Segment information (Details) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2026 USD ($)	Jun. 30, 2026 USD ($)	Mar. 31, 2026 USD ($)	Sep. 30, 2025 USD ($)	Jun. 30, 2025 USD ($)	Mar. 31, 2025 USD ($)	Sep. 30, 2026 USD ($) Segment	Sep. 30, 2025 USD ($)
Segment Reporting Information [Line Items]
Number of operating segments | Segment							1
Number of reportable segments | Segment							1
Segment Reporting, CODM, Profit (Loss) Measure, How Used, Description							The CODM assesses performance for the segment based on net loss, which is reported on the condensed consolidated statements of operations and comprehensive loss as net loss. The measure of segment assets is reported on the condensed consolidated balance sheets as total assets. When evaluating the Company’s financial performance, the CODM regularly reviews total revenues, total expenses and research and development expenses by program.
Collaboration revenue	$ 0			$ 0			$ 0	$ 6,941
Less:
General and administrative	(20,856)			(10,945)			(52,056)	(31,677)
Total operating expenses	(90,362)			(60,138)			(227,828)	(158,193)
Loss from operations	(90,362)			(60,138)			(227,828)	(151,252)
Interest income	4,579			2,681			15,079	8,758
Net loss	(85,783)	$ (73,127)	$ (53,839)	(57,457)	$ (43,397)	$ (41,640)	(212,749)	(142,494)
Single reportable segment
Segment Reporting Information [Line Items]
Collaboration revenue								6,941
Less:
Other direct research and development	13,265			6,404			31,565	15,081
Indirect research and development	21,062			13,143			57,768	36,593
General and administrative	14,530			6,997			36,652	21,246
Other segment expenses	13,765			7,334			32,077	19,632
Total operating expenses	90,362			60,138			227,828	158,193
Loss from operations	(90,362)			(60,138)			(227,828)	(151,252)
Interest income	4,579			2,681			15,079	8,758
Net loss	(85,783)			(57,457)			(212,749)	(142,494)
Single reportable segment | Varegacestat
Less:
Direct research and development expenses	12,579			12,495			33,128	39,615
Single reportable segment | IM-1021
Less:
Direct research and development expenses	9,578			2,874			19,789	7,669
Single reportable segment | IM-1617
Less:
Direct research and development expenses	1,629			5,465			4,496	9,397
Single reportable segment | IM-1340
Less:
Direct research and development expenses	1,725			3,322			7,261	4,811
Single reportable segment | IM-3050
Less:
Direct research and development expenses	$ 2,229			$ 2,104			$ 5,092	$ 4,149