X0306 4 2022-01-01 0 0001661998 Homology Medicines, Inc. FIXX 0001794702 Cohn Gabriel C/O HOMOLOGY MEDICINES INC., ONE PATRIOTS PARK BEDFORD MA 01730 0 1 0 0 Chief Medical Officer Common Stock 2022-01-01 4 M 0 4290 A 4290 D Common Stock 2022-01-05 4 S 0 1661 3.7801 D 2629 D Restricted Stock Units 2022-01-01 4 M 0 4290 0.00 D Common Stock 4290 8710 D Each Restricted Stock Unit ("RSU") represents a contingent right to receive one share of Issuer common stock. The sale reported in the Form 4 was effected pursuant to a Rule 10b5-1 instruction solely with the intent to cover withholding taxes in connection with the settlement of RSUs. The price reported is a weighted average price. The securities were sold in multiple transactions at per share prices ranging from $3.78 to $3.79. The Reporting Person undertakes to provide upon request the SEC staff, the Issuer, or any shareholder of the Issuer, full information regarding the number of securities sold at each separate price within the range set forth in this footnote 3. The RSUs have vested and settled or will vest and settle, as applicable, as to one third of the restricted stock units on each of the first three anniversaries of January 1, 2021 so that such RSUs will become fully vested on January 1, 2024. The RSUs do not have an expiration date. /s/ W. Bradford Smith, Attorney-in-Fact for Gabriel Cohn 2022-01-12