Panacea funds linked to Atara (NASDAQ: ATRA) director sell 313,446 shares

Rhea-AI Filing Summary

Atara Biotherapeutics, Inc. reported an insider filing showing that investment entities associated with Panacea Innovation executed an open-market sale of 313,446 shares of common stock at a weighted average price of $10.0975 per share, with individual trades between $10.00 and $10.50. The shares sold were held by Panacea Venture Healthcare Fund II, L.P. Following the sale, entities associated with Panacea report indirect holdings of 1,011,000 shares in one position and 307,894 shares in another. James Huang and Panacea Innovation Limited may be deemed to share beneficial ownership of these fund holdings, but each expressly disclaims beneficial ownership.

Insights

Insider trading and governance analyst

Large indirect fund sale, but positions remain sizable and ownership is disclaimed.

The filing shows an open-market sale of 313,446 Atara Biotherapeutics common shares at a weighted average of $10.0975, executed by Panacea Venture Healthcare Fund II, L.P. rather than directly by an individual executive.

After this transaction, Panacea-related entities still report indirect positions of 1,011,000 and 307,894 shares. Footnotes state James Huang and Panacea Innovation Limited may be deemed to share beneficial ownership through fund general partners, but each disclaims such beneficial ownership, which limits how directly this activity reflects personal trading intent.

The net effect in this filing is a net-sell of 313,446 shares with no derivative exercises or tax-withholding events. The absence of remaining derivative positions in the data suggests this is a straightforward portfolio move by the funds rather than an options-driven liquidity event.

Insider Trade Summary

Net Seller: 313,446 shares ($3,165,021)

Net Sell 2 txns

Insider Panacea Innovation Ltd, Huang James

Role null | null

Sold 313,446 shs ($3.17M)

Type	Security	Shares	Price	Value
Sale	Common Stock	313,446	$10.0975	$3.17M
holding	Common Stock	--	--	--

Holdings After Transaction: Common Stock — 1,011,000 shares (Indirect, See Footnote)

Footnotes (1)

1. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions ranging from $10.00 to $10.50, 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. Represents securities held by Panacea Venture Healthcare Fund II, L.P. 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. Represents securities held by Panacea Opportunity Fund I, L.P.

Key Figures

Shares sold: 313,446 shares Weighted average sale price: $10.0975 per share Indirect holdings after sale (position 1): 1,011,000 shares +2 more

5 metrics

Shares sold 313,446 shares Open-market sale of common stock

Weighted average sale price $10.0975 per share Common stock sale price, trades $10.00–$10.50

Indirect holdings after sale (position 1) 1,011,000 shares Total shares following transaction for one fund

Indirect holdings after sale (position 2) 307,894 shares Holding entry reported as of transaction date

Net buy/sell direction Net-sell of 313,446 shares Transaction summary for reported period

Key Terms

weighted average price, beneficial ownership, indirect ownership, open-market sale, +1 more

5 terms

weighted average price financial

"The price reported in Column 4 is a weighted average price."

Weighted average price is the average price of a security where each trade or component is counted according to its size, so bigger trades pull the average more than smaller ones. Think of it like calculating the average cost of a grocery haul where items you bought more of have greater influence on the final per-item cost. Investors use it to understand the true average price paid or received, judge execution quality, and compare trading performance against market movement.

beneficial ownership financial

"may be deemed to share beneficial ownership of the securities held"

Beneficial ownership means the person or entity that actually enjoys the benefits of owning shares or other assets — such as receiving dividends, voting rights, or price gains — even if the legal title is held in another name. For investors it matters because knowing who truly controls and profits from a company reveals who can influence decisions, exposes potential conflicts of interest or hidden concentration of power, and affects transparency and risk in the stock.

indirect ownership financial

"total_shares_following_transaction": "307894.0000" ... "ownership_type": "indirect""

open-market sale financial

"transaction_action": "open-market sale""

An open-market sale is when a shareholder sells existing shares directly on a public exchange to any willing buyer, rather than through a private deal. Think of it like putting goods on a busy market stall where price is set by supply and demand; for investors it matters because such sales increase available supply, can put short-term downward pressure on the stock price, and signal changes in liquidity or investor confidence.

ten percent owner regulatory

""is_ten_percent_owner": 1"

Form 4 Insider Transactions: What Each Field Means →

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
Estimated average burden
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 PANACEA CAPITAL

79 SCIENCE PARK DRIVE, #04-05

(Street)

SINGAPORE SINGAPORE 118264

(City) (State) (Zip)

SINGAPORE

(Country)

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)

2a. Foreign Trading Symbol

3. Date of Earliest Transaction (Month/Day/Year)
05/07/2026

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

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

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

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	05/07/2026		S		313,446	D	$10.0975(1)	1,011,000	I	See Footnote(2)(3)
Common Stock								307,894	I	See Footnotes(3)(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 PANACEA CAPITAL

79 SCIENCE PARK DRIVE, #04-05

(Street)

SINGAPORE SINGAPORE 118264

(City) (State) (Zip)

SINGAPORE

(Country)

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 PANACEA CAPITAL

79 SCIENCE PARK DRIVE, #04-05

(Street)

SINGAPORE SINGAPORE 118264

(City) (State) (Zip)

SINGAPORE

(Country)

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 sold in multiple transactions ranging from $10.00 to $10.50, 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.

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.

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

	Panacea Innovation Limited By: /s/ James Huang, Founding Managing Partner	05/11/2026
	/s/ James Huang	05/11/2026
	** 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.
* Form 4: SEC 1474 (03-26)

FAQ

What insider transaction did Atara Biotherapeutics (ATRA) report in this Form 4?

Atara Biotherapeutics reported an open-market sale of 313,446 common shares by Panacea Venture Healthcare Fund II, L.P. The weighted average sale price was $10.0975 per share, with trades executed between $10.00 and $10.50 during the reported transaction date.

Who is the primary seller in the Atara Biotherapeutics (ATRA) Form 4 filing?

The primary seller is Panacea Venture Healthcare Fund II, L.P., an investment fund associated with Panacea Innovation Limited. The filing notes that James Huang and Panacea Innovation Limited may be deemed to share beneficial ownership of the fund’s holdings but each disclaims such beneficial ownership.

How many Atara Biotherapeutics (ATRA) shares do Panacea-related entities hold after the sale?

After the reported sale, Panacea-related entities report indirect ownership of 1,011,000 Atara Biotherapeutics shares in one position and 307,894 shares in another. These holdings are reported through investment funds, and related reporting persons expressly disclaim beneficial ownership despite possible deemed ownership.

What price range did the Atara Biotherapeutics (ATRA) insider sale cover?

The reported weighted average sale price was $10.0975 per Atara Biotherapeutics share. According to the footnote, the 313,446 shares were sold in multiple transactions at prices ranging from $10.00 to $10.50, and detailed trade-level pricing is available upon request.

How is James Huang connected to the Atara Biotherapeutics (ATRA) insider sale?

James Huang is the sole owner of Panacea Innovation Limited, which controls the general partners of the Panacea funds holding Atara shares. The filing states he may be deemed to share beneficial ownership of the funds’ holdings but disclaims beneficial ownership of those securities.