CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Revenue:
Government contracts	$ 13,720	$ 7,241	$ 22,966	$ 12,713
Research and development collaborations	276	1,018	906	3,008
Total revenue	13,996	8,259	23,872	15,721
Costs and expenses:
Cost of government contracts revenue	2,687	5,102	5,307	8,123
Research and development	25,042	15,202	50,769	29,720
General and administrative	7,088	5,806	12,931	10,114
Total costs and expenses	34,817	26,110	69,007	47,957
Loss from operations	(20,821)	(17,851)	(45,135)	(32,236)
Other income (expense):
Investment income	134	20	256	32
Interest expense	(26)	(51)	(62)	(103)
Other income (expense)	72	18	(70)	18
Realized gains on marketable securities	0	0	0	615
Net loss	$ (20,641)	$ (17,864)	$ (45,011)	$ (31,674)
Basic and diluted net loss per share	$ (0.08)	$ (0.08)	$ (0.18)	$ (0.15)
Basic and diluted weighted average number of common shares outstanding (in shares)	268,083	217,178	254,727	213,075