UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 14A

Proxy Statement Pursuant to Section 14(a) of the

Securities Exchange Act of 1934

(Amendment No.     )

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¨ Preliminary Proxy Statement

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¨Definitive Proxy Statement

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¨Soliciting Material under §240.14a-12

Gossamer Bio, Inc.

(Name of Registrant as Specified In Its Charter)

(Name of Person(s) Filing Proxy Statement, if other than the Registrant)

Payment of Filing Fee (Check the appropriate box):

x No fee required.

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¨ Fee computed on table in exhibit required by Item 25(b) per Exchange Act Rules 14a-6(i)(1) and 0-11 with preliminary

ote “FOR” Proposal 2. 2. Ratification of the appointment of Ernst & Young LLP as our independent registered public accountants for the year ending December 31, 2020. TO ATTEND the Annual Meeting of Gossamer Bio, Inc., please visit www.proxydocs.com/GOSS for virtual meeting registration details. The control number located in the shaded gray box will be required to register. INTERNET www.investorelections.com/GOSS TELEPHONE (866) 648-8133 *E-MAIL paper@investorelections.com ACCOUNT NO.     SHARE