generally. The total number of shares
of Common Stock subject to an Option may, but need not, vest and therefore become exercisable in periodic installments that may, but need not, be equal. The Option may be subject to such other terms and conditions on

  
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the time or times when it may be exercised (which may be based on performance or other criteria) as the Board may deem appropriate. The vesting provisions of individual Options may vary. The
provisions of this subsection 6(f) are subject to any Option provisions governing the minimum number of shares of Common Stock as to which an Option may be exercised. 
 (g) Termination of Continuous Service. In the event an Optionholder’s Continuous Service terminates (for reasons other than Cause or upon the Optionholder’s death or Disability),
the Optionholder may exercise his or her Option (to the extent that the Optionholder was entitled to exercise such Option as of the date of termination) but only within such period of time ending on the earlier of (i) the date three
(3) months following the termination of the Optionholder’s Continuous Service (or such longer or shorter period specified in the Option Agreement, which period shall not be less than thirty (30) days for Options granted prior to the
Listing Date if necessary to comply with applicable state law, unless such termination is for Cause), or (ii) the expiration of the term of the Option as set forth in the Option Agreement. If, after termination, the Optionholder does not
exercise his or her Option within the time specified in the Option Agreement, the Option shall terminate. 
 (h)
Extension of Termination Date. An Optionholder’s Option Agreement may also provide that if the exercise of the Option following the termination of the Optionholder’s Continuous Service (for reasons other than Cause or upon the
Optionholder’s death or Disability) would be prohibited at any time solely because the issuance of shares of Common Stock would violate the registration requirements under the Securities Act, then the Option shall terminate on the earlier of
(i) the expiration of the term of the Option set forth in subsection 6(a) or (ii) the expiration of a period of three (3) months after the termination of the Optionholder’s Continuous Service during which the exercise of the
Option would not be in violation of such registration requirements. 
 (i) Disability of Optionholder. In the
event that an Optionholder’s Continuous Service terminates as a result of the Optionholder’s Disability, the Optionholder may exercise his or her Option (to the extent that the Optionholder was entitled to exercise such Option as of the
date of termination), but only within such period of time ending on the earlier of (i) the date twelve (12) months following such termination (or such longer or shorter period specified in the Option Agreement, which period shall not be
less than six (6) months for Options granted prior to the Listing Date if necessary to comply with applicable state laws) or (ii) the expiration of the term of the Option as set forth in the Option Agreement. If, after termination, the
Optionholder does not exercise his or her Option within the time specified herein, the Option shall terminate. 
 (j)
Death of Optionholder. In the event (i) an Optionholder’s Continuous Service terminates as a result of the Optionholder’s death or (ii) the Optionholder dies within the period (if any) specified in the Option Agreement
after the termination of the Optionholder’s Continuous Service for a reason other than death, then the Option may be exercised (to the extent the Optionholder was entitled to exercise such Option as of the date of death) by the
Optionholder’s estate, by a person who acquired the right to exercise the Option by bequest or inheritance or by a person designated to exercise the option upon the Optionholder’s death pursuant to subsection 6(d) or 6(e), but only within
the period ending on the earlier of (1) the 

  
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date eighteen (18) months following the date of death (or such longer or shorter period specified in the Option Agreement, which period shall not be less than six (6) months for Options
granted prior to the Listing Date if necessary to comply with applicable state laws) or (2) the expiration of the term of such Option as set forth in the Option Agreement. If, after death, the Option is not exercised within the time specified
herein, the Option shall terminate. 
 (k) Termination for Cause. In the event an Optionholder’s Continuous
Service is terminated for Cause, the Option shall terminate upon the termination date of such Optionholder’s Continuous Service and the Optionholder is prohibited from exercising his or her Option at the time of such termination. 

(l) Early Exercise. The Option may, but need not, include a provision whereby the Optionholder may elect at any time before
the Optionholder’s Continuous Service terminates to exercise the Option as to any part or all of the shares of Common Stock subject to the Option prior to the full vesting of the Option. Subject to the “Repurchase Limitation” in
subsection 10(g), any unvested shares of Common Stock so purchased may be subject to a repurchase option in favor of the Company or to any other restriction the Board determines to be appropriate. 

(m) Right of Repurchase. Subject to the “Repurchase Limitation” in subsection 10(g), the Option may, but
need not, include a provision whereby the Company may elect, prior to the Listing Date, to repurchase all or any part of the vested shares of Common Stock acquired by the Optionholder pursuant to the exercise of the Option. 

(n) Right of First Refusal. The Option may, but need not, include a provision whereby the Company may elect, prior to the
Listing Date, to exercise a right of first refusal following receipt of notice from the Optionholder of the intent to transfer all or any part of the shares of Common Stock received upon the exercise of the Option. Except as expressly provided in
this subsection 6(n), such right of first refusal shall otherwise comply with any applicable provisions of the Bylaws of the Company. 
  

	7.	PROVISIONS OF STOCK AWARDS OTHER THAN OPTIONS.

 (a) Stock Bonus Awards. Each stock bonus agreement shall be in such form and shall contain such
terms and conditions as the Board shall deem appropriate. The terms and conditions of stock bonus agreements may change from time to time, and the terms and conditions of separate stock bonus agreements need not be identical, but each stock bonus
agreement shall include (through incorporation of provisions hereof by reference in the agreement or otherwise) the substance of each of the following provisions: 

(i) Consideration. A stock bonus may be awarded in consideration for past services actually rendered to the
Company or an Affiliate for its benefit. 
 (ii) Vesting. Subject to the “Repurchase
Limitation” in subsection 10(g), shares of Common Stock awarded under the stock bonus agreement may, but need not, be 

  
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subject to a share repurchase option in favor of the Company in accordance with a vesting schedule to be determined by the Board. 

(iii) Termination of Participant’s Continuous Service. Subject to the “Repurchase Limitation”
in subsection 10(g), in the event a Participant’s Continuous Service terminates, the Company may reacquire any or all of the shares of Common Stock held by the Participant which have not vested as of the date of termination under the terms of
the stock bonus agreement. 
 (iv) Transferability. For a stock bonus award made before the Listing
Date, rights to acquire shares of Common Stock under the stock bonus agreement shall not be transferable except by will or by the laws of descent and distribution and shall be exercisable during the lifetime of the Participant only by the
Participant. For a stock bonus award made on or after the Listing Date, rights to acquire shares of Common Stock under the stock bonus agreement shall be transferable by the Participant only upon such terms and conditions as are set forth in the
stock bonus agreement, as the Board shall determine in its discretion, so long as Common Stock awarded under the stock bonus agreement remains subject to the terms of the stock bonus agreement. 

(b) Restricted Stock Awards. Each restricted stock purchase agreement shall be in such form and shall contain such terms
and conditions as the Board shall deem appropriate. The terms and conditions of the restricted stock purchase agreements may change from time to time, and the terms and conditions of separate restricted stock purchase agreements need not be
identical, but each restricted stock purchase agreement shall include (through incorporation of provisions hereof by reference in the agreement or otherwise) the substance of each of the following provisions: 

(i) Purchase Price. The purchase price under each restricted stock purchase agreement shall be such amount
as the Board shall determine and designate in such restricted stock purchase agreement. For restricted stock awards made prior to the Listing Date, the purchase price shall not be less than eighty-five percent (85%) of the Common Stock’s
Fair Market Value on the date such award is made or at the time the purchase is consummated. For restricted stock awards made on or after the Listing Date, the purchase price shall not be less than eighty-five percent (85%) of the Common
Stock’s Fair Market Value on the date such award is made or at the time the purchase is consummated. 

(ii) Consideration. The purchase price of Common Stock acquired pursuant to the restricted stock purchase
agreement shall be paid either: (i) in cash at the time of purchase; (ii) at the discretion of the Board, according to a deferred payment or other similar arrangement with the Participant; or (iii) in any other form of legal
consideration that may be acceptable to the Board in its discretion; provided, however, that at any time that the Company is incorporated in Delaware, then payment of the Common Stock’s “par value,” as defined in the Delaware General
Corporation Law, shall not be made by deferred payment. 
 (iii) Vesting. Subject to the
“Repurchase Limitation” in subsection 10(g), shares of Common Stock acquired under the restricted stock purchase agreement may, but need 

  
 12 

 
not, be subject to a share repurchase option in favor of the Company in accordance with a vesting schedule to be determined by the Board. 

(iv) Termination of Participant’s Continuous Service. Subject to the “Repurchase Limitation”
in subsection 10(g), in the event a Participant’s Continuous Service terminates, the Company may repurchase or otherwise reacquire any or all of the shares of Common Stock held by the Participant which have not vested as of the date of
termination under the terms of the restricted stock purchase agreement. 
 (v) Transferability. For
a restricted stock award made before the Listing Date, rights to acquire shares of Common Stock under the restricted stock purchase agreement shall not be transferable except by will or by the laws of descent and distribution and shall be
exercisable during the lifetime of the Participant only by the Participant. For a restricted stock award made on or after the Listing Date, rights to acquire shares of Common Stock under the restricted stock purchase agreement shall be transferable
by the Participant only upon such terms and conditions as are set forth in the restricted stock purchase agreement, as the Board shall determine in its discretion, so long as Common Stock awarded under the restricted stock purchase agreement remains
subject to the terms of the restricted stock purchase agreement. 
  

	8.	COVENANTS OF THE COMPANY. 

(a) Availability of Shares. During the terms of the Stock Awards, the Company shall keep available at all times the number
of shares of Common Stock required to satisfy such Stock Awards. 
 (b) Securities Law Compliance. The Company
shall seek to obtain from each regulatory commission or agency having jurisdiction over the Plan such authority as may be required to grant Stock Awards and to issue and sell shares of Common Stock upon exercise of the Stock Awards; provided,
however, that this undertaking shall not require the Company to register under the Securities Act the Plan, any Stock Award or any Common Stock issued or issuable pursuant to any such Stock Award. If, after reasonable efforts, the Company is unable
to obtain from any such regulatory commission or agency the authority which counsel for the Company deems necessary for the lawful issuance and sale of Common Stock under the Plan, the Company shall be relieved from any liability for failure to
issue and sell Common Stock upon exercise of such Stock Awards unless and until such authority is obtained. 
  

	9.	USE OF PROCEEDS FROM STOCK. 

Proceeds from the sale of Common Stock pursuant to Stock Awards shall constitute general funds of the Company. 

 

	10.	MISCELLANEOUS. 

 (a) Acceleration of Exercisability and Vesting. The Board shall have the power to accelerate the time at which a Stock Award may first be exercised or the time during which a Stock Award or
any part thereof will vest in accordance with the Plan, notwithstanding the 

  
 13 

 
provisions in the Stock Award stating the time at which it may first be exercised or the time during which it will vest. 
 (b) Stockholder Rights. No Participant shall be deemed to be the holder of, or to have any of the rights of a holder with respect to, any shares of Common Stock subject to such Stock Award
unless and until such Participant has satisfied all requirements for exercise of the Stock Award pursuant to its terms. 

(c) No Employment or other Service Rights. Nothing in the Plan or any instrument executed or Stock Award granted pursuant
thereto shall confer upon any Participant any right to continue to serve the Company or an Affiliate in the capacity in effect at the time the Stock Award was granted or shall affect the right of the Company or an Affiliate to terminate (i) the
employment of an Employee with or without notice and with or without Cause, (ii) the service of a Consultant pursuant to the terms of such Consultant’s agreement with the Company or an Affiliate or (iii) the service of a Director
pursuant to the Bylaws of the Company or an Affiliate, and any applicable provisions of the corporate law of the state in which the Company or the Affiliate is incorporated, as the case may be. 

(d) Incentive Stock Option $100,000 Limitation. To the extent that the aggregate Fair Market Value (determined at the time
of grant) of Common Stock with respect to which Incentive Stock Options are exercisable for the first time by any Optionholder during any calendar year (under all plans of the Company and its Affiliates) exceeds one hundred thousand dollars
($100,000), the Options or portions thereof which exceed such limit (according to the order in which they were granted) shall be treated as Nonstatutory Stock Options. 
 (e) Investment Assurances. The Company may require a Participant, as a condition of exercising or acquiring Common Stock under any Stock Award, (i) to give written assurances
satisfactory to the Company as to the Participant’s knowledge and experience in financial and business matters and/or to employ a purchaser representative reasonably satisfactory to the Company who is knowledgeable and experienced in financial
and business matters and that he or she is capable of evaluating, alone or together with the purchaser representative, the merits and risks of exercising the Stock Award; and (ii) to give written assurances satisfactory to the Company stating
that the Participant is acquiring Common Stock subject to the Stock Award for the Participant’s own account and not with any present intention of selling or otherwise distributing the Common Stock. The foregoing requirements, and any assurances
given pursuant to such requirements, shall be inoperative if (1) the issuance of the shares of Common Stock upon the exercise or acquisition of Common Stock under the Stock Award has been registered under a then currently effective registration
statement under the Securities Act or (2) as to any particular requirement, a determination is made by counsel for the Company that such requirement need not be met in the circumstances under the then applicable securities laws. The Company
may, upon advice of counsel to the Company, place legends on stock certificates issued under the Plan as such counsel deems necessary or appropriate in order to comply with applicable securities laws, including, but not limited to, legends
restricting the transfer of the Common Stock. 

  
 14 

 (f) Withholding Obligations. To the extent provided by the terms of a Stock
Award Agreement, the Participant may satisfy any federal, state or local tax withholding obligation relating to the exercise or acquisition of Common Stock under a Stock Award by any of the following means (in addition to the Company’s right to
withhold from any compensation paid to the Participant by the Company) or by a combination of such means: (i) tendering a cash payment; (ii) authorizing the Company to withhold shares of Common Stock from the shares of Common Stock
otherwise issuable to the Participant as a result of the exercise or acquisition of Common Stock under the Stock Award, provided, however, that no shares of Common Stock are withheld with a value exceeding the minimum amount of tax required to be
withheld by law; or (iii) delivering to the Company owned and unencumbered shares of Common Stock. 
 (g)
Repurchase Limitation. The terms of any repurchase option shall be specified in the Stock Award Agreement. The repurchase price for vested shares of Common Stock shall be the Fair Market Value of the shares of Common Stock on the date of
repurchase. The repurchase price for unvested shares of Common Stock shall be the lower of (i) the Fair Market Value of the shares of Common Stock on the date of repurchase or (ii) their original purchase price. However, the Company shall
not exercise its repurchase right until at least six (6) months (or such longer or shorter period of time necessary to avoid classification of the Stock Award as a liability for financial accounting purposes) have elapsed following
delivery of shares of Common Stock subject to the Stock Award, unless otherwise specifically provided by the Board. 

(h) Compliance with Section 409A. To the extent that the Board determines that any Stock Award granted hereunder is
subject to Section 409A of the Code, the Stock Award Agreement evidencing such Stock Award shall incorporate the terms and conditions necessary to avoid the consequences specified in Section 409A(a)(1) of the Code. To the extent
applicable, the Plan and Stock Award Agreements shall be interpreted in accordance with Section 409A of the Code. 

(i) Compliance with Exemption Provided by Rule 12h-1(f). If at the end of the Company’s most recently completed fiscal
year: (i) the aggregate of the number of persons who hold outstanding compensatory employee stock options to purchase shares of Common Stock granted pursuant to the Plan or otherwise (such persons, “Holders of Options”)
equals or exceeds five hundred (500), and (ii) the Company’s assets exceed $10 million, then the following restrictions shall apply during any period during which the Company does not have a class of its securities registered under
Section 12 of the Exchange Act and is not required to file reports under Section 15(d) of the Exchange Act: (A) the Options and, prior to exercise, the shares of Common Stock to be issued on exercise of the Options may not be
transferred until the Company is no longer relying on the exemption provided by Rule 12h-1(f) promulgated under the Exchange Act (“Rule 12h-1(f)”), except: (1) as permitted by Rule 701(c) promulgated under the Securities
Act, (2) to a guardian upon the disability of the Holder of Options, or (3) to an executor upon the death of the Holder of Options (collectively, the “Permitted Transferees”); provided, however, the following
transfers are permitted: (i) transfers by the Holder of Options to the Company, and (ii) transfers in connection with a change of control or other acquisition involving the Company, if following such transaction, the Options no longer
remain outstanding and the Company is no longer relying on the exemption provided by Rule 12h-1(f); provided 

  
 15 

 
further, that any Permitted Transferees may not further transfer the Options; (B) except as otherwise provided in (A) above, the Options and shares of Common Stock to be issued on
exercise of the Options are restricted as to any pledge, hypothecation, or other transfer, including any short position, any “put equivalent position” as defined by Rule 16a-1(h) promulgated under the Exchange Act, or any “call
equivalent position” as defined by Rule 16a-1(b) promulgated under the Exchange Act by the Holder of Options prior to exercise of an Option until the Company is no longer relying on the exemption provided by Rule 12h-1(f); and (C) at any
time that the Company is relying on the exemption provided by Rule 12h-1(f), the Company shall deliver to Holders of Options (whether by physical or electronic delivery or written notice of the availability of the information on an internet site)
the information required by Rule 701(e)(3), (4), and (5) promulgated under the Securities Act every six (6) months, including financial statements that are not more than one hundred eighty (180) days old; provided, however, that the
Company may condition the delivery of such information upon the Holder of Options’ agreement to maintain its confidentiality. 
  

	11.	ADJUSTMENTS UPON CHANGES IN STOCK. 

(a) Capitalization Adjustments. If any change is made in the Common Stock subject to the Plan, or subject to any Stock
Award, without the receipt of consideration by the Company (through merger, consolidation, reorganization, recapitalization, reincorporation, stock dividend, dividend in property other than cash, stock split, liquidating dividend, combination of
shares, exchange of shares, change in corporate structure or other transaction not involving the receipt of consideration by the Company) (individually, a “Capitalization Adjustment”), the Plan will be appropriately adjusted
in the class(es) and maximum number of securities subject to the Plan pursuant to subsection 4(a), the class(es) and maximum number of securities that may be issued pursuant to the exercise of Incentive Stock Options pursuant to subsection 4(d),and
the maximum number of securities subject to award to any person pursuant to subsection 5(c), and the outstanding Stock Awards will be appropriately adjusted in the class(es) and number of securities and price per share of Common Stock subject to
such outstanding Stock Awards. The Board shall make such adjustments, and its determination shall be final, binding and conclusive. (The conversion of any convertible securities of the Company shall not be treated as a transaction “without
receipt of consideration” by the Company.) 
 (b) Dissolution or Liquidation. In the event of a dissolution
or liquidation of the Company, then all outstanding Stock Awards shall terminate immediately prior to such event. 
 (c)
Asset Sale, Merger, Consolidation or Reverse Merger. In the event of (i) a sale of substantially all of the assets of the Company, (ii) a merger or consolidation in which the Company is not the surviving corporation, (iii) a
reverse merger in which the Company is the surviving corporation but the shares of Common Stock outstanding immediately preceding the merger are converted by virtue of the merger into other property, whether in the form of securities, cash or
otherwise, or (iv) any transaction or series of related transactions in which in excess of 50% of the Company’s voting power is transferred other than a transaction which is primarily a capital raising transaction (individually, a
“Corporate Transaction”), then any surviving corporation or acquiring corporation shall assume any Stock Awards outstanding under 

  
 16 

 
the Plan or shall substitute similar stock awards (including an award to acquire the same consideration paid to the stockholders in the Corporate Transaction for those outstanding under the
Plan). In the event any surviving corporation or acquiring corporation refuses to assume such Stock Awards or to substitute similar stock awards for those outstanding under the Plan, then with respect to Stock Awards held by Participants whose
Continuous Service has not terminated, the vesting of such Stock Awards (and, if applicable, the time during which such Stock Awards may be exercised) shall be accelerated in full, and the Stock Awards shall terminate if not exercised (if
applicable) at or prior to the Corporate Transaction. With respect to any other Stock Awards outstanding under the Plan, such Stock Awards shall terminate if not exercised (if applicable) prior to the Corporate Transaction. 

 

	12.	AMENDMENT OF THE PLAN AND STOCK AWARDS.

 (a) Amendment of Plan. The Board at any time, and from time to time, may amend the Plan. However,
except as provided in Section 11 relating to adjustments upon changes in Common Stock, no amendment shall be effective unless approved by the stockholders of the Company to the extent stockholder approval is necessary to satisfy the
requirements of Section 422 of the Code, Rule 16b-3 or any Nasdaq or securities exchange listing requirements. 

(b) Stockholder Approval. The Board may, in its sole discretion, submit any other amendment to the Plan for stockholder
approval, including, but not limited to, amendments to the Plan intended to satisfy the requirements of Section 162(m) of the Code and the regulations thereunder regarding the exclusion of performance-based compensation from the limit on
corporate deductibility of compensation paid to certain executive officers. 
 (c) Contemplated Amendments. It is
expressly contemplated that the Board may amend the Plan in any respect the Board deems necessary or advisable to provide eligible Employees with the maximum benefits provided or to be provided under the provisions of the Code and the regulations
promulgated thereunder relating to Incentive Stock Options and/or to bring the Plan and/or Incentive Stock Options granted under it into compliance therewith. 
 (d) No Impairment of Rights. Rights under any Stock Award granted before amendment of the Plan shall not be impaired by any amendment of the Plan unless (i) the Company requests the
consent of the Participant and (ii) the Participant consents in writing. 
 (e) Amendment of Stock Awards.
The Board at any time, and from time to time, may amend the terms of any one or more Stock Awards; provided, however, that the rights under any Stock Award shall not be impaired by any such amendment unless (i) the Company requests the consent
of the Participant and (ii) the Participant consents in writing. 
  

	13.	TERMINATION OR SUSPENSION OF THE PLAN. 

(a) Plan Term. The Board may suspend or terminate the Plan at any time. Unless sooner terminated, the Plan shall terminate
on the day before the tenth (10th) anniversary of the date the Plan is adopted by the Board or approved by the stockholders of the Company, 

  
 17 

 
whichever is earlier. No Stock Awards may be granted under the Plan while the Plan is suspended or after it is terminated. 

(b) No Impairment of Rights. Suspension or termination of the Plan shall not impair rights and obligations under any Stock
Award granted while the Plan is in effect except with the written consent of the Participant. 
  

	14.	EFFECTIVE DATE OF PLAN. 

The Plan shall become effective as determined by the Board, but no Stock Award shall be exercised (or, in the case of a stock bonus, shall
be granted) unless and until the Plan has been approved by the stockholders of the Company, which approval shall be within twelve (12) months before or after the date the Plan is adopted by the Board. 

 

	15.	CHOICE OF LAW. 

 The law of the State of California shall govern all questions concerning the construction, validity and interpretation of this Plan, without regard to such state’s conflict of laws rules. 

  
 18 

 AMBIT BIOSCIENCES CORPORATION 

FORM OF STOCK OPTION AGREEMENT 

[WITH SPECIAL VESTING ACCELERATION PROVISIONS]

 (INCENTIVE STOCK OPTION OR NONSTATUTORY
STOCK OPTION) 
 Pursuant to your Stock Option Grant Notice (“Grant Notice”) and this Stock Option
Agreement, Ambit Biosciences Corporation (the “Company”) has granted you an option under its Amended and Restated 2011 Equity Incentive Plan (the “Plan”) to purchase the number of shares of the Company’s Common Stock
indicated in your Grant Notice at the exercise price indicated in your Grant Notice. Defined terms not explicitly defined in this Stock Option Agreement but defined in the Plan shall have the same definitions as in the Plan. 

The details of your option are as follows: 
 1. VESTING. Subject to the limitations contained herein, your option will vest as provided in your Grant Notice, provided that vesting will cease upon the termination of your
Continuous Service. 
 a. Special Acceleration Provisions. Notwithstanding any other provisions of your Grant
Notice to the contrary, if (i) a Change in Control, as defined below, occurs and (ii) within thirteen (13) months after the date of such Change in Control your Continuous Service terminates due to an involuntary termination (not
including death or Disability) without Cause or due to a Constructive Termination, as defined below, then the vesting and exercisability of your option shall be accelerated in full or any reacquisition or repurchase rights held by the Company with
respect to Common Stock acquired pursuant to the early exercise of your option shall lapse in full, as appropriate. 
 For purposes of this
subsection 1(a) only, Change in Control means: (i) a sale or other disposition of all or substantially all of the assets of the Company; (ii) a merger or consolidation in which the Company is not the surviving entity and in which the
stockholders of the Company immediately prior to such consolidation or merger own less than fifty percent (50%) of the surviving entity’s voting power immediately after the transaction; (iii) a reverse merger in which the Company is
the surviving entity but the shares of Common Stock outstanding immediately preceding the merger are converted by virtue of the merger into other property, whether in the form of securities, cash or otherwise, and in which the stockholders of the
Company immediately prior to such reverse merger own less than fifty percent (50%) of the Company’s voting power immediately after the transaction; or (iv) after the Listing Date an acquisition by any person, entity or group within
the meaning of Section 13(d) or 14(d) of the Exchange Act, or any comparable successor provisions (excluding any employee benefit plan, or related trust, sponsored or maintained by the Company or subsidiary of the Company or other entity
controlled by the Company) of the beneficial ownership (within the meaning of Rule 13d-3 promulgated under the Exchange Act, or comparable successor rule) of securities of the 

  
 1 

 
Company representing at least fifty percent (50%) of the voting power entitled to vote in the election of directors. 
 For purposes of this subsection 1(a) only, Constructive Termination means: such person’s voluntary resignation following (i) a change in his or her position with the Company which materially
reduces his or her level of responsibility, (ii) a reduction in his or her level of base salary, or (iii) a relocation of such person’s place of employment by more than fifty (50) miles, provided and only in such change,
reduction or relocation is effected by the Company without the person’s consent. 
 b. Parachute Payments. In
the event that the acceleration of the vesting and exercisability of your option and/or the lapse of reacquisition or repurchase rights with respect to Common Stock acquired pursuant to the early exercise of your option provided for in subsection
1(a) and benefits otherwise payable to you (i) constitute “parachute payments” within the meaning of Section 280G of the Code, or any comparable successor provisions, and (ii) but for this subsection would be subject to the
excise tax imposed by Section 4999 of the Code, or any comparable successor provisions (the “Excise Tax”), then your benefits hereunder shall be either 
 1) provided to you in full, or 
 2) provided to you as to such
lesser extent which would result in no portion of such benefits being subject to the Excise Tax, 
 whichever of the foregoing amounts, when
taking into account applicable federal, state, local and foreign income and employment taxes, the Excise Tax, and any other applicable taxes, results in the receipt by you, on an after-tax basis, of the greatest amount of benefits, notwithstanding
that all or some portion of such benefits may be taxable under the Excise Tax. Unless the Company and you otherwise agree in writing, any determination required under this subsection shall be made in writing in good faith by the Accountants. In the
event of a reduction of benefits hereunder, you shall be given the choice of which benefits to reduce. For purposes of making the calculations required by this subsection, the Accountants may make reasonable assumptions and approximations concerning
applicable taxes and may rely on reasonable, good faith interpretations concerning the application of the Code, and other applicable legal authority. The Company and you shall furnish to the Accountants such information and documents as the
Accountants may reasonably request in order to make a determination under this subsection. The Company shall bear all costs the Accountants may reasonably incur in connection with any calculations contemplated by this subsection. 

If, notwithstanding any reduction described in this subsection, the IRS determines that you are liable for the Excise Tax as a result of the receipt of
the payment of benefits as described above, then you shall be obligated to pay back to the Company, within thirty (30) days after a final IRS determination or in the event that you challenge the final IRS determination, a final judicial
determination, a portion of the payment equal to the “Repayment Amount.” The Repayment Amount with respect to the payment of benefits shall be the smallest such amount, if any, as shall be required to be paid to the Company so that your
net after-tax proceeds with respect to any payment of benefits (after taking into account the payment of the Excise Tax and all other 

  
 2 

 
applicable taxes imposed on such payment) shall be maximized. The Repayment Amount with respect to the payment of benefits shall be zero if a Repayment Amount of more than zero would not result
in your net after-tax proceeds with respect to the payment of such benefits being maximized. If the Excise Tax is not eliminated pursuant to this paragraph, you shall pay the Excise Tax. 
 Notwithstanding any other provision of this subsection 1(b), if (i) there is a reduction in the payment of benefits as described in this subsection, (ii) the IRS later determines that you are
liable for the Excise Tax, the payment of which would result in the maximization of your net after-tax proceeds (calculated as if your benefits had not previously been reduced), and (iii) you pay the Excise Tax, then the Company shall pay to
you those benefits which were reduced pursuant to this subsection contemporaneously or as soon as administratively possible after you pay the Excise Tax so that your net after-tax proceeds with respect to the payment of benefits is maximized.

 2. NUMBER OF SHARES AND EXERCISE
PRICE. The number of shares of Common Stock subject to your option and your exercise price per share referenced in your Grant Notice may be adjusted from time to time for Capitalization Adjustments, as provided in the Plan.

 3. EXERCISE PRIOR TO VESTING
(“EARLY EXERCISE”). If permitted in your Grant Notice (i.e., the “Exercise Schedule” indicates that “Early Exercise” of your option is permitted) and subject to the provisions of your
option, you may elect at any time that is both (i) during the period of your Continuous Service and (ii) during the term of your option, to exercise all or part of your option, including the nonvested portion of your option; provided,
however, that: 
 a. a partial exercise of your option shall be deemed to cover first vested shares of Common Stock and
then the earliest vesting installment of unvested shares of Common Stock; 
 b. any shares of Common Stock so purchased
from installments that have not vested as of the date of exercise shall be subject to the purchase option in favor of the Company as described in the Company’s form of Early Exercise Stock Purchase Agreement; 

c. you shall enter into the Company’s form of Early Exercise Stock Purchase Agreement with a vesting schedule that will
result in the same vesting as if no early exercise had occurred; and 
 d. if your option is an incentive stock option,
then, as provided in the Plan, to the extent that the aggregate Fair Market Value (determined at the time of grant) of the shares of Common Stock with respect to which your option plus all other incentive stock options you hold are exercisable for
the first time by you during any calendar year (under all plans of the Company and its Affiliates) exceeds one hundred thousand dollars ($100,000), your option(s) or portions thereof that exceed such limit (according to the order in which they were
granted) shall be treated as nonstatutory stock options. 

  
 3 

 4. METHOD OF PAYMENT. Payment of
the exercise price is due in full upon exercise of all or any part of your option. You may elect to make payment of the exercise price in cash or by check or in any other manner permitted by your Grant Notice, which may include one or
more of the following: 
 a. In the Company’s sole discretion at the time your option is exercised and provided that
at the time of exercise the Common Stock is publicly traded and quoted regularly in The Wall Street Journal, pursuant to a program developed under Regulation T as promulgated by the Federal Reserve Board that, prior to the issuance of Common
Stock, results in either the receipt of cash (or check) by the Company or the receipt of irrevocable instructions to pay the aggregate exercise price to the Company from the sales proceeds. 

b. Provided that at the time of exercise the Common Stock is publicly traded and quoted regularly in The Wall Street
Journal, by delivery of already-owned shares of Common Stock either that you have held for the period required to avoid a charge to the Company’s reported earnings (generally six months) or that you did not acquire, directly or indirectly
from the Company, that are owned free and clear of any liens, claims, encumbrances or security interests, and that are valued at Fair Market Value on the date of exercise. “Delivery” for these purposes, in the sole discretion of the
Company at the time you exercise your option, shall include delivery to the Company of your attestation of ownership of such shares of Common Stock in a form approved by the Company. Notwithstanding the foregoing, you may not exercise your option by
tender to the Company of Common Stock to the extent such tender would violate the provisions of any law, regulation or agreement restricting the redemption of the Company’s stock. 

c. Pursuant to the following deferred payment alternative: 

1) Not less than one hundred percent (100%) of the aggregate exercise price, plus accrued interest, shall be due four
(4) years from date of exercise or, at the Company’s election, upon termination of your Continuous Service. 

2) Interest shall be compounded at least annually and shall be charged at the market rate of interest necessary to avoid a charge
to earnings for financial accounting purposes. 
 3) At any time that the Company is incorporated in Delaware, payment
of the Common Stock’s “par value,” as defined in the Delaware General Corporation Law, shall be made in cash and not by deferred payment. 
 4) In order to elect the deferred payment alternative, you must, as a part of your written notice of exercise, give notice of the election of this payment alternative and, in order to secure the
payment of the deferred exercise price to the Company hereunder, if the Company so requests, you must tender to the Company a promissory note and a security agreement covering the purchased shares of Common Stock, both in form and substance
satisfactory to the Company, or such other or additional documentation as the Company may request. 

  
 4 

 5. WHOLE SHARES. You may exercise your option
only for whole shares of Common Stock. 
 6. SECURITIES LAW
COMPLIANCE. Notwithstanding anything to the contrary contained herein, you may not exercise your option unless the shares of Common Stock issuable upon such exercise are then registered under the Securities Act or, if such shares
of Common Stock are not then so registered, the Company has determined that such exercise and issuance would be exempt from the registration requirements of the Securities Act. The exercise of your option must also comply with other applicable laws
and regulations governing your option, and you may not exercise your option if the Company determines that such exercise would not be in material compliance with such laws and regulations. 

7. TERM. You may not exercise your option before the commencement of its term or after its term expires. The
term of your option commences on the Date of Grant and expires upon the earliest of the following: 
 a. As
of the date of termination of your Continuous Service if such termination is for Cause; 
 b. three (3) months after
the termination of your Continuous Service for any reason other than Cause or your Disability or death, provided that if during any part of such three- (3-) month period your option is not exercisable solely because of the condition set forth in the
preceding paragraph relating to “Securities Law Compliance,” your option shall not expire until the earlier of the Expiration Date or until it shall have been exercisable for an aggregate period of three (3) months after the
termination of your Continuous Service; 
 c. twelve (12) months after the termination of your Continuous Service
due to your Disability; 
 d. eighteen (18) months after your death if you die either during your Continuous Service
or within three (3) months after your Continuous Service terminates; 
 e. the Expiration Date indicated in your
Grant Notice; or 
 f. the day before the tenth (10th) anniversary of the Date of Grant. 

If your option is an incentive stock option, note that, to obtain the federal income tax advantages associated with an “incentive stock
option,” the Code requires that at all times beginning on the date of grant of your option and ending on the day three (3) months before the date of your option’s exercise, you must be an employee of the Company or an Affiliate,
except in the event of your death or Disability. The Company has provided for extended exercisability of your option under certain circumstances for your benefit but cannot guarantee that your option will necessarily be treated as an “incentive
stock option” if you continue to provide services to the Company or an Affiliate as a Consultant or Director after your employment terminates or if you otherwise exercise your option more than three (3) months after the date your
employment terminates. 

  
 5 

 8. EXERCISE. 

a. You may exercise the vested portion of your option (and the unvested portion of your option if your Grant Notice
so permits) during its term by delivering a Notice of Exercise (in a form designated by the Company) together with the exercise price to the Secretary of the Company, or to such other person as the Company may designate, during regular business
hours, together with such additional documents as the Company may then require. 
 b. By exercising your
option you agree that, as a condition to any exercise of your option, the Company may require you to enter into an arrangement providing for the payment by you to the Company of any tax withholding obligation of the Company arising by reason of
(1) the exercise of your option, (2) the lapse of any substantial risk of forfeiture to which the shares of Common Stock are subject at the time of exercise, or (3) the disposition of shares of Common Stock acquired upon such
exercise. 
 c. If your option is an incentive stock option, by exercising your option you agree that you
will notify the Company in writing within fifteen (15) days after the date of any disposition of any of the shares of the Common Stock issued upon exercise of your option that occurs within two (2) years after the date of your option grant
or within one (1) year after such shares of Common Stock are transferred upon exercise of your option. 

d. By exercising your option you agree that the Company (or a representative of the underwriter(s)) may, in
connection with the first underwritten registration of the offering of any securities of the Company under the Securities Act, require that you not sell, dispose of, transfer, make any short sale of, grant any option for the purchase of, or enter
into any hedging or similar transaction with the same economic effect as a sale, any shares of Common Stock or other securities of the Company held by you, for a period of time specified by the underwriter(s) (not to exceed one hundred eighty
(180) days) following the effective date of the registration statement of the Company filed under the Securities Act. You further agree to execute and deliver such other agreements as may be reasonably requested by the Company and/or the
underwriter(s) that are consistent with the foregoing or that are necessary to give further effect thereto. In order to enforce the foregoing covenant, the Company may impose stop-transfer instructions with respect to your shares of Common Stock
until the end of such period. The underwriters of the Company’s stock are intended third party beneficiaries of this Section 8(d) and shall have the right, power and authority to enforce the provisions hereof as though they were a party
hereto. 
 9. TRANSFERABILITY. 

a. If your option is an incentive stock option, your option is not transferable, except by will or by the laws of
descent and distribution, and is exercisable during your life only by you. Notwithstanding the foregoing, by delivering written notice to the Company, in a form satisfactory to the Company, you may designate a third party who, in the event of your
death, shall thereafter be entitled to exercise your option. 

  
 6 

 b. If your option is a nonstatutory stock option, your option is not transferable,
except (i) by will or by the laws of descent and distribution, (ii) with the prior written approval of the Company, by instrument to an inter vivos or testamentary trust, in a form accepted by the Company, in which the option is to be
passed to beneficiaries upon the death of the trustor (settlor) and (iii) with the prior written approval of the Company, by gift, in a form accepted by the Company, to your “immediate family” as that term is defined in 17 C.F.R.
240.16a-1(e). The term “immediate family” is defined in 17 C.F.R. 240.16a-1(e) to mean any child, stepchild, grandchild, parent, stepparent, grandparent, spouse, sibling, mother-in-law, father-in-law, son-in-law, daughter-in-law,
brother-in-law, or sister-in-law, and includes adoptive relationships. Your option is exercisable during your life only by you or a transferee satisfying the above-stated conditions. The right of a transferee to exercise the transferred portion of
your option after termination of your Continuous Service shall terminate in accordance with your right to exercise your option as specified in your option. In the event that your Continuous Service terminates due to your death, your transferee will
be treated as a person who acquired the right to exercise your option by bequest or inheritance. In addition to the foregoing, the Company may require, as a condition of the transfer of your option to a trust or by gift, that your transferee enter
into an option transfer agreement provided by, or acceptable to, the Company. The terms of your option shall be binding upon your transferees, executors, administrators, heirs, successors, and assigns. Notwithstanding the foregoing, by delivering
written notice to the Company, in a form satisfactory to the Company, you may designate a third party who, in the event of your death, shall thereafter be entitled to exercise your option. 

10. RIGHT OF FIRST REFUSAL. Shares of Common Stock that you
acquire upon exercise of your option are subject to any right of first refusal that may be described in the Company’s bylaws in effect at such time the Company elects to exercise its right. The Company’s right of first refusal shall expire
on the Listing Date. 
 11. RIGHT OF REPURCHASE. To the extent
provided in the Company’s bylaws as amended from time to time, the Company shall have the right to repurchase all or any part of the shares of Common Stock you acquire pursuant to the exercise of your option. 

12. OPTION NOT A SERVICE CONTRACT. Your option
is not an employment or service contract, and nothing in your option shall be deemed to create in any way whatsoever any obligation on your part to continue in the employ of the Company or an Affiliate, or of the Company or an Affiliate to continue
your employment. In addition, nothing in your option shall obligate the Company or an Affiliate, their respective stockholders, Boards of Directors, Officers or Employees to continue any relationship that you might have as a Director or Consultant
for the Company or an Affiliate. 
 13. WITHHOLDING OBLIGATIONS. 

a. At the time you exercise your option, in whole or in part, or at any time thereafter as requested by the Company, you hereby
authorize withholding from payroll and any other amounts payable to you, and otherwise agree to make adequate provision for (including by means of a “cashless exercise” pursuant to a program developed under Regulation T as promulgated by
the Federal Reserve Board to the extent permitted by the Company), any sums 

  
 7 

 
required to satisfy the federal, state, local and foreign tax withholding obligations of the Company or an Affiliate, if any, which arise in connection with your option. 

b. Upon your request and subject to approval by the Company, in its sole discretion, and compliance with any applicable conditions
or restrictions of law, the Company may withhold from fully vested shares of Common Stock otherwise issuable to you upon the exercise of your option a number of whole shares of Common Stock having a Fair Market Value, determined by the Company as of
the date of exercise, not in excess of the minimum amount of tax required to be withheld by law. If the date of determination of any tax withholding obligation is deferred to a date later than the date of exercise of your option, share withholding
pursuant to the preceding sentence shall not be permitted unless you make a proper and timely election under Section 83(b) of the Code, covering the aggregate number of shares of Common Stock acquired upon such exercise with respect to which
such determination is otherwise deferred, to accelerate the determination of such tax withholding obligation to the date of exercise of your option. Notwithstanding the filing of such election, shares of Common Stock shall be withheld solely from
fully vested shares of Common Stock determined as of the date of exercise of your option that are otherwise issuable to you upon such exercise. Any adverse consequences to you arising in connection with such share withholding procedure shall be your
sole responsibility. 
 c. You may not exercise your option unless the tax withholding obligations of the Company and/or
any Affiliate are satisfied. Accordingly, you may not be able to exercise your option when desired even though your option is vested, and the Company shall have no obligation to issue a certificate for such shares of Common Stock or release such
shares of Common Stock from any escrow provided for herein. 
 14. NOTICES. Any notices provided
for in your option or the Plan shall be given in writing and shall be deemed effectively given upon receipt or, in the case of notices delivered by mail by the Company to you, five (5) days after deposit in the United States mail, postage
prepaid, addressed to you at the last address you provided to the Company. 
 15. GOVERNING
PLAN DOCUMENT. Your option is subject to all the provisions of the Plan, the provisions of which are hereby made a part of your option, and is further subject to all interpretations, amendments, rules and
regulations which may from time to time be promulgated and adopted pursuant to the Plan. In the event of any conflict between the provisions of your option and those of the Plan, the provisions of the Plan shall control. 

  
 8 

 AMBIT BIOSCIENCES CORPORATION 

FORM OF STOCK OPTION AGREEMENT 

[WITHOUT SPECIAL VESTING ACCELERATION PROVISIONS]

 (INCENTIVE STOCK OPTION OR NONSTATUTORY
STOCK OPTION) 
 Pursuant to your Stock Option Grant Notice (“Grant Notice”) and this Stock Option
Agreement, Ambit Biosciences Corporation (the “Company”) has granted you an option under its Amended and Restated 2011 Equity Incentive Plan (the “Plan”) to purchase the number of shares of the Company’s Common Stock
indicated in your Grant Notice at the exercise price indicated in your Grant Notice. Defined terms not explicitly defined in this Stock Option Agreement but defined in the Plan shall have the same definitions as in the Plan. 

The details of your option are as follows: 
 1. VESTING. Subject to the limitations contained herein, your option will vest as provided in your Grant Notice, provided that vesting will cease upon the termination of your
Continuous Service. 
 2. NUMBER OF SHARES AND
EXERCISE PRICE. The number of shares of Common Stock subject to your option and your exercise price per share referenced in your Grant Notice may be adjusted from time to time for Capitalization Adjustments, as
provided in the Plan. 
 3. EXERCISE PRIOR TO VESTING
(“EARLY EXERCISE”). If permitted in your Grant Notice (i.e., the “Exercise Schedule” indicates that “Early Exercise” of your option is permitted) and subject to the provisions of your
option, you may elect at any time that is both (i) during the period of your Continuous Service and (ii) during the term of your option, to exercise all or part of your option, including the nonvested portion of your option; provided,
however, that: 
 a. a partial exercise of your option shall be deemed to cover first vested shares of Common Stock and
then the earliest vesting installment of unvested shares of Common Stock; 
 b. any shares of Common Stock so purchased
from installments that have not vested as of the date of exercise shall be subject to the purchase option in favor of the Company as described in the Company’s form of Early Exercise Stock Purchase Agreement; 

c. you shall enter into the Company’s form of Early Exercise Stock Purchase Agreement with a vesting schedule that will
result in the same vesting as if no early exercise had occurred; and 
 d. if your option is an incentive stock option,
then, as provided in the Plan, to the extent that the aggregate Fair Market Value (determined at the time of grant) of the shares of Common Stock with respect to which your option plus all other incentive stock options you hold

  
 1 

 
are exercisable for the first time by you during any calendar year (under all plans of the Company and its Affiliates) exceeds one hundred thousand dollars ($100,000), your option(s) or portions
thereof that exceed such limit (according to the order in which they were granted) shall be treated as nonstatutory stock options. 
 4. METHOD OF PAYMENT. Payment of the exercise price is due in full upon exercise of all or any part of your option. You may elect to make payment
of the exercise price in cash or by check or in any other manner permitted by your Grant Notice, which may include one or more of the following: 
 a. In the Company’s sole discretion at the time your option is exercised and provided that at the time of exercise the Common Stock is publicly traded and quoted regularly in The Wall
Street Journal, pursuant to a program developed under Regulation T as promulgated by the Federal Reserve Board that, prior to the issuance of Common Stock, results in either the receipt of cash (or check) by the Company or the receipt of
irrevocable instructions to pay the aggregate exercise price to the Company from the sales proceeds. 
 b. Provided that
at the time of exercise the Common Stock is publicly traded and quoted regularly in The Wall Street Journal, by delivery of already-owned shares of Common Stock either that you have held for the period required to avoid a charge to the
Company’s reported earnings (generally six months) or that you did not acquire, directly or indirectly from the Company, that are owned free and clear of any liens, claims, encumbrances or security interests, and that are valued at Fair Market
Value on the date of exercise. “Delivery” for these purposes, in the sole discretion of the Company at the time you exercise your option, shall include delivery to the Company of your attestation of ownership of such shares of Common Stock
in a form approved by the Company. Notwithstanding the foregoing, you may not exercise your option by tender to the Company of Common Stock to the extent such tender would violate the provisions of any law, regulation or agreement restricting the
redemption of the Company’s stock. 
 c. Pursuant to the following deferred payment alternative: 

1) Not less than one hundred percent (100%) of the aggregate exercise price, plus accrued interest, shall be due four
(4) years from date of exercise or, at the Company’s election, upon termination of your Continuous Service. 

2) Interest shall be compounded at least annually and shall be charged at the market rate of interest necessary to avoid a charge
to earnings for financial accounting purposes. 
 3) At any time that the Company is incorporated in Delaware, payment
of the Common Stock’s “par value,” as defined in the Delaware General Corporation Law, shall be made in cash and not by deferred payment. 
 4) In order to elect the deferred payment alternative, you must, as a part of your written notice of exercise, give notice of the election of this payment alternative and,

  
 2 

 
in order to secure the payment of the deferred exercise price to the Company hereunder, if the Company so requests, you must tender to the Company a promissory note and a security agreement
covering the purchased shares of Common Stock, both in form and substance satisfactory to the Company, or such other or additional documentation as the Company may request. 
 5. WHOLE SHARES. You may exercise your option only for whole shares of Common Stock. 
 6. SECURITIES LAW COMPLIANCE. Notwithstanding anything to the contrary contained herein, you may not exercise your option unless the shares of
Common Stock issuable upon such exercise are then registered under the Securities Act or, if such shares of Common Stock are not then so registered, the Company has determined that such exercise and issuance would be exempt from the registration
requirements of the Securities Act. The exercise of your option must also comply with other applicable laws and regulations governing your option, and you may not exercise your option if the Company determines that such exercise would not be in
material compliance with such laws and regulations. 
 7. TERM. You may not exercise your option
before the commencement of its term or after its term expires. The term of your option commences on the Date of Grant and expires upon the earliest of the following: 

a. As of the date of termination of your Continuous Service if such termination is for Cause; 

b. three (3) months after the termination of your Continuous Service for any reason other than Cause or your Disability or
death, provided that if during any part of such three- (3-) month period your option is not exercisable solely because of the condition set forth in the preceding paragraph relating to “Securities Law Compliance,” your option shall not
expire until the earlier of the Expiration Date or until it shall have been exercisable for an aggregate period of three (3) months after the termination of your Continuous Service; 

c. twelve (12) months after the termination of your Continuous Service due to your Disability; 

d. eighteen (18) months after your death if you die either during your Continuous Service or within three (3) months
after your Continuous Service terminates; 
 e. the Expiration Date indicated in your Grant Notice; or 

f. the day before the tenth (10th) anniversary of the Date of Grant. 

If your option is an incentive stock option, note that, to obtain the federal income tax advantages associated with an “incentive stock
option,” the Code requires that at all times beginning on the date of grant of your option and ending on the day three (3) months before the date of your option’s exercise, you must be an employee of the Company or an Affiliate,
except in the event 

  
 3 

 
of your death or Disability. The Company has provided for extended exercisability of your option under certain circumstances for your benefit but cannot guarantee that your option will
necessarily be treated as an “incentive stock option” if you continue to provide services to the Company or an Affiliate as a Consultant or Director after your employment terminates or if you otherwise exercise your option more than three
(3) months after the date your employment terminates. 
 8. EXERCISE. 

a. You may exercise the vested portion of your option (and the unvested portion of your option if your Grant Notice
so permits) during its term by delivering a Notice of Exercise (in a form designated by the Company) together with the exercise price to the Secretary of the Company, or to such other person as the Company may designate, during regular business
hours, together with such additional documents as the Company may then require. 
 b. By exercising your
option you agree that, as a condition to any exercise of your option, the Company may require you to enter into an arrangement providing for the payment by you to the Company of any tax withholding obligation of the Company arising by reason of
(1) the exercise of your option, (2) the lapse of any substantial risk of forfeiture to which the shares of Common Stock are subject at the time of exercise, or (3) the disposition of shares of Common Stock acquired upon such
exercise. 
 c. If your option is an incentive stock option, by exercising your option you agree that you
will notify the Company in writing within fifteen (15) days after the date of any disposition of any of the shares of the Common Stock issued upon exercise of your option that occurs within two (2) years after the date of your option grant
or within one (1) year after such shares of Common Stock are transferred upon exercise of your option. 

d. By exercising your option you agree that the Company (or a representative of the underwriter(s)) may, in
connection with the first underwritten registration of the offering of any securities of the Company under the Securities Act, require that you not sell, dispose of, transfer, make any short sale of, grant any option for the purchase of, or enter
into any hedging or similar transaction with the same economic effect as a sale, any shares of Common Stock or other securities of the Company held by you, for a period of time specified by the underwriter(s) (not to exceed one hundred eighty
(180) days) following the effective date of the registration statement of the Company filed under the Securities Act. You further agree to execute and deliver such other agreements as may be reasonably requested by the Company and/or the
underwriter(s) that are consistent with the foregoing or that are necessary to give further effect thereto. In order to enforce the foregoing covenant, the Company may impose stop-transfer instructions with respect to your shares of Common Stock
until the end of such period. The underwriters of the Company’s stock are intended third party beneficiaries of this Section 8(d) and shall have the right, power and authority to enforce the provisions hereof as though they were a party
hereto. 
 9. TRANSFERABILITY. 

  
 4 

 a. If your option is an incentive stock option, your option is not transferable,
except by will or by the laws of descent and distribution, and is exercisable during your life only by you. Notwithstanding the foregoing, by delivering written notice to the Company, in a form satisfactory to the Company, you may designate a third
party who, in the event of your death, shall thereafter be entitled to exercise your option. 
 b. If your option is a
nonstatutory stock option, your option is not transferable, except (i) by will or by the laws of descent and distribution, (ii) with the prior written approval of the Company, by instrument to an inter vivos or testamentary trust, in a
form accepted by the Company, in which the option is to be passed to beneficiaries upon the death of the trustor (settlor) and (iii) with the prior written approval of the Company, by gift, in a form accepted by the Company, to your
“immediate family” as that term is defined in 17 C.F.R. 240.16a-1(e). The term “immediate family” is defined in 17 C.F.R. 240.16a-1(e) to mean any child, stepchild, grandchild, parent, stepparent, grandparent, spouse, sibling,
mother-in-law, father-in-law, son-in-law, daughter-in-law, brother-in-law, or sister-in-law, and includes adoptive relationships. Your option is exercisable during your life only by you or a transferee satisfying the above-stated conditions. The
right of a transferee to exercise the transferred portion of your option after termination of your Continuous Service shall terminate in accordance with your right to exercise your option as specified in your option. In the event that your
Continuous Service terminates due to your death, your transferee will be treated as a person who acquired the right to exercise your option by bequest or inheritance. In addition to the foregoing, the Company may require, as a condition of the
transfer of your option to a trust or by gift, that your transferee enter into an option transfer agreement provided by, or acceptable to, the Company. The terms of your option shall be binding upon your transferees, executors, administrators,
heirs, successors, and assigns. Notwithstanding the foregoing, by delivering written notice to the Company, in a form satisfactory to the Company, you may designate a third party who, in the event of your death, shall thereafter be entitled to
exercise your option. 
 10. RIGHT OF FIRST REFUSAL.
Shares of Common Stock that you acquire upon exercise of your option are subject to any right of first refusal that may be described in the Company’s bylaws in effect at such time the Company elects to exercise its right. The Company’s
right of first refusal shall expire on the Listing Date. 
 11. RIGHT OF
REPURCHASE. To the extent provided in the Company’s bylaws as amended from time to time, the Company shall have the right to repurchase all or any part of the shares of Common Stock you acquire pursuant to the exercise of
your option. 
 12. OPTION NOT A SERVICE
CONTRACT. Your option is not an employment or service contract, and nothing in your option shall be deemed to create in any way whatsoever any obligation on your part to continue in the employ of the Company or an Affiliate, or of
the Company or an Affiliate to continue your employment. In addition, nothing in your option shall obligate the Company or an Affiliate, their respective stockholders, Boards of Directors, Officers or Employees to continue any relationship that you
might have as a Director or Consultant for the Company or an Affiliate. 
 13. WITHHOLDING
OBLIGATIONS. 

  
 5 

 a. At the time you exercise your option, in whole or in part, or at any time
thereafter as requested by the Company, you hereby authorize withholding from payroll and any other amounts payable to you, and otherwise agree to make adequate provision for (including by means of a “cashless exercise” pursuant to a
program developed under Regulation T as promulgated by the Federal Reserve Board to the extent permitted by the Company), any sums required to satisfy the federal, state, local and foreign tax withholding obligations of the Company or an Affiliate,
if any, which arise in connection with your option. 
 b. Upon your request and subject to approval by the Company, in
its sole discretion, and compliance with any applicable conditions or restrictions of law, the Company may withhold from fully vested shares of Common Stock otherwise issuable to you upon the exercise of your option a number of whole shares of
Common Stock having a Fair Market Value, determined by the Company as of the date of exercise, not in excess of the minimum amount of tax required to be withheld by law. If the date of determination of any tax withholding obligation is deferred to a
date later than the date of exercise of your option, share withholding pursuant to the preceding sentence shall not be permitted unless you make a proper and timely election under Section 83(b) of the Code, covering the aggregate number of
shares of Common Stock acquired upon such exercise with respect to which such determination is otherwise deferred, to accelerate the determination of such tax withholding obligation to the date of exercise of your option. Notwithstanding the filing
of such election, shares of Common Stock shall be withheld solely from fully vested shares of Common Stock determined as of the date of exercise of your option that are otherwise issuable to you upon such exercise. Any adverse consequences to you
arising in connection with such share withholding procedure shall be your sole responsibility. 
 c. You may not exercise
your option unless the tax withholding obligations of the Company and/or any Affiliate are satisfied. Accordingly, you may not be able to exercise your option when desired even though your option is vested, and the Company shall have no obligation
to issue a certificate for such shares of Common Stock or release such shares of Common Stock from any escrow provided for herein. 
 14. NOTICES. Any notices provided for in your option or the Plan shall be given in writing and shall be deemed effectively given upon receipt or, in the case of notices
delivered by mail by the Company to you, five (5) days after deposit in the United States mail, postage prepaid, addressed to you at the last address you provided to the Company. 

15. GOVERNING PLAN DOCUMENT. Your option is subject to all the provisions of
the Plan, the provisions of which are hereby made a part of your option, and is further subject to all interpretations, amendments, rules and regulations which may from time to time be promulgated and adopted pursuant to the Plan. In the event of
any conflict between the provisions of your option and those of the Plan, the provisions of the Plan shall control. 

  
 6Exhibit 10.5

 Exhibit 10.5 
 AMBIT BIOSCIENCES CORPORATION EMPLOYMENT AGREEMENT 

This EMPLOYMENT AGREEMENT (this “Agreement”) is made
and entered into effective as of November 9th, 2011
(the “Effective Date”) by and among AMBIT BIOSCIENCES CORPORATION (the “Company”) and Michael A. Martino (the
“Executive”). The Company and Executive are hereinafter collectively referred to as the “Parties”, and individually referred to as a “Party”. 

RECITALS 

A. The Company desires assurance of the association and services of Executive in order to retain Executive’s experience, skills, abilities,
background and knowledge, and is willing to engage Executive’s services on the terms and conditions set forth in this Agreement. 
 B.
Executive desires to be in the employ of the Company, and is willing to accept such employment on the terms and conditions set forth in this Agreement. 
 AGREEMENT 
 In consideration of the foregoing Recitals and
the mutual promises and covenants herein contained, and for other good and valuable consideration, the Parties, intending to be legally bound, agree as follows: 
 1. EMPLOYMENT. 
 1.1 Title. Effective as of the
Effective Date, Executive’s position shall be Chief Executive Officer and President of the Company, subject to the terms and conditions set forth in this Agreement. Executive shall also serve as a member of the Company’s Board of Directors
(the “Board”) for so long as he continues to serve as Chief Executive Officer. At such time as Executive’s service as Chief Executive Officer terminates, he agrees to immediately resign as a member of the Board.

 1.2 Term. The term of this Agreement shall begin on the Effective Date and shall continue until it is terminated
pursuant to Section 4 herein (the “Term”). 
 1.3 Duties. Executive shall do and perform all
services, acts or things necessary or advisable to manage and conduct the business of the Company and that are normally associated with the position of Chief Executive Officer and President. Executive shall report to the Board. 

1.4 Policies and Practices. The employment relationship between the Parties shall be governed by this Agreement and by the
policies and practices established by the Company and/or the Board, or any designated committee thereof. In the event that the terms of this Agreement differ from or are in conflict with the Company’s policies or practices or the Company’s
Employee Handbook, this Agreement shall control. 

  
 1. 

 1.5 Location. Unless the Parties otherwise agree in writing, during the Term
Executive shall perform the services Executive is required to perform pursuant to this Agreement at the Company’s offices in San Diego, California, provided, however, that the Company may from time to time require
Executive to travel temporarily to other locations in connection with the Company’s business. 
 2.
LOYALTY; NONCOMPETITION; NONSOLICITATION. 
 2.1 Loyalty. During
Executive’s employment with the Company, Executive shall devote Executive’s full business energies, interest, abilities and productive time to the proper and efficient performance of Executive’s duties under this Agreement; provided,
however, that Executive shall be entitled to continue his service as a board member of Arzeda and shall be entitled to serve on the board of directors of such other companies as may be approved in advance by the Board, in each case so long as
Executive remains in compliance with Section 2.2 and such service does not interfere with Executive’s duties under this Agreement. 
 2.2 Agreement not to Participate in Company’s Competitors. During Executive’s employment with the Company, Executive agrees not to acquire, assume or participate in, directly or
indirectly, any position, investment or interest known by Executive to be adverse or antagonistic to the Company, its business, or prospects, financial or otherwise, or in any company, person, or entity that is, directly or indirectly, in
competition with the business of the Company or any of its Affiliates (as defined below). Ownership by Executive, in professionally managed funds over which the Executive does not have control or discretion in investment decisions, or as a passive
investment, of less than two percent (2%) of the outstanding shares of capital stock of any corporation with one or more classes of its capital stock listed on a national securities exchange or publicly traded on a national securities exchange
or in the over-the-counter market shall not constitute a breach of this Section. For purposes of this Agreement, “Affiliate,” means, with respect to any specific entity, any other entity that, directly or
indirectly, through one or more intermediaries, controls, is controlled by or is under common control with such specified entity. 
 2.3 Covenant not to Compete. During Executive’s employment with the Company, and during any post-termination period in which the Executive is receiving severance benefits from the Company, the
Executive shall not engage in competition with the Company and/or any of its Affiliates, either directly or indirectly, in any manner or capacity, as adviser, principal, agent, affiliate, promoter, partner, officer, director, employee, stockholder,
owner, co-owner, consultant, or member of any association or otherwise, in any phase of the business of developing, manufacturing and marketing of products or services that are in the same field of use or which otherwise compete with the products or
services of the Company, except with the prior written consent of the Board. 
 3. COMPENSATION
OF THE EXECUTIVE. 
 3.1 Base Salary. The Company shall pay Executive a
base salary at the annualized rate of Three Hundred and Seventy Five Thousand Dollars ($375,000.00) (the “Base Salary”), less payroll deductions and all required withholdings, payable in regular periodic
installments in accordance with the Company’s normal payroll practices. The Base Salary shall 

  
 2. 

 
be prorated for any partial year of employment on the basis of a 365-day fiscal year. Following the first closing of the next equity financing transaction in which the Company issues shares of
Preferred Stock to investors including new, external investors none of whom (together with their affiliates) are existing investors in the Company (“External Equity Financing”), the Board will review the Base
Salary and make appropriate adjustments so that the Base Salary is substantially equivalent to the 50th percentile of CEO base salaries when compared to an appropriate group of peer companies, as determined by the Board. It is the Company’s understanding that the Company’s existing investors
collectively are committed to providing additional funding for the Company assuming favorable data from the Company’s ongoing phase two clinical trial of its lead drug candidate. 

3.2 Discretionary Bonus. At the sole discretion of the Board, following each calendar year of employment Executive shall be
eligible to receive a discretionary cash bonus of up to fifty percent (50%) of Executive’s then-current base salary (the “Bonus”), based on Executive’s achievement relative to certain performance
goals (“Performance Goals”) to be established by the Board. The determination of whether Executive has met the Performance Goals for any given year, and if so, the amount of any Bonus that will be paid for such
year (if any), shall be determined by the Board in its sole and absolute discretion. In order to be eligible to earn or receive any Bonus, except as provided in Sections 4.5.3 and 4.5.4, Executive must remain employed by the Company through and
including the end of the year with respect to which such Bonus is being paid. 
 3.3 Stock Options. As soon as
practicable but in any event within 60 days following the Effective Date, Executive will be granted an option to purchase up to 5,684,706 shares of the Company’s Common Stock (the “Option”) pursuant to the
terms of the Company’s 2001 Equity Incentive Plan, as amended from time to time (the “Plan”), which Option represents a number of shares of Common Stock equal to approximately four and one-half percent
(4.5%) of the fully-diluted capitalization of the Company as of the Effective Date. For purposes of this section, “fully-diluted capitalization of the Company” means (1) all issued and outstanding
equity securities of the Company, (2) all shares issuable upon the conversion, exercise, or exchange of any outstanding options, warrants, or other convertible or exchangeable securities of the Company (but excluding shares issuable upon the
exercise of warrants that are not, as of the date of this agreement, exercisable), (3) all shares reserved for future issuance pursuant to the Plan and (4) all shares issuable to GrowthWorks Canadian Fund Limited Ltd.
(“GrowthWorks”) pursuant to the terms of the Amended and Restated Put Agreement among the Company, GrowthWorks and Ambit Biosciences (Canada) Corporation dated as of October 30, 2007, as amended. The
exercise price per share of the Option will be equal to the fair market value of a single share of Common Stock on the date the Option is granted, as determined in good faith by the Board. The Option will be governed by the Plan and shall be granted
pursuant to a separate stock option grant notice and stock option agreement. The Option is intended to be treated as an incentive stock option to the extent permitted under the applicable provisions of the Internal Revenue Code of 1986, as amended
(the “Code”). The Option will be subject to vesting as provided below. 
 (i)
2,842,353 of the shares subject to the Option (the “Time Vesting Shares”) shall be subject to vesting such that, subject to Executive’s continued employment with the Company, one-fourth (1/4) of the
Time Vesting Shares shall vest as of the first anniversary of 

  
 3. 

 
the Effective Date and l/48th of the Time Vesting Shares subject to the Option shall vest in equal monthly installments on the monthly anniversary of the Effective Date of each month for the thirty-six (36) months thereafter.

 (ii) 2,842,353 of the shares subject to the Option (the “Performance Vesting
Shares”) shall be subject to vesting such that, subject to Executive’s continued employment with the Company, (i) all of the Performance Vesting Shares will vest on the date following the date that the Company’s
common stock is publicly traded on a national securities exchange that is the 10th consecutive trading day where the volume-weighted average price for a share of the Company’s common stock, as reported by Bloomberg Financial L.P., is greater than or equal to $2.67 per share, as
adjusted for any stock splits, dividends and the like after the date hereof, (ii) all of the Performance Vesting Shares will vest on the date that is immediately prior to the closing date of a Covered Transaction (defined below) in which the
assets distributable or payable to the holders of the Company’s Series D-2 Preferred Stock and Series D-3 Preferred Stock (or the holders of shares of Common Stock issued upon conversion of the Series D-2 Preferred Stock and Series D-3
Preferred Stock) at the closing of and pursuant to such Covered Transaction have a fair market value as determined in good faith by the Board equal to or greater than, in the aggregate, the product of (A) $2.67 (as adjusted for any stock
splits, dividends and the like after the date hereof) and (B) the total number of shares of Series D-2 Preferred Stock and Series D-3 Preferred Stock (or such shares of Common Stock, as applicable) outstanding immediately prior to such Covered
Transaction (hereinafter, the “Price Threshold”) and (iii) 60% of the Performance Vesting Shares will vest on the date that is immediately prior to the closing date of a Covered Transaction that does not
meet the Price Threshold. 
 (iii) The Option shall immediately terminate with respect to any Performance Vesting Shares
that have not vested upon the occurrence of any Covered Transaction. However, if pursuant to the terms of such Covered Transaction, Contingent Consideration (defined below) may become payable to the stockholders of the Company following the Closing
thereof that may result in thereafter meeting the Price Threshold (a “Potential Qualifying Transaction”), then at such time following such Closing (if ever) as of which the total assets distributed or paid to
the holders of Series D-2 Preferred Stock and Series D-3 Preferred Stock (or the holders of shares of Common Stock issued upon conversion of the Series D-2 Preferred Stock and Series D-3 Preferred Stock), inclusive of such Contingent Consideration,
equal or exceed the Price Threshold and such event occurs no later than the five (5) year anniversary of the Closing of such Potential Qualifying Transaction (the “Post Transaction Vesting Date”), then
Executive shall be entitled to substitute benefits in respect of the terminated portion of the Option as provided in this below (the “Bonus Option Substitute Benefits”). The Bonus Option Substitute Benefits
shall be provided to Executive in the same form as the Covered Transaction consideration payments were made to such holders of Common Stock (the “Closing Stockholders”) in connection with the Covered Transaction
as if Executive had exercised and held all the shares subject to the Bonus Option (the “Bonus Option Shares”) immediately prior to the Closing. 

  
 4. 

 (iv) In order to give effect to the intent of the foregoing paragraph the following
provisions shall apply: 
 (A) The initial Bonus Option Substitute Benefits payment shall be made to you no later than thirty
(30) days following the Post-Transaction Vesting Date with respect to Executive’s share of any Covered Transaction consideration payable on or prior to such date, but shall be reduced by the aggregate amount that Executive would have been
required to pay to exercise the Option with respect to Performance Vesting Shares immediately prior to the Closing, either via a corresponding reduction of the applicable cash payment or a reduction of the number of shares or other property to be
issued to Executive, based upon the Board’s determination of the Fair Market Value of such shares or other property as of the Post-Transaction Vesting Date. 

(B) Following the Post-Transaction Vesting Date, Executive will share in any subsequent release of Contingent
Consideration Payments at the same time and on the same terms as the Closing Stockholders, as if Executive held all Performance Vesting Shares immediately prior to the Closing. However, if as of the fifth (5th) anniversary of the Closing any
Unvested Consideration (defined below) would otherwise continue to remain subject to outstanding Conditions (defined below) on payment, Executive shall be paid such portion of the Unvested Consideration related to such Conditions, subject to any
reduction made by the Board based on the Fair Market Value (as of the fifth (5th) anniversary of the Closing) of the Unvested Consideration as a result of the existence of the Conditions (that is, the present value of the pro-rata portion of the Contingent Consideration that may
be earned and otherwise payable to Executive in respect of the Performance Vesting Shares upon satisfaction of the Conditions), in a lump sum on the fifth (5th) anniversary of the Closing, 
 (v) Following the first closing during the term of Executive’s employment of the next equity financing transaction in which the Company issues shares of Preferred Stock to investors (other
than shares issued in the Second Tranche Closing pursuant to Section 2.2 of the Series D-2 and Series D-3 Preferred Stock and Warrant Purchase Agreement dated May 9, 2011 among the Company and the Purchasers named therein, as such
Agreement is in effect on the date hereof) (the “Next Equity Financing”), Executive will be granted an additional stock option pursuant to the Plan to purchase that number of shares of Common Stock of the
Company which, together with all shares of Common Stock of the Company issued or subject to stock options previously granted to Executive, represents in the aggregate not less than four and one-half percent (4.5%) of the fully-diluted
capitalization of the Company immediately following such Next Equity Financing; provided, however, that if such Next Equity Financing is an External Equity Financing, then solely for purposes of calculating the number of shares of Common Stock of
the Company issuable pursuant to such additional stock option, the number of shares issued pursuant to such External Equity Financing shall be deemed to be the number determined by dividing the aggregate consideration paid for the shares of
Preferred Stock issued in such External Equity Financing by the greater of (a) the price per share at which such shares of Preferred Stock were actually issued or (b) $0.70. Such option will have an exercise price equal to the fair market
value of the Company’s Common Stock on the date of grant. Fifty percent (50%) of the shares issuable pursuant to such additional option will be subject to time vesting commencing as of the date of grant of such option on terms
substantially consistent with the vesting applicable to the Time Vesting Shares as set forth above and the remainder of the shares issuable pursuant to such option will be subject to performance vesting on terms substantially consistent with the
vesting applicable to the Performance Vesting Shares as set forth above. 

  
 5. 

 (vi) For purposes of this Agreement, the following terms shall have the meanings set
forth below: 
 “Conditions” mean the same conditions (including but not limited to any escrow
arrangement, indemnity obligation, or earn-out) on payment imposed on the Company and/or its stockholders with respect to their rights to the Contingent Consideration. 
 “Contingent Consideration” means consideration payable with respect to a Covered Transaction after the closing of such Covered Transaction to the Company and/or its stockholders,
the receipt of which is contingent upon the passage of time or the occurrence or non-occurrence of some future event(s) or circumstance(s), including, without limitation, amounts of consideration paid at a subsequent closing, and amounts of
consideration subject to an escrow, a purchase price adjustment, an earn-out or indemnity claims. 
 “Covered
Transaction” means the occurrence, in a single transaction or in a series of related transactions of the first to occur of the following events that also constitutes a change in the ownership or effective control of the Company, or a
change in the ownership of a substantial portion of the Company’s assets, as described in Treasury Regulations Section 1.409A-3(i)(5): (1) a merger or consolidation of the Company in which the Company’s stockholders immediately
prior to such transaction do not immediately following such transaction own at least a majority of the surviving corporation’s voting shares; (2) a sale of all or substantially all of the Company’s assets or (3) a sale or other
transfer of shares of the Company’s capital stock as a result of which the Company’s stockholders immediately prior to such transaction do not immediately following such transaction own at least a majority of the surviving
corporation’s voting shares, other than a transaction involving the issuance of shares by the Company primarily for the purpose of raising capital for the Company. 
 “Unvested Consideration” means the portion of the Bonus Option Substitute Payments that are subject to the same Conditions on payment of Contingent Consideration as are imposed on
the Company or its stockholders generally. 
 3.4 Expense Reimbursements. The Company will reimburse Executive for all
reasonable business expenses Executive incurs in conducting his duties hereunder, pursuant to the Company’s usual expense reimbursement policies; provided that Executive supplies the appropriate substantiation for such expenses no later than
the end of the calendar month following the month in which such expenses were incurred by Executive. 
 3.5 Changes to
Compensation. Executive’s compensation will be reviewed annually and may be increased from time to time in the Company’s sole discretion. 
 3.6 Employment Taxes. All of Executive’s compensation shall be subject to customary withholding taxes and any other employment taxes as are commonly required to be collected or withheld by the
Company. 
 3.7 Benefits. Executive shall, in accordance with Company policy and the terms of the applicable plan
documents, be eligible to participate in benefits under any benefit plan or arrangement that may be in effect from time to time and made available to the Company’s senior management employees. 

  
 6. 

 3.8 Holidays and Vacation. Executive shall be eligible to accrue four (4) weeks
of paid vacation per year and will receive paid Company holidays in accordance with Company policy. 
 4.
TERMINATION. 
 4.1 Termination by the Company. Executive’s employment with the Company is at will
and may be terminated by the Company at any time and for any reason, or for no reason, including, but not limited to, under the following conditions: 
 4.1.1 Termination by the Company for Cause. The Company may terminate Executive’s employment under this Agreement for “Cause” (as defined below) by delivery of written notice to
Executive. Any notice of termination given pursuant to this section shall effect termination as of the date of the notice, or as of such other date specified in the notice. 
 4.1.2 Termination by the Company without Cause. The Company may terminate Executive’s employment under this Agreement without Cause at any time and for any reason, or for no reason. Such
termination shall be effective on the date Executive is so informed by the Company. 
 4.2 Termination By Executive.
Executive may terminate his employment with the Company at any time and for any reason, or for no reason, upon thirty (30) days written notice to the Company. 
 4.3 Termination for Death or Complete Disability. Executive’s employment with the Company shall automatically terminate effective upon the date of Executive’s death or Complete Disability
(as defined below). 
 4.4 Termination by Mutual Agreement of the Parties. Executive’s employment with the Company
may be terminated at any time upon a mutual agreement in writing of the Parties. Any such termination of employment shall have the consequences specified in such agreement. 
 4.5 Compensation Upon Termination. 
 4.5.1 Death or Complete
Disability. If Executive’s employment is terminated by death or Complete Disability, the Company shall pay to Executive, or to Executive’s heirs, Executive’s base salary and accrued and unused vacation benefits earned through the
date of termination at the rate in effect at the time of termination, less standard deductions and withholdings. The Company shall thereafter have no further obligations to Executive and/or Executive’s heirs under this Agreement, except as
otherwise provided by law (and except as provided otherwise in Executive’s stock option agreements with the Company). 

  
 7. 

 4.5.2 Termination For Cause If the Company terminates Executive’s
employment for Cause, then the Company shall pay Executive’s base salary and accrued and unused vacation benefits earned through the date of termination, at the rate in effect at the time of termination, less standard deductions and
withholdings. The Company shall thereafter have no further obligations to Executive under this Agreement, except as otherwise provided by law (and except as provided otherwise in Executive’s stock option agreements with the Company).

 4.5.3 Termination Without Cause Not In Connection with a Covered Transaction. If the Company terminates
Executive’s employment without Cause at any time other than upon the occurrence of, or within the twelve (12) months immediately following, the effective date of a Covered Transaction, the Company shall pay Executive’s base salary and
accrued and unused vacation benefits earned through the date of termination, at the rate in effect at the time of termination, less standard deductions and withholdings. In addition, if Executive furnishes to the Company an executed waiver and
release of claims in the form attached hereto as Exhibit A (the “Release”) within the time period specified therein, but in no event later than forty-five (45) days following Executive’s
termination, and if Executive allows such Release to become effective in accordance with its terms, then (i) Executive shall be entitled to severance payments in the form of continuation of his base salary, at the rate in effect at the time of
termination, for a period of six (6) months following the termination date, (ii) so long as Executive shall have been employed with the Company for least six (6) months of the calendar year in which such termination occurred,
Executive shall be entitled to receive a pro rata portion (determined based on the number of days actually employed in such year relative to 365) of the Bonus that would have been payable to Executive subject to and in accordance with
Section 3.2 with respect to such year had Executive remained employed with the Company for the full year, payable following the end of such year at such time as performance bonuses with respect to such year are normally determined and actually
paid to other Company executives, (iii) the Company shall pay directly to the insurance provider the premium for COBRA continuation coverage for the Executive and the Executive’s family for a period of twelve (12) months following the
termination date or until the effective date of new healthcare coverage eligibility available through new employment, whichever comes first and (iv) the vesting of any unvested Time Vesting Shares subject to the Option shall accelerate such
that Executive shall become vested in one hundred percent (100%) of the Time Vesting Shares on the effective date of the Release. Such severance payments will be subject to standard payroll deductions and withholdings and will be made on the
Company’s regular payroll cycle, provided, however, that any severance payments otherwise scheduled to be made prior to the effective date of the Release shall accrue and be paid in the first payroll period that follows such effective date and
except as provided in clause (iii) above. The Company shall thereafter have no further obligations to Executive under this Agreement, except as otherwise provided by law (and except as provided otherwise in Executive’s stock option
agreements with the Company). 
 4.5.4 Termination Without Cause In Connection with a Covered Transaction. If the
Company terminates Executive’s employment without Cause upon the occurrence of, or within the twelve (12) months immediately following, the effective date of a Covered Transaction, the Company shall pay Executive’s base salary and
accrued and unused vacation benefits earned through the date of termination, at the rate in effect at the time of termination, less standard deductions and withholdings. In addition, if Executive furnishes to the Company an executed Release within
the time period specified therein, but in no event later than 

  
 8. 

 
forty-five (45) days following Executive’s termination, and if Executive allows such Release to become effective in accordance with its terms, then (i) Executive shall be entitled
to severance payments in the form of continuation of his base salary, at the rate in effect at the time of termination, for a period of twelve (12) months following the termination date, (ii) so long as Executive shall have been employed
with the Company for least six (6) months of the calendar year in which such termination occurred, Executive shall be entitled to receive a pro rata portion (determined based on the number of days actually employed in such year relative to 365)
of the Bonus that would have been payable to Executive subject to and in accordance with Section 3.2 with respect to such year had Executive remained employed with the Company for the full year, payable following the end of such year at such
time as performance bonuses with respect to such year are normally determined and actually paid to other Company executives, (iii) the Company shall pay directly to the insurance provider the premium for COBRA continuation coverage for the
Executive and the Executive’s family during such twelve (12) month period or until the effective date of new healthcare coverage eligibility available through new employment, whichever comes first and (iv) the vesting of any unvested
Time Vesting Shares subject to the Option shall accelerate such that Executive shall become vested in one hundred percent (100%) of the Time Vesting Shares on the effective date of the Release. Such severance payments will be subject to
standard payroll deductions and withholdings and will be made on the Company’s regular payroll cycle, provided, however, that any severance payments otherwise scheduled to be made prior to the effective date of the Release shall accrue and be
paid in the first payroll period that follows such effective date and except as provided in clause (iii) above. The Company shall thereafter have no further obligations to Executive under this Agreement, except as otherwise provided by law (and
except as provided otherwise in Executive’s stock option agreements with the Company). 
 4.6 Additional Definitions.
For purposes of this Agreement, the following terms shall have the following meanings: 
 4.6.1 “Complete
Disability” shall mean the inability of Executive to perform Executive’s duties under this Agreement, whether with or without reasonable accommodation, because Executive has become permanently disabled within the meaning of any
policy of disability income insurance covering employees of the Company then in force. In the event the Company has no policy of disability income insurance covering employees of the Company in force when Executive becomes disabled, the term
“Complete Disability” shall mean the inability of Executive to perform Executive’s duties under this Agreement, whether with or without reasonable accommodation, by reason of any incapacity, physical or mental, which the
Board, based upon medical advice or an opinion provided by a licensed physician acceptable to the Board, determines to have incapacitated Executive from satisfactorily performing all of Executive’s usual services for the Company, with or
without reasonable accommodation, for a period of at least one hundred twenty (120) days during any twelve (12) month period (whether or not consecutive). Based upon such medical advice or opinion, the determination of the Board shall be
final and binding and the date such determination is made shall be the date of such Complete Disability for purposes of this Agreement. 
 4.6.2 “Cause” shall mean the occurrence of any of the following: (i) Executive’s conviction of any felony or any crime involving fraud or dishonesty
that has a material adverse effect on the Company; (ii) Executive’s active participation (whether by 

  
 9. 

 
affirmative act or material omission) in a fraud, act of dishonesty or other act of misconduct against the Company and/or its affiliates; (iii) conduct by Executive which, based upon a good
faith and reasonable factual investigation by the Board, demonstrates Executive’s gross unfitness to serve; (iv) Executive’s material violation of any statutory or fiduciary duty, or duty of loyalty, owed to the Company;
(v) Executive’s breach of any material term of any material contract between such Executive and the Company and the failure to cure such breach within 30 days of written notice; and (vi) Executive’s repeated violation of any
material Company policy. An occurrence of “cause” as set forth in the preceding sentence shall be based upon a good faith determination by the Board. Executive’s Complete Disability shall not constitute Cause as set forth herein. The
determination that a termination is for Cause shall be by the Board in its sole and exclusive judgment and discretion. 
 4.7
Survival of Certain Sections. Sections 2, 3.4, 4 through 13, 16, and 18 of this Agreement will survive the termination of this Agreement. 
 4.8 Parachute Payment. If any payment or benefit the Executive would receive pursuant to this Agreement (“Payment”) would (i) constitute a “Parachute
Payment” within the meaning of Section 280G of the Code, and (ii) but for this sentence, be subject to the excise tax imposed by Section 4999 of the Code (the “Excise Tax”),
then such Payment shall be equal to the Reduced Amount. The “Reduced Amount” shall be either (x) the largest portion of the Payment that would result in no portion of the Payment being subject to the
Excise Tax or (y) the largest portion, up to and including the total of the Payment, whichever amount, after taking into account all applicable federal, state and local employment taxes, income taxes, and the Excise Tax (all computed at the
highest applicable marginal rate), results in the Executive’s receipt, on an after-tax basis, of the greatest economic benefit notwithstanding that all or some portion of the Payment may be subject to the Excise Tax. If a reduction in payments
or benefits constituting Parachute Payments is necessary so that the Payment equals the Reduced Amount, reduction shall occur in the manner that results in the greatest economic benefit for you. If more than one method of reduction will result in
the same economic benefit, the items so reduced will be reduced pro rata. 
 In the event it is subsequently determined by the
Internal Revenue Service that some portion of the Reduced Amount (as determined pursuant to clause (x) in the preceding paragraph) is subject to the Excise Tax, Executive agrees to promptly return to the Company a sufficient amount of the
Payment so that no portion of the Reduced Amount is subject to the Excise Tax. For the avoidance of doubt, if the Reduced Amount is determined in accordance with clause (y) in the preceding paragraph, Executive will have no obligation to return
any portion of the Payment pursuant to the preceding sentence. 
 Unless Executive and the Company agree on an alternative
accounting or law firm, the accounting firm then engaged by the Company for general tax compliance purposes shall perform the foregoing calculations. If the accounting firm so engaged by the Company is serving as accountant or auditor for the
individual, entity or group effecting the Change in Control, the Company shall appoint a nationally recognized accounting, law or consulting firm to make the determinations required hereunder. The Company shall bear all expenses with respect to the
determinations by such accounting, law or consulting firm required to be made hereunder. 

  
 10.

 The Company shall use commercially reasonable efforts such that the accounting, law or
consulting firm engaged to make the determinations hereunder shall provide its calculations, together with detailed supporting documentation, to Executive and the Company within fifteen (15) calendar days after the date on which
Executive’s right to a Payment is triggered (if requested at that time by the Executive or the Company) or such other time as requested by the Executive or the Company. 
 In the event the payment of any amounts pursuant to this letter agreement would result in Executive being subject to an Excise Tax (without giving effect to any reduction in such payments to the Reduced
Amount), at Executive’s request in Executive’s sole discretion, the Company will use its commercially reasonable best efforts to obtain a vote of the stockholders of the Company approving such payments in the manner set forth in
Section 280G(b)(5)(B) of the Code and the Treasury Regulations issued thereunder such that the payments would not be subject to the Excise Tax if the required stockholder approval is obtained. In the event Executive so requests that such a vote
be taken, Executive agrees to execute a waiver and enter into such additional agreements as may be reasonably requested by the Company in relation thereto, including, without limitation, agreeing that the portion of such payments that would
otherwise, if made, result in Executive becoming liable for the Excise Tax will not be made if the required stockholder approval is not obtained. 
 4.9 Application of Internal Revenue Code Section 409A. Notwithstanding anything to the contrary set forth herein, any payments and benefits provided under this Agreement (the
“Severance Benefits”) that constitute “deferred compensation” within the meaning of Section 409A of the Code and the regulations and other guidance thereunder and any state law of similar effect (collectively
“Section 409A”) shall not commence in connection with Executive’s termination of employment unless and until Executive has also incurred a “separation from service” (as such term is defined in Treasury
Regulation Section 1.409A-l(h) (“Separation From Service”), unless the Company reasonably determines that such amounts may be provided to Executive without causing Executive to incur the additional 20% tax under
Section 409 A. 
 It is intended that each installment of the Severance Benefits payments provided for in this Agreement is
a separate “payment” for purposes of Treasury Regulation Section 1.409A-2(b)(2)(i). For the avoidance of doubt, it is intended that payments of the Severance Benefits set forth in this Agreement satisfy, to the greatest extent
possible, the exemptions from the application of Section 409A provided under Treasury Regulation Sections 1.409A-l(b)(4), 1.409A-l(b)(5) and 1.409A-l(b)(9). However, if the Company (or, if applicable, the successor entity thereto) determines
that the Severance Benefits constitute “deferred compensation” under Section 409A and Executive is, on the termination of service, a “specified employee” of the Company or any successor entity thereto, as such term is
defined in Section 409A(a)(2)(B)(i) of the Code, then, solely to the extent necessary to avoid the incurrence of the adverse personal tax consequences under Section 409A, the timing of the Severance Benefit payments shall be delayed until
the earlier to occur of: (i) the date that is six months and one day after Executive’s Separation From Service, or (ii) the date of Executive’s death (such applicable date, the “Specified Employee Initial Payment
Date”), the Company (or the successor entity thereto, as applicable) shall (A) pay to Executive a lump sum amount equal to the sum of the Severance Benefit payments that Executive would otherwise have received through the Specified
Employee 

  
 11.

 
Initial Payment Date if the commencement of the payment of the Severance Benefits had not been so delayed pursuant to this Section and (B) commence paying the balance of the Severance
Benefits in accordance with the applicable payment schedules set forth in this Agreement. 
 Notwithstanding anything to the
contrary set forth herein, Executive shall receive the Severance Benefits described above, if and only if Executive duly executes and returns to the Company within the applicable time period set forth therein, but in no event more than forty-five
days following Separation From Service, the Release and permits the Release to become effective in accordance with its terms. Notwithstanding any other payment schedule set forth in this Agreement, none of the Severance Benefits will be paid or
otherwise delivered prior to the effective date of the Release. Except to the extent that payments may be delayed until the Specified Employee Initial Payment Date pursuant to the preceding paragraph, on the first regular payroll pay day following
the effective date of the Release, the Company will pay Executive the Severance Benefits Executive would otherwise have received under the Agreement on or prior to such date but for the delay in payment related to the effectiveness of the Release,
with the balance of the Severance Benefits being paid as originally scheduled. All amounts payable under the Agreement will be subject to standard payroll taxes and deductions. 

5. CONFIDENTIAL AND PROPRIETARY INFORMATION. 

As a condition of employment, Executive agrees to execute and abide by the Company’s standard form of Proprietary Information and
Inventions Agreement (“PIIA”). 
 6. ASSIGNMENT AND
BINDING EFFECT. 
 This Agreement shall be binding upon and inure to the benefit of Executive
and Executive’s heirs, executors, personal representatives, assigns, administrators and legal representatives. Because of the unique and personal nature of Executive’s duties under this Agreement, neither this Agreement nor any rights or
obligations under this Agreement shall be assignable by Executive. This Agreement shall be binding upon and inure to the benefit of the Company and its successors, assigns and legal representatives. Any such successor of the Company will be deemed
substituted for the Company under the terms of this Agreement for all purposes. For this purpose, “successor” means any person, firm, corporation or other business entity which at any tie, whether by purchase, merger or otherwise, directly
or indirectly acquires all or substantially all of the assets or business of the Company. 
 7. NOTICES.

 All notices or demands of any kind required or permitted to be given by the Company or Executive under this Agreement
shall be given in writing and shall be personally delivered (and receipted for) or faxed during normal business hours or mailed by certified mail, return receipt requested, postage prepaid, addressed as follows: 

If to the Company: 
 Ambit Biosciences Corporation 
 4215 Sorrento Valley Boulevard 

San Diego, CA 92121 
 Attention: Chairman of the Board 

  
 12.

 If to Executive: 

Michael A. Martino 
 PO Box 5000 PMB 190 
 Rancho Santa Fe, CA 92067 

Any such written notice shall be deemed given on the earlier of the date on which such notice is personally delivered or three (3) days after its
deposit in the United States mail as specified above. Either Party may change its address for notices by giving notice to the other Party in the manner specified in this Section. 

8. CHOICE OF LAW. 

This Agreement shall be construed and interpreted in accordance with the internal laws of the State of California without regard to its
conflict of laws principles. 
 9. INTEGRATION. 

This Agreement, including Exhibit A and the PIIA, contains the complete, final and exclusive agreement of the Parties relating to the
terms and conditions of Executive’s employment and the termination of Executive’s employment, and supersedes any and all prior and/or contemporaneous oral and written employment agreements or arrangements between the Parties regarding
Executive’s service with the Company. 
 10. AMENDMENT. 

This Agreement cannot be amended or modified except by a written agreement signed by Executive and the Company. 

11. WAIVER. 
 No term, covenant or condition of this Agreement or any breach thereof shall be deemed waived, except with the written consent of the Party against whom the wavier is claimed, and any waiver or any such
term, covenant, condition or breach shall not be deemed to be a waiver of any preceding or succeeding breach of the same or any other term, covenant, condition or breach. 
 12. SEVERABILITY. 
 The finding by a court of competent
jurisdiction of the unenforceability, invalidity or illegality of any provision of this Agreement shall not render any other provision of this 

  
 13.

 
Agreement unenforceable, invalid or illegal. Such court shall have the authority to modify or replace the invalid or unenforceable term or provision with a valid and enforceable term or
provision, which most accurately represents the Parties’ intention with respect to the invalid or unenforceable term, or provision. 
 13. INTERPRETATION; CONSTRUCTION. 
 The
headings set forth in this Agreement are for convenience of reference only and shall not be used in interpreting this Agreement. This Agreement has been drafted by legal counsel representing the Company, but the Executive has been encouraged to
consult with, and has consulted with, Executive’s own independent counsel and tax advisors with respect to the terms of this Agreement. The Parties acknowledge that each Party and its counsel has reviewed and revised, or had an opportunity to
review and revise, this Agreement, and any rule of construction to the effect that any ambiguities are to be resolved against the drafting party shall not be employed in the interpretation of this Agreement. 

14. REPRESENTATIONS AND WARRANTIES. 

Executive represents and warrants that Executive is not restricted or prohibited, contractually or otherwise, from entering into and
performing each of the terms and covenants contained in this Agreement, and that Executive’s execution and performance of this Agreement will not violate or breach any other agreements between the Executive and any other person or entity.

 15. COUNTERPARTS. 
 This Agreement may be executed in two counterparts, each of which shall be deemed an original, all of which together shall contribute one and the same instrument. 

16. ARBITRATION. 
 To ensure the rapid and economical resolution of disputes that may arise in connection with the Executive’s employment with the Company, Executive and the Company agree that any and all disputes,
claims, or causes of action, in law or equity, arising from or relating to Executive’s employment, or the termination of that employment, will be resolved, to the fullest extent permitted by law, by final, binding and confidential arbitration
pursuant to both the substantive and procedural provisions of the Federal Arbitration Act in San Diego, California conducted by the Judicial Arbitration and Mediation Services/Endispute, Inc. (“JAMS”}, or its
successors, under the then current rules of JAMS for employment disputes; provided that the arbitrator shall: (a) have the authority to compel adequate discovery for the resolution of the dispute and to award such relief as would otherwise be
permitted by law; and (b) issue a written arbitration decision including the arbitrator’s essential findings and conclusions and a statement of the award. Accordingly, Executive and the Company hereby waive any right to a jury trial. Both
Executive and the Company shall be entitled to all rights and remedies that either Executive or the Company would be entitled to pursue in a court of law. The Company shall pay any JAMS filing fee and shall pay the arbitrator’s fee. Nothing in
this Agreement is intended to prevent either Executive or the Company from obtaining injunctive relief in court to prevent irreparable harm pending the conclusion of any such arbitration. Notwithstanding the foregoing,

  
 14.

 
Executive and the Company each have the right to resolve any issue or dispute involving confidential, proprietary or trade secret information, or intellectual property rights, by Court action
instead of arbitration. 
 17. TRADE SECRETS OF OTHERS.

 It is the understanding of both the Company and Executive that Executive shall not divulge to the Company and/or its
subsidiaries any confidential information or trade secrets belonging to others, including Executive’s former employers, nor shall the Company and/or its Affiliates seek to elicit from Executive any such information. Consistent with the
foregoing, Executive shall not provide to the Company and/or its Affiliates, and the Company and/or its Affiliates shall not request, any documents or copies of documents containing such information. 

18. ADVERTISING WAIVER. 
 Executive agrees to permit the Company, and persons or other organizations authorized by the Company, to use, publish and distribute advertising or sales promotional literature concerning the products
and/or services of the Company, or the machinery and equipment used in the provision thereof, in which Executive’s name and/or pictures of Executive taken in the course of Executive’s provision of services to the Company appear. Executive
hereby waives and releases any claim or right Executive may otherwise have arising out of such use, publication or distribution. 

[REMAINDER OF THIS PAGE INTENTIONALLY LEFT
BLANK] 

  
 15.

 IN WITNESS
WHEREOF, the Parties have executed this Agreement as of the date first above written. 
  

			
	AMBIT BIOSCIENCES CORPORATION
		
	By:	 	 /s/ Faheem Hasnain

	Its:	 	 Chairman

		
	Dated:	 	 11/16/11

	
	EXECUTIVE:
	
	 /S/ MICHAEL A.
MARTINO

	MICHAEL A. MARTINO
		
	Dated:	 	 9 Nov 2011

 [SIGNATURE PAGE TO EMPLOYMENT
AGREEMENT] 

 EXHIBIT A 
 RELEASE AND WAIVER OF CLAIMS 
 TO BE SIGNED ON OR FOLLOWING THE
SEPARATION DATE ONLY 
 In consideration of the payments and other benefits set forth in the Employment Agreement of
November     , 2011, to which this form is attached, I, Michael A. Martino, hereby furnish AMBIT BIOSCIENCES CORPORATION (the
“Company”), with the following release and waiver (“Release and Waiver”). 
 In
exchange for the consideration provided to me by the Employment Agreement that I am not otherwise entitled to receive, I hereby generally and completely release the Company and its current and former directors, officers, employees, stockholders,
partners, agents, attorneys, predecessors, successors, parent and subsidiary entities, insurers, affiliates, and assigns (collectively, the “Released Parties”) from any and all claims, liabilities and obligations, both known
and unknown, that arise out of or are in any way related to events, acts, conduct, or omissions occurring prior to or on the date that I sign this Agreement (collectively, the “Released Claims”). The Released Claims include,
but are not limited to: (a) all claims arising out of or in any way related to my employment with the Company, or the termination of that employment; (b) all claims related to my compensation or benefits from the Company including salary,
bonuses, commissions, vacation pay, expense reimbursements, severance pay, fringe benefits, stock, stock options, or any other ownership interests in the Company; (c) all claims for breach of contract, wrongful termination, and breach of the
implied covenant of good faith and fair dealing; (d) all tort claims, including claims for fraud, defamation, emotional distress, and discharge in violation of public policy; and (e) all federal, state, and local statutory claims,
including claims for discrimination, harassment, retaliation, misclassification, attorneys’ fees, or other claims arising under the federal Civil Rights Act of 1964 (as amended), the federal Americans with Disabilities Act of 1990, the federal
Age Discrimination in Employment Act of 1967 (as amended) (the “ADEA”), the California Labor Code, and the California Fair Employment and Housing Act (as amended). Notwithstanding the foregoing, the following are not included
in the Released Claims (the “Excluded Claims”): (a) any rights or claims for indemnification I may have pursuant to any written indemnification agreement with the Company to which I am a party, the charter, bylaws, or
operating agreements of the Company, or under applicable law; (b) any rights or claims to unemployment compensation, funds accrued in my 401k account, or any vested equity incentives; (c) any rights that are not waivable as a matter of
law; or (d) any claims arising from the breach of this Agreement. I hereby represent and warrant that, other than the Excluded Claims, I am not aware of any claims I have or might have against any of the Released Parties that are not included
in the Released Claims. 
 I also acknowledge that I have read and understand Section 1542 of the California Civil Code
which reads as follows: “A general release does not extend to claims which the creditor does not know or suspect to exist in his or her favor at the time of executing the release, which if known by him or her must have materially affected
his or her settlement with the debtor.” I hereby expressly waive and relinquish all rights and benefits under that Section and any law of any jurisdiction of similar effect with respect to any claims I may have against the Company.

 I acknowledge that, among other rights, I am waiving and releasing any rights I may have
under ADEA, that this Release and Waiver is knowing and voluntary, and that the consideration given for this Release and Waiver is in addition to anything of value to which I was already entitled as an executive of the Company. If I am 40 years of
age or older upon execution of this Release and Waiver, I further acknowledge that I have been advised, as required by the Older Workers Benefit Protection Act, that: (a) the release and waiver granted herein does not relate to claims under the
ADEA which may arise after this Release and Waiver is executed; (b) I should consult with an attorney prior to executing this Release and Waiver; and (c) I have twenty-one (21) days from the date of termination of my employment with
the Company in which to consider this Release and Waiver (although I may choose voluntarily to execute this Release and Waiver earlier); (d) I have seven (7) days following the execution of this Release and Waiver to revoke my consent to
this Release and Waiver; and (e) this Release and Waiver shall not be effective until the seven (7) day revocation period has expired without my having previously revoked this Release and Waiver. 

I acknowledge my continuing obligations under my Proprietary Information and Inventions Agreement. Pursuant to the Proprietary
Information and Inventions Agreement I understand that among other things, I must not use or disclose any confidential or proprietary information of the Company and I must immediately return all Company property and documents (including all
embodiments of proprietary information) and all copies thereof in my possession or control. I understand and agree that my right to the severance pay I am receiving in exchange for my agreement to the terms of this Release and Waiver is contingent
upon my continued compliance with my Proprietary Information and Inventions Agreement. 
 This Release and Waiver constitutes
the complete, final and exclusive embodiment of the entire agreement between the Company and me with regard to the subject matter hereof. I am not relying on any promise or representation by the Company that is not expressly stated herein. This
Release and Waiver may only be modified by a writing signed by both me and a duly authorized officer of the Company. 
  

					
	Date:                     	  	By:	  	  

		  		  	Michael A. Martino

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