Condensed Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Condensed Consolidated Statements of Operations and Comprehensive Loss
Collaboration revenue	$ 942	$ 1,464
Operating expenses:
Research and development	14,853	14,072
General and administrative	7,182	4,914
Total operating expenses	22,035	18,986
Operating loss	(21,093)	(17,522)
Other income:
Interest income	588	253
Other income	399	395
Total other income	987	648
Loss before income taxes	(20,106)	(16,874)
Income tax benefit	180	226
Net loss	(19,926)	(16,648)
Other comprehensive income
Net unrealized gain on available-for-sale-securities, net of tax expense of $244 for the three months ended March 31, 2017	120	377
Total other comprehensive income	120	377
Comprehensive loss	$ (19,806)	$ (16,271)
Net loss per share, basic and diluted	$ (0.63)	$ (0.65)
Weighted-average common shares outstanding, basic and diluted	31,759,870	25,791,591