STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating expenses
Research and development	$ 61,858	$ 33,287	$ 18,506
General and administrative	29,560	12,434	3,748
Total operating expenses	91,418	45,721	22,254
Loss from operations	(91,418)	(45,721)	(22,254)
Interest income (expense), net	6,201	2,375	(1,302)
Other expense, net	(155)	(192)	(287)
Loss before benefit from income taxes	(85,372)	(43,538)	(23,843)
Provision for (benefit from) income taxes	0	0	(291)
Net loss	(85,372)	(43,538)	(23,552)
Unrealized gain (loss) on marketable securities, net of tax	152	(15)	0
Comprehensive loss	$ (85,220)	$ (43,553)	$ (23,552)
Net loss per common share:
Basic and diluted	$ (1.89)	$ (2.20)	$ (14.54)
Weighted-average number of common shares outstanding:
Basic and diluted	45,191	19,833	1,620