Consolidated Statements of Operations (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Consolidated Statements of Operations [Abstract]
Grant Revenue	$ 195	$ 582	$ 0
Expenses:
Research & development	21,570	17,230	17,136
Selling, general & administrative	16,444	7,864	8,392
Total expenses	38,014	25,094	25,528
Operating loss	(37,819)	(24,512)	(25,528)
Change in fair value of common stock warrant liability	555	3,560	6,422
Other income / (expense):
Interest and other income	6	13	288
Interest and other expense	(57)	(26)	(357)
Other income / (expense), net	(51)	(13)	(69)
Net loss	$ (37,315)	$ (20,965)	$ (19,175)
Net loss per common share - basic and diluted (in dollars per share)	$ (0.95)	$ (0.93)	$ (1.65)
Weighted average number of common shares outstanding - basic and diluted (in shares)	39,396	22,660	11,602