Nature of the business (Details) - USD ($) $ in Thousands	Sep. 30, 2026	Dec. 31, 2025	Sep. 30, 2025
Nature of the business
Accumulated deficit	$ 940,913	$ 728,164
Non-restricted cash and cash equivalents	212,842	653,482	$ 272,639
Marketable securities	$ 248,740	$ 0