Prepaid expenses and other current assets (Details) - USD ($) $ in Thousands |
Dec. 31, 2018 |
Dec. 31, 2017 |
|---|---|---|
| Prepaid expenses and other current assets | ||
| Prepaid clinical | $ 728 | $ 1,718 |
| Prepaid insurance | 673 | 137 |
| Other prepaid expenses and current assets | 383 | 105 |
| Total prepaid expenses and other current assets | $ 1,784 | $ 1,960 |