Statements of Operations (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended			112 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2012
Revenue	$ 800	$ 667		$ 1,467
Operating expenses:
Research and development	83,446	57,083	12,910	212,345
General and administrative	19,523	14,984	11,636	88,318
Total operating expenses	102,969	72,067	24,546	300,663
Loss from operations	(102,169)	(71,400)	(24,546)	(299,196)
Other income, net	(13)	39	765	4,701
Change in fair value of warrants	6,050	7,583	(8,889)	10,771
Net loss	$ (96,132)	$ (63,778)	$ (32,670)	$ (283,724)
Basic and diluted net loss per share	$ (1.22)	$ (0.97)	$ (0.71)
Weighted average common shares outstanding used to compute basic and diluted net loss per share	78,546,112	66,003,789	46,003,996