STATEMENT OF CHANGES IN STOCKHOLDERS' EQUITY (USD $) In Thousands, except Share data	Total	Preferred Stock	Common Stock	Additional Paid-in Capital Common Stock	Additional Paid-in Capital Warrants	Deficit Accumulated During the Development Stage	Securities Offering	Securities Offering Common Stock	Securities Offering Additional Paid-in Capital Common Stock	Collaboration Agreement	Collaboration Agreement Common Stock	Collaboration Agreement Additional Paid-in Capital Common Stock
Beginning Balance at Dec. 31, 2010	$ 30,553		$ 48	$ 131,530	$ 22,789	$ (123,814)
Beginning Balance (in shares) at Dec. 31, 2010			48,466,562
Stock-based compensation	1,900			1,900
Exercise of employee stock options (in shares)			460,887
Exercise of employee stock options	904			904
Exercise of warrants to purchase common stock (in shares)			2,377,571
Exercise of warrants to purchase common stock	12,703		2	21,768	(9,067)
Issuance of restricted common stock			75,000
Repurchase of shares of common stock (in shares)			(15,190)
Repurchase of shares of common stock	(78)			(78)
Forfeiture of unvested restricted common stock (in shares)			(16,667)
Forfeiture of unvested restricted common stock
Net loss	(50,534)					(50,534)
Issuance of common stock (in shares)								11,040,000			6,063,161
Issuance of common stock							59,806	11	59,795	28,858	7	28,851
Ending Balance at Sep. 30, 2011	$ 84,112		$ 68	$ 244,670	$ 13,722	$ (174,348)
Ending Balance (in shares) at Sep. 30, 2011			68,451,324