Joint Filer Information

Names:	Deerfield Mgmt III, L.P., Deerfield Mgmt HIF, L.P., Deerfield Management Company, L.P., Deerfield Private Design Fund III, L.P., Deerfield Healthcare Innovations Fund, L.P., Deerfield Partners, L.P., Deerfield Mgmt, L.P.
Address:	780 Third Avenue, 37th Floor New York, NY 10017
Designated Filer:	James E. Flynn
Issuer and Ticker Symbol:	Homology Medicines, Inc. [FIXX]
Date of Event Requiring Statement:	April 12, 2019

The undersigned, Deerfield Mgmt III, L.P., Deerfield Mgmt HIF, L.P., Deerfield Management Company, L.P., Deerfield Private Design Fund III, L.P., Deerfield Healthcare Innovations Fund, L.P., Deerfield Mgmt, L.P. and Deerfield Partners, L.P. are jointly filing the attached Changes in Beneficial Ownership on Form 4 with James E. Flynn with respect to the beneficial ownership of securities of Homology Medicines, Inc.

Signatures:

DEERFIELD MGMT HIF, L.P. By: J.E. Flynn Capital HIF, LLC, General Partner By: /s/ Jonathan Isler Jonathan Isler, Attorney-In-Fact	DEERFIELD MGMT III, L.P. By: J.E. Flynn Capital III, LLC, General Partner By: /s/ Jonathan Isler Jonathan Isler, Attorney-In-Fact
DEERFIELD MANAGEMENT COMPANY, L.P. By: Flynn Management LLC, General Partner By: /s/ Jonathan Isler Jonathan Isler, Attorney-In-Fact	DEERFIELD PRIVATE DESIGN FUND III, L.P. By: Deerfield Mgmt III, L.P., General Partner By: J.E. Flynn Capital III, LLC, General Partner By: /s/ Jonathan Isler Jonathan Isler, Attorney-In-Fact
DEERFIELD HEALTHCARE INNOVATIONS FUND, L.P. By: Deerfield Mgmt HIF, L.P., General Partner By: J.E. Flynn Capital HIF, LLC, General Partner By: /s/ Jonathan Isler Jonathan Isler, Attorney-In-Fact DEERFIELD MGMT, L.P. By: J.E. Flynn Capital, LLC, General Partner By: /s/ Jonathan Isler Jonathan Isler, Attorney-In-Fact	DEERFIELD PARTNERS, L.P. By: Deerfield Mgmt, L.P., General Partner By: J.E. Flynn Capital, LLC, General Partner By: /s/ Jonathan Isler Jonathan Isler, Attorney-In-Fact