Atara Biotherapeutics (ATRA) CAO sells 2,414 shares to cover RSU tax

Rhea-AI Filing Summary

Atara Biotherapeutics Chief Accounting Officer Yanina Grant-Huerta reported the sale of 2,414 shares of common stock. The shares were sold on May 18, 2026 at a weighted average price of $9.1286 per share, in multiple trades between $9.12 and $9.40.

According to the disclosure, these shares were sold automatically to satisfy tax withholding obligations tied to the vesting of previously granted restricted stock units under a sale-to-cover provision. After the transaction, Grant-Huerta directly holds 49,636 shares of Atara common stock.

Insider Trade Summary

Net Seller: 2,414 shares ($22,036)

Net Sell 1 txn

Insider Grant-Huerta Yanina

Role Chief Accounting Officer

Sold 2,414 shs ($22K)

Type	Security	Shares	Price	Value
Sale	Common Stock	2,414	$9.1286	$22K

Holdings After Transaction: Common Stock — 49,636 shares (Direct, null)

Footnotes (1)

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. Represents the weighted average price. The shares were sold in multiple transactions at prices ranging from $9.12 to $9.40, inclusive. The Reporting Person undertakes to provide to the Issuer, any securityholder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth above.

Key Figures

Shares sold: 2,414 shares Weighted average sale price: $9.1286 per share Post-transaction holdings: 49,636 shares

3 metrics

Shares sold 2,414 shares Common stock sold on May 18, 2026

Weighted average sale price $9.1286 per share Average across multiple trades between $9.12 and $9.40

Post-transaction holdings 49,636 shares Direct common stock held after the sale

Key Terms

restricted stock units, sale-to-cover, weighted average price, open-market sale

4 terms

restricted stock units financial

"vesting of previously granted restricted stock units, pursuant to a sale-to-cover provision"

Restricted stock units are a type of company reward where employees are promised shares of stock, but they only fully own these shares after meeting certain conditions, like staying with the company for a set time. They matter because they can become valuable assets and are often used to motivate employees to help the company succeed.

sale-to-cover financial

"pursuant to a sale-to-cover provision in the award agreement"

weighted average price financial

"Represents the weighted average price. The shares were sold in multiple transactions"

Weighted average price is the average price of a security where each trade or component is counted according to its size, so bigger trades pull the average more than smaller ones. Think of it like calculating the average cost of a grocery haul where items you bought more of have greater influence on the final per-item cost. Investors use it to understand the true average price paid or received, judge execution quality, and compare trading performance against market movement.

open-market sale financial

"transaction_action": "open-market sale""

An open-market sale is when a shareholder sells existing shares directly on a public exchange to any willing buyer, rather than through a private deal. Think of it like putting goods on a busy market stall where price is set by supply and demand; for investors it matters because such sales increase available supply, can put short-term downward pressure on the stock price, and signal changes in liquidity or investor confidence.

Form 4 Insider Transactions: What Each Field Means →

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
Estimated average burden
hours per response:			0.5

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 CALIFORNIA 91320

(City) (State) (Zip)

UNITED STATES

(Country)

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

2a. Foreign Trading Symbol

3. Date of Earliest Transaction (Month/Day/Year)
05/18/2026

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

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

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

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	05/18/2026		S(1)		2,414	D	$9.1286(2)	49,636	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. Represents the weighted average price. The shares were sold in multiple transactions at prices ranging from $9.12 to $9.40, inclusive. The Reporting Person undertakes to provide to the Issuer, any securityholder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth above.

	/s/ John Chao, Attorney-in-Fact for Yanina Grant-Huerta	05/20/2026
	** 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.
* Form 4: SEC 1474 (03-26)

FAQ

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

Atara Biotherapeutics reported that Chief Accounting Officer Yanina Grant-Huerta sold 2,414 shares of common stock. The sale occurred on May 18, 2026 and was linked to tax withholding obligations from vesting restricted stock units under a sale-to-cover provision.

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

The 2,414 Atara shares were sold at a weighted average price of $9.1286 per share. The filing notes multiple transactions executed within a price range from $9.12 to $9.40, and offers to provide full trade details upon request to interested parties.

Why did Atara Biotherapeutics’ CAO sell 2,414 shares according to the Form 4?

The sale was executed automatically to cover tax withholding obligations arising from the vesting of previously granted restricted stock units. This type of sale-to-cover transaction is compensation-related and reflects a mechanism for paying taxes rather than a discretionary open-market sale.

How many Atara Biotherapeutics (ATRA) shares does Yanina Grant-Huerta hold after this transaction?

Following the reported sale of 2,414 shares, Yanina Grant-Huerta directly holds 49,636 shares of Atara common stock. This post-transaction holding figure, disclosed in the Form 4, helps investors understand the remaining equity stake after the tax-related sale.

Was the Atara Biotherapeutics (ATRA) insider sale part of multiple trades on the same day?

Yes. The Form 4 states the 2,414 shares were sold in multiple transactions on May 18, 2026. Prices ranged from $9.12 to $9.40 per share, with a disclosed weighted average price of $9.1286 and an offer to provide full price breakdown details upon request.