Stock Plans - Stock-based compensation expense (Details) - USD ($) $ in Thousands |
3 Months Ended | 6 Months Ended | ||
|---|---|---|---|---|
Jun. 30, 2022 |
Jun. 30, 2021 |
Jun. 30, 2022 |
Jun. 30, 2021 |
|
| Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost | ||||
| Total stock-based compensation | $ 217 | $ 447 | $ 443 | $ 695 |
| Research and development | ||||
| Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost | ||||
| Total stock-based compensation | 123 | 214 | 246 | 334 |
| General and administrative | ||||
| Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost | ||||
| Total stock-based compensation | $ 94 | $ 233 | $ 197 | $ 361 |