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 NY NY 10022	40000	235200	7210235	01/12/2026	NASDAQ
Common Stock	Jefferies 520 Madison Avenue NY NY 10022	20000	117600.00	7210235	01/12/2026	NASDAQ
Common Stock	JP Morgan 270 Park Avenue NY NY 10017	20554	120858.00	7210235	01/12/2026	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

01/12/2026

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

FORM 144