[Form 4] Atara Biotherapeutics, Inc. Insider Trading Activity

Rhea-AI Filing Summary

Atara Biotherapeutics, Inc. reported insider share sales by an officer related to tax withholding. The company’s Chief Accounting Officer, Yanina Grant-Huerta, reported three sales of Atara common stock on 11/17/2025 totaling 1,804 shares at weighted average prices between $13.186 and $13.191 per share. After these transactions, she beneficially owned 33,454 shares of common stock directly.

The filing explains that the shares were sold automatically under a sale-to-cover provision to satisfy tax withholding obligations upon the vesting of previously granted restricted stock units, with prices reflecting broker-handled sales for a group of employees on that date.

SEC Form 4

FORM 4

UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940

OMB APPROVAL

OMB Number:			3235-0287
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Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan for the purchase or sale of equity securities of the issuer that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

1. Name and Address of Reporting Person^*

Grant-Huerta Yanina

(Last) (First) (Middle)

C/O ATARA BIOTHERAPEUTICS, INC.

1280 RANCHO CONEJO BOULEVARD

(Street)

THOUSAND OAKS CA 91320

(City) (State) (Zip)

2. Issuer Name and Ticker or Trading Symbol
Atara Biotherapeutics, Inc. [ ATRA ]

5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

	Director		10% Owner
X	Officer (give title below)		Other (specify below)
	Chief Accounting Officer

3. Date of Earliest Transaction (Month/Day/Year)
11/17/2025

4. If Amendment, Date of Original Filed (Month/Day/Year)

6. Individual or Joint/Group Filing (Check Applicable Line)

X	Form filed by One Reporting Person
	Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	3. Transaction Code (Instr. 8)		4. Securities Acquired (A) or Disposed Of (D) (Instr. 3, 4 and 5)			5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4)	6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
			Code	V	Amount	(A) or (D)	Price
Common Stock	11/17/2025		S(1)		1,645	D	$13.186(2)	33,613	D
Common Stock	11/17/2025		S(1)		85	D	$13.188(2)	33,528	D
Common Stock	11/17/2025		S(1)		74	D	$13.191(2)	33,454	D

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Transaction Date (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	4. Transaction Code (Instr. 8)		5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5)		6. Date Exercisable and Expiration Date (Month/Day/Year)		7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4)		8. Price of Derivative Security (Instr. 5)	9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)	10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
				Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares

Explanation of Responses:

1. Shares sold automatically to satisfy tax withholding obligations in connection with the vesting of previously granted restricted stock units, pursuant to a sale-to-cover provision in the award agreement.

2. The sale price of the reporting person's shares represents the weighted average price of all shares sold by a broker on November 17, 2025 on behalf of a group of employees of the Issuer to satisfy the payment of withholding tax liability of such employees.

	/s/ John Chao, Attorney-in-Fact for Yanina Grant-Huerta	11/19/2025
	** 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).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.

FAQ

What insider transaction did Atara Biotherapeutics (ATRA) disclose in this Form 4?

The filing reports that Chief Accounting Officer Yanina Grant-Huerta sold a total of 1,804 shares of Atara Biotherapeutics common stock on 11/17/2025.

Why did the Atara Biotherapeutics (ATRA) officer sell shares on November 17, 2025?

The shares were sold automatically to satisfy tax withholding obligations related to the vesting of previously granted restricted stock units, under a sale-to-cover provision in the award agreement.

At what prices were the Atara Biotherapeutics (ATRA) shares sold in this Form 4?

The reported sales occurred at weighted average prices of approximately $13.186, $13.188, and $13.191 per share, based on broker-handled sales on 11/17/2025.

How many Atara Biotherapeutics (ATRA) shares does the reporting person own after the transactions?

Following the reported sales, the Chief Accounting Officer beneficially owned 33,454 shares of Atara Biotherapeutics common stock directly.

Who signed the Atara Biotherapeutics (ATRA) Form 4 for these transactions?

The Form 4 was signed by John Chao as Attorney-in-Fact for Yanina Grant-Huerta on 11/19/2025.

Are these Atara Biotherapeutics (ATRA) insider sales part of a group transaction?

The explanation notes that the weighted average sale price reflects shares sold by a broker on 11/17/2025 on behalf of a group of employees to cover their withholding tax liabilities.