Sec Form 4 Filing - Atlas Venture Fund IX, L.P. @ Surface Oncology, Inc. - 2018-04-23

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 Atlas Venture Fund IX, L.P. 2. Issuer Name and Ticker or Trading Symbol Surface Oncology, Inc. [ SURF] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director X __ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) 25 FIRST STREET, SUITE 303 3. Date of Earliest Transaction (MM/DD/YY) 04/23/2018 (Street) CAMBRIDGE, MA02141 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) _____ Form filed by One Reporting Person __ X __ 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 04/23/2018 C 3,181,817 A 4,545,453 D ( 2 ) Common Stock 04/23/2018 P 100,000 A $ 15 4,645,453 D ( 2 )

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 A Preferred Stock ( 1 ) 04/23/2018 C 7,000,000 ( 1 ) ( 1 ) Common Stock 3,181,817 ( 1 ) ( 1 ) 0 D ( 2 )

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other Atlas Venture Fund IX, L.P. 25 FIRST STREET, SUITE 303 CAMBRIDGE, MA02141 X Atlas Venture Associates IX, L.P. 25 FIRST STREET, SUITE 303 CAMBRIDGE, MA02141 X Atlas Venture Associates IX, LLC 25 FIRST STREET, SUITE 303 CAMBRIDGE, MA02141 X Signatures Atlas Venture Fund IX, LP, By: Atlas VentureAssociates IX, LP, its general partner, By: Atlas VentureAssociates IX, LLC, its general partner, By: FrankCastellucci, General Counsel /s/ Frank Castellucci 04/23/2018 Signature of Reporting Person Date Atlas Venture Associates IX, LP, By: Atlas Venture Associates IX, LLC, its general partner, By: Frank Castellucci, General Counsel /s/ Frank Castellucci 04/23/2018 Signature of Reporting Person Date Atlas Venture Associates IX, LLC, By:Frank Castellucci, Generl Counsel /s/ Frank Castellucci 04/23/2018 Signature of Reporting Person Date

Explanation of Responses:

( 1 )The Series A Preferred Stock automatically converted into the Issuer's common stock on a 2.2-for-1 basis at the closing of the Issuer's initial publicoffering without payment or further consideration and had no expiration date. ( 2 )The shares are held directly by Atlas Venture Fund IX, L.P. ("Atlas Venture Fund IX"). The general partner of Atlas Venture Fund IX is AtlasVenture Associates IX, L.P. ("AVA IX LP"). Atlas Venture Associates IX, LLC ("AVA IX LLC") is the general partner of AVA IX LP. Each of AVAIX LP and AVA IX LLC disclaims Section 16 beneficial ownership of the securities held by Atlas Venture Fund IX, except to the extent of itspecuniary interest therein, if any.

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).

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