Exhibit 99.1

Joint Filing Agreement

The undersigned hereby agree that the Statement on Schedule 13G dated November 13, 2017 with respect to the shares of Common Stock of Syndax Pharmaceuticals, Inc., and any further amendments thereto executed by each and any of the undersigned shall be filed on behalf of each of the undersigned pursuant to and in accordance with the provisions of Rule 13d-1(k)(1) under the Securities Exchange Act of 1934, as amended.

Dated: November 13, 2017

BIOTECHNOLOGY VALUE FUND, L.P.		BVF INC.
By:	BVF Partners L.P., its general partner		/s/ Mark N. Lampert
By:	BVF Inc., its general partner	By:	Mark N. Lampert
			President
By:	/s/ Mark N. Lampert
	Mark N. Lampert
	President	/s/ Mark N. Lampert
		MARK N. LAMPERT

BIOTECHNOLOGY VALUE FUND II, L.P.
By:	BVF Partners L.P., its general partner
By:	BVF Inc., its general partner
By:	/s/ Mark N. Lampert
	Mark N. Lampert
	President

BVF PARTNERS L.P.
By:	BVF Inc., its general partner
By:	/s/ Mark N. Lampert
	Mark N. Lampert
	President

BVF PARTNERS OS LTD.
By:	BVF Partners L.P., its sole member
By:	BVF Inc., its general partner
By:	/s/ Mark N. Lampert
	Mark N. Lampert
	President

Biotechnology Value Trading Fund OS LP
By:	BVF Partners L.P., its investment manager
By:	BVF Inc., its general partner
By:	/s/ Mark N. Lampert
	Mark N. Lampert
	President