Condensed Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Revenue:
Collaboration revenue - related party	$ 3,015	$ 2,710
Total revenue	3,015	2,710
Operating expenses:
Research and development expenses	20,143	15,416
General and administrative expenses	8,762	7,210
Total operating expenses	28,905	22,626
Loss from operations	(25,890)	(19,916)
Other income (expense):
Interest income	775	268
Other income (expense):	(359)	(56)
Total other income, net	416	212
Net loss	$ (25,474)	$ (19,704)
Net loss per share attributable to common stockholders, basic and diluted	$ (0.63)	$ (0.50)
Weighted average common shares outstanding, basic and diluted	40,368,536	39,186,130
Other comprehensive (loss) income:
Unrealized (loss) gain on investments, net of tax of $0	$ (2)	$ 78
Total other comprehensive (loss) income	(2)	78
Comprehensive loss	$ (25,476)	$ (19,626)