EXHIBIT 99.1

AGREEMENT

In accordance with Rule 13d-1(k)(1) under the Securities Exchange Act of 1934, as amended, the undersigned hereby agree that this Statement on Schedule 13G relating to the Common Stock of CymaBay Therapeutics, Inc. is being filed with the Securities and Exchange Commission on behalf of each of them.

February 13, 2018

BAKER BROS. ADVISORS LP
By:	Baker Bros. Advisors (GP) LLC, its general partner
By:	/s/ Scott L. Lessing
	Name: Scott L. Lessing Title: President
BAKER BROS. ADVISORS (GP) LLC
By:	/s/ Scott L. Lessing
	Name: Scott L. Lessing Title: President
/s/ Julian C. Baker
Julian C. Baker
/s/ Felix J. Baker
Felix J. Baker