[Form 4] Atara Biotherapeutics, Inc Insider Trading Activity

Rhea-AI Filing Summary

Yanina Grant-Huerta, Chief Accounting Officer and Director of Atara Biotherapeutics (ATRA), reported automatic share sales on August 18, 2025 to satisfy tax withholding obligations tied to the vesting of previously granted restricted stock units. The filing lists three automatic dispositions executed via broker at weighted-average prices of approximately $11.61 per share, resulting in reported beneficial ownership of 35,258 shares after the transactions. The sales were executed pursuant to a sale-to-cover provision in the award agreement and the report was signed by an attorney-in-fact on August 20, 2025.

Positive

• Disclosure compliance: Form 4 was filed and signed, showing adherence to Section 16 reporting requirements
• Routine equity plan action: Sales were sale-to-cover transactions tied to RSU vesting, a common administrative practice

Negative

• Reduction in beneficial ownership: Reported beneficial ownership after transactions is 35,258 shares, reflecting a decrease due to sales
• Insider sales executed: Automatic dispositions occurred on 08/18/2025 at an average price of approximately $11.61 per share

Insights

Financial Analyst

TL;DR: Routine sale-to-cover for RSU tax withholding; no new compensation grants or unusual trading patterns disclosed.

The Form 4 shows automatic dispositions on August 18, 2025 tied to RSU vesting, not open-market discretionary sales. The reported weighted-average price (~$11.61) reflects broker execution on behalf of multiple employees, and the post-transaction beneficial ownership is 35,258 shares. For investors, this is a routine administrative event that reduces the officer's share count but does not, by itself, indicate a change in company outlook or material insider reallocation.

Corporate Governance Expert

TL;DR: Disclosure meets Section 16 reporting requirements; sale-to-cover practice is standard and indicates compliance.

The disclosure explicitly states the sales were automatic to satisfy tax withholding on vested RSUs and were handled via broker sale-to-cover. The filing is properly executed by an attorney-in-fact and includes an explanation of the sale price calculation. This demonstrates adherence to reporting protocols and internal equity compensation procedures, with no indications of undisclosed agreements or exceptions.

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)
08/18/2025

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	08/18/2025		S(1)		55	D	$11.609(2)	37,012	D
Common Stock	08/18/2025		S(1)		86	D	$11.613(2)	36,926	D
Common Stock	08/18/2025		S(1)		1,668	D	$11.614(2)	35,258	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 August 18, 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	08/20/2025
	** 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.
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FAQ

What did Yanina Grant-Huerta report on Form 4 for ATRA?

The filing reports automatic sales of vested RSUs executed on 08/18/2025 to satisfy tax withholding, resulting in 35,258 shares beneficially owned.

Why were shares sold according to the Form 4 for ATRA?

The Form 4 states the shares were sold automatically pursuant to a sale-to-cover provision to satisfy tax withholding obligations from RSU vesting.

How many shares were sold and at what price in the ATRA Form 4?

The filing lists dispositions of 55, 86, and 1,668 shares on 08/18/2025, with reported weighted-average prices around $11.61 per share.

Who signed the Form 4 for Yanina Grant-Huerta?

The Form 4 was signed by John Chao, Attorney-in-Fact for Yanina Grant-Huerta on 08/20/2025.

Does the Form 4 indicate any discretionary open-market insider selling?

No. The Form 4 explains the sales were automatic sale-to-cover transactions tied to RSU vesting, not discretionary open-market sales disclosed as separate trades.