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

Rhea-AI Filing Summary

Richard Aranda, Chief Medical Officer of Gossamer Bio, Inc. (GOSS), reported receiving a performance stock unit award of 162,500 common stock units on 10/01/2025. The award carries a $0 purchase price and will vest in full upon the earlier of (i) approval of a new drug application for seralutinib or (ii) a change in control, provided vesting occurs on or before the fourth anniversary of the grant date and subject to the reporting person’s continuous service. After the reported transaction, the filing shows 369,356 shares beneficially owned directly and 2,539 shares beneficially owned indirectly through a family trust. The filing was signed by an attorney-in-fact on 10/02/2025.

Positive

• 162,500 performance stock units awarded, vesting upon NDA approval for seralutinib or a change in control
• Award vests within a defined four-year window, linking compensation to a material milestone
• Post-transaction beneficial ownership explicitly stated: 369,356 direct and 2,539 indirect shares

Negative

• None.

Insights

Corporate Governance Analyst

Insider awarded 162,500 performance stock units tied to seralutinib approval or change in control.

The award is structured as performance stock units with vesting contingent on a regulatory milestone (NDA approval for seralutinib) or a corporate transaction, and it must vest within four years. This ties executive compensation directly to a specific product outcome and an exit event.

The filing discloses post-transaction beneficial ownership of 369,356 shares directly and 2,539 indirectly, providing a clear view of the reporting person’s current stake.

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^*

Aranda Richard

(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 Medical 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	369,356	D
Common Stock								2,539	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 Richard Aranda report on Form 4 for GOSS?

He reported receiving a performance stock unit award of 162,500 common stock units on 10/01/2025 with a $0 price.

What are the vesting conditions for the 162,500 performance stock units?

The units vest in full upon the earlier of (i) approval of a new drug application for seralutinib or (ii) a change in control, on or prior to the fourth anniversary of the grant date, subject to continuous service.

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

The filing shows 369,356 shares beneficially owned directly and 2,539 shares beneficially owned indirectly through a family trust.

What price was reported for the granted units?

The Form 4 reports a $0 price for the performance stock unit award.

Who signed the Form 4 filing for the reporting person?

The filing was signed by /s/ Jeff Boerneke, Attorney-in-Fact on 10/02/2025.