X0306 4 2018-12-10 0 0001661998 Homology Medicines, Inc. FIXX 0001589315 5AM Ventures IV, L.P. 501 2ND STREET, SUITE 350 SAN FRANCISCO CA 94107 0 0 1 0 0001589314 5AM Partners IV, LLC 501 2ND STREET, SUITE 350 SAN FRANCISCO CA 94107 0 0 1 0 0001219014 ROCKLAGE SCOTT M 501 2ND STREET, SUITE 350 SAN FRANCISCO CA 94107 0 0 1 0 0001240357 DIEKMAN JOHN D 501 2ND STREET, SUITE 350 SAN FRANCISCO CA 94107 0 0 1 0 0001598549 Schwab Andrew J. 501 2ND STREET, SUITE 350 SAN FRANCISCO CA 94107 0 0 1 0 0001593361 5AM Co-Investors IV, L.P. 501 2ND STREET, SUITE 350 SAN FRANCISCO CA 94107 0 0 1 0 Common Stock 2018-12-10 4 S 0 14952 26.0051 D 5904884 I See footnote Common Stock 2018-12-10 4 S 0 623 26.0051 D 246035 I See footnote The shares are held by 5AM Ventures IV, L.P. ("Ventures IV"). 5AM Partners IV, LLC ("Partners IV") is the sole general partner of Ventures IV. Dr. John Diekman, Andrew J. Schwab and Dr. Scott M. Rocklage, are the managing members of Partners IV, and have shared voting and investment power over the shares beneficially owned by Ventures IV. Each of Partners IV, Dr. Diekman, Mr. Schwab, and Dr. Rocklage disclaims beneficial ownership of such shares except to the extent of its or their pecuniary interest therein. The shares are held by 5AM Co-Investors IV, L.P. ("Co-Investors IV"). Partners IV is the sole general partner of Co-Investors IV. Dr. John Diekman, Andrew J. Schwab and Dr. Scott M. Rocklage, are the managing members of Partners IV, and have shared voting and investment power over the shares beneficially owned by Co-Investors IV. Each of Partners IV, Dr. Diekman, Mr. Schwab, and Dr. Rocklage disclaims beneficial ownership of such shares except to the extent of its or their pecuniary interest therein. 5AM VENTURES IV, L.P. By: 5AM Partners IV, LLC, its General Partner /s/ Scott M. Rocklage Managing Member 2018-12-12 5AM CO-INVESTORS IV, L.P. By: 5AM Partners IV, LLC, its General Partner /s/ Scott M. Rocklage Managing Member 2018-12-12 5AM PARTNERS IV, LLC /s/ Scott M. Rocklage Managing Member 2018-12-12 /s/ Scott M. Rocklage 2018-12-12 /s/ John D. Diekman 2018-12-12 /s/ Andrew J. Schwab 2018-12-12