[Form 4] Gossamer Bio, Inc. Insider Trading Activity

Rhea-AI Filing Summary

Sandra Milligan, a director of Gossamer Bio, purchased 26,050 shares of the company's common stock on 08/19/2025 at $1.92 per share, increasing her beneficial ownership to 58,050 shares. The transaction is reported on a Form 4 covering non-derivative securities. The filing indicates the purchase was reported individually by the reporting person.

Positive

• Director purchase reported: Sandra Milligan acquired 26,050 shares, signaling a director-level purchase of company stock
• Clear post-transaction ownership: Beneficial ownership increased to 58,050 shares, which is explicitly disclosed

Negative

• None.

Insights

Securities Analyst

TL;DR: A company director bought 26,050 shares at $1.92, raising her stake to 58,050 shares; the transaction is disclosed on Form 4.

The reported non-derivative purchase is straightforward: 26,050 shares acquired at $1.92 per share, with beneficial ownership thereafter of 58,050 shares. As disclosed, the filing was made by one reporting person and identifies the reporting person as a director. There are no derivative instruments, dispositions, or additional explanatory remarks in the filing. Based solely on the filing text, the item is a routine insider purchase disclosure required under Section 16 and contains no further material context such as intent, plan, or aggregated holdings beyond the post-transaction total.

Corporate Governance Expert

TL;DR: Director-level insider purchased shares and reported the change; disclosure complies with Section 16 reporting requirements.

The Form 4 documents a standard reported acquisition by a director. It confirms the reporting persons relationship to the issuer as a director and that the form was filed by one reporting person. The filing contains no amendments, no derivative security activity, and no explanatory remarks beyond the transaction details. From a governance disclosure perspective, the filing provides the necessary transaction-level information but does not include contextual notes such as trading plan references or beneficial ownership thresholds.

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^*

Milligan Sandra

(Last) (First) (Middle)

3115 MERRYFIELD ROW, SUITE 120

(Street)

SAN DIEGO CA 92121

(City) (State) (Zip)

2. Issuer Name and Ticker or Trading Symbol
Gossamer Bio, Inc. [ GOSS ]

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

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

3. Date of Earliest Transaction (Month/Day/Year)
08/19/2025

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

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

X	Form filed by One Reporting Person
	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	08/19/2025		P		26,050	A	$1.92	58,050	D

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

Explanation of Responses:

Remarks:

	/s/ Jeff Boerneke, Attorney-in-Fact	08/20/2025
	** 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 transaction did GOSS director Sandra Milligan report on Form 4?

She reported a non-derivative purchase of 26,050 shares of Gossamer Bio common stock.

At what price were the GOSS shares purchased in the Form 4?

The reported purchase price was $1.92 per share.

How many GOSS shares does Sandra Milligan beneficially own after the reported transaction?

The filing shows she beneficially owns 58,050 shares following the transaction.

Was the Form 4 filed by more than one reporting person for this transaction?

No. The filing indicates the Form was filed by one reporting person.

Does the Form 4 report any derivative transactions or dispositions for Sandra Milligan?

No. The filing lists only a non-derivative acquisition and shows no derivative securities or dispositions.