Stock-Based Compensation - Summary of Recognized Compensation Cost Related to Employee and Non-employee Stock-Based Compensation Activity (Detail) - USD ($) |
3 Months Ended | 9 Months Ended | ||
|---|---|---|---|---|
Sep. 30, 2018 |
Sep. 30, 2017 |
Sep. 30, 2018 |
Sep. 30, 2017 |
|
| Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items] | ||||
| Stock-based compensation expense | $ 806,411 | $ 127,359 | $ 2,763,890 | $ 394,268 |
| Research and development [Member] | ||||
| Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items] | ||||
| Stock-based compensation expense | 139,492 | 88,443 | 313,505 | 276,778 |
| General and administrative [Member] | ||||
| Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items] | ||||
| Stock-based compensation expense | $ 666,919 | $ 38,916 | $ 2,450,385 | $ 117,490 |