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 Sierra Oncology, Inc.

Date: August 16, 2021				XXXXXXX LIFE SCIENCES VIII, L.P.
				By FHM Life Sciences VIII, L.P., its general partner
				By FHM Life Sciences VIII, L.L.C., its general partner
				By:		/s/ Xxxxx X. Xxxxxx
						Xxxxx X. Xxxxxx, Chief Financial Officer
Date: August 16, 2021				FHM LIFE SCIENCES VIII, L.P.
				By FHM Life Sciences VIII, L.L.C., its general partner
				By:		/s/ Xxxxx X. Xxxxxx
						Xxxxx X. Xxxxxx, Chief Financial Officer
Date: August 16, 2021				FHM LIFE SCIENCES VIII, L.L.C.
				By:		/s/ Xxxxx X. Xxxxxx
						Xxxxx X. Xxxxxx, Chief Financial Officer
Date: August 16, 2021				XXXXXXX HEALTHCARE VI, L.P.
				By: FHM VI, L.P., its General Partner
				By: FHM VI, LLC, its General Partner
				By:		/s/ Xxxxx X. Xxxxxx
						Xxxxx X. Xxxxxx, Chief Financial Officer
Date: Xxxxxx 00, 0000				XXX XX, X.X.
				By: FHM VI, LLC, its General Partner
				By:		/s/ Xxxxx X. Xxxxxx
						Xxxxx X. Xxxxxx, Chief Financial Officer
Date: August 16, 2021				FHM VI, LLC
				By:		/s/ Xxxxx X. Xxxxxx
						Xxxxx X. Xxxxxx, Chief Financial Officer
Date: August 16, 2021				XXXXXXX LIFE SCIENCES PUBLIC FUND L.P.
				By: FHMLSP, L.P., its General Partner
				By: FHMLSP, L.L.C., its General Partner
				By:		/s/ Xxxxx X. Xxxxxx
						Xxxxx X. Xxxxxx, Chief Financial Officer

Date: August 16, 2021				FHMLSP, L.P.
				By: FHMLSP, L.L.C., its General Partner
				By:		/s/ Xxxxx X. Xxxxxx
						Xxxxx X. Xxxxxx, Chief Financial Officer
Date: August 16, 2021				FHMLSP, L.L.C.
				By:		/s/ Xxxxx X. Xxxxxx
						Xxxxx X. Xxxxxx, Chief Financial Officer
Date: August 16, 2021				By:		*
						Xxxxx X. Xxxxxx
Date: August 16, 2021				By:		*
						Xxxxxxx X. Xxxxx
Date: August 16, 2021				By:		*
						Xxxx Xxxxxxx
Date: August 16, 2021				By:		*
						Xxxxx Xxxxx
Date: August 16, 2021				By:		*
						Xxxxxx Every
Date: August 16, 2021				By:		**
						Xxxxxx Xxx
Date: August 16, 2021				By:		**
						Xxxxx Xxxxx
Date: August 16, 2021				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 February 24, 2017.

** 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 is included herewith as Exhibit B.