STATEMENTS OF OPERATIONS (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
STATEMENTS OF OPERATIONS [Abstract]
Government contracts	$ 5,583	$ 5,008	$ 17,328	$ 8,843
Research and development collaboration	182		182
Total revenue	5,765	5,008	17,510	8,843
Costs and expenses:
Cost of government contracts revenue	3,838	2,190	12,740	3,763
Research and development	6,395	4,049	16,649	13,474
General and administrative	2,381	2,737	8,291	8,926
Total costs and expenses	12,614	8,976	37,680	26,163
Loss from operations	(6,849)	(3,968)	(20,170)	(17,320)
Other income (expense):
Interest income	39	22	111	106
Interest expense	(6)	(2)	(12)	(6)
Change in fair value of warrant liability	(401)	736	(401)	1,973
Loss from operations before income tax	(7,217)	(3,212)	(20,472)	(15,247)
Income tax expense				412
Net loss	$ (7,217)	$ (3,212)	$ (20,472)	$ (15,659)
Basic and diluted net loss per share	$ (0.05)	$ (0.03)	$ (0.16)	$ (0.14)
Basic and diluted weighted average number of common shares outstanding	134,178	115,107	127,246	113,053