Condensed Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Revenue:
Collaboration revenue - related party	$ 3,766	$ 3,015
Grant revenue	205
Total revenue	3,971	3,015
Operating expenses:
Research and development expenses	23,460	20,143
General and administrative expenses	8,777	8,762
Total operating expenses	32,237	28,905
Loss from operations	(28,266)	(25,890)
Other income (expense):
Interest income (expense), net	347	416
Total other income (expense), net	347	416
Net loss	$ (27,919)	$ (25,474)
Net loss per share attributable to common stockholders, basic and diluted	$ (0.69)	$ (0.63)
Weighted average common shares outstanding, basic and diluted	40,628,434	40,368,536
Other comprehensive income (loss):
Unrealized gain (loss) on investments, net of tax of $0	$ 40	$ (2)
Total other comprehensive income (loss)	40	(2)
Comprehensive loss	$ (27,879)	$ (25,476)