CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Operating expenses:
Research and development	$ 7,857	$ 10,640	$ 18,020	$ 20,059
General and administrative	2,910	2,956	6,016	5,842
Total operating expenses	10,767	13,596	24,036	25,901
Loss from operations	(10,767)	(13,596)	(24,036)	(25,901)
Interest income and other expense, net	156	618	490	1,280
Net loss	$ (10,611)	$ (12,978)	$ (23,546)	$ (24,621)
Net loss per share, basic and diluted (in dollars per share)	$ (0.36)	$ (0.44)	$ (0.80)	$ (0.84)
Shares used to compute net loss per share, basic and diluted (in shares)	29,428,249	29,309,150	29,419,741	29,301,505
Other comprehensive loss:
Unrealized gain on marketable securities	$ 10	$ 28	$ 24	$ 73
Comprehensive loss	$ (10,601)	$ (12,950)	$ (23,522)	$ (24,548)