Panacea funds trim Atara Biotherapeutics (ATRA) stake with 80,554-share sale

Rhea-AI Filing Summary

Panacea-affiliated investment funds reported an insider sale of Atara Biotherapeutics, Inc. common stock. On January 12, 2026, Panacea Venture Healthcare Fund II, L.P. sold 80,554 shares of Atara common stock in an open-market transaction at a weighted average price of $6.0707 per share, with individual trades ranging from $5.9888 to $6.2838.

After this sale, Panacea Venture Healthcare Fund II, L.P. held 1,324,446 shares of Atara common stock indirectly for the reporting persons, and Panacea Opportunity Fund I, L.P. held an additional 48,736 shares. Panacea Innovation Ltd and James Huang are reporting persons because of their control of the general partners of these funds and may be deemed to share beneficial ownership of these holdings, although each disclaims such beneficial ownership.

Insights

Equity analyst

Panacea-managed funds reported a moderate insider sale but keep a large remaining stake.

The filing shows that Panacea Venture Healthcare Fund II, L.P., an entity associated with Panacea Innovation Ltd and director James Huang, sold 80,554 shares of Atara Biotherapeutics common stock on January 12, 2026. The shares were sold in multiple trades at prices between $5.9888 and $6.2838, resulting in a weighted average sale price of $6.0707 per share.

Despite this sale, the funds retain sizable exposure. Following the transaction, Panacea Venture Healthcare Fund II, L.P. held 1,324,446 shares, and Panacea Opportunity Fund I, L.P. held 48,736 shares of Atara common stock indirectly for the reporting persons. The filing explains that the reporting persons may be deemed to share beneficial ownership of these fund-held positions but each disclaims such beneficial ownership, underscoring that the economic interest and decision-making primarily reside at the fund level.

From an investment perspective, the event reflects portfolio activity by large fund holders rather than a complete exit. The funds remain significant indirect holders after the sale, and the transaction code "S" identifies the activity as a sale of non-derivative common stock. Subsequent company filings may provide additional context on any future changes in these indirect holdings.

SEC Form 4

FORM 4

UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940

OMB APPROVAL

OMB Number:			3235-0287
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hours per response:			0.5

Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan for the purchase or sale of equity securities of the issuer that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

1. Name and Address of Reporting Person^*

Panacea Innovation Ltd

(Last) (First) (Middle)

C/O MAPLES CORPORATE SERVICES LIMITED,

UGLAND HOUSE

(Street)

GRAND CAYMAN E9 KY1-1104

(City) (State) (Zip)

2. Issuer Name and Ticker or Trading Symbol
Atara Biotherapeutics, Inc. [ ATRA ]

5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

	Director	X	10% Owner
	Officer (give title below)		Other (specify below)

3. Date of Earliest Transaction (Month/Day/Year)
01/12/2026

4. If Amendment, Date of Original Filed (Month/Day/Year)

6. Individual or Joint/Group Filing (Check Applicable Line)

	Form filed by One Reporting Person
X	Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	3. Transaction Code (Instr. 8)		4. Securities Acquired (A) or Disposed Of (D) (Instr. 3, 4 and 5)			5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4)	6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
			Code	V	Amount	(A) or (D)	Price
Common Stock	01/12/2026		S		80,554	D	$6.0707(3)	1,324,446	I	See Footnotes(1)(2)
Common Stock								48,736	I	See Footnotes(2)(4)

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Transaction Date (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	4. Transaction Code (Instr. 8)		5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5)		6. Date Exercisable and Expiration Date (Month/Day/Year)		7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4)		8. Price of Derivative Security (Instr. 5)	9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)	10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
				Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares

1. Name and Address of Reporting Person^*

Panacea Innovation Ltd

(Last) (First) (Middle)

C/O MAPLES CORPORATE SERVICES LIMITED,

UGLAND HOUSE

(Street)

GRAND CAYMAN E9 KY1-1104

(City) (State) (Zip)

Relationship of Reporting Person(s) to Issuer

	Director	X	10% Owner
	Officer (give title below)		Other (specify below)

1. Name and Address of Reporting Person^*

Huang James

(Last) (First) (Middle)

C/O MAPLES CORPORATE SERVICES LIMITED,

UGLAND HOUSE

(Street)

GRAND CAYMAN E9 KY1-1104

(City) (State) (Zip)

Relationship of Reporting Person(s) to Issuer

X	Director	X	10% Owner
	Officer (give title below)		Other (specify below)

Explanation of Responses:

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

2. 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.

3. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions ranging from $5.9888 to $6.2838, inclusive. The Reporting Person undertake to provide to the Issuer, any securityholder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth above.

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

	Panacea Innovation Limited By: /s/ James Huang, Founding Managing Partner	01/14/2026
	/s/ James Huang	01/14/2026
	** Signature of Reporting Person	Date
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FAQ

Who reported the insider transaction in Atara Biotherapeutics (ATRA)?

The transaction was reported by Panacea Innovation Ltd and James Huang as reporting persons, based on their control relationships with the general partners of Panacea Venture Healthcare Fund II, L.P. and Panacea Opportunity Fund I, L.P..

How many Atara Biotherapeutics shares were sold in this Form 4 filing?

Panacea Venture Healthcare Fund II, L.P. sold 80,554 shares of Atara Biotherapeutics, Inc. common stock in an open-market transaction on January 12, 2026.

What was the sale price for the Atara Biotherapeutics shares?

The filing reports a weighted average sale price of $6.0707 per share, with individual trades executed in a price range from $5.9888 to $6.2838.

How many Atara Biotherapeutics shares do the Panacea funds hold after the sale?

After the reported sale, Panacea Venture Healthcare Fund II, L.P. held 1,324,446 shares and Panacea Opportunity Fund I, L.P. held 48,736 shares of Atara Biotherapeutics common stock.

Does James Huang directly own the Atara Biotherapeutics shares reported in this Form 4?

The filing explains that the shares are held by Panacea Venture Healthcare Fund II, L.P. and Panacea Opportunity Fund I, L.P.. The reporting persons, including James Huang, may be deemed to share beneficial ownership due to their control of the funds’ general partners, but each disclaims such beneficial ownership.

What is the relationship of the reporting persons to Atara Biotherapeutics?

Panacea Innovation Ltd is a 10% owner of Atara Biotherapeutics, Inc., and James Huang is both a director and a 10% owner, as indicated in the filing.