Summarized Quarterly Data - Summarized Quarterly Data (Detail) - USD ($) |
3 Months Ended | 12 Months Ended | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|
Dec. 31, 2015 |
Sep. 30, 2015 |
Jun. 30, 2015 |
Mar. 31, 2015 |
Dec. 31, 2014 |
Sep. 30, 2014 |
Jun. 30, 2014 |
Mar. 31, 2014 |
Dec. 31, 2015 |
Dec. 31, 2014 |
|
| Quarterly Financial Information Disclosure [Abstract] | ||||||||||
| Research and development expense | $ 1,708,302 | $ 1,837,743 | $ 2,188,138 | $ 2,419,961 | $ 2,176,388 | $ 3,088,373 | $ 2,874,977 | $ 1,852,116 | $ 8,154,144 | $ 9,991,855 |
| General and administrative expense | 842,777 | 819,703 | 976,418 | 1,025,261 | 738,012 | 732,800 | 616,888 | 1,070,479 | 3,664,159 | 3,158,179 |
| Net loss | $ (2,624,152) | $ (2,735,400) | $ (3,241,163) | $ (3,520,748) | $ (2,919,803) | $ (3,825,354) | $ (3,547,040) | $ (2,955,484) | $ (12,121,463) | $ (13,247,681) |
| Net loss per common share, basic and diluted | $ (0.37) | $ (0.42) | $ (0.52) | $ (0.58) | $ (0.48) | $ (0.63) | $ (0.59) | $ (0.49) | $ (1.87) | $ (2.20) |
| Weighted average shares outstanding, basic and diluted | 7,123,163 | 6,494,845 | 6,212,803 | 6,103,783 | 6,065,841 | 6,054,250 | 6,027,672 | 6,002,936 | 6,485,794 | 6,032,560 |