Statements Of Operations (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended		106 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012
Research contract revenue	$ 200	$ 200	$ 400	$ 267	$ 1,067
Operating expenses:
Research and development, including costs of research contracts	18,264	9,125	32,249	33,766	161,148
General and administrative	4,902	3,923	9,750	7,275	78,545
Total operating expenses	23,166	13,048	41,999	41,041	239,693
Loss from operations	(22,966)	(12,848)	(41,599)	(40,774)	(238,626)
Other income, net	3	9	(23)	7	4,691
Change in fair value of warrants	(650)	2,115	(6,461)	(8,965)	(1,740)
Net income (loss)	$ (23,613)	$ (10,724)	$ (48,083)	$ (49,732)	$ (235,675)
Net income (loss) per share - basic	$ (0.30)	$ (0.16)	$ (0.62)	$ (0.78)
Net income (loss) per share - diluted	$ (0.30)	$ (0.16)	$ (0.62)	$ (0.78)
Weighted average common shares outstanding to compute net income (loss) per share - basic	78,514,718	67,229,098	77,067,424	63,839,723
Weighted average common shares outstanding to compute net income (loss) per share - diluted	78,514,718	67,229,098	77,067,424	63,839,723