Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands |
Mar. 31, 2020 |
Dec. 31, 2019 |
|---|---|---|
| Accrued Expenses and Other Current Liabilities | ||
| Accrued employee compensation and benefits | $ 2,717 | $ 5,045 |
| Accrued external research and development expenses | 5,087 | 6,715 |
| Accrued manufacturing facility expenses | 1,277 | 2,824 |
| Accrued general and administrative expenses | 916 | 1,136 |
| Other | 294 | 322 |
| Accrued expenses and other current liabilities | $ 10,291 | $ 16,042 |