Accrued Expenses and Other Current Liabilities - Schedule of Accrued Expenses and Other Liabilities (Detail) - USD ($)	Sep. 30, 2017	Dec. 31, 2016
Accrued Liabilities and Other Liabilities [Abstract]
Accrued professional services	$ 885,549	$ 689,135
Accrued board of director compensation	81,414	606,199
Accrued payroll and employee benefits	1,070,006	957,719
Accrued interest	536	169,790
Accrued research and development costs	1,559,808	549,902
Total	$ 3,597,313	$ 2,972,745