Consolidated Statements of Operations (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Revenues:
Product sales	$ 312	$ 0	$ 0
Grant revenue	2,523	388	195
Total revenues	2,835	388	195
Expenses:
Cost of product sales	2,671	517	0
Research and development	26,690	27,661	21,570
Selling, general & administrative	16,732	16,718	16,444
Total expenses	46,093	44,896	38,014
Operating loss	(43,258)	(44,508)	(37,819)
Change in fair value of common stock warrant liability	3,791	761	555
Other income / (expense):
Interest and other income	6	3	6
Interest and other expense	(4,597)	(1,471)	(57)
Other income / (expense), net	(4,591)	(1,468)	(51)
Net loss	$ (44,058)	$ (45,215)	$ (37,315)
Net loss per common share
Basic (in dollars per share)	$ (0.52)	$ (0.82)	$ (0.95)
Diluted (in dollars per share)	$ (0.56)	$ (0.82)	$ (0.95)
Weighted-average number of common shares outstanding
Basic (in shares)	85,095	55,258	39,396
Diluted (in shares)	86,025	55,258	39,396