Consolidated Statements of Operations (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Operating expenses:
Research and development	$ 10,273	$ 10,533	$ 6,376
General and administrative	7,566	8,472	6,403
Total operating expenses	17,839	19,005	12,779
Operating lossl	(17,839)	(19,005)	(12,779)
Other income (expense):
Interest income	5	15	35
Interest expense	(136)	(130)	(72)
Modification of warrants		(765)
Derivatives gain (loss)	(376)	(18,871)	17,480
Other income (expense), net	(507)	(19,751)	17,443
Net income (loss)	$ (18,346)	$ (38,756)	$ 4,664
Net income (loss) per share, basic (in dollars per share)	$ (0.21)	$ (0.52)	$ 0.07
Net income (loss) per share, diluted (in dollars per share)	$ (0.21)	$ (0.52)	$ 0.06
Weighted average number of common shares outstanding, basic (in shares)	88,323,044	73,991,686	63,226,899
Weighted average number of common shares outstanding, diluted (in shares)	88,323,044	73,991,686	71,919,419