Bryan Giraudo - 02 Jan 2026 Form 4 Insider Report for Gossamer Bio, Inc. (GOSS)

Role: COO/CFO
Signature: /s/ Jeff Boerneke, Attorney-in-Fact
Issuer symbol: GOSS
Transactions as of: 02 Jan 2026
Net transactions value: $0
Form type: 4
Filing time: 05 Jan 2026, 16:39:34 UTC
Previous filing: 02 Oct 2025
SEC: View on sec.gov

Reporting Owners (1)

Name	Relationship	Address	Signature	Signature date	CIK
Giraudo Bryan	COO/CFO	3115 MERRYFIELD ROW, SUITE 120, SAN DIEGO	/s/ Jeff Boerneke, Attorney-in-Fact	05 Jan 2026	0001740847

Transactions Table

Type	Sym	Class	Transaction	Value $	Shares	Change %	* Price $	Shares After	Date	Ownership	Footnotes
transaction	GOSS	Common Stock	Award	$0	+115,750	+42%	$0.000000	389,737	02 Jan 2026	Direct	F1
holding	GOSS	Common Stock						480,010	02 Jan 2026	By family trust

Derivative Securities (e.g., puts, calls, warrants, options, convertible securities)

Type	Sym	Class	Transaction	Value $	Shares	Change %	* Price $	Shares After	Date	Underlying Class	Amount	Exercise Price	Ownership	Footnotes
transaction	GOSS	Stock Option (Right to Buy)	Award	$0	+693,750		$0.000000	693,750	02 Jan 2026	Common Stock	693,750	$2.88	Direct	F2

* An asterisk sign (*) next to the price indicates that the price is likely invalid.

Explanation of Responses:

Id	Content
F1	Represents restricted stock unit award, which will vest in four equal annual installments in accordance with the terms of the award and subject to the Reporting Person's continuous service to the Issuer on each vesting date.
F2	25% of the total number of shares subject to the option will vest on January 2, 2027 and 1/48th of the total number of shares subject to the option vest on the last day of each one-month period thereafter, subject to the Reporting Person's continuous service to the Issuer on each such vesting date.