SEC FORM 4

SEC FORM 4SEC 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

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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^*

Aranda Richard

(Last)

(First)

(Middle)

3115 MERRYFIELD ROW, SUITE 120

(Street)

SAN DIEGO

CALIFORNIA

92121

(City)

(State)

(Zip)

UNITED STATES

(Country)

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

2a. Foreign Trading Symbol

3. Date of Earliest Transaction (Month/Day/Year)
03/19/2026

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

X	Form filed by One Reporting Person
	Form filed by More than One Reporting Person

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

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)
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	Code	V	Amount	(A) or (D)	Price		6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)

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)
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)	Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares	8. Price of Derivative Security (Instr. 5)		10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
Stock Option (Right to Buy)	$2.88	03/19/2026		D⁽¹⁾			562,500	⁽²⁾	01/01/2036	Common Stock	562,500	⁽¹⁾	0	D
Stock Option (Right to Buy)	$1.13	03/19/2026		D⁽¹⁾			572,000	⁽²⁾	03/03/2035	Common Stock	572,000	⁽¹⁾	0	D
Stock Option (Right to Buy)	$0.97	03/19/2026		D⁽¹⁾			487,500	⁽²⁾	01/01/2034	Common Stock	487,500	⁽¹⁾	0	D
Stock Option (Right to Buy)	$0.838	03/19/2026		D⁽¹⁾			162,500	⁽²⁾	11/19/2033	Common Stock	162,500	⁽¹⁾	0	D
Stock Option (Right to Buy)	$1.21	03/19/2026		D⁽¹⁾			157,500	⁽²⁾	03/19/2033	Common Stock	157,500	⁽¹⁾	0	D
Stock Option (Right to Buy)	$2.16	03/19/2026		D⁽¹⁾			157,500	⁽²⁾	12/06/2032	Common Stock	157,500	⁽¹⁾	0	D
Stock Option (Right to Buy)	$1.36	03/19/2026		D⁽¹⁾			126,667	⁽²⁾	01/05/2032	Common Stock	126,667	⁽¹⁾	0	D
Stock Option (Right to Buy)	$1.36	03/19/2026		D⁽¹⁾			20,000	⁽²⁾	06/21/2031	Common Stock	20,000	⁽¹⁾	0	D
Stock Option (Right to Buy)	$1.36	03/19/2026		D⁽¹⁾			40,000	⁽²⁾	02/25/2031	Common Stock	40,000	⁽¹⁾	0	D
Stock Option (Right to Buy)	$1.36	03/19/2026		D⁽¹⁾			22,784	⁽²⁾	02/14/2030	Common Stock	22,784	⁽¹⁾	0	D
Stock Option (Right to Buy)	$1.36	03/19/2026		D⁽¹⁾			9,167	⁽²⁾	12/23/2029	Common Stock	9,167	⁽¹⁾	0	D
Stock Option (Right to Buy)	$1.36	03/19/2026		D⁽¹⁾			30,000	⁽²⁾	03/25/2029	Common Stock	30,000	⁽¹⁾	0	D
Stock Option (Right to Buy)	$0.45	03/19/2026		A⁽¹⁾		562,500		⁽²⁾	01/01/2036	Common Stock	562,500	⁽¹⁾	562,500	D
Stock Option (Right to Buy)	$0.45	03/19/2026		A⁽¹⁾		572,000		⁽²⁾	03/03/2035	Common Stock	572,000	⁽¹⁾	572,000	D
Stock Option (Right to Buy)	$0.45	03/19/2026		A⁽¹⁾		487,500		⁽²⁾	01/01/2034	Common Stock	487,500	⁽¹⁾	487,500	D
Stock Option (Right to Buy)	$0.45	03/19/2026		A⁽¹⁾		162,500		⁽²⁾	11/19/2033	Common Stock	162,500	⁽¹⁾	162,500	D
Stock Option (Right to Buy)	$0.45	03/19/2026		A⁽¹⁾		157,500		⁽²⁾	03/19/2033	Common Stock	157,500	⁽¹⁾	157,500	D
Stock Option (Right to Buy)	$0.45	03/19/2026		A⁽¹⁾		157,500		⁽²⁾	12/06/2032	Common Stock	157,500	⁽¹⁾	157,500	D
Stock Option (Right to Buy)	$0.45	03/19/2026		A⁽¹⁾		126,667		⁽²⁾	01/05/2032	Common Stock	126,667	⁽¹⁾	126,667	D
Stock Option (Right to Buy)	$0.45	03/19/2026		A⁽¹⁾		20,000		⁽²⁾	06/21/2031	Common Stock	20,000	⁽¹⁾	20,000	D
Stock Option (Right to Buy)	$0.45	03/19/2026		A⁽¹⁾		40,000		⁽²⁾	02/25/2031	Common Stock	40,000	⁽¹⁾	40,000	D
Stock Option (Right to Buy)	$0.45	03/19/2026		A⁽¹⁾		22,784		⁽²⁾	02/14/2030	Common Stock	22,784	⁽¹⁾	22,784	D
Stock Option (Right to Buy)	$0.45	03/19/2026		A⁽¹⁾		9,167		⁽²⁾	12/23/2029	Common Stock	9,167	⁽¹⁾	9,167	D
Stock Option (Right to Buy)	$0.45	03/19/2026		A⁽¹⁾		30,000		⁽²⁾	03/25/2029	Common Stock	30,000	⁽¹⁾	30,000	D

Explanation of Responses:

1. Effective as of March 19, 2026 (the "Repricing Date"), the Issuer approved a one-time repricing of certain outstanding stock options (the "Repriced Options") granted under the Issuer's 2019 Incentive Award Plan (the "2019 Plan"), which reduced the per share exercise price of each Repriced Option to $0.45 (the "Option Repricing"). Except as modified by the Option Repricing, all other terms and conditions of the Repriced Options, including, without limitation, any provisions with respect to vesting and term of the Repriced Options, remain in full force and effect.

2. This stock option award was issued pursuant to the 2019 Plan and becomes exercisable in accordance with the vesting schedule specified in the award agreement and as previously reported on applicable Form 4, subject to the Reporting Person's continued service with the Issuer as of the applicable vesting date.

Remarks:

	/s/ Jeff Boerneke, Attorney-in-Fact	03/20/2026
	** 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.
* Form 4: SEC 1474 (03-26)

SEC Form 4 filed by Aranda Richard