Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenues:
Collaborative research and development revenue from related party			$ 6,060
Operating expenses:
Research and development	$ 33,183	$ 33,815	33,541
General and administrative	14,506	13,584	11,634
Total operating expenses	47,689	47,399	45,175
Loss from operations	(47,689)	(47,399)	(39,115)
Other income (expense):
Interest income	384	494	501
Interest expense		(24)	(59)
Total other income, net	384	470	442
Net loss	$ (47,305)	$ (46,929)	$ (38,673)
Basic and diluted net loss per common share	$ (1.08)	$ (1.08)	$ (0.95)
Shares used to compute basic and diluted net loss per common share	43,890	43,275	40,916