X0202 4 2005-04-29 0 0001060736 SEATTLE GENETICS INC /WA SGEN 0001244390 Baker Bros. Capital (GP), LLC 667 MADISON AVENUE NEW YORK NY 10021 1 0 1 0 0001087939 BAKER JULIAN 667 MADISON AVENUE NEW YORK NY 10021 0 0 1 0 0001087940 BAKER FELIX 667 MADISON AVENUE NEW YORK NY 10021 1 0 1 0 Common Stock 2005-04-29 4 P 0 133 3.9991 A 57806 I See Footnote Common Stock 2005-04-29 4 P 0 257 3.9879 A 58063 I See Footnote Common Stock 2005-04-29 4 P 0 17376 4.00 A 75439 I See Footnote In addition to Baker Bros. Capital (GP), LLC, this Form 4 is being filed jointly by Julian C. Baker and Felix J. Baker, each of whom has the same business address as Baker Bros. Capital (GP), LLC and may be deemed to have a pecuniary interest in securities owned by it. Because of certain relationships with other security holders of the Issuer, the Reporting Persons have filed on Schedule 13D as if they were a member of a group with such shareholders. (Continued in footnote 2.) However, the Reporting Persons disclaim that they and any other person or persons, including those persons with whom the Reporting Persons have filed a Schedule 13D, in fact constitute a "group" for purposes of Section 13(d)(3) of the Securities Exchange Act of 1934, as amended, or Rule 13d-5 thereunder or that they are the beneficial owners of securities owned by any such other persons, and each of them disclaims beneficial ownership of securities reported herein except to the extent of their pecuniary interest, if any, therein. Felix J. Baker is a director of the Issuer. Represents 68 shares of common stock purchased directly by Baker Bros. Investments, L.P., and 65 shares of common stock purchased directly by Baker Bros. Investments II, L.P. Represents 29,613 shares of common stock owned directly by Baker Bros. Investments, L.P., and 28,193 shares of common stock owned directly by Baker Bros. Investments II, L.P. Baker Bros. Investments, L.P., and Baker Bros. Investments II, L.P., are each limited partnerships of which the sole general partner is Baker Bros. Capital, L.P., a limited partnership of which the sole general partner is Baker Bros. Capital (GP), LLC. Felix J. Baker and Julian C. Baker are the controlling members of Baker Bros. Capital (GP), LLC. Represents 131 shares of common stock purchased directly by Baker Bros. Investments, L.P., and 126 shares of common stock purchased directly by Baker Bros. Investments II, L.P. Represents 29,744 shares of common stock owned directly by Baker Bros. Investments, L.P., and 28,319 shares of common stock owned directly by Baker Bros. Investments II, L.P. Baker Bros. Investments, L.P., and Baker Bros. Investments II, L.P., are each limited partnerships of which the sole general partner is Baker Bros. Capital, L.P., a limited partnership of which the sole general partner is Baker Bros. Capital (GP), LLC. Felix J. Baker and Julian C. Baker are the controlling members of Baker Bros. Capital (GP), LLC. Represents 8,867 shares of common stock purchased directly by Baker Bros. Investments, L.P., and 8,509 shares of common stock purchased directly by Baker Bros. Investments II, L.P. Represents 38,611 shares of common stock owned directly by Baker Bros. Investments, L.P., and 36,828 shares of common stock owned directly by Baker Bros. Investments II, L.P. Baker Bros. Investments, L.P., and Baker Bros. Investments II, L.P., are each limited partnerships of which the sole general partner is Baker Bros. Capital, L.P., a limited partnership of which the sole general partner is Baker Bros. Capital (GP), LLC. Felix J. Baker and Julian C. Baker are the controlling members of Baker Bros. Capital (GP), LLC. /s/ Julian C. Baker, as Managing Member of Baker Bros. Capital (GP), LLC 2005-05-03 /s/ Julian C. Baker 2005-05-03 /s/ Felix J. Baker 2005-05-03