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

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(17) The reported price is a weighted average price. These shares
were traded in multiple transactions at prices ranging from $50.46 to $50.50. 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.

(18) The reported price is a weighted average price. These shares
were traded in multiple transactions at prices ranging from $50.24 to $50.90. 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.

(19) The reported price is a weighted average price. These shares
were traded in multiple transactions at prices ranging from $51.05 to $51.05. 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.

(20) The reported price is a weighted average price. These shares
were traded in multiple transactions at prices ranging from $50.16 to $50.75. 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.

(21) The reported price is a weighted average price. These shares
were traded in multiple transactions at prices ranging from $50.17 to $50.61. 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.

(22) The reported price is a weighted average price. These shares
were traded in multiple transactions at prices ranging from $50.66 to $51.60. 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.

(23) The reported price is a weighted average price. These shares
were traded in multiple transactions at prices ranging from $50.42 to $50.50. 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.

(24) The reported price is a weighted average price. These shares
were traded in multiple transactions at prices ranging from $50.70 to $51.33. 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.

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