Statements Of Operations (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended		109 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012
Research contract revenue	$ 200	$ 200	$ 600	$ 467	$ 1,267
Operating expenses:
Research and development, including costs of research contracts	16,215	10,667	48,464	44,433	177,363
General and administrative	5,712	3,742	15,462	11,017	84,257
Total operating expenses	21,927	14,409	63,926	55,450	261,620
Loss from operations	(21,727)	(14,209)	(63,326)	(54,983)	(260,353)
Other income (expense), net	(42)	19	(65)	26	4,649
Change in fair value of warrants	3,945	13,388	(2,516)	4,423	2,205
Net loss	$ (17,824)	$ (802)	$ (65,907)	$ (50,534)	$ (253,499)
Net loss per share - basic	$ (0.23)	$ (0.01)	$ (0.85)	$ (0.77)
Net loss per share - diluted	$ (0.23)	$ (0.01)	$ (0.85)	$ (0.77)
Weighted average common shares outstanding to compute net loss per share - basic	78,670,222	68,104,934	77,605,590	65,277,084
Weighted average common shares outstanding to compute net loss per share - diluted	78,670,222	68,104,934	77,605,590	65,277,084