Exhibit 99.1

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.

Dated: September 19, 2016

FLAGSHIP VENTURES FUND 2007, L.P.
By:	Flagship Ventures 2007 General Partner LLC
By:	/s/ Noubar B. Afeyan, Ph.D.
Name:	Noubar B. Afeyan, Ph.D.
Title:	Manager

FLAGSHIP VENTURES 2007 GENERAL PARTNER LLC
By:	/s/ Noubar B. Afeyan, Ph.D.
Name:	Noubar B. Afeyan, Ph.D.
Title:	Manager

FLAGSHIP VENTURES FUND IV, L.P.
By:	Flagship Ventures Fund IV General Partner LLC
By:	/s/ Noubar B. Afeyan, Ph.D.
Name:	Noubar B. Afeyan, Ph.D.
Title:	Manager

FLAGSHIP VENTURES FUND IV-RX, L.P.
By:	Flagship Ventures Fund IV General Partner LLC
By:	/s/ Noubar B. Afeyan, Ph.D.
Name:	Noubar B. Afeyan, Ph.D.
Title:	Manager

FLAGSHIP VENTURES FUND IV GENERAL PARTNER LLC
By:	/s/ Noubar B. Afeyan, Ph.D.
Name:	Noubar B. Afeyan, Ph.D.
Title:	Manager

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

NOUBAR B. AFEYAN, PH.D.

/s/ Edwin M. Kania, Jr.

EDWIN M. KANIA, JR.