AGREEMENT

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 13G need be filed with respect to the ownership by each of the undersigned of Common Stock of Gritstone Oncology, Inc.

Date: February 14, 2019				XXXXXXX HEALTHCARE VII, L.P.
				By FHM VII, L.P., its general partner
				By FHM VII, L.L.C., its general partner
				By:		/s/ Xxxxx X. Xxxxxx
						Xxxxx X. Xxxxxx, Chief Financial Officer
Date: February 14, 2019				XXXXXXX HEALTHCARE VII-A, L.P.
				By FHM VII, L.P., its general partner
				By FHM VII, L.L.C., its general partner
				By:		/s/ Xxxxx X. Xxxxxx
						Xxxxx X. Xxxxxx, Chief Financial Officer
Date: February 14, 2019				FHM VII, L.P.
				By FHM VII, L.L.C., its general partner
				By:		/s/ Xxxxx X. Xxxxxx
						Xxxxx X. Xxxxxx, Chief Financial Officer
Date: February 14, 2019				FHM VII, L.L.C.
				By:		/s/ Xxxxx X. Xxxxxx
						Xxxxx X. Xxxxxx, Chief Financial Officer
Date: February 14, 2019				By:		*
						Xxxxx Xxxxxx
Date: February 14, 2019				By:		*
						Xxxxxxx Xxxxx
Date: February 14, 2019				By:		*
						Xxxxx Xxxxx
Date: February 14, 2019				By:		*
						Xxxxxx Every

Date: February 14, 2019				By:		*
						Xxxxx Xxxxxxx
Date: February 14, 2019				By:		*
						Xxxx Xxxxxxx
Date: February 14, 2019				*By:		/s/ Xxxxx X. Xxxxxx
						Xxxxx X. Xxxxxx, as Attorney-in-Fact

This Agreement was executed by Xxxxx X. Xxxxxx on behalf of the individuals listed above pursuant to a Power of Attorney, a copy of which was filed with the SEC on March 29, 2016.