CONDENSED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Revenue
Research and development revenue	$ 1,072	$ 3,004	$ 2,299	$ 5,789
Costs and expenses:
Research and development	4,337	4,327	8,535	8,740
General and administrative	1,887	2,776	3,931	5,963
Total costs and expenses	6,224	7,103	12,466	14,703
Loss from operations	(5,152)	(4,099)	(10,167)	(8,914)
Interest income	52	28	86	64
Other income		54		282
Net loss	(5,100)	(4,017)	(10,081)	(8,568)
Unrealized gain (loss) on marketable securities		(8)	29	3
Comprehensive loss	$ (5,100)	$ (4,025)	$ (10,052)	$ (8,565)
Basic and diluted net loss per share:
Net loss per share (in dollars per share)	$ (0.07)	$ (0.06)	$ (0.15)	$ (0.14)
Weighted average basic and diluted common shares outstanding (in shares)	71,062	62,754	68,275	62,747