X0306 4 2018-04-02 0 0001661998 Homology Medicines, Inc. FIXX 0001605598 ARCH Venture Fund VIII, L.P. 8755 WEST HIGGINS ROAD, SUITE 1025 CHICAGO IL 60631 0 0 1 0 0001617237 ARCH Venture Fund VIII Overage, L.P. 8755 WEST HIGGINS ROAD, SUITE 1025 CHICAGO IL 60631 0 0 1 0 0001616176 ARCH Venture Partners VIII, L.P. 8755 WEST HIGGINS ROAD, SUITE 1025 CHICAGO IL 60631 0 0 1 0 0001616165 ARCH Venture Partners VIII, LLC 8755 WEST HIGGINS ROAD, SUITE 1025 CHICAGO IL 60631 0 0 1 0 0001219039 CRANDELL KEITH 8755 WEST HIGGINS ROAD, SUITE 1025 CHICAGO IL 60631 0 0 1 0 0001219043 BYBEE CLINTON 8755 WEST HIGGINS ROAD, SUITE 1025 CHICAGO IL 60631 0 0 1 0 0001219042 NELSEN ROBERT 8755 WEST HIGGINS ROAD, SUITE 1025 CHICAGO IL 60631 0 0 1 0 Common Stock 2018-04-02 4 C 0 6068695 0.00 A 6068695 I See footnote Series A Preferred Stock 2018-04-02 4 C 0 4683238 0.00 D Common Stock 4683238 0 I See footnote Series B Preferred Stock 2018-04-02 4 C 0 1385457 0.00 D Common Stock 1385457 0 I See footnote Following the transactions reported herein, includes 1,196,827 shares of common stock held of record by ARCH Venture Fund VIII Overage, L.P. ("ARCH Fund Overage") and 4,871,868 shares of common stock held of record by ARCH Venture Fund VIII, L.P. ("ARCH Fund VIII"). The sole general partner of ARCH Fund VIII is ARCH Venture Partners VIII, L.P. ("ARCH Partners VIII"). The sole general partner of ARCH Partners VIII and ARCH Fund Overage is ARCH Venture Partners VIII, LLC ("ARCH VIII LLC"). ARCH Partners VIII may therefore be deemed to beneficially own the securities held by ARCH Fund VIII and ARCH VIII LLC may be deemed to beneficially own the securities held by ARCH Fund VIII and ARCH Fund Overage. ARCH Partners VIII and ARCH VIII LLC disclaim beneficial ownership of such securities, except to the extent of any pecuniary interest therein. The managing directors of ARCH VIII LLC are Keith L. Crandell, Clinton Bybee and Robert Nelsen, and they may be deemed to beneficially own the shares held by ARCH Fund VIII and ARCH Fund Overage. Messrs. Crandell, Bybee and Nelsen disclaim beneficial ownership of such shares, except to the extent of any pecuniary interest therein. Upon closing of the Issuer's initial public offering, each share of preferred stock was automatically converted into one share of the Issuer's common stock. ARCH Venture Fund VIII, L.P., By: ARCH Venture Partners VIII, L.P., its General Partner, By: ARCH Venture Partners VIII, LLC, its General Partner, By: /s/ Mark McDonnell, as Attorney-in-Fact for Keith, Crandell, Managing Director 2018-04-02 ARCH Venture Fund VIII Overage, L.P., ARCH Venture Partners VIII, LLC, its General Partner, By: /s/ Mark McDonnell, as Attorney-in-Fact for Keith, Crandell, Managing Director 2018-04-02 ARCH Venture Partners VIII, L.P., By: ARCH Venture Partners VIII, LLC, its General Partner, By: /s/ Mark McDonnell, as Attorney-in-Fact for Keith, Crandell, Managing Director 2018-04-02 ARCH Venture Partners VIII, LLC, By: /s/ Mark McDonnell, as Attorney-in-Fact for Keith, Crandell, Managing Director 2018-04-02 Keith Crandell, Managing Director, By: /s/ Mark McDonnell, as Attorney-in-Fact 2018-04-02 Clinton Bybee, Managing Director, By: /s/ Mark McDonnell, as Attorney-in-Fact 2018-04-02 Robert Nelsen, Managing Director, By: /s/ Mark McDonnell, as Attorney-in-Fact 2018-04-02