[Form 4] Atara Biotherapeutics, Inc Insider Trading Activity

Rhea-AI Filing Summary

Panacea Innovation Ltd, a reporting person linked to Atara Biotherapeutics, Inc. (ATRA), acquired 55,000 shares of Atara common stock on 08/15/2025 at a weighted-average price of $12.1895 per share. After the transaction, the reporting persons disclose beneficial ownership of 1,405,000 shares held indirectly. The filing identifies Panacea Innovation Limited and James Huang (who is the sole owner of Panacea Innovation Limited) as reporting persons and explains that Panacea entities hold securities through Panacea Venture Healthcare Fund II, L.P. and Panacea Opportunity Fund I, L.P.; the filing also includes a disclaimer that the reporting persons may be deemed to share beneficial ownership but disclaim such ownership. The price reported is a weighted average of multiple purchases ranging from $11.83 to $12.44.

Positive

• Insider-affiliated purchase: 55,000 shares acquired on 08/15/2025 shows a controlled-party acquisition
• Transparent pricing: Weighted-average price disclosed at $12.1895 with a purchase range of $11.83–$12.44
• Clear ownership disclosure: Post-transaction indirect beneficial ownership reported as 1,405,000 shares and ownership chain explained

Negative

• None.

Insights

Securities Analyst

TL;DR: Insider-affiliated entity bought 55,000 ATRA shares at ~$12.19, modestly increasing indirect stake to 1.405M shares.

The purchase reported on Form 4 is a clear, documented open-market acquisition by an entity controlled by James Huang. The weighted-average price and disclosed price range provide transparent execution detail. The post-transaction indirect beneficial ownership of 1,405,000 shares is significant for disclosure purposes but the filing does not state percentage ownership relative to outstanding shares, limiting assessment of scale. No options or derivative transactions were reported. Impact is generally positive as insider-affiliated purchases can signal alignment, but materiality depends on company share count and investor context.

Corporate Governance Expert

TL;DR: Filing shows compliant disclosure of insider-related purchases and ownership chain with appropriate signatures.

The Form 4 properly lists both the reporting entity (Panacea Innovation Ltd) and an individual (James Huang) with director and 10% owner checkboxes. The filing includes explanatory footnotes clarifying ownership structure and a standard disclaimer regarding shared beneficial ownership. The disclosure is procedurally complete: transaction date, weighted-average price range, and post-transaction holdings are reported, and the form is signed. The filing does not include any amendments or related-party transaction statements beyond ownership linkage.

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)
08/15/2025

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	08/15/2025		P		55,000	A	$12.1895(1)	1,405,000	I	See Footnotes(2)(3)

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. The price reported in Column 4 is a weighted average price. These shares were purchased in multiple transactions ranging from $11.83 to $12.44, 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 purchased at each separate price within the range set forth above.

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

3. 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.

	Panacea Innovation Limited By: /s/ James Huang, Founding Managing Partner	08/19/2025
	/s/ James Huang	08/19/2025
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.

FAQ

What shares were purchased in the ATRA Form 4 filed by Panacea Innovation Ltd?

The filing reports the acquisition of 55,000 shares of Atara common stock on 08/15/2025.

At what price were the ATRA shares purchased by the reporting persons?

The weighted-average price reported is $12.1895 per share, with purchases in the range $11.83 to $12.44.

What is the reported beneficial ownership after the transaction?

The filing reports 1,405,000 shares beneficially owned following the reported transaction, held indirectly.

Who are the reporting persons in the Form 4 for ATRA?

The reporting persons are Panacea Innovation Limited and James Huang, each indicated as a director and 10% owner.

Does the filing explain the ownership structure behind the holdings?

Yes. Footnotes state that Panacea entities hold securities through Panacea Venture Healthcare Fund II, L.P. and Panacea Opportunity Fund I, L.P. and that James Huang is the sole owner of Panacea Innovation Limited.