X0306 4/A 2020-12-17 2020-12-21 0 0001718108 Surface Oncology, Inc. SURF 0001671219 Atlas Venture Fund IX, L.P. 56 WAREHAM STREET, FLOOR 3 BOSTON MA 02118 0 0 1 0 0001671208 Atlas Venture Associates IX, L.P. 56 WAREHAM STREET, FLOOR 3 BOSTON MA 02118 0 0 1 0 0001671207 Atlas Venture Associates IX, LLC 56 WAREHAM STREET, FLOOR 3 BOSTON MA 02118 0 0 1 0 Common Stock 2020-12-17 4 S 0 1700000 8.10 D 2945453 D Represents shares sold by Atlas Venture Fund IX, L.P. ("Atlas IX"). Atlas Venture Associates IX, L.P. ("AVA IX LP") is the general partner of Atlas IX. Atlas Venture Associates IX, LLC ("AVA IX LLC") is the general partner of AVA IX LP. Each of Atlas IX, AVA IX LP and AVA IX LLC disclaims Section 16 beneficial ownership of the securities held by Atlas IX, except to the extent of their pecuniary interest therein, if any. This report shall not be deemed to an admission that any of the Reporting Persons is the beneficial owner of such securities for purposes of Section 16 or for any other purpose. The high, low and average for the shares sold were all $8.10. Each of the Reporting Persons undertake to provide to the issuer, any security holder of the issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in footnote (2) of this Form 4. Represents shares held directly by Atlas IX. The general partner of the Atlas IX is AVA IX LP. AVA IX LLC is the general partner of AVA IX LP. Each of AVA IX LP and AVA IX LLC disclaims Section 16 beneficial ownership of the securities held by the Atlas IX except to the extent of its pecuniary interest therein, if any. This Amendment to the Form 4 originally filed by the Reporting Persons on December 21, 2020 is filed to amend the share price in Table I from $18.10 to $8.10. Atlas Venture Associates IX, L,P,, By: Atlas Venture Associates IX, LLC, its general partner, By: /s/ Frank Castellucci, General Counsel 2020-12-21 Atlas Venture Associates IX, LLC, By: /s/ Frank Castellucci, General Counsel 2020-12-21 Atlas Venture Fund IX, L.P. By: Atlas Venture Associates IX, L.P, its general partner, By: Atlas Venture Associates IX, LLC, its general partner By: /s/ Frank Castellucci, General Counsel 2020-12-21