Accrued Expenses - Schedule of Accrued Expenses and Other Current Liabilities (Detail) - USD ($)	Sep. 30, 2021	Dec. 31, 2020
Accrued Liabilities And Other Liabilities [Abstract]
Accrued professional services	$ 729,434	$ 1,350,194
Accrued payroll and employee benefits	2,006,675	2,351,599
Accrued interest	19,423	13,016
Accrued research and development	15,943,874	7,316,876
Lease obligation, current portion (see Note 6)	401,743	356,716
Deferred revenue	19,753	19,753
Total accrued expenses	$ 19,120,902	$ 11,408,154