13D Filing: Baker Bros. Advisors and Seattle Genetics Inc (SGEN)

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SIGNATURE

After reasonable inquiry and to the best of my
knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

May 17, 2017

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
FBB2, LLC
By: /s/ Julian C. Baker
Name: Julian C. Baker
Title: Manager
FBB3 LLC
By: /s/ Julian C. Baker
Name: Julian C. Baker
Title: Manager

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