Summary of significant accounting policies - Proceeds from grants (Details) - USD ($) $ in Thousands	1 Months Ended		3 Months Ended
	Aug. 31, 2022	May 31, 2022	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023
Summary of significant accounting policies
Grant awarded, amount		$ 3,800
Cash proceeds	$ 500		$ 3,500
Reduction of research and development expense			1,400	$ 100
Grant receivable			$ 226
Deferred liabilities					$ 327