Insider files to sell 1,405,000 shares

ATRA reported a proposed sale of 1,405,000 shares of Common Stock via a Form 144.

Rhea-AI Filing Summary

ATRA reported a proposed sale of 1,405,000 shares of Common Stock via a Form 144. The filing states the shares were purchased in multiple open‑market transactions from January 2025 through August 2025 and in a registered direct financing in May 2025, with planned brokerage transactions on 08/15/2025.

Key Figures

Shares proposed for sale: 1,405,000 shares Planned sale date: 08/15/2025 Acquisition period: January–August 2025 +1 more

4 metrics

Shares proposed for sale 1,405,000 shares listed under Securities To Be Sold

Planned sale date 08/15/2025 scheduled brokerage transactions date

Acquisition period January–August 2025 purchased in multiple open market transactions

Registered direct financing May 2025 one source of the purchased shares

Key Terms

Form 144, registered direct financing, brokerage transactions

3 terms

Form 144 regulatory

"Securities To Be Sold | Common Stock | 08/15/2025"

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.

registered direct financing financial

"purchased in multiple open market transactions from January 2025 through August 2025 as well as a registered direct financing in May 2025"

A registered direct financing is when a company sells newly registered securities directly to a limited number of investors under an existing registration, skipping the broad public marketing of a typical offering; think of it as putting approved items on a store shelf and arranging a private sale to select buyers. Investors care because it can quickly raise cash while creating new shares or debt that may dilute existing ownership, affect the share price and change the company’s financial runway.

brokerage transactions market

"The Common Stock was purchased ... | Brokerage transactions"

FAQ

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

What does the ATRA Form 144 report say was filed?

It reports a proposed sale of 1,405,000 shares of Common Stock. The filing notes purchases occurred January–August 2025 and a registered direct financing in May 2025, with brokerage transactions listed for 08/15/2025.

When were the shares reported to have been acquired for ATRA?

The shares were acquired between January 2025 and August 2025. The filing specifies multiple open‑market purchases during that period and a registered direct financing that closed in May 2025.

How many ATRA shares are proposed for sale in the Form 144?

The Form 144 lists 1,405,000 shares proposed for sale. The planned method of sale is via brokerage transactions with the listed sale date of 08/15/2025.

What sale method does the ATRA Form 144 indicate?

Brokerage transactions are listed as the method of sale. The filing identifies planned brokerage transactions and records cash as the consideration for the listed sale amount on 08/15/2025.

Does the Form 144 show any lockup or resale restrictions for ATRA shares?

The provided excerpt does not state specific lockup or resale restrictions. It only lists acquisition sources (open market and a registered direct financing) and the intended brokerage sale method on 08/15/2025.

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

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Accepted by SEC EDGAR 05/07/2026 - 08:30 PM EDT 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	0002010692
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	1280 Rancho Conejo Blvd Thousand Oaks CALIFORNIA 91320
Phone	805-623-4211
Name of Person for Whose Account the Securities are To Be Sold	Panacea Innovation Ltd
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	10% Stockholder

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	Cantor Fitzgerald 110 East 59th Street New York NY 10022	313446	3165020.99	8178114	05/07/2026	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	08/15/2025	The Common Stock was purchased in multiple open market transactions from January 2025 through August 2025 as well as a registered direct financing in May 2025.	Brokerage transactions			1405000	08/15/2025	Cash

* 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

Nothing to Report

144: Remarks and Signature

Remarks	The shares that are sold are held of record by Panacea Venture Healthcare Fund II, L.P.
Date of Notice	05/07/2026
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/ James Huang, Founding Managing Partner
ATTENTION: Intentional misstatements or omission of facts constitute Federal Criminal Violations (See 18 U.S.C. 1001)