X0306 4 2019-02-12 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 2019-02-12 4 C 0 3454 A 3454 I By family trust Common Stock 2019-02-12 4 P 0 1550 16.00 A 501498 D Common Stock 22222 I By trust FBO son Series B Preferred Stock 2019-02-12 4 C 0 15543 D Common Stock 3454 0 I By family trust The shares of the Issuer's Series B Preferred Stock automatically converted into shares of the Issuer's Common Stock, for no additional consideration, at a ratio of 4.5 to one share, immediately prior to the consummation of the Issuer's initial public offering. The Series B Preferred Stock had no expiration date. Includes 369,871 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 Corporation on each such vesting date. The shares are also subject to certain accelerated vesting provisions as set forth in more detail in the employment agreement between the Issuer and the Reporting Person. /s/ Jeff Boerneke, Attorney-in-Fact 2019-02-12