Condensed Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Revenue:
Total revenue	$ 539	$ 157
Operating expenses:
Research and development	90,565	54,193
General and administrative	24,517	19,550
Total operating expenses	115,082	73,743
Loss from operations	(114,543)	(73,586)
Other income (expense):
Other income, net	1,955	4,232
Total other income (expense), net	1,955	4,232
Net loss before income taxes	(112,588)	(69,354)
Provision for income taxes	(575)	(377)
Net loss	(113,163)	(69,731)
Foreign currency translation adjustment	5	(25)
Unrealized loss on marketable securities	(383)
Comprehensive loss	$ (113,541)	$ (69,756)
Net loss per common share — basic	$ (1.51)	$ (1.15)
Basic weighted-average common shares outstanding	75,005,187	60,847,683
Net loss per common share — diluted	$ (1.51)	$ (1.15)
Diluted weighted-average common shares outstanding	75,005,187	60,847,683
Collaboration Revenue [Member]
Revenue:
Total revenue	$ 202	$ 157
Grant Revenue [Member]
Revenue:
Total revenue	$ 337