Atara Biotherapeutics (ATRA) CAO sells 2,104 shares to cover taxes

Rhea-AI Filing Summary

Atara Biotherapeutics Chief Accounting Officer Yanina Grant-Huerta reported open-market sales of 2,104 shares of common stock on March 2, 2026. The shares were sold automatically to cover tax withholding on vesting restricted stock units at weighted average prices around $5.08 per share. Following these transactions, she directly holds 31,750 shares, including 400 shares acquired through the company’s employee stock purchase plan.

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

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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)
03/02/2026

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	03/02/2026		S(1)		24	D	$5.077(2)	33,830(3)	D
Common Stock	03/02/2026		S(1)		1,603	D	$5.081(2)	32,227	D
Common Stock	03/02/2026		S(1)		377	D	$5.082(2)	31,850	D
Common Stock	03/02/2026		S(1)		100	D	$5.083(2)	31,750	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 March 2, 2026 on behalf of a group of employees of the Issuer to satisfy the payment of withholding tax liability of such employees.

3. This amount includes 400 shares purchased under the Issuer's Employee Stock Purchase Plan on November 28, 2025.

	/s/ John Chao, Attorney-in-Fact for Yanina Grant-Huerta	03/04/2026
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
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FAQ

What insider transaction did Atara Biotherapeutics (ATRA) report for Yanina Grant-Huerta?

Atara Biotherapeutics reported that Chief Accounting Officer Yanina Grant-Huerta sold 2,104 shares of common stock on March 2, 2026. These sales were automatic to cover tax withholding on vesting restricted stock units, rather than discretionary open-market selling for investment purposes.

At what prices were the Atara Biotherapeutics (ATRA) insider shares sold?

The reported Atara Biotherapeutics insider sales occurred at weighted average prices around $5.08 per share. Individual sale tranches were priced at $5.077, $5.081, $5.082, and $5.083, reflecting broker-handled transactions executed on March 2, 2026 for tax withholding purposes.

How many Atara Biotherapeutics (ATRA) shares does the CAO hold after the reported sales?

After the reported tax-withholding sales, Atara Biotherapeutics Chief Accounting Officer Yanina Grant-Huerta directly holds 31,750 shares of common stock. This total includes 400 shares purchased under the company’s Employee Stock Purchase Plan on November 28, 2025, as disclosed in the filing footnotes.

Were the Atara Biotherapeutics (ATRA) insider sales discretionary or for tax withholding?

The Atara Biotherapeutics insider sales were made automatically to satisfy tax withholding obligations on vesting restricted stock units. According to the footnotes, a broker sold shares on behalf of a group of employees under sale-to-cover provisions, rather than through discretionary investment decisions by the insider.

What role does the reporting person hold at Atara Biotherapeutics (ATRA)?

The reporting person, Yanina Grant-Huerta, serves as Chief Accounting Officer at Atara Biotherapeutics. Her Form 4 filing details tax-related open-market sales of common stock and confirms her remaining direct ownership position following the March 2, 2026 transactions disclosed in the report.

How many Atara Biotherapeutics (ATRA) insider sale transactions were reported on March 2, 2026?

The Form 4 shows four separate sale transactions for Atara Biotherapeutics common stock on March 2, 2026. These tranches totaled 2,104 shares sold, all classified as open-market sales executed by a broker to cover withholding tax obligations tied to vesting restricted stock units.