BOTHELL, Wash.--(BUSINESS WIRE)--Seattle Genetics, Inc. (Nasdaq: SGEN) announced today that the underwriters of its previously announced public offering of common stock have exercised in full their over-allotment option to purchase an additional 1,756,097 shares of common stock. Including this option exercise, total gross proceeds from the offering of an aggregate of 13,463,415 shares at a price to the public of $41.00 per share will be approximately $552 million, before deducting underwriting