Condensed Consolidated Statements of Operations and Comprehensive Loss (unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Operating expenses:
Research and development	$ 6,765	$ 3,333	$ 26,716	$ 10,047
General and administrative	2,267	612	6,629	1,312
Total operating expenses	9,032	3,945	33,345	11,359
Loss from operations	(9,032)	(3,945)	(33,345)	(11,359)
Other income, net	625	635	1,488	635
Loss before income taxes	(8,407)	(3,310)	(31,857)	(10,724)
Net loss	$ (8,407)	$ (3,310)	$ (31,857)	$ (10,724)
Net loss per share, basic and diluted	$ (0.30)	$ (0.75)	$ (1.23)	$ (2.79)
Weighted-average common shares used in computing net loss per share, basic and diluted	28,046,723	4,408,094	25,895,933	3,839,306
Other comprehensive loss:
Net loss	$ (8,407)	$ (3,310)	$ (31,857)	$ (10,724)
Unrealized losses on marketable securities, net of income tax expense	(46)		(76)
Comprehensive loss	$ (8,453)	$ (3,310)	$ (31,933)	$ (10,724)