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	$ 3,064	$ 4,290
Operating expenses:
Research and development	12,256	10,106
General and administrative	3,571	2,296
Total operating expenses	15,827	12,402
Other income:
Interest income	360	51
Total other income	360	51
Net loss	(12,403)	(8,061)
Other comprehensive loss:
Unrealized loss on marketable securities	(13)
Comprehensive loss	(12,416)	(8,061)
Net loss attributable to ordinary shareholders - basic	$ (12,403)	$ (8,061)
Net loss per share attributable to common stockholders — basic and diluted	$ (0.54)	$ (6.02)
Weighted-average number of common shares used in net loss per share attributable to common stockholders — basic and diluted	22,816,521	1,338,475