STATEMENT OF CHANGES IN STOCKHOLDERS' EQUITY (USD $) In Thousands, except Share data	Total	Common Stock	Additional Paid-in Capital Common Stock	Additional Paid-in Capital Warrants	Deficit Accumulated During the Development Stage
Beginning Balance at Dec. 31, 2011	$ 71,607	$ 69	$ 246,519	$ 12,611	$ (187,592)
Beginning Balance (in shares) at Dec. 31, 2011		69,206,044
Stock-based compensation	1,212		1,212
Exercise of warrants to purchase common stock (in shares)		76,515
Exercise of warrants to purchase common stock	182		281	(99)
Issuance of restricted common stock		145,302
Forfeiture of unvested restricted common stock		(9,380)
Expired warrants			5,433	(5,433)
Issuance of common stock in a securities offering, net of commission and expenses of $3,426 (in shares)		10,114,401
Issuance of common stock in a securities offering, net of commission and expenses of $3,426	49,169	11	49,158
Net loss	(24,470)				(24,470)
Ending Balance at Mar. 31, 2012	$ 97,700	$ 80	$ 302,603	$ 7,079	$ (212,062)
Ending Balance (in shares) at Mar. 31, 2012		79,532,882