Condensed Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Operating expenses:
Research and development	$ 44,318	$ 38,684	$ 86,145	$ 80,098
In process research and development	15	15,000	45	17,805
General and administrative	11,263	11,655	22,609	22,403
Total operating expenses	55,596	65,339	108,799	120,306
Loss from operations	(55,596)	(65,339)	(108,799)	(120,306)
Other income (expense), net
Interest income	141	898	334	2,496
Interest expense	(4,834)	(2,491)	(9,614)	(3,198)
Other income	457	62	606	64
Total other expense, net	(4,236)	(1,531)	(8,674)	(638)
Net loss	(59,832)	(66,870)	(117,473)	(120,944)
Other comprehensive income (loss):
Foreign currency translation, net of tax	162	78	(210)	(9)
Unrealized gain (loss) on marketable securities, net of tax	(46)	994	(115)	318
Other comprehensive income (loss)	116	1,072	(325)	309
Comprehensive loss	$ (59,716)	$ (65,798)	$ (117,798)	$ (120,635)
Net loss per share, basic (in dollars per share)	$ (0.80)	$ (1.00)	$ (1.58)	$ (1.88)
Net loss per share, diluted (in dollars per share)	$ (0.80)	$ (1.00)	$ (1.58)	$ (1.88)
Weighted average common shares outstanding, basic (in shares)	74,672,882	66,599,915	74,384,805	64,245,119
Weighted average common shares outstanding, diluted (in shares)	74,672,882	66,599,915	74,384,805	64,245,119