Segment reporting (Details) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2025 USD ($)	Mar. 31, 2025 USD ($)	Jun. 30, 2024 USD ($)	Mar. 31, 2024 USD ($)	Jun. 30, 2025 USD ($) segment	Jun. 30, 2024 USD ($)
Segment Reporting [Abstract]
Number of operating segments | segment					1
Segment Reporting Information [Line Items]
Revenue from collaboration agreements	$ 6,463		$ 12,006		$ 13,701	$ 15,045
General and administrative	8,767		9,695		18,097	19,983
Total operating expenses	34,964		33,448		71,366	68,706
Non-operating income	(2,481)		(3,726)		(5,323)	(7,584)
Net loss	(26,020)	$ (26,322)	(17,716)	$ (28,361)	(52,342)	(46,077)
Reportable Segment
Segment Reporting Information [Line Items]
Revenue from collaboration agreements	0		0		0	0
Reportable Segment | Operating Segments
Segment Reporting Information [Line Items]
Development expenses	12,605		11,645		27,155	22,646
Research expenses	8,846		7,589		16,570	14,807
General and administrative	8,521		7,833		17,142	16,220
Total operating expenses	29,972		27,067		60,867	53,673
Non-operating income	(2,481)		(3,726)		(5,323)	(7,584)
Adjustments or reconciling items	(1,471)		(5,625)		(3,202)	(12)
Net loss	$ (26,020)		$ (17,716)		$ (52,342)	$ (46,077)