Sec Form 4 Filing - Christian Waage @ Gossamer Bio, Inc. - 2019-02-12

FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person Christian Waage 2. Issuer Name and Ticker or Trading Symbol Gossamer Bio, Inc. [ GOSS] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director _____ 10% Owner X __ Officer (give title below) _____ Other (specify below) EVP & General Counsel (Last) (First) (Middle) 3013 SCIENCE PARK ROAD 3. Date of Earliest Transaction (MM/DD/YY) 02/12/2019 (Street) SAN DIEGO, CA92121 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) __ X __ Form filed by One Reporting Person _____ Form filed by More than One Reporting Person (City) (State) (Zip)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned 1.Title of Security (Instr. 3) 2. Transaction Date (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Common Stock 02/12/2019 C 3,454 A 3,454 I By family trust Common Stock 02/12/2019 P 1,550 A $ 16 501,498 ( 2 ) D Common Stock 22,222 I By trust FBO son

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned ( e.g. , puts, calls, warrants, options, convertible securities) 1. Title of Derivative Security (Instr. 3) 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 4. Transaction Code (Instr. 8) 5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5) 6. Date Exercisable and Expiration Date (MM/DD/YY) 7. Title and Amount of Underlying Securities (Instr. 3 and 4) 8. Price of Derivative Security (Instr. 5) 9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4) 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4) 11. Nature of Indirect Beneficial Ownership (Instr. 4) Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares Series B Preferred Stock ( 1 ) 02/12/2019 C 15,543 ( 1 ) ( 1 ) Common Stock 3,454 ( 1 ) 0 I By family trust

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other Christian Waage 3013 SCIENCE PARK ROAD SAN DIEGO, CA92121 EVP & General Counsel Signatures /s/ Jeff Boerneke, Attorney-in-Fact 02/12/2019 Signature of Reporting Person Date

Explanation of Responses:

( 1 )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. ( 2 )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.

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.

* If the form is filed by more than one reporting person, see Instruction 4(b)(v).

** Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).

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