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

Rhea-AI Filing Summary

Robert Paul Smith Jr., identified as an Officer (Chief Commercial Officer) of Gossamer Bio, Inc. (GOSS), reported a securities acquisition on 10/01/2025. The filing shows an award of 162,500 performance stock units issued at $0 that will vest in full upon the earlier of (i) approval of a new drug application for seralutinib or (ii) a change in control, in either case on or before the fourth anniversary of the grant, and subject to his continuous service to the company. The filing also discloses 25,000 shares held indirectly by a family trust. The Form 4 was submitted by one reporting person and signed by an attorney-in-fact on 10/02/2025.

Positive

• 162,500 performance stock units awarded tying pay to seralutinib NDA approval or change in control
• 25,000 shares held indirectly by a family trust, increasing disclosed insider alignment

Negative

• None.

Insights

Compensation & Equity Plan Specialist

Performance award of 162,500 units vests on NDA approval or change in control.

The grant is structured as performance stock units that carry no immediate cash cost ($0) to the reporting person and vest only upon specific corporate events: approval of an NDA for seralutinib or a change in control, each capped at the fourth anniversary of the grant. This aligns executive payout to milestone outcomes and ties potential equity realization to either product approval or corporate transaction.

The award remains subject to the reporting person's continuous service, which can forfeit units if employment terminates before vesting.

Insider Ownership & Disclosure Analyst

Reporting shows direct and indirect ownership totaling 187,500 shares (162,500 direct, 25,000 indirect).

The Form 4 records a direct beneficial interest in 162,500 performance stock units and an indirect holding of 25,000 shares via a family trust. The filing was made as an individual report and executed by an attorney-in-fact, indicating formal compliance with Section 16 reporting requirements.

No derivative instruments, exercised options, or cash purchases are reported in this filing.

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^*

Smith Robert Paul JR

(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)
	Chief Commercial Officer

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		162,500(1)	A	$0	162,500	D
Common Stock								25,000	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 did Robert Paul Smith Jr. report on Form 4 for GOSS?

He reported an award of 162,500 performance stock units granted on 10/01/2025 and 25,000 shares held indirectly by a family trust.

When do the 162,500 performance stock units vest?

They vest in full upon the earlier of approval of an NDA for seralutinib or a change in control, on or prior to the fourth anniversary of the grant, subject to continuous service.

Was there a cash price paid for the awarded units?

No cash price is reported; the units are listed with a $0 price in the Form 4.

Who filed and signed the Form 4 for this transaction?

The Form 4 was filed by one reporting person and the signature on the filing is by Jeff Boerneke, Attorney-in-Fact dated 10/02/2025.

Does the filing show any derivative securities or exercised options?

No. Table II for derivative securities shows no reported transactions or holdings in this filing.