Statements of Operations (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		115 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2013
Research contract revenue	$ 200	$ 200	$ 1,667
Operating expenses:
Research and development, including costs of research contracts	19,112	13,985	231,457
General and administrative	4,671	4,848	92,989
Total operating expenses	23,783	18,833	324,446
Loss from operations	(23,583)	(18,633)	(322,779)
Other income (expense), net	(4)	(26)	4,697
Change in fair value of warrants	10,788	(5,811)	21,559
Net loss	$ (12,799)	$ (24,470)	$ (296,523)
Net loss per share-basic and diluted	$ (0.15)	$ (0.32)
Weighted average common shares outstanding to compute net loss per share-basic and diluted	82,906,080	75,620,130