Document:

Amendment No.1 to Executive Change in Control Severance Benefits Agreement

 Exhibit 10.9(iv) 

AMENDMENT NO. 1 TO AMENDED AND RESTATED 
 EXECUTIVE CHANGE IN CONTROL 
 SEVERANCE BENEFITS AGREEMENT 

This AMENDMENT NO. 1 TO AMENDED AND
RESTATED EXECUTIVE CHANGE IN CONTROL SEVERANCE BENEFITS AGREEMENT (the “Amendment”) is made and
entered into, as of July 26, 2012 (the “Effective Date”), between ONYX PHARMACEUTICALS, INC., a Delaware corporation
(“Company”), and KAYE FOSTER-CHEEK (“Executive”). As of the Effective Date, the Company and Executive
hereby amend that certain AMENDED AND RESTATED EXECUTIVE CHANGE IN CONTROL SEVERANCE BENEFITS
AGREEMENT between the Company and Executive dated May 18, 2011 (the “Agreement”), a copy of which is attached hereto as Exhibit A, as follows:

 1. AMENDMENT OF SECTION 2.2. Section 2.2 of the
Agreement is hereby amended and restated to read in its entirety as follows: 
 “2.2 Cash Severance Benefits. The
Company shall make a cash severance payment in a lump sum to Executive in an amount equal to the product of (i) the sum of (a) Executive’s Base Salary and (b) Executive’s Target Bonus, and (ii) the quotient obtained by
dividing twenty-six (26) by twelve (12), less applicable tax withholdings. This lump sum will be paid on the sixtieth (60th) day following the date of the Covered Termination, but in no event later than as provided in Section 3.4
below.” 
 2. ADDITION OF SECTION 5.10. A new Section 5.10 is
hereby added to the Agreement to read in its entirety as follows: 
 “5.10 “Target
Bonus” means the greater of (i) the target annual incentive bonus, expressed in dollars, which Executive is eligible to earn in the fiscal year in which a Covered Termination occurs, or (ii) the target
annual incentive bonus, expressed in dollars, which Executive is eligible to earn in the fiscal year in which a Change in Control occurs.” 
 3. MISCELLANEOUS. This Amendment constitutes the complete, final and exclusive embodiment of the entire agreement between the Company and Executive with regard to amendment of the
Agreement. It is entered into without reliance on any promise or representation, written or oral, other than those expressly contained herein, and it supersedes any other such promises, warranties or representations. Any provisions of the Agreement
contrary to this Amendment are hereby superseded and replaced, and the remaining portions of the Agreement remain in full force and effect. This Amendment cannot be modified or amended except in writing approved by the Company’s Board of
Directors or a duly authorized committee thereof and signed by an executive officer of the Company (other than Executive) and Executive. This Amendment will bind the heirs, personal representatives, successors and assigns of both Executive and the
Company, and inure to the benefit of both Executive and the Company, their heirs, successors and assigns. If any provision of this Amendment is determined to be invalid or unenforceable, in whole or in part, this determination shall not affect any
other provision of this Amendment and the provision in question shall be modified so as to be rendered enforceable in a manner consistent with the intent of the parties insofar as possible under applicable law. This Amendment shall be construed and
enforced in accordance with the laws of the State of 

 
California without regard to conflicts of law principles. Any ambiguity in this Amendment shall not be construed against either party as the drafter. Any waiver of a breach of this Amendment, or
rights hereunder, shall be in writing and shall not be deemed to be a waiver of any successive breach or rights hereunder. This Amendment may be executed in counterparts which shall be deemed to be part of one original, and facsimile signatures and
signatures transmitted via PDF shall be equivalent to original signatures. 
 [Signature Page Follows] 

 IN WITNESS WHEREOF, the parties have executed this Amendment as of the date first written
above. 
  

							
	 ONYX PHARMACEUTICALS, INC.

A Delaware Corporation
	  		 	 KAYE FOSTER-CHEEK
 An Individual

				
	By:	 	 /s/ N. Anthony Coles
	  		 	 /s/ Kaye Foster-Cheek

	Name:	 	N. Anthony Coles	  		 	
	Title:	 	President & CEO	  		 	

 EXHIBIT A 

AMENDED AND RESTATED 
 EXECUTIVE CHANGE IN CONTROL 
 SEVERANCE BENEFITS AGREEMENT 

This AMENDED AND RESTATED EXECUTIVE CHANGE
IN CONTROL SEVERANCE BENEFITS AGREEMENT (the “Agreement”) is entered into as of May 18, 2011 (the “Effective
Date”), between KAYE FOSTER-CHEEK (“Executive”) and ONYX PHARMACEUTICALS, INC. (the
“Company”) and amends and restates the prior Executive Change in Control Severance Benefits Agreement between the Company and Executive dated September 30, 2010 (the “Original Date”). This
Agreement is intended to provide Executive with certain compensation and benefits in the event that Executive is subject to a qualifying termination of employment in connection with a Change in Control. Certain capitalized terms used in this
Agreement are defined in Article 5. 
 The Company and Executive hereby agree as follows: 

ARTICLE 1 

SCOPE OF AND CONSIDERATION FOR THIS
AGREEMENT 
 1.1 The Company desires to continue to employ Executive in the position of SVP, Global
Human Resources, and Executive wishes to continue to be employed by the Company in such position. 
 1.2 The Company and
Executive wish to clarify the compensation and benefits the Executive shall be eligible to receive upon a Covered Termination as well as the manner of compliance with, or exemption from, Code Section 409A and recent proposed health care
regulations. 
 1.3 The duties and obligations of the Company to Executive under this Agreement shall be in consideration
for Executive’s past services to the Company, Executive’s continued employment with the Company, and, with respect to the benefits described in Article 2, Executive’s execution of an effective Release in accordance with
Section 3.1. 
 1.4 This Agreement supersedes and replaces all prior agreements, plans, policies and understandings
on the subjects contained herein, including, but not limited to all prior executive change in control severance benefits agreements (together, the “Prior Agreements”). 

ARTICLE 2 

SEVERANCE BENEFITS 
 2.1 Severance Benefits. Upon a Covered Termination, and subject to the terms and conditions of this Agreement, Executive shall be entitled to receive the benefits set forth in this Article 2.

  
 1. 

 2.2 Cash Severance Benefits. The Company shall make a cash severance payment in a
lump sum to Executive in an amount equal to the product of (i) Executive’s Base Salary, and (ii) the quotient obtained by dividing twenty-six (26) by twelve (12), less applicable tax withholdings. This lump sum will be paid on
the sixtieth (60th) day following the date of the Covered Termination, but in no event later than as provided in Section 3.4 below. 
 2.3 Health Continuation Coverage. 
 (a) Provided that Executive is
eligible for, and has made the necessary elections pursuant to COBRA under a health, dental, or vision plan sponsored by the Company, Executive shall be entitled to payment, as and when due to the COBRA carrier, by the Company in an amount equal to
the monthly total of the applicable premiums (inclusive of premiums for Executive’s eligible dependents for such health, dental, or vision plan coverage as in effect immediately prior to the date of the Covered Termination) for such health,
dental, or vision plan coverage, less applicable tax withholdings, until the earliest to occur of (i) eighteen (18) months after Executive’s termination date, (ii) the date Executive becomes eligible for coverage under a health,
dental, or vision insurance plan of a subsequent employer and (iii) the date Executive or his dependents cease to be eligible for COBRA coverage. In no way limiting Section 3.5 below, these payments will be subject to any applicable tax
withholdings (including tax withholdings necessary to ensure that the provision of this benefit is not deemed a discriminatory practice giving rise to penalties to the Company under applicable laws) and will be counted as coverage pursuant to COBRA
to the maximum extent permitted under applicable law. Executive shall be required to notify the Company immediately if Executive becomes eligible for coverage under a health, dental, or vision insurance plan of a subsequent employer. Upon the
conclusion of such period of insurance premium payments made by the Company, Executive will be responsible for the entire payment of such premiums required under COBRA for the remaining duration of the COBRA period, if any. 

(b) For purposes of this Section 2.3, (i) references to COBRA shall be deemed to refer also to analogous provisions of
state law, and (ii) the amount of the payment from the Company shall not include any amounts payable by Executive under a Code Section 125 health care reimbursement plan, which amounts, if any, are the sole responsibility of Executive.

 2.4 Continued Life Insurance Benefit. Provided the Executive converts his coverage under the Company’s basic
group life insurance policy into individual coverage, the Company shall pay, directly to the provider, as and when due, an amount equal to the same percentage of the cost of such premiums for such basic (but not supplemental) group life insurance
coverage that the Company paid prior to the Covered Termination, less applicable tax withholdings, until the earliest to occur of (i) eighteen (18) months after Executive’s termination date, (ii) the date Executive becomes
eligible for coverage under a group life insurance plan or policy of a subsequent employer and (iii) the date Executive ceases to be eligible for such conversion coverage. Executive shall be required to notify the Company in writing immediately
if Executive becomes eligible for coverage by a life insurance plan or policy of a subsequent employer. 
 2.5 Outplacement
Assistance. On behalf of Executive, the Company shall reimburse Executive for reasonable outplacement services actually incurred for a period of one 

  
 2. 

 
(1) year following a Covered Termination with an outplacement service provider selected by the Company; provided, however, that the total cost to the Company of such outplacement
services shall not exceed twenty-five thousand dollars ($25,000), less applicable tax withholdings. 
 2.6 Stock Awards.
The stock awards granted to Executive prior to the Original Date were modified to contain, and stock awards granted to Executive on or after the Original Date do and/or shall contain, the following provisions: 

(a) Vesting and Exercisability. The vesting and exercisability of Executive’s then-outstanding stock awards shall be
accelerated in full upon a Covered Termination. 
 (b) Term. Executive shall have twelve (12) months following
a Covered Termination in which to exercise any outstanding stock options, but in no event shall such period exceed the expiration of the term of the stock option as set forth in the stock option agreement, including any early termination required in
connection with a Change in Control. 
 ARTICLE 3 
 LIMITATIONS AND CONDITIONS ON BENEFITS 

3.1 Release Prior to Payment of Benefits. Upon the occurrence of a Covered Termination, and prior to the
provision or payment of any benefits under this Agreement on account of such Covered Termination, Executive must execute a general waiver and release in substantially the form attached hereto and incorporated herein as Exhibit A,
Exhibit B, or Exhibit C, as appropriate (each a “Release”), and such release must become effective in accordance with its terms and in all cases not later than the 60th day after the Covered Termination. The Company may modify the
Release in its discretion to comply with changes in applicable law until the date of a Covered Termination. Such Release shall specifically relate to all of Executive’s rights and claims in existence at the time of such execution and shall
confirm Executive’s obligations under the Company’s standard form of proprietary information and inventions agreement. It is understood that, as specified in the applicable Release, Executive has a certain number of calendar days to
consider whether to execute such Release. If Executive does not execute such Release within the applicable period, no benefits shall be provided or payable under this Agreement pursuant to a Covered Termination. It is further understood that if
Executive is age 40 or older at the time of a Covered Termination, Executive may revoke the applicable Release within seven (7) calendar days after its execution. If Executive revokes such Release within such subsequent seven (7) day
period, no benefits shall be provided or payable under this Agreement pursuant to such Covered Termination. 
 3.2 Parachute
Payments. 
 (a) Parachute Payment Limitation. If any payment or benefit (including payments and benefits
pursuant to this Agreement) Executive would receive in connection with a Change in Control from the Company or otherwise (“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”), 

  
 3. 

 
then the Company shall cause to be determined, before any amounts of the Payment are paid to Executive, which of the following two alternative forms of payment shall be paid to Executive:
(i) payment in full of the entire amount of the Payment (a “Full Payment”), or (ii) payment of only a part of the Payment so that Executive receives the largest payment possible without the imposition of the Excise
Tax (a “Reduced Payment”). A Full Payment shall be made in the event that the quotient obtained by dividing (i) the excess of (a) the Full Payment, over (b) the Reduced Payment, by (ii) the Reduced
Payment, is greater than ten percent (10%). A Reduced Payment shall be made in the event that the quotient obtained by dividing (i) the excess of (a) the Full Payment, over (b) the Reduced Payment, by (ii) the Reduced Payment, is
less than or equal to ten percent (10%). If a Reduced Payment is made, (i) the Payment shall be paid only to the extent permitted under the Reduced Payment alternative, and Executive shall have no rights to any additional payments and/or
benefits constituting the Payment, and (ii) reduction in payments and/or benefits shall occur in the following order: (1) reduction of cash payments; (2) cancellation of accelerated vesting of equity awards other than stock options;
(3) cancellation of accelerated vesting of stock options; and (4) reduction of other benefits paid to Executive. Within any such category of payments and benefits (that is, (1), (2), (3) or (4)), a reduction shall occur first with
respect to amounts that are not “deferred compensation” within the meaning of Internal Revenue Code Section 409A and then with respect to amounts that are. In the event that acceleration of compensation from a category of
Executive’s equity awards is to be reduced, such acceleration of vesting shall be canceled in the reverse order of the date of grant. 
 (b) The independent registered public accounting firm engaged by the Company for general audit purposes as of the day prior to the effective date of the Change in Control shall make all
determinations required to be made under this Section 3.2. If the independent registered public 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 independent registered public accounting firm to make the determinations required hereunder. The Company shall bear all expenses with respect to the determinations by such independent registered
public accounting firm required to be made hereunder. 
 (c) The independent registered public accounting firm engaged to
make the determinations hereunder shall provide its calculations, together with detailed supporting documentation, to the Company and Executive 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 Company or Executive) or such other time as reasonably requested by the Company or Executive. If the independent registered public accounting firm determines that no Excise Tax is payable with respect to a
Payment, either before or after the application of the Reduced Amount, it shall furnish the Company and Executive with documentation that no Excise Tax will be imposed with respect to such Payment. Any good-faith determinations of the accounting
firm made hereunder shall be final, binding and conclusive upon the Company and Executive. 
 3.3 Certain Reductions and
Offsets. To the extent that any federal, state or local laws, including, without limitation, the Worker Adjustment and Retraining Notification Act (the “WARN Act”) or any other so-called “plant closing” laws,
require the Company to give advance notice or make a payment of any kind to Executive because of Executive’s involuntary termination due to a layoff, reduction in force, plant or facility closing, sale of business, change

  
 4. 

 
in control, or any other similar event or reason, the benefits payable under this Agreement shall be correspondingly reduced. The benefits provided under this Agreement are intended to satisfy
any and all statutory obligations that may arise out of Executive’s involuntary termination of employment for the foregoing reasons, and the parties shall construe and enforce the terms of this Agreement accordingly. 

3.4 Application of Section 409A. All payments provided under this Agreement are intended to constitute separate payments for
purposes of Code Section 409A, including but not limited to Treasury Regulation Section 1.409A-2(b)(2). 
 (a) The cash severance payment provided under Section 2.2 shall be paid no later than March 15th of the calendar year following the calendar year in which the Covered Termination occurs. It is the intention of the
preceding sentence to apply the “short-term deferral rule” set forth in Treasury Regulation Section 1.409A-1(b)(4) to such payments. If it is determined that the cash severance payments do not satisfy the requirements for
exemption under Treasury Regulation Section 1.409A-1(b)(4), such payments are intended to be compliant with Treasury Regulation Sections 1.409A-3(a) and will be construed as such, and paid not later than the later of
(x) December 31st of the year of the Covered
Termination and (y) the 15th day of the third
calendar month following the date of the Covered Termination. 
 (b) Amounts paid pursuant to Section 2.3 (that is,
continued health insurance premiums) are intended to be exempt from Code Section 409A pursuant to Treasury Regulation Section 1.409A-1(b)(9)(v)(B) and to the extent not so exempt, that it is paid in compliance with Code Section 409A
under Treasury Regulation Section 1.409A-3(i)(1)(iv), the provisions of which are expressly incorporated by reference herein. 
 (c) The continued life insurance benefit provided under Section 2.4 is intended to be exempt from Code Section 409A under Treasury Regulation Section 1.409A-1(b)(9)(v)(C) and
(D), and to the extent not so exempt, that it is paid in compliance with Code Section 409A under Treasury Regulation Section 1.409A-3(i)(1)(iv), the provisions of which are expressly incorporated by reference herein. 

(d) The outplacement assistance payments provided under Section 2.5 are intended to be exempt from Code Section 409A
pursuant to Treasury Regulation Section 1.409A-1(b)(9)(v)(A) and to the extent not so exempt, that it is paid in compliance with Code Section 409A under Treasury Regulation Section 1.409A-3(i)(1)(iv), the provisions of which
are expressly incorporated by reference herein (with the amount of expenses eligible for reimbursement in a given calendar month equal to the monthly pro-rata amount of the total allowance). 

(e) Payments pursuant to Section 2.6 are intended to be exempt from Code Section 409A pursuant to Treasury
Regulation Sections 1.409A-1(b)(4), (5) and (6). 
 (f) Notwithstanding any provision to the contrary in
this Agreement, if Executive is deemed by the Company at the time of his separation from service to be a “specified employee” for purposes of Code Section 409A(a)(2)(B)(i), and if any of the payments upon separation from service set
forth herein and/or under any other agreement with the Company are 

  
 5. 

 
deemed to be “deferred compensation”, then to the extent delayed commencement of any portion of such payments is required in order to avoid a prohibited distribution under Code
Section 409A(a)(2)(B)(i) and the related adverse taxation under Section 409A, such payments shall not be provided prior to the earliest of (i) the expiration of the six-month period measured from the date of Executive’s
separation from service with the Company, (ii) the date of Executive’s death or (iii) such earlier date as permitted under Section 409A without the imposition of adverse taxation. Upon the first business day following the
expiration of such applicable Code Section 409A(a)(2)(B)(i) period, all payments deferred pursuant to this paragraph shall be paid in a lump sum to Executive or the applicable benefit carrier, and any remaining payments due shall be paid as
otherwise provided herein or in the applicable agreement. No interest shall be due on any amounts so deferred. 
 3.5 Tax
Withholding. All payments under this Agreement shall be subject to applicable withholding for federal, state and local income and employment taxes. Executive authorizes withholding from payroll and any other amounts payable to Executive, and
otherwise agrees to make adequate provision, for any sums required to satisfy the federal, state, local and foreign tax withholding obligations of the Company that arise in connection with the payments and benefits provided under this Agreement.

 3.6 Indebtedness of Executive. If Executive is indebted to the Company on the effective date of a Covered Termination,
the Company reserves the right to offset any severance payments under this Agreement by the amount of such indebtedness. 

ARTICLE 4 

OTHER RIGHTS AND BENEFITS 

Nothing in the Agreement shall prevent or limit Executive’s continuing or future participation in any benefit, bonus, incentive or
other plans, programs, policies or practices provided by the Company and for which Executive may otherwise qualify, nor shall anything herein limit or otherwise affect such rights as Executive may have under other agreements with the Company. Except
as otherwise expressly provided herein, amounts that are vested benefits or that Executive is otherwise entitled to receive under any plan, policy, practice or program of the Company at or subsequent to the date of a Change in Control shall be
payable in accordance with such plan, policy, practice or program. 
 ARTICLE 5 

DEFINITIONS 
 Unless otherwise provided, for purposes of the Agreement, the following definitions shall apply: 
 5.1 “Base Salary” means the greater of (i) Executive’s annual base salary (excluding incentive pay, premium pay, commissions, relocation assistance or benefits,
housing allowances, overtime, bonuses, and other forms of special or variable compensation) as in effect on the date of a Covered Termination, or (ii) Executive’s annual base salary (excluding incentive pay, premium pay, commissions,
relocation assistance or benefits, housing allowances, overtime, bonuses, and other forms of special or variable compensation) as in effect on the date of a Change in Control. 

  
 6. 

 5.2 “Board” means the Board of Directors of the Company.

 5.3 “Change in Control” means one or more of the following events: 

(a) A consummated sale or other disposition of all or substantially all of the assets of the Company (other than a sale to an
entity in which at least fifty percent (50%) of the combined voting power of the voting securities of such entity are owned by the stockholders of the Company in substantially the same proportions as their ownership of the Company immediately
prior to such sale). 
 (b) Any person, entity or group (other than the Company, a subsidiary or affiliate of the
Company, or a Company employee benefit plan, including any trustee of such plan acting as trustee) becomes the beneficial owner, directly or indirectly, of securities of the Company representing fifty percent (50%) or more of the combined
voting power of the Company’s then outstanding securities other than by virtue of a merger, consolidation or similar transaction. 
 (c) A consummated merger, consolidation or similar transaction involving (directly or indirectly) the Company, immediately after the consummation of which, the stockholders immediately prior to the
consummation of such transaction do not own, directly or indirectly, outstanding voting securities representing more than fifty percent (50%) of the combined outstanding voting power of the surviving entity in such transaction or more than
fifty percent (50%) of the combined outstanding voting power of the parent of the surviving entity in such transaction. 

Notwithstanding the foregoing, to the extent that the Company determines that any of the payments or benefits to Executive under this
Agreement or otherwise that are payable in connection with a Change in Control constitute deferred compensation under Section 409A that may only be paid on a qualifying transaction (that is, the payments and benefits are not otherwise
“exempt” under 409A), the foregoing definition of Change in Control shall apply only to the extent the transaction also meets the definition used for purposes of Treasury Regulation Section 1.409A-3(a)(5), that is, as defined
under Treasury Regulation Section 1.409A-3(i)(5). 
 5.4 “COBRA” means the Consolidated
Omnibus Budget Reconciliation Act of 1985, as amended. 
 5.5 “Code” means the Internal Revenue
Code of 1986, as amended. 
 5.6 “Company” means Onyx Pharmaceuticals, Inc. or, following a
Change in Control, the surviving entity resulting from such transaction, or any subsequent surviving entity resulting from any subsequent Change in Control. 
 5.7 “Constructive Termination” means a voluntary termination of employment by Executive resulting in a “separation from service” with the Company within the
meaning of 

  
 7. 

 
Treasury Regulation Section 1.409A-1(h) within a period of ninety (90) days after Executive provides written notice to the Company of the initial occurrence of one of the following
actions taken without Executive’s written consent (which written notice must be provided within ninety (90) days after the initial occurrence of one of the following actions, and must reasonably specify the particulars of the action);
provided, however, following the receipt of notice by the Company, the Company shall have a period of thirty (30) days during which to remedy the action giving rise to a Constructive Termination; provided, further, if such action
is remedied by the Company during such period, Constructive Termination shall be deemed not to have occurred: 
 (a) the
assignment to Executive of duties or responsibilities that results in a material diminution in Executive’s function as in effect immediately prior to the effective date of the Change in Control; provided, however, that a change in
Executive’s title or reporting relationships shall not constitute a Constructive Termination; 
 (b) a material
reduction in Executive’s Base Salary, unless the reduction is made pursuant to an across-the-board reduction of the base salaries of all executive officers of the Company of no more than ten percent (10%); 

(c) an adverse change in Executive’s business location that increases his or her one way commute by more than thirty-five
(35) miles; 
 (d) a material breach by the Company of any provision of this Agreement; or 

(e) any failure by the Company to obtain the assumption of the material terms of this Agreement by any successor or assign of the
Company, such assumption to be effective no later than the effective date of a Change in Control. 
 5.8
“Covered Termination” means an Involuntary Termination Without Cause or a Constructive Termination, either of which occurs within twenty-four (24) months following the effective date of a Change in Control.

 5.9 “Involuntary Termination Without Cause” means Executive’s dismissal or discharge for
reasons other than Cause (and other than as a result of death or disability) resulting in a “separation from service” with the Company within the meaning of Treasury Regulation Section 1.409A-1(h). For this purpose, “Cause”
means that, in the reasonable determination of the Company, Executive (i) has committed an intentional act or acted with gross negligence that has materially injured the business of the Company; (ii) has intentionally refused or failed to
follow lawful and reasonable directions of the Board or the appropriate individual to whom Executive reports; (iii) has willfully and habitually neglected Executive’s duties for the Company; or (iv) has been convicted of a felony
involving moral turpitude that is likely to inflict or has inflicted material injury on the business of the Company. Notwithstanding the foregoing, Cause shall not exist based on conduct described in clause (ii) or (iii) unless the conduct
described in such clause has not been cured within fifteen (15) days following Executive’s receipt of written notice from the Company specifying the particulars of the conduct constituting Cause. 

  
 8. 

 ARTICLE 6 
 GENERAL PROVISIONS 
 6.1 Employment
Status. This Agreement does not constitute a contract of employment or impose upon Executive any obligation to remain as an employee, or impose on the Company any obligation (i) to retain Executive as an employee, (ii) to change the
status of Executive as an at-will employee or (iii) to change the Company’s policies regarding termination of employment. 
 6.2 Notices. Any notices provided hereunder must be in writing, and such notices or any other written communication shall be deemed effective upon the earlier of personal delivery (including
personal delivery by facsimile) or the third day after mailing by first class mail, to the Company at its primary office location or to Executive at Executive’s address as listed in the Company’s payroll records. Any payments made by the
Company to Executive under the terms of this Agreement shall be delivered to Executive either in person or at the address as listed in the Company’s payroll records. 
 6.3 Severability. Whenever possible, each provision of this Agreement will be interpreted in such manner as to be effective and valid under applicable law, but if any provision of this Agreement is
held to be invalid, illegal or unenforceable in any respect under any applicable law or rule in any jurisdiction, such invalidity, illegality or unenforceability will not affect any other provision or any other jurisdiction, but this Agreement will
be reformed, construed and enforced in such jurisdiction as if such invalid, illegal or unenforceable provisions had never been contained herein. 
 6.4 Waiver. If either party should waive any breach of any provision of this Agreement, he or it shall not thereby be deemed to have waived any preceding or succeeding breach of the same or any
other provision of this Agreement. 
 6.5 Arbitration. Unless otherwise prohibited by law or specified below, all
disputes, claims and causes of action, in law or equity, arising from or relating to this Agreement or its enforcement, performance, breach, or interpretation, including but not limited to statutory claims, shall be resolved solely and exclusively
by final and binding arbitration held in San Francisco, California through JAMS, Inc. (“JAMS”) under the then-existing JAMS employment law arbitration rules. However, nothing in this Section 6.5 is intended to prevent
either party from obtaining injunctive relief in court to prevent irreparable harm pending the conclusion of any such arbitration. By agreeing to this arbitration procedure, both Executive and the Company waive the right to resolve any such
dispute through a trial by jury or judge, or administrative proceeding. 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, to include the arbitrator’s essential findings and conclusions and a statement of the award. The arbitrator shall be authorized to award any or all remedies that Executive or the Company
would be entitled to seek in a court of law. The Company shall pay all JAMS’ arbitration fees in excess of the amount of court fees that would be required if the dispute were decided in a court of law. Each party in any such arbitration shall
be responsible for its own attorneys’ fees, costs and necessary disbursement; 

  
 9. 

 
provided, however, that in the event one party refuses to arbitrate and the other party seeks to compel arbitration by court order, if such other party prevails, it shall be entitled to
recover reasonable attorneys’ fees, costs and necessary disbursements. Pursuant to California Civil Code Section 1717, each party warrants that it was represented by counsel in the negotiation and execution of this Agreement, including the
attorneys’ fees provision herein. 
 6.6 Complete Agreement. This Agreement, including Exhibit A,
Exhibit B and Exhibit C, constitutes the entire agreement between Executive and the Company and is the complete, final, and exclusive embodiment of their agreement with regard to this subject matter, wholly superseding all written
and oral agreements with respect to payments and benefits to Executive in the event of employment termination. It is entered into without reliance on any promise or representation other than those expressly contained herein. 

6.7 Amendment or Termination of Agreement; Continuation of Agreement. This Agreement may be changed or terminated only upon the
mutual written consent of the Company and Executive. The written consent of the Company to a change or termination of this Agreement must be signed by an executive officer of the Company (other than Executive) after such change or termination has
been approved by the Board or duly authorized committee thereof. Unless so terminated, this Agreement shall continue in effect for as long as Executive continues to be employed by the Company or by any surviving entity following any Change in
Control. In other words, if, following a Change in Control, Executive continues to be employed by the surviving entity without a Covered Termination and the surviving entity then undergoes a Change in Control, following which Executive is terminated
by the subsequent surviving entity in a Covered Termination, then Executive shall receive the benefits described in Article 2 hereof. 
 6.8 Counterparts. This Agreement may be executed in separate counterparts, any one of which need not contain signatures of more than one party, but all of which taken together will constitute one
and the same Agreement. Signatures transmitted via facsimile shall be deemed equivalent to originals. 
 6.9 Headings.
The headings of the Articles and Sections hereof are inserted for convenience only and shall not be deemed to constitute a part hereof nor to affect the meaning thereof. 
 6.10 Successors and Assigns. This Agreement is intended to bind and inure to the benefit of and be enforceable by Executive, and the Company, and any surviving entity resulting from a Change in
Control and upon any other person who is a successor by merger, acquisition, consolidation or otherwise to the business formerly carried on by the Company, and their respective successors, assigns, heirs, executors and administrators, without regard
to whether or not such person actively assumes any rights or duties hereunder; provided, however, that Executive may not assign any duties hereunder and may not assign any rights hereunder without the written consent of the Company, which
consent shall not be withheld unreasonably. 
 6.11 Choice of Law. All questions concerning the construction, validity
and interpretation of this Agreement will be governed by the law of the State of California, without regard to such state’s conflict of laws rules. 

  
 10.

 6.12 Construction of Agreement. In the event of a conflict between the text of the
Agreement and any summary, description or other information regarding the Agreement, the text of the Agreement shall control. 

6.13 Loss of ISO Status. The Executive acknowledges and agrees that by virtue of entering into this Agreement, all stock options
awarded to Executive prior to the Original Date and/or Effective Date of this Agreement and which are both (a) designated “Incentive Stock Options” and (b) “In the Money” by virtue of the fact that such options have an
exercise price per share less than the fair market value of one share of the Company’s common stock as of the Original Date and/or Effective Date of this Agreement, may lose their status as tax favored incentive stock options. Executive further
acknowledges and agrees that upon exercise of such options, to the extent the options are not incentive stock options, Executive will have to make suitable arrangements with the Company to satisfy all applicable federal and state income and
employment withholding taxes owing as a result of such exercise. 
 6.14 Circular 230 Disclaimer. THE
FOLLOWING DISCLAIMER IS PROVIDED IN ACCORDANCE WITH THE INTERNAL REVENUE
SERVICE’S CIRCULAR 230 (31 C.F.R. PART 10). ANY TAX ADVICE CONTAINED IN THIS
AGREEMENT IS INTENDED TO BE PRELIMINARY, FOR DISCUSSION PURPOSES ONLY, AND
NOT FINAL. ANY SUCH ADVICE IS NOT INTENDED TO BE USED FOR
MARKETING, PROMOTING OR RECOMMENDING ANY TRANSACTION OR FOR THE USE OF
ANY PERSON IN CONNECTION WITH THE PREPARATION OF ANY TAX RETURN.
ACCORDINGLY, THIS ADVICE IS NOT INTENDED OR WRITTEN TO BE USED, AND
IT CANNOT BE USED, BY ANY PERSON FOR THE PURPOSE OF AVOIDING
TAX PENALTIES THAT MAY BE IMPOSED ON SUCH PERSON.  

IN WITNESS WHEREOF, the parties have executed this Agreement on the Effective Date
written above. 
  

							
	ONYX PHARMACEUTICALS, INC.	 		 	EXECUTIVE
				
	By:	 	 /s/ Suzanne M. Shema
	 		 	 /s/ Kaye Foster-Cheek

	Name:	 	Suzanne M. Shema	 		 	      Kaye Foster-Cheek
	Title:	 	Senior Vice President, General Counsel	 		 	

 Exhibit A: Release (Individual Termination — Age 40 or Older) 

Exhibit B: Release (Individual and Group Termination — Under Age 40) 
 Exhibit C: Release (Group Termination — Age 40 or Older) 

  
 11.

 EXHIBIT A  

RELEASE 

(INDIVIDUAL TERMINATION — AGE 40 OR OLDER) 

 Certain capitalized terms used in this Release are defined in the Amended and Restated Executive Change in Control Severance
Benefits Agreement (the “Agreement”) which I have executed and of which this Release is a part. 
 I
hereby acknowledge and reaffirm my continuing obligations under the Company’s proprietary information and inventions agreement that I signed in connection with my employment. 

I 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 my release of any claims, including but not limited to my release of unknown and unsuspected
claims. 
 Except as otherwise set forth in this Release, in exchange for the benefits I will receive under the Agreement which
I am not otherwise entitled to receive, and as required by the Agreement, I hereby generally and completely release, acquit and forever discharge the Company and its parent, subsidiary, and affiliated entities, along with its and their predecessors
and successors and their respective directors, officers, employees, shareholders, stockholders, partners, agents, attorneys, insurers, affiliates and assigns (collectively, the “Released Parties”), of and from any and all
claims, liabilities and obligations, both known and unknown, that arise from or are in any way related to events, acts, conduct, or omissions occurring at any time prior to and including the date that I sign this Release (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, other incentive compensation, vacation pay and the redemption thereof, expense reimbursements, severance payments, fringe benefits, stock, stock
options, or any other ownership or equity 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 (including but not limited to claims based on or
arising from the Agreement); (d) all tort claims, including but not limited to claims for fraud, defamation, emotional distress, and discharge in violation of public policy; and (e) all federal, state, and local statutory claims, including
but not limited to claims for discrimination, harassment, retaliation, attorneys’ fees, or other claims arising under the federal Civil Rights Act of 1964 (as amended), the federal Americans with Disabilities Act of 1990 (as amended), the
federal Age Discrimination in Employment Act of 1967 (as amended) (the “ADEA”), 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 

  
 1. 

 
agreement with the Company to which I am a party, the charter, bylaws, or under applicable law; (b) any rights which are not waivable as a matter of law; or (c) any claims for breach of
the Agreement arising after the date that I sign the Release. In addition, nothing in this Release prevents me from filing, cooperating with, or participating in any investigation or proceeding before the Equal Employment Opportunity Commission, the
Department of Labor, the California Department of Fair Employment and Housing, or any other government agency, except that I hereby waive my right to any monetary benefits in connection with any such claim, charge, investigation, or proceeding. 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 acknowledge that I am knowingly and voluntarily waiving and releasing any rights I may have under the ADEA, that the consideration
given for the Release is in addition to anything of value to which I was already entitled, and that I have been advised by this writing, as required by the ADEA, that: (a) my release of claims does not apply to any rights or claims that arise
after the date I sign this Release; (b) I should consult with an attorney prior to signing this Release (although I may choose voluntarily not to do so); (c) I have twenty-one (21) days to consider this Release (although I may choose
voluntarily to sign it sooner); (d) I have seven (7) days following the date I sign this Release to revoke it by providing written notice of my revocation to the Chairman of the Company’s Board of Directors; and (e) this Release
will not be effective until the date upon which the revocation period has expired unexercised, which will be the eighth day after I sign this Release (the “Effective Date”). 

I hereby represent that I have been paid all compensation owed and for all hours worked, have received all the leave and leave benefits
and protections for which I am eligible, pursuant to the Family and Medical Leave Act or otherwise, and have not suffered any on-the-job injury for which I have not already filed a workers’ compensation claim. 

In addition to the above: (a) I agree not to disparage the Company or any of the other Released Parties in any manner likely
to be harmful to its or their business, business reputations, or personal reputations; (b) I agree to return, no later than my employment termination date, all Company property, documents, information, and materials, including but not
limited to any and all embodiments (e.g., notes, computer-recorded information) of the Company’s proprietary or confidential information (and all reproductions thereof, in whole or in part) in my possession or control; and (c) I will not
voluntarily provide assistance, information or advice, directly or indirectly (including through agents or attorneys), to any person or entity in connection with any claim or cause of action of any kind brought against the Company or its officers,
directors, or affiliated entities, nor induce or encourage any person or entity to bring such claims; provided that it shall not violate this covenant if I testify truthfully when required to do so by a valid subpoena or under similar compulsion of
law. 
  

			
	EXECUTIVE
	
	  

		
	Date:	 	  

  
 2. 

 EXHIBIT B 

RELEASE 

(INDIVIDUAL AND GROUP TERMINATION — UNDER
AGE 40) 
 Certain capitalized terms used in this Release are defined in the Amended and Restated Executive
Change in Control Severance Benefits Agreement (the “Agreement”) which I have executed and of which this Release is a part. 
 I hereby acknowledge and reaffirm my continuing obligations under the Company’s proprietary information and inventions agreement that I signed in connection with my employment. 

I 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 my release of any claims, including but not limited to my release of unknown and unsuspected
claims. 
 Except as otherwise set forth in this Release, in exchange for the benefits I will receive under the Agreement which
I am not otherwise entitled to receive, and as required by the Agreement, I hereby generally and completely release, acquit and forever discharge the Company and its parent, subsidiary, and affiliated entities, along with its and their predecessors
and successors and their respective directors, officers, employees, shareholders, stockholders, partners, agents, attorneys, insurers, affiliates and assigns (collectively, the “Released Parties”), of and from any and all
claims, liabilities and obligations, both known and unknown, that arise from or are in any way related to events, acts, conduct, or omissions occurring at any time prior to and including the date that I sign this Release (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, other incentive compensation, vacation pay and the redemption thereof, expense reimbursements, severance payments, fringe benefits, stock, stock
options, or any other ownership or equity 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 (including but not limited to claims based on or
arising from the Agreement); (d) all tort claims, including but not limited to claims for fraud, defamation, emotional distress, and discharge in violation of public policy; and (e) all federal, state, and local statutory claims, including
but not limited to claims for discrimination, harassment, retaliation, attorneys’ fees, or other claims arising under the federal Civil Rights Act of 1964 (as amended), the federal Americans with Disabilities Act of 1990 (as amended), 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 under applicable law; 

  
 1. 

 (b) any rights which are not waivable as a matter of law; or (c) any claims for breach of the
Agreement arising after the date that I sign the Release. In addition, nothing in this Release prevents me from filing, cooperating with, or participating in any investigation or proceeding before the Equal Employment Opportunity Commission, the
Department of Labor, the California Department of Fair Employment and Housing, or any other government agency, except that I hereby waive my right to any monetary benefits in connection with any such claim, charge, investigation or proceeding. 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 acknowledge that the consideration given under the Agreement for the waiver and release in the preceding paragraph hereof is in
addition to anything of value to which I was already entitled. I further acknowledge that I have been advised by this writing that: (a) my waiver and release do not apply to any rights or claims that may arise on or after the date I sign this
Release; (b) I have the right to consult with an attorney prior to signing this Release (although I may choose voluntarily not to do so); and (C) I have twenty-one (21) days to consider this Release (although I may choose voluntarily
to sign this Release earlier). This Release will be effective as of the date that I sign and return it to the Company (the “Effective Date”). 
 I hereby represent that I have been paid all compensation owed and for all hours worked, have received all the leave and leave benefits and protections for which I am eligible, pursuant to the Family and
Medical Leave Act or otherwise, and have not suffered any on-the-job injury for which I have not already filed a workers’ compensation claim. 
 In addition to the above: (a) I agree not to disparage the Company or any of the other Released Parties in any manner likely to be harmful to its or their business, business reputations, or
personal reputations; (b) I agree to return, no later than my employment termination date, all Company property, documents, information, and materials, including but not limited to any and all embodiments (e.g., notes, computer-recorded
information) of the Company’s proprietary or confidential information (and all reproductions thereof, in whole or in part) in my possession or control; and (c) I will not voluntarily provide assistance, information or advice, directly or
indirectly (including through agents or attorneys), to any person or entity in connection with any claim or cause of action of any kind brought against the Company or its officers, directors, or affiliated entities, nor induce or encourage any
person or entity to bring such claims; provided that it shall not violate this covenant if I testify truthfully when required to do so by a valid subpoena or under similar compulsion of law. 

 

			
	EXECUTIVE
	
	  

		
	Date:	 	  

  
 2. 

 EXHIBIT C 

RELEASE 

(GROUP TERMINATION — AGE 40 OR OLDER) 

Certain capitalized terms used in this Release are defined in the Amended and Restated Executive Change in Control Severance Benefits
Agreement (the “Agreement”) which I have executed and of which this Release is a part. 
 I hereby
acknowledge and reaffirm my continuing obligations under the Company’s proprietary information and inventions agreement that I signed in connection with my employment. 
 I 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 my release of any claims, including but not limited to my release of unknown and unsuspected claims. 

Except as otherwise set forth in this Release, in exchange for the benefits I will receive under the Agreement which I am not otherwise
entitled to receive, and as required by the Agreement, I hereby generally and completely release, acquit and forever discharge the Company and its parent, subsidiary, and affiliated entities, along with its and their predecessors and successors and
their respective directors, officers, employees, shareholders, stockholders, partners, agents, attorneys, insurers, affiliates and assigns (collectively, the “Released Parties”), of and from any and all claims,
liabilities and obligations, both known and unknown, that arise from or are in any way related to events, acts, conduct, or omissions occurring at any time prior to and including the date that I sign this Release (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, other incentive compensation, vacation pay and the redemption thereof, expense reimbursements, severance payments, fringe benefits, stock, stock
options, or any other ownership or equity 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 (including but not limited to claims based on or
arising from the Agreement); (d) all tort claims, including but not limited to claims for fraud, defamation, emotional distress, and discharge in violation of public policy; and (e) all federal, state, and local statutory claims, including
but not limited to claims for discrimination, harassment, retaliation, attorneys’ fees, or other claims arising under the federal Civil Rights Act of 1964 (as amended), the federal Americans with Disabilities Act of 1990 (as amended), the
federal Age Discrimination in Employment Act of 1967 (as amended) (the “ADEA”), 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 

  
 1. 

 
agreement with the Company to which I am a party, the charter, bylaws, or under applicable law; (b) any rights which are not waivable as a matter of law; or (c) any claims for breach of
the Agreement arising after the date that I sign the Release. In addition, nothing in this Release prevents me from filing, cooperating with, or participating in any investigation or proceeding before the Equal Employment Opportunity Commission, the
Department of Labor, the California Department of Fair Employment and Housing, or any other government agency, except that I hereby waive my right to any monetary benefits in connection with any such claim, charge, investigation, or proceeding. 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 acknowledge that I am knowingly and voluntarily waiving and releasing any rights I may have under the ADEA, that the consideration
given for the Release is in addition to anything of value to which I was already entitled, and that I have been advised by this writing, as required by the ADEA, that: (a) my release of claims does not apply to any rights or claims that arise
after the date I sign this Release; (b) I should consult with an attorney prior to signing this Release (although I may choose voluntarily not to do so); (c) I have forty-five (45) days to consider this Release (although I may choose
voluntarily to sign it sooner); (d) I have seven (7) days following the date I sign this Release to revoke it by providing written notice of my revocation to the Chairman of the Company’s Board of Directors; and (e) this Release
will not be effective until the date upon which the revocation period has expired unexercised, which will be the eighth day after I sign this Release (the “Effective Date”). 

In addition, I acknowledge that I have received with this Release a written disclosure as required under Title 29 U.S. Code
Section 626(f)(1)(H)), which includes information concerning the job titles and ages of all employees who were terminated as part of this group termination, the criteria used by the Company in selecting employees for the group termination, and
the job titles and ages of all employees of the Company in the same job classification or organizational unit who were not terminated as part of this group termination. 
 I hereby represent that I have been paid all compensation owed and for all hours worked, have received all the leave and leave benefits and protections for which I am eligible, pursuant to the Family and
Medical Leave Act or otherwise, and have not suffered any on-the-job injury for which I have not already filed a workers’ compensation claim. 

  
 2. 

 In addition to the above: (a) I agree not to disparage the Company or any of the
other Released Parties in any manner likely to be harmful to its or their business, business reputations, or personal reputations; (b) I agree to return, no later than my employment termination date, all Company property, documents,
information, and materials, including but not limited to any and all embodiments (e.g., notes, computer-recorded information) of the Company’s proprietary or confidential information (and all reproductions thereof, in whole or in part) in my
possession or control; and (c) I will not voluntarily provide assistance, information or advice, directly or indirectly (including through agents or attorneys), to any person or entity in connection with any claim or cause of action of any kind
brought against the Company or its officers, directors, or affiliated entities, nor induce or encourage any person or entity to bring such claims; provided that it shall not violate this covenant if I testify truthfully when required to do so by a
valid subpoena or under similar compulsion of law. 
  

			
	EXECUTIVE
	
	  

		
	Date:	 	  

  
 3.Letter Agreement between the Company and John Osborn

 Exhibit 10.23 

 

			
	 

	  	 MAIN 650.266.0000 FAX 650.266.0100

249 EAST GRAND AVENUE —
SOUTH SAN FRANCISCO — CALIFORNIA 94080

 May 18, 2012 
 John Osborn 
 Dear John: 
 On behalf of Onyx Pharmaceuticals, it is a great pleasure to extend you this offer of employment as the Senior Vice President, Global Corporate Affairs, reporting to Tony Coles. In making this offer, we
are expressing our enthusiastic support for the skills and commitment you will bring to our exciting team. Please note that this offer, in its entirety, is contingent on approval by the Compensation Committee of Onyx’s Board of Directors. We
are pleased to offer you the following: 
 Salary: Your semi-monthly salary will be $17,916.66, totaling $430,000 per year. Future
increases will be awarded at the Company’s discretion on the basis of performance. 
 Bonus: You are eligible, at the end of each
year, to receive an annual bonus amount of up to 45% of your base salary if Onyx achieves its corporate objectives and you achieve the performance objectives set for you. If you leave at any time during a year, you are not eligible for any prorated
amount of your unearned target bonus for that year. Bonus payments will be subject to required deductions and withholdings. The Company shall have the sole discretion to determine whether you have earned any bonus set forth in this paragraph and, if
so, the amount of any such bonus. 
 At Onyx, our salary merit increases, equity grants, and potential bonus amounts are based upon the
assumption that an employee has provided services to the Company for the entire calendar year. Therefore, if you join Onyx at any time between January 1 and September 30 of the calendar year, your potential salary merit increase, equity
grants, and potential bonus, if any is awarded, will be prorated for the actual amount of service you provide during that calendar year. If you join Onyx after September 30 of the calendar year, you will not be considered eligible for a salary
merit increase, equity grant, or bonus for that performance year. 
 Stock: Subject to approval by our Board of Directors, you will be
granted an option to purchase 87,360 Onyx shares at the market price on your start date. The options will be issued pursuant to the Company’s standard Option Agreement. These options will be exercisable in installments based upon your continued
employment as follows: 25% after the first twelve months, l/48th per month thereafter, for a total of a four-year vesting period. In addition to these options, Onyx employees are eligible for annual option grants based on individual performance. If
you join Onyx after September 30 of any calendar year, you will not be considered eligible for an annual stock grant for that performance year. 
 We will also recommend to the Compensation Committee of our Board of Directors, at its first meeting after you join the Company, that you be granted 11,000 restricted shares of Onyx stock on that date,
vesting of which will be determined by the Board of Directors based on your and the Company’s achievement of certain performance objectives detailed in the Grant Agreement. 

  

			
	  
	  	onyx-pharm.com

 

 
  Page
 2
 
 Osborn, John 
 May 15, 2012 
  

 Benefits: You will be eligible to participate in the Company’s medical, dental, vision, EAP,
life insurance, and short and long-term disability insurance programs pursuant to the terms of these plans and our vacation, sick and holiday programs in accordance with company policy. You may also sign up to participate in our 401(k) Retirement
Savings Plan and our Employee Stock Purchase Plan. In addition, you may choose to have additional Voluntary Term Life coverage for you and your eligible dependents. 
 Sign-on Bonus: As soon as is administratively practicable after your start date, Onyx will pay you a Sign-on Bonus in the amount of one hundred thirty eight thousand dollars ($138,000), less
appropriate deductions and withholding. In the event that your employment with the company terminates before the one-year anniversary of your start date, you will be expected to repay the net amount of your Sign-on Bonus in full. 

Housing Assistance: Onyx will provide you with Housing Assistance for your first two (2) years of employment, totaling no more than one
hundred eight thousand dollars ($108,000), less applicable deductions and withholding. This assistance may take one of two forms, or a combination of the two, provided that the aggregate gross benefit paid does not exceed $108,000 and that no
benefit is paid after the two-year anniversary of your start date. The first allowable form of payment is the direct provision of corporate housing. The second allowable form of payment is coverage of airfare and hotel expenses related to travel
between your Pennsylvania home and Onyx’s South San Francisco office, all such travel to be conducted in accordance with applicable Onyx policy. 
 Relocation: Onyx will provide you with a net Relocation Allowance of $200,000 for expenses involved in relocating to the San Francisco Bay Area. The payment will be made according to the following
schedule: 
  

	 	•	 	 Twenty-five percent (25%) or $50,000 as soon as practicable after you start work at Onyx. 

 

	 	•	 	 The remaining seventy-five (75%) or $150,000 will be paid as: 1) Rental Subsidy and/or 2) as Home Purchase Assistance.

  

	 	•	 	 Under the terms of the Rental Subsidy, Onyx will pay you $50,000 annually during each of the first three (3) years; equal payments of $12,500 per
quarter, for a balance of $150,000 to be used as deemed appropriate for rental assistance and/or in conjunction with home purchase assistance in the San Francisco Bay Area. 

 

	 	•	 	 The combined balance of the payments for the Rental Subsidy and/or Home Purchase Assistance shall in no event exceed the balance of the rental
subsidy/home purchase assistance of $150,000. 

  

	 	•	 	 Onyx payroll will include the funds as an allowance on your paycheck. 

 In addition, Onyx will pay for the actual movement of your household goods, as well as your and your family’s one-way travel to the Bay Area, in accordance with company policy. You will be required
to reimburse 100% of the Relocation Allowance and movement of household goods and one-way travel if your employment with the Company terminates within 1 year of your start date. If your employment terminates after the first anniversary of your start
date but within 2 years of your start date, you will be required to repay 50% of the Relocation Allowance and actual cost of movement of household goods and one-way travel. This offer is contingent upon your signing our Employee Confidential
Information and Inventions Assignment Agreement and providing legally required evidence of your right to work in the United States, as well as, Onyx’s successful completion of your references and background check. We ask that you return one
signed copy of the enclosed Employee Confidential Information and Inventions Assignment Agreement and this offer letter. In consideration of your employment, you also agree to conform to the rules and standards of the Company. 

  

			
	  
	  	onyx-pharm.com

 

 
  Page
 3
 
 Osborn, John 
 May 15, 2012 
  

 In accordance with Federal Law, all new employees are required to present evidence of their eligibility
to be employed in the United States. Accordingly, we request that you provide us with a copy of an appropriate document for this purpose within 72 hours of your employment date. 
 Your employment is “at will.” You or Onyx may terminate your employment at any time, with or without cause, and with or without notice. This letter, when signed by you, will constitute the
agreement between Onyx and you respecting the position, and supersedes all prior negotiations and agreements pertaining to the position, whether written or oral. No employee or representative of the Company, other than its CEO (or designee), has the
authority to make any expressed or implied agreement contrary to the foregoing. Further, the CEO at Onyx may not alter the at-will nature of the employment relationship or enter into any employment agreement for a specific time unless the CEO (or
designee) and you both sign a written agreement that clearly and expressly specifies the intent of doing so. 
 We are very enthusiastic about
the prospect of having you on the Onyx team and we are confident that you will make a valuable contribution to the success of the company. 
 If
this arrangement is acceptable to you, please indicate your acceptance of the terms of this employment offer by signing and dating one copy and returning it, along with the signed Employee Confidential Information and Inventions Assignment
Agreement, to me. This offer of employment will expire on Tuesday, May 29, 2012 unless accepted prior to that date. 
 Should you have any
questions regarding the provisions of employment, please contact me at (650) 266-2543. 
 Sincerely, 

/s/ N. Anthony Coles,
M.D.                             
 N. Anthony Coles, M.D. 
 President and Chief Executive Officer 

I accept Onyx Pharmaceuticals’ offer of employment on the terms stated. 

 

					
	 /s/ John Osborn
	  	 23 May 2012
	 	 1 June 2012

	Accepted (signature)	  	Date	 	Estimated Start Date

  

			
	  
	  	onyx-pharm.com

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