Seattle Genetics Inc (SGEN): Baker Bros. Keeps Buying Shares

Page 11 of 15

Page 11 of 15 SEC Filing
Name Date Number of Shares Transaction Price/Share Footnotes
667, L.P. 02/24/16 4,850 Purchase 29.7746 1
Baker Brothers Life Sciences, L.P. 02/24/16 43,056 Purchase 29.7746 1
667, L.P. 02/24/16 466 Purchase 28.4650
Baker Brothers Life Sciences, L.P. 02/24/16 4,134 Purchase 28.4650
667, L.P. 02/24/16 7,593 Purchase 28.5233 2
Baker Brothers Life Sciences, L.P. 02/24/16 67,407 Purchase 28.5233 2
667, L.P. 02/25/16 14,447 Purchase 29.8633 3
Baker Brothers Life Sciences, L.P. 02/25/16 128,255 Purchase 29.8633 3
667, L.P. 02/26/16 4,485 Purchase 30.1342 4
Baker Brothers Life Sciences, L.P. 02/26/16 39,815 Purchase 30.1342 4
667, L.P. 02/29/16 5,955 Purchase 30.5484 5
Baker Brothers Life Sciences, L.P. 02/29/16 54,439 Purchase 30.5484 5
667, L.P. 02/29/16 18,866 Purchase 30.3425 6
Baker Brothers Life Sciences, L.P. 02/29/16 172,462 Purchase 30.3425 6
667, L.P. 03/01/16 2,386 Purchase 31.2443 7
Baker Brothers Life Sciences, L.P. 03/01/16 21,814 Purchase 31.2443 7
667, L.P. 03/02/16 32,934 Purchase 32.7574 8
Baker Brothers Life Sciences, L.P. 03/02/16 301,066 Purchase 32.7574 8
667, L.P. 03/02/16 6,508 Purchase 32.2400
Baker Brothers Life Sciences, L.P. 03/02/16 59,492 Purchase 32.2400
667, L.P. 03/04/16 4,496 Purchase 31.6820 9
Baker Brothers Life Sciences, L.P. 03/04/16 41,104 Purchase 31.6820 9
667, L.P. 03/04/16 23,908 Purchase 32.4927 10
Baker Brothers Life Sciences, L.P. 03/04/16 218,550 Purchase 32.4927 10
667, L.P. 03/07/16 4,597 Purchase 33.6757 11
Baker Brothers Life Sciences, L.P. 03/07/16 40,921 Purchase 33.6757 11
667, L.P. 03/07/16 1,590 Purchase 33.7250 12
Baker Brothers Life Sciences, L.P. 03/07/16 14,157 Purchase 33.7250 12
667, L.P. 03/08/16 5,504 Purchase 32.1486 13
Baker Brothers Life Sciences, L.P. 03/08/16 48,996 Purchase 32.1486 13
667, L.P. 03/08/16 9,968 Purchase 32.1658 14
Baker Brothers Life Sciences, L.P. 03/08/16 88,732 Purchase 32.1658 14

(1) The reported price is a weighted average price. These shares
were traded in multiple transactions at a prices ranging from $29.00 to $29.94. The Reporting Persons undertake to provide the
Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission (the “Staff”), upon
request, full information regarding the number of shares traded at each separate price within the ranges set forth in this footnote.

(2) The reported price is a weighted average
price. These shares were traded in multiple transactions at prices ranging from $28.50 to $28.57. The Reporting Persons undertake
to provide the Issuer, any security holder of the Issuer, or the Staff, upon request, full information regarding the number of
shares traded at each separate price within the ranges set forth in this footnote.

(3) The reported price is a weighted average
price. These shares were traded in multiple transactions at prices ranging from $29.55 to $30.00. The Reporting Persons undertake
to provide the Issuer, any security holder of the Issuer, or the Staff, upon request, full information regarding the number of
shares traded at each separate price within the ranges set forth in this footnote.

(4) The reported price is a weighted average price. These shares
were traded in multiple transactions at prices ranging from $29.84 to $30.50. The Reporting Persons undertake to provide the Issuer,
any security holder of the Issuer, or the Staff, upon request, full information regarding the number of shares traded at each separate
price within the ranges set forth in this footnote.

Page 11 of 15 Pages

Follow Seagen Inc. (NASDAQ:SGEN)

Page 11 of 15