X0609 4 2026-03-19 0 0001728117 Gossamer Bio, Inc. GOSS 0001352620 Hasnain Faheem 3115 MERRYFIELD ROW, SUITE 120 SAN DIEGO CA 92121 1 1 0 0 President & CEO 0 Stock Option (Right to Buy) 2.88 2026-03-19 4 D 0 1680000 D 2036-01-01 Common Stock 1680000 0 D Stock Option (Right to Buy) 1.13 2026-03-19 4 D 0 1540000 D 2035-03-03 Common Stock 1540000 0 D Stock Option (Right to Buy) 0.97 2026-03-19 4 D 0 1312500 D 2034-01-01 Common Stock 1312500 0 D Stock Option (Right to Buy) 0.838 2026-03-19 4 D 0 437500 D 2033-11-19 Common Stock 437500 0 D Stock Option (Right to Buy) 1.21 2026-03-19 4 D 0 544500 D 2033-03-19 Common Stock 544500 0 D Stock Option (Right to Buy) 2.16 2026-03-19 4 D 0 544500 D 2032-12-06 Common Stock 544500 0 D Stock Option (Right to Buy) 11.94 2026-03-19 4 D 0 650000 D 2032-01-05 Common Stock 650000 0 D Stock Option (Right to Buy) 9.79 2026-03-19 4 D 0 325000 D 2031-02-25 Common Stock 325000 0 D Stock Option (Right to Buy) 12.10 2026-03-19 4 D 0 47000 D 2030-06-16 Common Stock 47000 0 D Stock Option (Right to Buy) 22.10 2026-03-19 4 D 0 43500 D 2029-03-25 Common Stock 43500 0 D Stock Option (Right to Buy) 0.45 2026-03-19 4 A 0 1680000 A 2036-01-01 Common Stock 1680000 1680000 D Stock Option (Right to Buy) 0.45 2026-03-19 4 A 0 1540000 A 2035-03-03 Common Stock 1540000 1540000 D Stock Option (Right to Buy) 0.45 2026-03-19 4 A 0 1312500 A 2034-01-02 Common Stock 1312500 1312500 D Stock Option (Right to Buy) 0.45 2026-03-19 4 A 0 437500 A 2033-11-19 Common Stock 437500 437500 D Stock Option (Right to Buy) 0.45 2026-03-19 4 A 0 544500 A 2033-03-19 Common Stock 544500 544500 D Stock Option (Right to Buy) 0.45 2026-03-19 4 A 0 544500 A 2032-12-06 Common Stock 544500 544500 D Stock Option (Right to Buy) 0.45 2026-03-19 4 A 0 650000 A 2032-01-05 Common Stock 650000 650000 D Stock Option (Right to Buy) 0.45 2026-03-19 4 A 0 325000 A 2031-02-25 Common Stock 325000 325000 D Stock Option (Right to Buy) 0.45 2026-03-19 4 A 0 47000 A 2030-06-16 Common Stock 47000 47000 D Stock Option (Right to Buy) 0.45 2026-03-19 4 A 0 43500 A 2029-03-25 Common Stock 43500 43500 D 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. 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. /s/ Jeff Boerneke, Attorney-in-Fact 2026-03-20