Document:

EX-10.12

 Exhibit 10.12 

ATARA BIOTHERAPEUTICS, INC. 

EMPLOYMENT AGREEMENT 

This Employment Agreement (the “Agreement”) is made and entered into as of March 11, 2014, by and between Atara
Biotherapeutics, Inc., a Delaware corporation (the “Company”) and John McGrath (“Executive”). From and following the date hereof, this Agreement shall replace and supersede that certain letter agreement between the
Company and Executive dated December 5, 2012 (the “Prior Agreement”). 

RECITALS 

WHEREAS, the Company and Executive are currently parties to the Prior Agreement and wish to enter into
this Agreement as set forth herein in connection with a share exchange, pursuant to which each of Nina Biotherapeutics, Inc., Pinta Biotherapeutics, Inc. and Santa Maria Biotherapeutics, Inc. (each a “Project Entity”) shall become
wholly-owned subsidiaries of the. Company (the “Share Exchange”); 
 NOW
THEREFORE, in consideration of the mutual promises and covenants contained herein and certain other good and valuable consideration, the receipt and sufficiency of which are hereby acknowledged, the parties agree as
follows: 
 AGREEMENT 

1. Duties and Scope of Employment. Executive will remain employed as the Company’s Chief Financial Officer, reporting to
the Company’s Chief Executive Officer. This is a full-time position. Executive’s responsibilities will encompass, but are not limited to finance, facilities, accounting, human resources and other functions. While Executive renders services
to the Company, Executive will not engage in any other employment, consulting or other business activity (whether full-time or part-time) that would create a conflict of interest with the Company. By signing this Agreement, Executive reaffirms to
the Company that Executive has no contractual commitments or other legal obligations that would prohibit Executive from performing his duties for the Company. 

2. Cash Compensation. The Company will pay Executive a salary at the rate of $280,000 per year (the “Base
Salary”), payable in accordance with the Company’s standard payroll schedule. This salary will be subject to adjustment pursuant to the Company’s employee compensation policies in effect from time to time. In addition, Executive
will be eligible to be considered for an incentive bonus for each fiscal year of the Company. The bonus (if any) will be awarded based on the achievement of milestones to be established mutually by Executive and the Chief Executive Officer.
Executive’s target bonus will be equal to 25% of the Base Salary. Any bonus earned for a fiscal year will be paid within 2 1⁄2 months after the close of
that fiscal year, but only if Executive is still employed by the Company at the time of payment. The determinations of the Company with respect to Executive’s bonus will be final and binding. 

3. Employee Benefits. The Company’s benefits, payroll and other human resource management services will continue to be
provided through TriNet Employer Group, Inc. (“TriNet”), a professional employer organization. As a result of the Company’s arrangement with TriNet, TriNet will be considered Executive’s “employer of record” for
these purposes. In addition, Executive will be entitled to accrue up to 160 hours of paid time off (PTO) in accordance with the Company’s paid time off policy, as in effect from time to tittle. 

  
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 4. Equity Compensation. Executive currently holds restricted stock units (the
“Prior Awards”) covering 218,437 shares of the Company’s common stock (post Share Exchange). These equity awards will continue to be governed by the terms of the applicable equity plans and award agreements 

5. Taxes. All payments made by the Company (or any Company affiliate) to Executive or Executive’s estate or beneficiaries
will be subject to tax withholding pursuant to any applicable laws or regulations. Executive will be solely liable and responsible for the payment of Executive’s taxes arising as a result of any payment provided to Executive in connection with
Executive’s employment including without limitation any unexpected or adverse tax consequences. Any such payments or benefits provided to Executive are intended to be exempt from or comply with the requirements of section 409A of the Code. In
the event any payment or benefit is deemed to be subject to section 409A of the Code, Executive consents to the Company adopting such conforming amendments as the Company deems necessary, in its reasonable discretion, to comply with section 409A of
the Code. In addition, if Executive is a specified employee (within the meaning of Code Section 409A) at the time of Executive’s separation from service, then to the extent necessary to comply with Code Section 409A and avoid the
imposition of taxes under Code Section 409A, the payment of certain benefits owed to Executive under this Agreement will be delayed and instead paid (without interest) to Executive upon the earlier of the first business day of the seventh month
following Executive’s separation from service or Executive’s death. Additionally, no payments or benefits will constitute excess parachute payments as defined under Code Section 280G. 

6. Proprietary Information and Inventions Agreement. Executive previously signed standard Proprietary Information and Inventions
Agreements with the Company and each Entity dated as of January 22, 2013 (collectively the “PIIA”), which remain in full force and effect pursuant to its terms. 

7. Employment Relationship. Employment with the Company is for no specific period of time. Executive’s employment with the
Company is “at will,” meaning that either Executive or the Company may terminate Executive’s employment at any time and for any reason, with or without cause. Any contrary representations that may have been made to Executive is
superseded by this Employment Agreement. This is the full and complete agreement between Executive and the Company on this term. Although Executive’s job duties, title, compensation and benefits, as well as the Company’s personnel policies
and procedures, may change from time to time, the “at will” nature of Executive’s employment may only be changed in an express written agreement signed by Executive and a duly authorized officer of the Company (other than Executive).

 8. Miscellaneous. All forms of compensation referred to in this Employment Agreement are subject to reduction to reflect
applicable withholding and payroll taxes and other deductions required by law. Executive is encouraged to obtain Executive’s own tax advice regarding Executive’s compensation from the Company. Executive agrees that the Company does not
have a duty to design its compensation policies in a manner that minimizes Executive’s tax liabilities, and Executive will not make any claim against the Company or its Board of Directors related to tax liabilities arising from Executive’s
compensation. 
 9. Interpretation, Amendment and Enforcement. This Agreement, and any equity agreements referred to herein,
supersede and replace the Prior Agreement and any other prior agreements, representations or understandings (whether written, oral, implied or otherwise) between Executive and the Company and, together with the PIIA, constitutes the complete
agreement between Executive and the Company regarding the subject matter set forth herein. This Agreement may not be amended or modified, except by an express written agreement signed by both Executive and a duly

  
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authorized officer of the Company. The terms of this Agreement and the resolution of any disputes as to the meaning, effect, performance or validity of this Agreement arising out of, related to,
or in any way connected with, this Agreement, Executive’s employment with the Company or any other relationship between Executive and the Company (the “Disputes”) will be governed by California law, excluding laws relating to
conflicts or choice of law. Executive and the Company submit to the exclusive personal jurisdiction of the federal and state courts located in California in connection with any Dispute or any claim related to any Dispute. 

10. Severance. 

(a) General. If Executive is subject to a Termination Without Cause following a Change in Control, then Executive will be
entitled to the benefits described in this Section 10. However, this Section 10 will not apply unless Executive (i) has returned all Company property in Executive’s possession, (ii) as a result of such Termination Without
Cause following a Change in Control, is no longer an employee or consultant of the Company, any Entity, or any Other Entity, (iii) has executed a general release of all employment-related claims that Executive may have against the Company or
persons affiliated with the Company and (iv) if so requested, has executed a genera’ release of all employment-related claims that Executive may have against each Entity or persons affiliated with such Entity. Executive must execute and
return any such releases on or before the dates specified in the corresponding release (in each case, the “Release Deadline”). The Release Deadline will in no event be later than 50 days after Executive’s Separation. 

(b) Cash Severance on Termination Without Cause. If Executive is subject to a Termination Without Cause following a Change in
Control, then the Company will pay Executive a lump-sum severance payment equal to six months’ Base Salary, at Executive’s final Base Salary rate. Such amount will be paid to Executive in accordance with the Company’s standard payroll
procedures within 60 days after Executive’s Separation. However, if the 60-day period described in the preceding sentence spans two calendar years, then the payment will in any event be made in the second calendar year. 

11. Definitions. The following terms have the mewling set forth below wherever they are used in this Agreement: 

“Cause” means (a) Executive’s unauthorized use or disclosure of the Company’s confidential information or
trade secrets, which use or disclosure causes material harm to the Company, (b) Executive’s material breach of any agreement between Executive and the Company, (c) Executive’s material failure to comply with the Company’s
written policies or rules, (d) Executive’s conviction of, or Executive’s plea of “guilty” or “no contest” to, a felony under the laws of the United States or any State, (e) Executive’s gross negligence or
willful misconduct in connection with the performance of Executive’s duties for the Company, which negligence or misconduct results in material harm to the Company, (f) Executive’s continuing failure to perform lawful and reasonable
assigned duties after receiving written notification of the failure from the Company and a reasonable opportunity to correct such failure following Executive’s receipt of that notice, or (g) Executive’s failure to cooperate in good
faith with a governmental or internal investigation of the Company or its directors, officers or employees, if the Company has requested Executive’s cooperation. 

“Change in Control” means, 

(i) the merger, consolidation, recapitalization, or reorganization of the Company, other than a merger, consolidation,
recapitalization or reorganization which would result in the voting securities of the Company outstanding immediately prior 

  
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thereto continuing to represent (either by remaining outstanding or by being converted into voting securities of the surviving entity) more than fifty percent (50%) of the total voting power
represented by the voting securities of the Company or such surviving entity outstanding immediately after such merger, consolidation, recapitalization or reorganization; 

(ii) the sale or disposition by the Company’s stockholders of more than fifty percent (50%) of the total
voting securities of the Company; 
 (iii) a complete liquidation or dissolution of the Company; 

(iv) the sale or disposition by the Company of all or substantially all of its assets; or 

(v) the exclusive licensing to a third party of all or substantially all of the Company’s intellectual property.

 Notwithstanding the foregoing, the following transactions shall not constitute a Change in Control: (i) a transaction the sole
purpose of which is to change the state of the Company’s incorporation or to create a holding company that will be owned in substantially the same proportions by the persons who held the Company’s securities immediately before such
transaction; (ii) a transaction or series of related transactions involving the sale of securities by the Company primarily for financing purposes; (iii) a merger or consolidation involving the Company and one or more companies under
common management control with the Company; or (iv) an IPO. If the timing of payments provided under an RSU Award agreement is based on or triggered by a Change in Control then, to extent necessary to avoid violating Code Section 409A, a
Change in Control must also constitute a “change in control event” (as defined under Code Section 409A regulations and applicable guidance). 

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

“IPO” means an initial public offering by the applicable Entity or the Company of its equity securities pursuant to an
effective registration statement filed with the SEC. 
 “Project Entity Change in Control” means, with, respect to an
Entity: 
 (i) a merger, spin-off or similar transaction involving (directly or indirectly) a Project Entity and,
immediately after the consummation of such merger, spin-off or similar transaction, the stockholders of the Company immediately prior thereto do not own, directly or indirectly, either (A) outstanding voting securities representing more than
50% of the combined outstanding voting power of the Project Entity in such transaction or (B) more than 50% of the combined outstanding voting power of the parent of the Project Entity in such transaction, in each case in substantially the same
proportions as their ownership of the outstanding voting securities of the Company immediately prior to such transaction; 

(ii) the sale or disposition by the Company of all or substantially all of the assets of a Project Entity; or 

(iii) the exclusive licensing to a third party of all or substantially all of the Project Entity’s intellectual
property. 

  
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 Notwithstanding the foregoing, the following transactions shall not constitute a Change in
Control: (i) a transaction the sole purpose of which is to change the state of such Entity’s incorporation or to create a holding company that will be owned in substantially the same proportions by the persons who held the applicable
Entity’s securities immediately before such transaction; (ii) a transaction or series of related transactions involving the sale of securities by such Entity primarily for financing purposes; (iii) a merger or consolidation involving
such Entity and one or more companies under common management control with such Entity; or (iv) an IPO. If the timing of payments provided under an RSU Award agreement is based on or triggered by a Project Entity Change in Control then, to
extent necessary to avoid violating Code Section 409A, a Project Entity Change in Control must also constitute a “change in control event” (as defined under Code Section 409A regulations and applicable guidance). 

“Separation” means a “separation from service,” as defined in the regulations under Section 409A of the Code.

 “Termination Without Cause” means a Separation as a result of a termination of Executive’s employment by the
Company other than for Cause or due to Executive’s death or disability, provided that Executive is willing and able to continue performing services within the meaning of Treasury Regulation 1.409A-1(n)(1). 

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 IN WITNESS WHEREOF, the parties have executed
this Employment Agreement as of the date set forth above. 
  

			
	ATARA BIOTHERAPEUTICS, INC.
	
	 /s/ Isaac Ciechanover, M.D.

	By:	 	Isaac Ciechanover, M.D.
	Title:	 	Chief Executive Officer
	
	JOHN MCGRATH
	
	 /s/ John McGrath

  
 [Signature Page to
Employment Agreement]EX-10.13

 Exhibit 10.13 

ATARA BIOTHERAPEUTICS, INC. 

EMPLOYMENT AGREEMENT 

This Employment Agreement (the “Agreement”) is made and entered into as of March 31, 2014, by and between Atara
Biotherapeutics, Inc., a Delaware corporation (the “Company”) and Mitchall Clark (“Executive”). From and following the date hereof, this Agreement shall replace and supersede that certain letter agreement between
the Company and Executive dated March 10th, 2014 (the “Prior Agreement”). 
 RECITALS 

WHEREAS, the Company and Executive are currently parties to the Prior Agreement and wish to enter into
this Agreement as set forth herein in connection with a share exchange, pursuant to which each of Nina Biotherapeutics, Inc., Pinta Biotherapeutics, Inc. and Santa Maria Biotherapeutics, Inc. (each a “Project Entity”) shall become
wholly-owned subsidiaries of the Company (the “Share Exchange”); 
 NOW
THEREFORE, in consideration of the mutual promises and covenants contained herein and certain other good and valuable consideration, the receipt and sufficiency of which are hereby acknowledged, the parties agree as
follows: 
 AGREEMENT 

1. Duties and Scope of Employment. Executive will remain employed as the Company’s Chief Regulatory and Quality Assurance
Officer, reporting to the Company’s Chief Executive Officer. This is a full-time position. Executive’s initial responsibilities will include, but not be limited to, implementation of the Company’s Regulatory strategies, including all
communications worldwide with appropriate regulatory agencies, filings of all relevant applications, and all related activities. In addition, Executive will be responsible for all oversight and implementation of the Company’s quality assurance
programs covering manufacturing and clinical activities. While Executive renders services to the Company, Executive will not engage in any other employment, consulting or other business activity (whether full-time or part-time) that would create a
conflict of interest with the Company. By signing this Agreement, Executive reaffirms to the Company that Executive has no contractual commitments or other legal obligations that would prohibit Executive from performing his duties for the Company,
other than during the Transition Period as described in Section 8 below. 
 2. Cash Compensation. The Company will pay
Executive a base salary at the rate of $290,000 per year (the “Base Salary”), subject to normal payroll deductions and required withholdings, and payable in accordance with the Company’s standard payroll schedule. This salary
will be subject to adjustment from time to time pursuant to the Company’s employee compensation policies in effect. Executive also will be eligible for an annual bonus of up to 25% of Executive’s Base Salary, based on achievement of
corporate performance (including financial) objectives, as well as personal performance objectives, payable at the discretion of the Chief Executive Officer of the Company and the Board of Directors. Corporate performance objectives will be
established at the sole discretion of the Board of Directors, and Executive’s personal performance objectives will be mutually agreed upon in writing between Executive and the Chief Executive Officer of the Company on an annual basis.
Executive’s annual bonus is also subject to payroll deductions and required withholdings. Any bonus earned for a fiscal year will be paid within 2% months after the close of that fiscal year, but only if Executive is still employed by the
Company at the time of payment. The determinations of the Company with respect to Executive’s bonus will be final and binding, and while the Company expects the Company’s success and Executive’s individual contributions will warrant
that a bonus be paid, there are no guarantees that such payment will be made. 

  
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 3. Employee Benefits. The Company’s benefits, payroll and other human resource
management services will continue to be provided through TriNet Employer Group, Inc. (“TriNet”), a professional employer organization. As a result of the Company’s arrangement with TriNet, TriNet will be considered
Executive’s “employer of record” for these purposes. In addition, Executive will be entitled to accrue up to 160 hours of paid time off in accordance with the Company’s paid time off policy, as in effect from time to time.
Executive’s annual vacation benefit will be no less than twenty-five (25) paid days off per year. 
 Executive’s position,
duties, goals, work location and compensation may be modified based on Executive’s performance and the evolving needs of the Company. Additionally the Company reserves the right to modify benefits, contribution and reimbursement levels from
time to time, as it deems necessary. 
 4. Equity Compensation. Executive currently holds restricted stock units (the
“Prior Awards”) covering 149,997 shares of the Company’s common stock (post Share Exchange). These equity awards will continue to be governed by the terms of the applicable equity plans and award agreements. 

5. Taxes. All payments made by the Company (or any Company affiliate) to Executive or Executive’s estate or beneficiaries
will be subject to tax withholding pursuant to any applicable laws or regulations. Executive will be solely liable and responsible for the payment of Executive’s taxes arising as a result of any payment provided to Executive in connection with
Executive’s employment including without limitation any unexpected or adverse tax consequences. Any such payments or benefits provided to Executive are intended to be exempt from or comply with the requirements of section 409A of the Code. In
the event any payment or benefit is deemed to be subject to section 409A of the Code, Executive consents to the Company adopting such conforming amendments as the Company deems necessary, in its reasonable discretion, to comply with section 409A of
the Code. In addition, if Executive is a specified employee (within the meaning of Code Section 409A) at the time of Executive’s separation from service, then to the extent necessary to comply with Code Section 409A and avoid the
imposition of taxes under Code Section 409A, the payment of certain benefits owed to Executive under this Agreement will be delayed and instead paid (without interest) to Executive upon the earlier of the first business day of the seventh month
following Executive’s separation from service or Executive’s death. Additionally, no payments or benefits will constitute excess parachute payments as defined under Code Section 280G. 

6. Proprietary Information and Inventions Agreement. Executive previously signed standard Proprietary Information and Inventions
Agreements with the Company and each Entity dated as of March 10, 2014 (collectively the “PIIA”), which remain in full force and effect pursuant to its terms. 

7. Employment Relationship. Employment with the Company is for no specific period of time. Executive’s employment with the
Company is “at will,” meaning that either Executive or the Company may terminate Executive’s employment at any time and for any reason, with or without cause. Any contrary representations that may have been made to Executive is
superseded by this Employment Agreement. This is the full and complete agreement between Executive and the Company on this term. Although Executive’s job duties, title, compensation and benefits, as well as the Company’s personnel policies
and procedures, may change from time to time, the “at will” nature of Executive’s employment may only be changed in an express written agreement signed by Executive and a duly authorized officer of the Company (other than Executive).

  
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 8. Transition Period. The Company recognizes Executive is currently engaged as a
Consultant to various clients and, as a result of accepting this position with the Company, Executive will be required to wind down Executive’s consulting business in an orderly manner. Immediately upon acceptance of this position with the
Company, Executive was required to inform all existing clients that Executive will be ending Executive’s consultancy with them in the immediate future. The Company will provide for a period to effectuate this transition (the “Transition
Period”) as follows: in the first thirty days of employment with the Company, beginning March 13th, 2014, Executive will provide three (3) days a week of service to the Company with the balance of the work week allocated to
Executive’s existing clients; in the second thirty days of employment with the Company, Executive will provide four (4) days a week of service to the Company with the balance of the work week allocated to Executive’s existing clients;
and, in the third thirty days of employment with the Company, and thereafter, Executive will provide full-time service to the Company, recognizing a de minimis amount of time may still be required from time-to-time to satisfy Executive’s
obligations to the consulting clients engaged at the time Executive accepted this position with the Company. During the Transition Period, the Base Salary will be adjusted on a pro-rata basis appropriate to the time allocation outlined in this
Section 8. The vesting of Executive’s equity awards will commence as described in the equity agreements without regard to the Transition Period. Should the wind down of Executive’s services to Executive’s existing consulting
clients occur sooner than described in the Transition Period, the Company will accelerate Executive’s transition, and the associated effect on the Base Salary, based upon the facts presented by Executive to the Chief Executive Officer. 

9. Work Location. Should the Company office locations be consolidated at some time in the future, and that consolidated location
would necessitate Executive’s residential relocation beyond ninety (90) miles from the existing Company office in Thousand Oaks, California, the Company will endeavor in good faith to reach an agreement with Executive allowing for
Executive’s continued employment with the Company without requiring the relocation of Executive’s residence. There is no guarantee provided herein, either explicit or implied, that such an agreement will be reached nor will Executive be
required to continue as an employee of the Company should such an agreement not be reached. 
 10. Miscellaneous. All forms of
compensation referred to in this Employment Agreement are subject to reduction to reflect applicable withholding and payroll taxes and other deductions required by law. Executive is encouraged to obtain Executive’s own tax advice regarding
Executive’s compensation from the Company. Executive agrees that the Company does not have a duty to design its compensation policies in a manner that minimizes Executive’s tax liabilities, and Executive will not make any claim against the
Company or its Board of Directors related to tax liabilities arising from Executive’s compensation. 
 11. Interpretation,
Amendment, and Enforcement. This Agreement, and any equity agreements referred to herein, supersede and replace the Prior Agreement and any other prior agreements, representations or understandings (whether written, oral, implied or
otherwise) between Executive and the Company and, together with the NIA, constitutes the complete agreement between Executive and the Company regarding the subject matter set forth herein. This Agreement may not be amended or modified, except by an
express written agreement signed by both Executive and a duly authorized officer of the Company. The terms of this Agreement and the resolution of any disputes as to the meaning, effect, performance or validity of this Agreement arising out of,
related to, or in any way connected with, this Agreement, Executive’s employment with the Company or any other relationship between Executive and the Company (the “Disputes”) will be governed by California law, excluding laws
relating to conflicts or choice of law. Executive and the Company submit to the exclusive personal jurisdiction of the federal and state courts located in California in connection with any Dispute or any claim related to any Dispute. 

  
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 12. Definitions. The following terms have the meaning set forth below wherever they
are used in this Agreement: 
 “Code” means the Internal Revenue Code of 1986, as amended. 

* * * * * 

  
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 IN WITNESS WHEREOF, the
parties have executed this Employment Agreement as of the date set forth above. 
  

			
	ATARA BIOTHERAPEUTICS, INC.
	
	 /s/ Issac Ciechanover

	By:	 	Isaac Ciechanover, M.D.
	Title:	 	Chief Executive Officer
	
	MITCHALL CLARK
	
	 /s/ Mitchall Clark

 [Signature Page to Employment Agreement]

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