Annual report pursuant to Section 13 and 15(d)

Selected Quarterly Financial Data (Unaudited) - Summary of Unaudited Quarterly Financial Data (Detail)

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Selected Quarterly Financial Data (Unaudited) - Summary of Unaudited Quarterly Financial Data (Detail) - USD ($)
3 Months Ended 12 Months Ended
Dec. 31, 2019
Sep. 30, 2019
Jun. 30, 2019
Mar. 31, 2019
Dec. 31, 2018
Sep. 30, 2018
Jun. 30, 2018
Mar. 31, 2018
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]                      
Loss from operations $ (6,470,661) $ (7,626,575) $ (7,407,479) $ (6,361,733) $ (8,844,512) $ (7,799,290) $ (7,496,454) $ (6,984,169) $ (27,866,448) $ (31,124,425) $ (26,563,757)
Net income (loss) $ (10,355,484) $ (5,359,118) $ (8,666,906) $ 11,587,015 $ 5,935,696 $ (4,377,747) $ (20,135,892) $ (19,106,481) $ (12,794,493) $ (37,684,424) $ (15,517,658)
Net income (loss) per share of common stock, basic and diluted $ (1.11) $ (0.67) $ (1.09) $ 1.46 $ 0.75 $ (0.57) $ (2.73) $ (2.59) $ (1.54) $ (4.95) $ (2.79)