Nature of the business (Details) - USD ($) $ in Thousands	Sep. 30, 2025	Dec. 31, 2024	Sep. 30, 2024
Nature of the business
Accumulated deficit	$ 658,264	$ 515,770
Non-restricted cash and cash equivalents	272,639	143,351	$ 155,568
Marketable securities	$ 0	$ 73,952

Amount of accumulated undistributed earnings (deficit).

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant