Condensed Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Operating expenses:
Research and development	$ 16,241	$ 12,733	$ 47,873	$ 32,143
General and administrative	4,810	3,680	14,125	8,469
Total operating expenses	21,051	16,413	61,998	40,612
Loss from operations	(21,051)	(16,413)	(61,998)	(40,612)
Other income (expense):
Interest income	507	482	1,914	859
Interest expense	(605)	(7)	(1,258)	(228)
Total other income (expense), net	(98)	475	656	631
Net loss attributable to common stockholders	(21,149)	(15,938)	(61,342)	(39,981)
Other comprehensive gain (loss):
Unrealized gain (loss) on marketable securities	(10)		1
Total other comprehensive gain (loss):	(10)		1
Comprehensive loss	$ (21,159)	$ (15,938)	$ (61,341)	$ (39,981)
Net loss per share attributable to common stockholders, basic and diluted	$ (0.82)	$ (0.81)	$ (2.38)	$ (5.45)
Weighted average common shares outstanding, basic and diluted	25,829,105	19,619,239	25,814,593	7,332,052