X0306 4 2018-04-02 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 2018-04-02 4 C 0 5392037 0 A 6722076 I See footnotes Series A Preferred Stock 2018-04-02 4 C 0 4204502 0 D Common Stock 4204502 0 I See footnote Series B Preferred Stock 2018-04-02 4 C 0 1187535 0 D Common Stock 1187535 0 I See footnote Following the transactions reported herein, includes 6,453,195 shares of Common Stock held of record by 5AM Ventures IV, L.P. ("Ventures IV") and 268,881 shares of Common Stock held of record by 5AM Co-Investors IV, L.P. ("Co-Investors IV"). 5AM Partners IV, LLC ("Partners IV") is the sole general partner of Ventures IV and 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 Ventures IV and 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. Upon closing of the Issuer's initial public offering, each share of Series A Preferred Stock and Series B Preferred Stock was automatically converted into one share of the Issuer's common stock. 5AM VENTURES IV, L.P. By: 5AM Partners IV, LLC, its General Partner /s/ Scott M. Rocklage Managing Member 2018-04-04 5AM CO-INVESTORS IV, L.P. By: 5AM Partners IV, LLC, its General Partner /s/ Scott M. Rocklage Managing Member 2018-04-04 5AM PARTNERS IV, LLC /s/ Scott M. Rocklage Managing Member 2018-04-04 /s/ Scott M. Rocklage 2018-04-04 /s/ John D. Diekman 2018-04-04 /s/ Andrew J. Schwab 2018-04-04