Stock-based compensation - Equity Incentive Plan (Details) - Stock Option Plan [Member] - USD ($) $ in Thousands |
12 Months Ended | |
|---|---|---|
Mar. 31, 2025 |
Mar. 31, 2024 |
|
| Equity Incentive Plan [Abstract] | ||
| Compensation expense | $ 730 | $ 913 |
| Research and Development Expenses [Member] | ||
| Equity Incentive Plan [Abstract] | ||
| Compensation expense | 216 | 198 |
| General and Administrative Expenses [Member] | ||
| Equity Incentive Plan [Abstract] | ||
| Compensation expense | $ 514 | $ 715 |