X0306 4 2019-09-27 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 2019-09-27 4 P 0 1000 16.6542 A 4454 I By family trust Common Stock 501498 D Common Stock 22222 I By trust FBO son This transaction was executed in multiple trades at prices ranging from $16.63 to $16.69 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 282,848 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. /s/ Jeff Boerneke, Attorney-in-Fact 2019-09-27