Summarized Quarterly Data - Summarized Quarterly Data (Detail) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Research and development expense	$ 1,502,032	$ 1,339,343	$ 2,095,149	$ 2,015,076	$ 1,708,302	$ 1,837,743	$ 2,188,138	$ 2,419,961	$ 6,951,600	$ 8,154,144
General and administrative expense	822,325	830,092	802,655	1,137,753	842,777	819,703	976,418	1,025,261	3,592,825	3,664,159
Change in fair value of warrant liability	(796,560)	198,945							(597,615)
Net loss	$ (1,527,343)	$ (3,025,281)	$ (2,970,498)	$ (3,225,409)	$ (2,624,152)	$ (2,735,400)	$ (3,241,163)	$ (3,520,748)	$ (10,748,531)	$ (12,121,463)
Net loss per common share, basic and diluted	$ (0.12)	$ (0.29)	$ (0.41)	$ (0.45)	$ (0.37)	$ (0.42)	$ (0.52)	$ (0.58)	$ (1.15)	$ (1.87)
Weighted average shares outstanding, basic and diluted	12,305,360	10,614,692	7,217,577	7,168,005	7,123,163	6,494,845	6,212,803	6,103,783	9,338,068	6,485,794