Condensed Consolidated Statements of Operations (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Revenue:
Total revenue	$ 1,399		$ 15,095
Operating expenses:
Research and development	14,853	$ 12,451	40,287	$ 43,882
General and administrative	6,839	5,672	20,015	14,823
Total operating expenses	21,692	18,123	60,302	58,705
Loss from operations	(20,293)	(18,123)	(45,207)	(58,705)
Other income (expense):
Interest income	36	88	77	549
Other (expense) income, net	(24)	2	(107)	(23)
Total other income (expense)	12	90	(30)	526
Loss before income tax expense	(20,281)	(18,033)	(45,237)	(58,179)
Income tax expense	(26)		(118)
Net loss	$ (20,307)	$ (18,033)	$ (45,355)	$ (58,179)
Net loss per share, basic and diluted	$ (0.31)	$ (0.29)	$ (0.69)	$ (1.18)
Weighted-average common shares outstanding, basic and diluted	65,789,449	62,240,412	65,675,915	49,473,350
License [Member]
Revenue:
Total revenue			$ 12,000
Development Fee [Member]
Revenue:
Total revenue	$ 1,399		$ 3,095