Hyllengren Eric J Form 3 Filed 2023-04-07

Exhibit 24

POWER OF ATTORNEY

The undersigned, as a Section 16 reporting person of Atara Biotherapeutics, Inc. (the "Company"), hereby constitutes and appoints Jeff Kiekhofer, Amar Murugan, John Chao and Kathleen Klaben the undersigned's true and lawful attorneys-in-fact to:

1. Complete and execute Forms 3, 4 and 5 and other forms and all amendments thereto as such attorneys-in-fact shall in their discretion determine to be required or advisable pursuant to Section 16 of the Securities Exchange Act of 1934 (as amended) and the rules and regulations promulgated thereunder, or any successor laws and regulations, as a consequence of the undersigned's ownership, acquisition or disposition of securities of the Company; and

2. Do all acts necessary in order to file such forms with the Securities and Exchange Commission, any securities exchange or national association, the Company and such other person or agency as the attorneys-in-fact shall deem appropriate.

The undersigned hereby ratifies and confirms all that said attorneys-in-fact and agents shall do or cause to be done by virtue hereof. The undersigned acknowledges that the foregoing attorneys-in-fact, in serving in such capacity at the request of the undersigned, is not assuming, nor is the Company assuming, any of the undersigned's responsibilities to comply with Section 16 of the Securities Exchange Act of 1934 (as amended).

This Power of Attorney shall remain in full force and effect until the undersigned is no longer required to file Forms 3, 4 and 5 with respect to the undersigned's holdings of and transactions in securities issued by the Company, unless earlier revoked by the undersigned in a signed writing delivered to the Company and the foregoing attorneys-in-fact.

The undersigned hereby terminates all prior powers of attorney regarding the subject matter hereof.

IN WITNESS WHEREOF, the undersigned has caused this Power of Attorney to be executed as of March 30, 2023.

	Signature:	/s/ Eric Hyllengren
		Eric Hyllengren

1. Title of Derivative Security (Instr. 4)	2. Date Exercisable and Expiration Date (Month/Day/Year)		3. Title and Amount of Securities Underlying Derivative Security (Instr. 4)		4. Conversion or Exercise Price of Derivative Security	5. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 5)	6. Nature of Indirect Beneficial Ownership (Instr. 5)
1. Title of Derivative Security (Instr. 4)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares	4. Conversion or Exercise Price of Derivative Security		6. Nature of Indirect Beneficial Ownership (Instr. 5)
Employee Stock Option (Right to Buy)	08/20/2022	09/03/2025	Common Stock	47,500	$39.85	D
Employee Stock Option (Right to Buy)	02/06/2023	02/05/2029	Common Stock	11,500	$38.47	D
Employee Stock Option (Right to Buy)	04/01/2023	02/28/2030	Common Stock	12,526	$12.15	D
Employee Stock Option (Right to Buy)	⁽³⁾	02/28/2030	Common Stock	3,724	$12.15	D
Employee Stock Option (Right to Buy)	04/01/2023	02/28/2031	Common Stock	9,530	$17.105	D
Employee Stock Option (Right to Buy)	⁽⁴⁾	02/28/2031	Common Stock	8,768	$17.105	D
Employee Stock Option (Right to Buy)	04/01/2023	02/29/2032	Common Stock	6,540	$10.21	D
Employee Stock Option (Right to Buy)	⁽⁵⁾	02/29/2032	Common Stock	17,608	$10.21	D
Employee Stock Option (Right to Buy)	04/01/2023	02/28/2033	Common Stock	8,298	$3.91	D
Employee Stock Option (Right to Buy)	⁽⁵⁾	02/28/2033	Common Stock	290,417	$3.91	D

1.	Includes an aggregate 194,599 restricted stock units ("RSUs"), which are comprised of: (i) 5,297 RSUs that vest as to 1/4th of the shares on May 15, 2023 and each of the next three (3) "Quarterly Vesting Dates" (as defined herein); (ii) 6,066 RSUs that vest as to 1/8th of shares on May 15, 2023 and each of the next seven (7) Quarterly Vesting Dates; (iii) 18,697 RSUs that vest as to 1/3rd of shares on November 15, 2023, November 15, 2024 and November 15, 2025; (iv) 11,777 RSUs that vest as to 1/12th of shares on May 15, 2023 and each of the next eleven (11) Quarterly Vesting Dates; (v) 20,000 RSUs that vest as to 1/2nd of shares on November 15, 2023 and 1/2nd on November 15, 2024; and (vi) 132,762 RSUs that vest as to 1/12th of shares on May 15, 2023 and each of the next eleven (11) Quarterly Vesting Dates, each of which is subject to the reporting person's continuous service.
2.	"Quarterly Vesting Date" means March 1, May 15, August 15, and November 15 of each year, provided that if such date falls on a weekend or holiday, the "Quarterly Vesting Date" shall be the first (1st) business day after such date.
3.	1/11th of shares subject to the stock option vest and become exercisable on May 1, 2023, and the remaining shares vest in equal monthly installments over the following ten (10) months, subject to the reporting person's continuous service.
4.	1/23rd of shares subject to the stock option vest and become exercisable on May 1, 2023, and the remaining shares vest in equal monthly installments over the following twenty-two (22) months, subject to the reporting person's continuous service.
5.	1/35th of shares subject to the stock option vest and become exercisable on May 1, 2023, and the remaining shares vest in equal monthly installments over the following thirty-four (34) months, subject to the reporting person's continuous service.
Remarks: Exhibit 24 - Power of Attorney

	Signatures
	/s/ Jeff Kiekhofer, Attorney-in-Fact for Eric J. Hyllengren	04/07/2023
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).
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