EXHIBIT A

AGREEMENT

Pursuant to Rule 13d-1(k)(1) under the Securities Exchange Act of 1934, the undersigned hereby agree that only one statement containing the information required by Schedule 13D need be filed with respect to the ownership by each of the undersigned of Common Stock of Phathom Pharmaceuticals, Inc.

Date: November 4, 2019	FRAZIER LIFE SCIENCES IX, L.P.
	By FHMLS IX, L.P., its general partner
	By FHMLS IX, L.L.C., its general partner
	By:	/s/ Steve R. Bailey
		Steve R. Bailey, Chief Financial Officer
Date: November 4, 2019	FHMLS IX, L.P.
	By FHMLS IX, L.L.C., its general partner
	By:	/s/ Steve R. Bailey
		Steve R. Bailey, Chief Financial Officer
Date: November 4, 2019	FHMLS IX, L.L.C.
	By:	/s/ Steve R. Bailey
		Steve R. Bailey, Chief Financial Officer
Date: November 4, 2019	By:	*
		James Topper
Date: November 4, 2019	By:	*
		Patrick Heron
Date: November 4, 2019	*By:	/s/ Steve R. Bailey
		Steve R. Bailey, as Attorney-in-Fact

This Agreement was executed by Steve R. Bailey on behalf of the individuals listed above pursuant to a Power of Attorney, a copy of which was filed with the SEC on July 31, 2017.