STATEMENTS OF OPERATIONS (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
STATEMENTS OF OPERATIONS [Abstract]
Government contracts	$ 5,472	$ 3,441
Research and development collaborations	1,990	392
Total revenue	7,462	3,833
Costs and expenses:
Cost of government contracts revenue	3,021	1,712
Research and development	14,518	9,256
General and administrative	4,308	2,870
Total costs and expenses	21,847	13,838
Loss from operations	(14,385)	(10,005)
Other income (expense):
Interest income	12	48
Interest expense	(52)	(22)
Realized gains on investments	615
Loss from operations before income tax	(13,810)	(9,979)
Income tax expense		17
Net loss	$ (13,810)	$ (9,996)
Basic and diluted net loss per share	$ (0.07)	$ (0.07)
Basic and diluted weighted average number of common shares outstanding	208,927	148,448