Consolidated Statements of Operations (Unaudited) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Consolidated Statements of Operations (Unaudited) [Abstract]
Grant Revenue	$ 72	$ 0
Expenses:
Research & development	8,472	4,533
Selling, general & administrative	4,220	2,047
Total expenses	12,692	6,580
Operating loss	(12,620)	(6,580)
Change in fair value of common stock warrant liability	162	(3,434)
Other income / (expense):
Interest and other income	1	2
Interest and other expense	(178)	(4)
Other income / (expense), net	(177)	(2)
Net loss	$ (12,635)	$ (10,016)
Net loss per common share - basic and diluted (in dollars per share)	$ (0.29)	$ (0.37)
Weighted average number of common shares outstanding - basic and diluted (in shares)	43,657	27,162