Seattle Genetics Inc (SGEN): Baker Bros. Advisors Raises Stake

Page 10 of 16 – SEC Filing

The Adviser has voting and investment power over the Stock Options,
Common Stock underlying such Stock Options, Restricted Stock and Common Stock held by Felix Baker. The Adviser GP, and Felix J.
Baker and Julian C. Baker as principals of the Adviser GP, may be deemed to have the power to vote or direct the vote of and the
power to dispose or direct the disposition of the Stock Options, Common Stock underlying such Stock Options, Restricted Stock and
Common Stock of the Issuer held by Felix J. Baker.

(c) The following transactions in the Issuer’s
Common Stock were effected by the Funds noted below during the sixty days preceding the filing of this statement using working
capital of the applicable purchasing Fund. All purchase transactions were effected in the open market directly with a broker-dealer.
Except as disclosed herein, none of the Reporting Persons or their affiliates has effected any other transactions in securities
of the Issuer during the past 60 days.

Page 10 of 16