Flagship Ventures Fund V SC 13D Foghorn Therapeutics / Flagship Ventures Fund V ownership change

Exhibit 1

CUSIP No. 344174 10 7

JOINT FILING AGREEMENT

The persons below hereby agree that the Schedule 13D to which this agreement is attached as an exhibit, as well as all future amendments to such Schedule 13D, shall be filed jointly on behalf of each of them. This agreement is intended to satisfy the requirements of Rule 13d-1(k)(1)(iii) under the Securities Exchange Act of 1934.

Dated: October 29, 2020

FLAGSHIP VENTURES FUND V, L.P.
By:	Flagship Ventures Fund V General Partner LLC
By:	/s/ Noubar B. Afeyan, Ph.D.
Name:	Noubar B. Afeyan, Ph.D.
Title:	Manager
FLAGSHIP VENTURES FUND V GENERAL PARTNER LLC
By:	/s/ Noubar B. Afeyan, Ph.D.
Name:	Noubar B. Afeyan, Ph.D.
Title:	Manager
FLAGSHIP VENTURES OPPORTUNITIES FUND I, L.P.
By:	Flagship Ventures Opportunities Fund I General Partner LLC
By:	/s/ Noubar B. Afeyan, Ph.D.
Name:	Noubar B. Afeyan, Ph.D.
Title:	Manager
FLAGSHIP VENTURES OPPORTUNITIES FUND I GENERAL PARTNER LLC
By:	/s/ Noubar B. Afeyan, Ph.D.
Name:	Noubar B. Afeyan, Ph.D.
Title:	Manager
FLAGSHIP PIONEERING SPECIAL OPPORTUNITIES FUND II, L.P.
By:	Flagship Pioneering Special Opportunities Fund II General Partner LLC
By:	Flagship Pioneering, Inc.
By:	/s/ Noubar B. Afeyan, Ph.D.
Name:	Noubar B. Afeyan, Ph.D.
Title:	CEO, Sole Shareholder & Director

CUSIP No. 344174 10 7

FLAGSHIP PIONEERING SPECIAL OPPORTUNITIES FUND II GENERAL PARTNER LLC
By:	Flagship Pioneering, Inc.
By:	/s/ Noubar B. Afeyan, Ph.D.
Name:	Noubar B. Afeyan, Ph.D.
Title:	CEO, Sole Shareholder & Director
FLAGSHIP PIONEERING, INC.
By:	/s/ Noubar B. Afeyan, Ph.D.
Name:	Noubar B. Afeyan, Ph.D.
Title:	CEO, Sole Shareholder & Director

/s/ Noubar B. Afeyan, Ph.D.

NOUBAR B. AFEYAN, PH.D.