Statements of Operations (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended			124 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013
Revenue	$ 800	$ 800	$ 667	$ 2,267
Operating expenses:
Research and development	42,852	83,446	57,083	255,197
General and administrative	15,661	19,523	14,984	103,979
Total operating expenses	58,513	102,969	72,067	359,176
Loss from operations	(57,713)	(102,169)	(71,400)	(356,909)
Other income (expense), net	(579)	(13)	39	4,122
Change in fair value of warrants	1,185	6,050	7,583	11,956
Net loss	$ (57,107)	$ (96,132)	$ (63,778)	$ (340,831)
Basic and diluted net loss per share	$ (0.66)	$ (1.22)	$ (0.97)
Weighted average common shares outstanding used to compute basic and diluted net loss per share	85,943,175	78,546,112	66,003,789