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

Rhea-AI Filing Summary

Gossamer Bio, Inc. (GOSS) Chief Operating and Financial Officer Bryan Giraudo reported an award of 181,250 performance stock units on 10/01/2025. The award is a non‑cash grant that will vest in full upon the earlier of: approval of a new drug application for seralutinib or a change in control, provided vesting occurs on or before the fourth anniversary of the grant and the reporting person remains in continuous service. Following the reported grant, Mr. Giraudo beneficially owns 273,987 shares directly and 480,010 shares indirectly through a family trust, for combined reported beneficial ownership disclosed on the form.

Positive

• 181,250 performance stock units granted to align executive incentives with seralutinib approval
• Reporting person holds 273,987 shares directly and 480,010 indirectly, indicating significant insider stake

Negative

• None.

Insights

Corporate Governance Analyst

Insider received performance-based equity tied to a regulatory milestone.

The award of 181,250 performance stock units vests only on the earlier of seralutinib new drug application approval or a change in control, with a four‑year outer vesting limit and a continuous service requirement. This structure aligns executive compensation with a specific regulatory outcome rather than time‑based tenure.

The filing names Mr. Bryan Giraudo as COO/CFO and shows direct ownership of 273,987 shares and indirect ownership of 480,010 shares, reflecting his reported economic exposure to the company.

Compensation & Equity Structuring Specialist

Grant is a performance stock unit conditioned on a product approval or change in control.

The instrument is a performance stock unit award granted on 10/01/2025 with no cash price paid, per the form. Vesting is binary and event‑driven, tying potential dilution to a single material milestone: NDA approval of seralutinib or change in control within four years.

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).

1. Name and Address of Reporting Person^*

Giraudo Bryan

(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)

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

3. Date of Earliest Transaction (Month/Day/Year)
10/01/2025

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	10/01/2025		A		181,250(1)	A	$0	273,987	D
Common Stock								480,010	I	By family trust

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:

1. Represents performance stock unit award, which will vest in full upon the earlier of (i) the approval of a new drug application for seralutinib or (ii) a change in control, in either case on or prior to the fourth anniversary of the grant date, and subject to the Reporting Person's continuous service to the Issuer.

Remarks:

	/s/ Jeff Boerneke, Attorney-in-Fact	10/02/2025
	** 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 Bryan Giraudo report on Form 4 for GOSS?

He reported receipt of 181,250 performance stock units on 10/01/2025.

What are the vesting conditions for the awarded performance stock units?

They vest in full upon the earlier of approval of a new drug application for seralutinib or a change in control, on or before the fourth anniversary of the grant, and subject to continuous service.

How many shares does the reporting person beneficially own after the transaction?

The form reports 273,987 shares beneficially owned directly and 480,010 indirectly through a family trust.

What role does the reporting person hold at Gossamer Bio?

The filing identifies Bryan Giraudo as COO/CFO.

When was the Form 4 filed and signed by the attorney-in-fact?

The signature block shows the form was executed by an attorney-in-fact on 10/02/2025.