Baker Bros. Advisors SC 13D Zymeworks / BAKER BROS. ADVISORS ownership change

Exhibit 99.1

JOINT FILING AGREEMENT

Pursuant to Rule 13d-1(k)(1) under the Securities Exchange Act of 1934, as amended, 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 the shares of Common Stock of Zymeworks Inc.

This Agreement may be executed in any number of counterparts, each of which shall be deemed an original.

EXECUTED as of this 25^th day of March 2020

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