Exhibit 1

JOINT FILING AGREEMENT

This Agreement will confirm the agreement by and among the undersigned that the Schedule 13D filed with the Securities and Exchange Commission on the date hereof with respect to the beneficial ownership by the undersigned of the Common Shares of Sierra Oncology, Inc. is being filed, and all amendments thereto will be filed, on behalf of each of the persons and entities named below, in accordance with Rule 13d-1 under the Securities Exchange Act of 1934, as amended. This Agreement may be executed in two or more counterparts, each of which shall be deemed an original, but all of which together shall constitute one and the same instrument.

Dated as of February 10, 2020

ABINGWORTH BIOVENTURES VII, LP
By:	Abingworth LLP, its Manager
By:	/s/ John Heard
	Name:  John Heard
	Title:    Authorized Signatory

ABINGWORTH LLP
By:	/s/ John Heard
	Name:  John Heard
	Title:    Authorized Signatory