Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Operating expenses:
Research and development	$ 35,095	$ 15,191
General and administrative	11,148	3,195
Total operating expenses	46,243	18,386
Loss from operations	(46,243)	(18,386)
Other income (expense):
Interest income	1,726	57
Change in fair value of preferred stock warrant liability	(162)	(17)
Change in fair value of derivative liability	(1,629)	(283)
Other expense	(53)	(19)
Total other expense, net	(118)	(262)
Net loss	(46,361)	(18,648)
Comprehensive loss	(46,361)	(18,648)
Reconciliation of net loss to net loss attributable to common stockholders:
Net loss	(46,361)	(18,648)
Accretion of issuance costs on redeemable convertible preferred stock	(2,243)	(85)
Net loss attributable to common stockholders-basic and diluted	$ (48,604)	$ (18,733)
Net loss per share attributable to common stockholders-basic and diluted (Note 13)	$ (3.62)	$ (8.38)
Weighted-average number of common shares used in computing net loss per share attributable to common stockholders-basic and diluted	13,435,478	2,235,865