Gossamer Bio, Inc. — Director's Dealing 2019

Feb 12, 2019

SEC Form 4 — Statement of Changes in Beneficial Ownership

Issuer: Gossamer Bio, Inc. (GOSS)
CIK: 0001728117
Period of Report: 2019-02-12

Reporting Person: ARCH Venture Partners IX, LLC (10% Owner)
Reporting Person: ARCH Venture Fund IX Overage, L.P. (10% Owner)
Reporting Person: ARCH Venture Partners IX Overage, L.P. (10% Owner)
Reporting Person: ARCH Venture Fund IX, L.P. (10% Owner)
Reporting Person: ARCH Venture Partners IX, L.P. (10% Owner)
Reporting Person: NELSEN ROBERT (10% Owner)
Reporting Person: CRANDELL KEITH (10% Owner)
Reporting Person: BYBEE CLINTON (10% Owner)

Non-Derivative Transactions

Date	Security	Code	Shares	Price	A/D	Holdings After	Ownership
2019-02-12	Common Stock	C	3682539	—	Acquired	3682539	Indirect
2019-02-12	Common Stock	C	345419	—	Acquired	4027958	Indirect
2019-02-12	Common Stock	C	3682539	—	Acquired	3682539	Indirect
2019-02-12	Common Stock	C	345419	—	Acquired	4027958	Indirect

Derivative Transactions

Date	Security	Exercise Price	Code	Shares	A/D	Expiration	Underlying	Ownership
2019-02-12	Series A Preferred Stock	$	C	16571429	Disposed		Common Stock (3682539)	Indirect
2019-02-12	Series A Preferred Stock	$	C	16571428	Disposed		Common Stock (3682539)	Indirect
2019-02-12	Series B Preferred Stock	$	C	1554388	Disposed		Common Stock (345419)	Indirect
2019-02-12	Series B Preferred Stock	$	C	1554388	Disposed		Common Stock (345419)	Indirect

Footnotes

F1: The shares of the Issuer's Series A Preferred Stock and 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 A Preferred Stock and Series B Preferred Stock had no expiration date.

F2: These shares are directly held by ARCH Venture Fund IX, L.P. ("ARCH IX"). ARCH Venture Partners IX, L.P. ("GPLP"), as the sole general partner of ARCH IX, may be deemed to beneficially own the shares held by ARCH IX. ARCH Venture Partners IX, LLC ("GPLLC"), as the sole general partner of GPLP, may be deemed to beneficially own the shares held by GPLP. As managing directors of GPLLC, each of Keith Crandell, Clinton Bybee and Robert Nelsen (the "ARCH Managing Directors"), may be deemed to beneficially own the shares held by GPLLC.

F3: Each of GPLP, ARCH Venture Partners IX Overage, L.P. ("Overage GPLP"), GPLLC and the ARCH Managing Directors disclaims beneficial ownership of the securities reported herein, except to the extent of their pecuniary interest therein, if any.

F4: These shares are directly held by ARCH Venture Fund IX Overage, L.P. ("ARCH Overage"). Overage GPLP, as the sole general partner of ARCH Overage, may be deemed to beneficially own the shares held by ARCH Overage. GPLLC, as the sole general partner of Overage GPLP, may be deemed to beneficially own the shares held by Overage GPLP. As managing directors of GPLLC, each of the ARCH Managing Directors may be deemed to beneficially own the shares held by GPLLC.