Condensed Consolidated Statements of Operations and Comprehensive Loss (unaudited) - 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	$ 3,808	$ 8,589	$ 8,454	$ 17,717
General and administrative	2,751	2,746	5,629	5,177
Total operating expenses	6,559	11,335	14,083	22,894
Loss from operations	(6,559)	(11,335)	(14,083)	(22,894)
Other income (expense):
Interest income (expense), net	(103)	78	(157)	229
Other expense, net	(314)	(16)	(321)	(27)
Other income (expense), net	(417)	62	(478)	202
Net loss	$ (6,976)	$ (11,273)	$ (14,561)	$ (22,692)
Net loss per share attributable to common stockholders—basic and diluted	$ (0.26)	$ (0.54)	$ (0.56)	$ (1.09)
Weighted-average common shares outstanding—basic and diluted	26,878,962	20,903,298	25,808,043	20,859,251
Net loss	$ (6,976)	$ (11,273)	$ (14,561)	$ (22,692)
Comprehensive loss	$ (6,976)	$ (11,273)	$ (14,561)	$ (22,692)