13D Filings
Atara Biotherapeutics, Inc.
ATRA
Amendment
Ownership

16.10%

Total Shares

1,318,894

Issuer CIK

1604464

Event Date

May 6, 2026

Accepted

May 11, 2026, 06:49 PM

Reporting Persons (6)
Joint Filing

This is a joint filing. The reported shares may overlap between reporting persons and should not be summed.

NameType% of ClassAggregateSole VotingShared Voting
Panacea Innovation Limited
CO
16.10%1,318,89401,318,894
James Huang
Individual
16.10%1,318,89401,318,894
Panacea Venture Healthcare Fund II, L.P.
Partnership
12.40%1,011,00001,011,000
Panacea Venture Healthcare Fund II GP Company, Ltd.
CO
12.40%1,011,00001,011,000
Panacea Opportunity Fund I, L.P.
Partnership
3.80%307,8990307,899
Panacea Opportunity Fund I GP Company, Ltd.
CO
3.80%307,8990307,899
Disclosure Items (2)

Security Title

Common Stock

Issuer Name

Atara Biotherapeutics, Inc.

Issuer Address

1280 Rancho Conejo Blvd, Thousand Oaks, CA, 91320

Percentage of Class

The information contained on the cover pages is incorporated by reference into this Item 5. Panacea Venture Healthcare Fund II, L.P. is the record holder of 1,011,000 shares of Common Stock, and Panacea Opportunity Fund I, L.P. is the record holder of 307,894 shares of Common Stock. The ownership information presented herein represents beneficial ownership of Common Stock as of the date of this filing, based upon 8,178,114 shares of Common Stock outstanding as of March 10, 2026 as disclosed in the Issuer's Definitive Proxy Statement filed with the Securities and Exchange Commission on April 24, 2026. James Huang is the sole owner of Panacea Innovation Limited, which is the sole owner of Panacea Venture Healthcare Fund II GP Company, Ltd. and Panacea Opportunity Fund I GP Company, Ltd., which are the general partners of Panacea Venture Healthcare Fund II, L.P. and Panacea Opportunity Fund I, L.P., respectively. As a result, Panacea Venture Healthcare Fund II GP Company, Ltd. and Panacea Opportunity Fund I GP Company, Ltd. may be deemed to share beneficial ownership of the securities held of record by Panacea Venture Healthcare Fund II, L.P. and Panacea Opportunity Fund I, L.P., respectively. Panacea Innovation Limited and Mr. Huang may be deemed to share beneficial ownership of the securities beneficially owned by the foregoing entities, but each disclaims such beneficial ownership.

Number of Shares

The information contained on the cover pages is incorporated by reference into this Item 5.

Transactions

On May 7, 2026, Panacea Venture Healthcare Fund II, L.P. sold 313,446 shares of Common Stock in open market transactions at a weighted average price of $10.0975 per share. The Reporting Persons undertake to provide, upon request by the staff of the Securities and Exchange Commission, the Issuer, or a security holder of the Issuer, full information regarding the number of shares sold at each separate price for this transaction.

Shareholders

None.

Date of 5% Ownership

Not applicable