Condensed Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Operating expenses:
Research and development	$ 43,190	$ 41,846	$ 129,335	$ 121,944
In process research and development	15	275	60	18,080
General and administrative	12,459	11,448	35,068	33,851
Total operating expenses	55,664	53,569	164,463	173,875
Loss from operations	(55,664)	(53,569)	(164,463)	(173,875)
Other income (expense), net
Interest income	191	580	525	3,076
Interest expense	(4,889)	(4,715)	(14,503)	(7,913)
Other income (loss)	115	(108)	721	(44)
Total other expense, net	(4,583)	(4,243)	(13,257)	(4,881)
Net loss	(60,247)	(57,812)	(177,720)	(178,756)
Other comprehensive income (loss):
Foreign currency translation, net of tax	(64)	68	(274)	59
Unrealized gain (loss) on marketable securities, net of tax	(73)	(293)	(188)	25
Other comprehensive income (loss)	(137)	(225)	(462)	84
Comprehensive loss	$ (60,384)	$ (58,037)	$ (178,182)	$ (178,672)
Net loss per share, basic (in dollars per share)	$ (0.80)	$ (0.80)	$ (2.38)	$ (2.67)
Net loss per share, diluted (in dollars per share)	$ (0.80)	$ (0.80)	$ (2.38)	$ (2.67)
Weighted average common shares outstanding, basic (in shares)	75,001,510	72,245,897	74,592,632	66,931,512
Weighted average common shares outstanding, diluted (in shares)	75,001,510	72,245,897	74,592,632	66,931,512