Consolidated Statements of Operations and Comprehensive Loss - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Income Statement [Abstract]
Revenues	$ 137,623	$ 721,636	$ 975,139	$ 2,934,330
Operating expenses:
Research and development	13,272,412	16,594,250	25,150,312	23,781,781
General and administrative	3,658,653	2,545,356	7,480,073	4,877,273
Impairment loss on construction-in-progress	8,070,000		8,070,000
Total operating expenses	25,001,065	19,139,606	40,700,385	28,659,054
Loss from operations	(24,863,442)	(18,417,970)	(39,725,246)	(25,724,724)
Other income (expense):
Interest expense	(22,226)	(3,308)	(33,897)	(5,193)
Interest income	32,863	81,458	75,362	233,027
Other income (expense), net	26,098	(5,878)	(7,034)	19,664
Total other income, net	36,735	72,272	34,431	247,498
Net loss before income tax benefit	(24,826,707)	(18,345,698)	(39,690,815)	(25,477,226)
Income tax benefit	0	1,578,782	0	4,824,661
Net loss	(24,826,707)	(16,766,916)	(39,690,815)	(20,652,565)
Other comprehensive income (loss) - unrealized gain (loss) on short-term investments	1,141	20,888	6,277	(11,547)
Comprehensive loss	$ (24,825,566)	$ (16,746,028)	$ (39,684,538)	$ (20,664,112)
Net loss per share, basic and diluted	$ (0.60)	$ (0.94)	$ (0.99)	$ (1.25)
Weighted-average common shares outstanding, basic and diluted	41,356,643	17,886,853	40,142,561	16,498,719