Summarized Quarterly Data - Summarized Quarterly Data (Detail) (USD $)	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013
Quarterly Financial Information Disclosure [Abstract]
Research and development expense	$ 2,176,388	$ 3,088,373	$ 2,874,977	$ 1,852,116	$ 636,423	$ 78,731	$ 130,846	$ 110,981	$ 9,991,855	$ 956,980
General and administrative expense	738,012	732,800	616,888	1,070,479	944,359	406,862	72,578	221,049	3,158,179	1,644,848
Net loss	$ (2,919,803)	$ (3,825,354)	$ (3,547,040)	$ (2,955,484)	$ (1,616,698)	$ (485,904)	$ (239,871)	$ (493,992)	$ (13,247,681)	$ (2,836,465)
Net loss per common share, basic and diluted	$ (0.48)	$ (0.63)	$ (0.59)	$ (0.49)	$ (0.27)	$ (0.41)	$ (0.21)	$ (0.44)	$ (2.20)	$ (1.20)
Weighted average shares outstanding, basic and diluted	6,065,841	6,054,250	6,027,672	6,002,936	5,971,236	1,190,212	1,137,125	1,133,375	6,032,560	2,368,006