POWER OF ATTORNEY

With respect to holdings of and transactions in securities issued by

Homology Medicines, Inc. (the "Company"), the undersigned hereby constitutes and

appoints the individuals named on Schedule A attached hereto and as may be

amended from time to time, or any of them signing singly, with full power of

substitution and resubstitution, to act as the undersigned's true and lawful

attorney-in-fact to:

1. prepare, execute in the undersigned's name and on the undersigned's

behalf, and submit to the United States Securities and Exchange

Commission (the "SEC") a Form ID, including amendments thereto, and

any other documents necessary or appropriate to obtain and/or

regenerate codes and passwords enabling the undersigned to make

electronic filings with the SEC of reports required by Section 16(a)

of the Securities Exchange Act of 1934, as amended, or any rule or

regulation of the SEC;

2. execute for and on behalf of the undersigned, Forms 3, 4, and 5 in

accordance with Section 16 of the Securities Exchange Act of 1934,

as amended, and the rules thereunder;

3. do and perform any and all acts for and on behalf of the undersigned

which may be necessary or desirable to complete and execute any such

Form 3, 4, or 5, complete and execute any amendment or amendments

thereto, and timely file such form with the SEC and any stock

exchange or similar authority; and

4. take any other action of any type whatsoever in connection with the

foregoing which, in the opinion of such attorney-in-fact, may be of

benefit to, in the best interest of, or legally required by, the

undersigned, it being understood that the documents executed by such

attorney-in-fact on behalf of the undersigned pursuant to this Power

of Attorney shall be in such form and shall contain such terms and

conditions as such attorney-in-fact may approve in such attorney-in-

fact's discretion.

The undersigned hereby grants to each such attorney-in-fact full power

and authority to do and perform any and every act and thing whatsoever

requisite, necessary, or proper to be done in the exercise of any of the rights

and powers herein granted, as fully to all intents and purposes as the

undersigned might or could do if personally present, with full power of

substitution and resubstitution or revocation, hereby ratifying and confirming

all that such attorney-in-fact, or such attorneys-in-fact substitute or

substitutes, shall lawfully do or cause to be done by virtue of this Power of

Attorney and the rights and powers herein granted.

The undersigned acknowledges that the foregoing attorneys-in-fact, in

serving in such capacity at the request of the undersigned, are not assuming,

nor is the Company assuming, any of the undersigned's responsibilities to comply

with Section 16 of the Securities Exchange Act of 1934, as amended.

This Power of Attorney shall remain in full force and effect until the

undersigned is no longer required to file Forms 3, 4, and 5 with respect to the

undersigned's holdings of and transactions in securities issued by Homology

Medicines, Inc., unless earlier revoked by the undersigned in a signed writing

delivered to the foregoing attorneys-in-fact.

IN WITNESS WHEREOF, the undersigned has caused this Power of Attorney to

be executed as of this 11th day of March, 2018.

Signature: /s/ Matthew Patterson

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Print Name: Matthew Patterson

Schedule A

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Individuals Appointed as Attorney-in-Fact with Full Power of

Substitution and Resubstitution:

W. Bradford Smith

Paul Alloway

Albert Seymour

Patterson Matthew R 4