Prepaid Expenses and Other Current Assets - Prepaid Expenses and Other Current Assets (Detail) - USD ($)	Jun. 30, 2018	Dec. 31, 2017
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Prepaid research fees	$ 211,124	$ 388,977
Prepaid insurance	306,689	638,139
Prepaid pre-commercialization fees	8,925	65,000
Prepaid subscription fees	69,068	23,347
Prepaid rent	20,828
Other	60,707	58,281
Total prepaid expenses and other current assets	$ 677,341	$ 1,173,744