CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Revenues:
Revenue from collaborative agreements	$ 1,278	$ 1,893
Revenue from government agreements	777	953
Total revenues	2,055	2,846
Costs and expenses:
Research and development	32,801	27,346
General and administrative	7,462	6,133
Total costs and expenses	40,263	33,479
Loss from operations	(38,208)	(30,633)
Other income	553	270
Net loss	(37,655)	(30,363)
Other comprehensive income (loss):
Unrealized gain (loss) on investments	(26)	57
Comprehensive loss	$ (37,681)	$ (30,306)
Basic and diluted net loss per common share (in dollars per share)	$ (1.08)	$ (0.88)
Basic and diluted weighted average common shares outstanding (in shares)	34,958,228	34,503,845