X0609 4 2026-06-04 0 0001728117 Gossamer Bio, Inc. GOSS 0002015114 Nathan Steven D false 3115 MERRYFIELD ROW, SUITE 120 SAN DIEGO CA 92121 1 0 0 0 0 Stock Option (Right to Buy) 0.178 2026-06-04 4 A 0 115000 0 A 2036-06-03 Common Stock 115000 115000 D Award made pursuant to Non-Employee Director Compensation Program. The entire number of shares subject to this option becomes fully vested and exercisable on the first to occur of (a) the first anniversary of the grant date or (b) the next occurring annual meeting of the Issuer's stockholders, subject to the Reporting Person's continued service on the board of directors of the Issuer through such vesting date. /s/ Christian Waage, Attorney-in-Fact 2026-06-05