Panacea Innovation Ltd - 17 Mar 2026 Form 4 Insider Report for Atara Biotherapeutics, Inc. (ATRA)

Reporting relationship: 10%+ Owner
Issuer ticker: ATRA
Reported as of: 17 Mar 2026
Net transaction value: $0
SEC form: 4
Accepted by SEC: 19 Mar 2026, 16:30:10 UTC
Prior SEC filing: 14 Jan 2026
Next SEC filing: 11 May 2026
Source filing: View source filing
Reporting owner signature: Panacea Innovation Limited By: /s/ James Huang, Founding Managing Partner

Key filing fact

Panacea Innovation Ltd filed Form 4 for Atara Biotherapeutics, Inc. (ATRA) on 19 Mar 2026.

Key facts

This page summarizes Panacea Innovation Ltd's Form 4 filing for Atara Biotherapeutics, Inc. (ATRA).
3 reported transactions and 1 derivative row are listed below.
Accepted by SEC: 19 Mar 2026, 16:30.

Change

Previous filing in this sequence was filed on 14 Jan 2026.
Current net transaction value: $0.

Research use

This tells you what this filing adds before you inspect full transaction and derivative tables.
You can trace every row back to the original SEC filing document.

Evidence

Filed on Form 4

Ownership activity is grounded in SEC Form 4 disclosures.

View source filing

Reporting Owners (2)

CIK 0002010692 Primary reporting owner

Panacea Innovation Ltd

Relationship: 10%+ Owner
Address: C/O MAPLES CORPORATE SERVICES LIMITED,, UGLAND HOUSE, GRAND CAYMAN, CAYMAN ISLANDS
Signature: Panacea Innovation Limited By: /s/ James Huang, Founding Managing Partner
Signature date: 19 Mar 2026

CIK 0001573160

Huang James

Relationship: Director, 10%+ Owner
Address: C/O MAPLES CORPORATE SERVICES LIMITED,, UGLAND HOUSE, GRAND CAYMAN, CAYMAN ISLANDS
Signature: /s/ James Huang
Signature date: 19 Mar 2026

Reported non-derivative transactions

Shares, units, or other non-derivative securities reported in this filing.

ATRA transaction

Common Stock

Options Exercise

Transaction value
Shares: +259,163
Change %: +532%
Price: $0.000100^*
Shares after: 307,899
Date: 17 Mar 2026
Ownership: See Footnotes
Footnotes: F1, F2

ATRA transaction

Common Stock

Tax liability

Transaction value
Shares: -5
Change %: -0%
Price: $5.23^*
Shares after: 307,894
Date: 17 Mar 2026
Ownership: See Footnotes
Footnotes: F1, F2

ATRA holding

Common Stock

No transaction description listed

Transaction value
Shares
Change %
Price
Shares after: 1,324,446
Date: 17 Mar 2026
Ownership: See Footnotes
Footnotes: F2, F3

Reported derivative securities

Options, warrants, convertible securities, or similar derivative positions disclosed in the filing.

ATRA transaction Derivative

Warrants

Options Exercise

Transaction value
Shares: -259,163
Change %: -100%
Price: $6.61^*
Shares after: 0
Date: 17 Mar 2026
Ownership: See Footnotes
Underlying class: Common Stock
Underlying amount: 259,163
Exercise price: $0.000100
Footnotes: F1, F2, F4

^* marks a reported price that did not pass the local price check.

Additional SEC filing notes

Filing notes and footnotes

Explanation of responses 4 footnotes

Footnote F1

Represents securities held by Panacea Opportunity Fund I, L.P.

Footnote F2

James Huang is the sole owner of Panacea Innovation Limited, which is the sole owner of Panacea Venture Healthcare Fund II GP Company, Ltd. ("Fund II GP") and Panacea Opportunity Fund I GP Company, Ltd. ("Opportunity Fund GP"), which are the general partners of Panacea Venture Healthcare Fund II, L.P. and Panacea Opportunity Fund I, L.P. As a result, each of the Reporting Persons 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., but each disclaims such beneficial ownership.

Footnote F3

Represents securities held by Panacea Venture Healthcare Fund II, L.P.

Footnote F4

The warrants are immediately exercisable and do not expire. Pursuant to the terms of the warrants, no portion of the warrants held by a holder may be exercised to the extent that, after giving effect to the attempted exercise, such holder, together with such holder's affiliates and any other person whose beneficial ownership of the Issuer's common stock would be aggregated with such holder's for the purposes of Section 13(d) of the Exchange Act, would beneficially own in excess of 19.99% of the outstanding common stock.