Condensed Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Revenue:
Total revenue		$ 7,254	$ 22,254	$ 18,701
Operating expenses:
Research and development	$ 16,420	10,833	49,218	27,615
General and administrative	3,087	3,074	10,093	9,230
Total operating expenses	19,507	13,907	59,311	36,845
Loss from operations	(19,507)	(6,653)	(37,057)	(18,144)
Interest income, net	658	582	1,927	1,292
Net loss	$ (18,849)	$ (6,071)	$ (35,130)	$ (16,852)
Net loss per share, basic and diluted	$ (0.52)	$ (0.17)	$ (0.98)	$ (0.53)
Weighted average common shares used to compute net loss per share, basic and diluted	36,405	35,475	36,021	32,072
Collaboration Revenue
Revenue:
Total revenue		$ 7,254	$ 22,254	$ 18,701