Net Loss Per Share - Schedule of Computation of Basic and Diluted Net Loss Per Share (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Numerator
Net loss	$ (39,171,152)	$ (46,425,390)
Less: preferred stock accretion and other deemed dividends	(3,307,800)	(4,930,010)
Net loss attributable to common stockholders	$ (42,478,952)	$ (51,355,400)
Denominator
Weighted-average common shares outstanding, basic and diluted	2,802,382	431,878
Net loss per share attributable to common stockholders, basic and diluted	$ (15.16)	$ (118.91)