Stockholders' Equity

12 Months Ended

Dec. 31, 2011

Stockholders' Equity [Abstract]

Stockholders' Equity

11. Stockholders' equity

Common stock

In February 2011, the Company completed an underwritten public offering of 11,500,000 shares of its common stock. The public offering price of $15.50 per share resulted in net proceeds to the Company of approximately $168.1 million, after deducting underwriting discounts and commissions and offering expenses.

In August 2009, the Company completed an underwritten public offering of 12,650,000 shares of its common stock at a price to the public of $10.75 per share, resulting in net proceeds of $128.2 million.

In February 2009, the Company completed an offering of 5,740,000 shares of its common stock at $9.72 per share resulting in net proceeds of $52.5 million.

In May 2009, the Company completed a private placement of 1,178,163 shares of its common stock at $9.72 per share to Baker Brothers Life Sciences, L.P. and its affiliated investment funds, or BBLS. Net proceeds of the private placement were approximately $11.5 million. One of the Company's directors is a Managing Director of Baker Bros. Advisors, LLC, which is affiliated with BBLS and its affiliated investment funds. As a result, the sale and issuance of these shares was subject to stockholder approval which was obtained at the Company's annual meeting of stockholders held on May 15, 2009.

In May 2011, following stockholder approval, the Company amended its Certificate of Incorporation to increase the number of authorized shares of the Company's common stock from 150,000,000 shares to 250,000,000 shares.

At December 31, 2011, shares of common stock reserved for future issuance are as follows (in thousands):

Stock options and RSUs outstanding	14,266
Stock options and RSUs available for grant	1,891
Employee stock purchase plan shares available for issuance	799
Total	16,956

Employee Stock Purchase Plan

The Company has an Amended and Restated 2000 Employee Stock Purchase Plan, or the Stock Purchase Plan, with a total of 799,000 shares of common stock available for issuance as of December 31, 2011. Activity under the Stock Purchase Plan for the years ended December 31, was as follows:

Year	Shares Purchased		Weighted-average purchase price per share
2011		229,014	$	11.03
2010		173,379	$	8.68
2009		146,692	$	8.46

Prior to 2011, shares were purchased at 85 percent of the fair market value of the Company's common stock on either the first day of an offering period or the last day of each six month purchase period, whichever was lower. An offering period could last for up to two years. Under the current terms of the Stock Purchase Plan, shares are purchased at the lower of 85 percent of the fair market value of the Company's common stock on either the first day or the last day of each six month offering period.