CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenue
Total revenue	$ 3,335	$ 12,926	$ 0
Expenses
Research and development	182,866	93,872	58,085
General and administrative	42,573	21,681	13,450
Total operating expenses	225,439	115,553	71,535
Loss from operations	(222,104)	(102,627)	(71,535)
Other income, net	8,848	4,209	1,105
Net loss	(213,256)	(98,418)	(70,430)
Unrealized gain (loss) on available-for-sale investments	(410)	0	54
Comprehensive loss	$ (212,846)	$ (98,418)	$ (70,484)
Basic and diluted net loss per share (USD per share)	$ (5.69)	$ (3.19)	$ (2.78)
Weighted average common shares outstanding, basic and diluted (shares)	37,467,505	30,897,717	25,290,222