X0306 4 2020-10-14 0 0001728117 Gossamer Bio, Inc. GOSS 0001553179 Christian Waage 3013 SCIENCE PARK ROAD SAN DIEGO CA 92121 0 1 0 0 EVP & General Counsel Common Stock 2020-10-14 4 P 0 2500 9.5272 A 6954 I By family trust Common Stock 547998 D Common Stock 22222 I By trust FBO son This transaction was executed in multiple trades at prices ranging from $9.52 to $9.53 per share. The price reported above reflects the weighted average sale price for the entire number of shares purchased. Information on the exact number of shares purchased at each sale price can be obtained from the Issuer upon request. Includes 141,435 shares subject to forfeiture, which shares will vest in equal monthly installments as set forth in the restricted stock agreement between the Issuer and Reporting Person so that all of the shares will be released from the forfeiture restriction on November 18, 2021, subject to the Reporting Person's continuous service to the Issuer on each such vesting date. Also includes 46,500 restricted stock units granted in February 2020, which shares will vest in three equal annual installments in accordance with the terms of the award and subject to the Reporting Person's continuous service to the Issuer on each vesting date. /s/ Jeff Boerneke, Attorney-in-Fact 2020-10-14