ATRA RSU Settlement: 6,393 Shares Reported

ATRA submitted a Form 144 notice reporting the settlement and disposition of Common Stock tied to employee equity.

Rhea-AI Filing Summary

ATRA submitted a Form 144 notice reporting the settlement and disposition of Common Stock tied to employee equity. The filing shows 6,393 shares settled on 05/15/2026 as payment for vested RSUs issued under an S-8 registration, and a prior sale of 2,104 shares on 03/02/2026.

Insights

Corporate Counsel

Routine Rule 144 notice for RSU settlement and a recent small disposition.

The filing lists the settlement of 6,393 shares on 05/15/2026 as equity compensation under an S-8 registration plan. It also records a prior sale of 2,104 shares on 03/02/2026.

These items are administrative disclosures under Rule 144; cash‑flow treatment and holder identities beyond the named individual are limited to the excerpts provided. Subsequent filings would state any additional transfers or resale intentions.

Key Figures

RSU settlement: 6,393 shares Prior sale: 2,104 shares Broker-dealer: Morgan Stanley Smith Barney LLC +3 more

6 metrics

RSU settlement 6,393 shares settled on 05/15/2026 under S-8 plan

Prior sale 2,104 shares sold on 03/02/2026 by Yanina Grant-Huerta

Broker-dealer Morgan Stanley Smith Barney LLC listed as handling common stock transactions

Exchange listing NASDAQ exchange noted in the excerpt

Reference date 05/18/2026 date appearing in filer information area

Document reference number 9,371,144 numeric string appearing near filer information on 05/18/2026

Key Terms

S-8 Registration Plan, RSU, Form 144

3 terms

S-8 Registration Plan regulatory

"Settlement of vested RSUs issued under an S-8 Registration Plan"

RSU financial

"Settlement of vested RSUs issued under an S-8 Registration Plan"

Restricted stock units (RSUs) are a form of company shares given to employees as part of their compensation, usually with certain restrictions or conditions, such as remaining with the company for a set period. When these restrictions lift, employees receive actual shares that they can sell or hold. For investors, RSUs can impact a company's stock supply and reflect the company's commitment to attracting and retaining talent.

Form 144 regulatory

"Securities Sold During The Past 3 Months"

Form 144 is a document that investors must file with the government when they plan to sell a large number of shares of a company's stock. It helps ensure transparency so everyone knows how many shares are being sold and when, which can impact the stock's price.

FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

What does ATRA's Form 144 report about RSU settlement?

The filing reports 6,393 shares settled on 05/15/2026 as payment for vested RSUs issued under an S-8 registration plan. This entry records equity compensation being settled into common stock.

Did any insider or holder sell shares recently for ATRA?

Yes; the filing shows a reported sale of 2,104 shares by Yanina Grant-Huerta on 03/02/2026. The entry appears in the "Securities Sold During The Past 3 Months" section of the notice.

Who is listed as the broker or dealer handling the transaction?

The broker/dealer shown is Morgan Stanley Smith Barney LLC Executive Services with an address in Sandy, UT. The excerpt ties this party to the listed common stock transactions.

Does the Form 144 state whether proceeds go to the issuer or selling holders?

The excerpt lists the transactions as equity compensation (settlement of RSUs) and a prior sale; it does not specify proceeds allocation beyond those labels in the provided content.

AI-generated analysis. How Rhea-AI works. Not financial advice.

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Accepted by SEC EDGAR 05/18/2026 - 04:44 PM Learn about SEC filing dates

Form 144 Filer Information	UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 Form 144 NOTICE OF PROPOSED SALE OF SECURITIES PURSUANT TO RULE 144 UNDER THE SECURITIES ACT OF 1933
FORM 144

144: Filer Information

Filer CIK	0002064348
Filer CCC	XXXXXXXX
Is this a LIVE or TEST Filing?	LIVE TEST
Submission Contact Information
Name
Phone
E-Mail Address

144: Issuer Information

Name of Issuer	Atara Biotherapeutics, Inc.
SEC File Number	001-36548
Address of Issuer	c/o Atara Biotherapeutics, Inc. 1280 Rancho Conejo Boulevard Thousand Oaks CALIFORNIA 91320
Phone	805-623-4211
Name of Person for Whose Account the Securities are To Be Sold	Grant-Huerta Yanina
See the definition of "person" in paragraph (a) of Rule 144. Information is to be given not only as to the person for whose account the securities are to be sold but also as to all other persons included in that definition. In addition, information shall be given as to sales by all persons whose sales are required by paragraph (e) of Rule 144 to be aggregated with sales for the account of the person filing this notice.
Relationship to Issuer	Officer

144: Securities Information

Title of the Class of Securities To Be Sold	Name and Address of the Broker	Number of Shares or Other Units To Be Sold	Aggregate Market Value	Number of Shares or Other Units Outstanding	Approximate Date of Sale	Name the Securities Exchange
Common Stock	Morgan Stanley Smith Barney LLC Executive Services 200 W Civic Center Drive, 4th Floor Sandy UT 84070	2754	28861.92	9371144	05/18/2026	NASDAQ

Furnish the following information with respect to the acquisition of the securities to be sold and with respect to the payment of all or any part of the purchase price or other consideration therefor:

144: Securities To Be Sold

Title of the Class	Date you Acquired	Nature of Acquisition Transaction	Name of Person from Whom Acquired	Is this a Gift?	Date Donor Acquired	Amount of Securities Acquired	Date of Payment	Nature of Payment *
Common Stock	05/15/2026	Settlement of vested RSUs issued under an S-8 Registration Plan	Issuer			6393	05/15/2026	Equity compensation for services rendered

* If the securities were purchased and full payment therefor was not made in cash at the time of purchase, explain in the table or in a note thereto the nature of the consideration given. If the consideration consisted of any note or other obligation, or if payment was made in installments describe the arrangement and state when the note or other obligation was discharged in full or the last installment paid.

Furnish the following information as to all securities of the issuer sold during the past 3 months by the person for whose account the securities are to be sold.

144: Securities Sold During The Past 3 Months

Name and Address of Seller	Title of Securities Sold	Date of Sale	Amount of Securities Sold	Gross Proceeds
Yanina Grant-Huerta 1280 Rancho Conejo Boulevard Thousand Oaks CA 91320	Common Stock	03/02/2026	2104	10690.91

144: Remarks and Signature

Remarks	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.
Date of Notice	05/18/2026
ATTENTION:
The person for whose account the securities to which this notice relates are to be sold hereby represents by signing this notice that he does not know any material adverse information in regard to the current and prospective operations of the Issuer of the securities to be sold which has not been publicly disclosed. If such person has adopted a written trading plan or given trading instructions to satisfy Rule 10b5-1 under the Exchange Act, by signing the form and indicating the date that the plan was adopted or the instruction given, that person makes such representation as of the plan adoption or instruction date.
Signature	/s/ John Chao, Attorney-in-Fact for Yanina Grant-Huerta
ATTENTION: Intentional misstatements or omission of facts constitute Federal Criminal Violations (See 18 U.S.C. 1001)