Condensed Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Operating expenses:
Research and development	$ 14,910	$ 15,610	$ 47,503	$ 46,751
General and administrative	5,272	5,886	16,185	16,936
Total operating expenses	20,182	21,496	63,688	63,687
Loss from operations	(20,182)	(21,496)	(63,688)	(63,687)
Other (expense) income:
Interest (expense) income, net	(713)	81	(1,353)	1,032
Other income (expense), net	39	(218)	646	(218)
Other (expense) income, net	(674)	(137)	(707)	814
Loss before income taxes	(20,856)	(21,633)	(64,395)	(62,873)
Income tax expense	(67)	0	(221)	0
Net loss	$ (20,923)	$ (21,633)	$ (64,616)	$ (62,873)
Net loss per share attributable to common stockholders, basic and diluted (in dollars per share)	$ (0.45)	$ (0.67)	$ (1.74)	$ (1.96)
Weighted-average number of common shares outstanding, basic and diluted (in shares)	46,168,013	32,060,747	37,050,907	32,009,571
Comprehensive loss:
Net loss	$ (20,923)	$ (21,633)	$ (64,616)	$ (62,873)
Other comprehensive loss:
Unrealized gain (loss) on investments, net of tax of $0	0	(1)	0	18
Comprehensive loss	$ (20,923)	$ (21,634)	$ (64,616)	$ (62,855)