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SEGMENT REPORTING - Schedule of Segment Reporting Information, by Segment (Details) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2025	Jun. 30, 2025	Mar. 31, 2025	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Sep. 30, 2025	Sep. 30, 2024
Segment Reporting Information [Line Items]
Total segment revenue	$ 14,262			$ 388			$ 243,676	$ 508
Research and development	(19,519)			(49,225)			(111,731)	(127,998)
Stock-based compensation	(3,986)			(8,817)			(21,391)	(25,672)
Depreciation expense							(1,109)	(897)
Income tax (provision) benefit	1,424			0			(6,397)	0
Net income (loss)	(7,280)	$ (30,696)	$ 148,451	(52,956)	$ (45,257)	$ (43,114)	110,475	(141,327)
Reportable Segment
Segment Reporting Information [Line Items]
Total segment revenue	14,262			388			243,676	508
Compensation costs (excluding stock based compensation)	(9,568)			(11,830)			(37,187)	(35,186)
Stock-based compensation	(3,986)			(8,817)			(21,391)	(25,672)
Depreciation expense	(395)			(315)			(1,109)	(897)
Other segment items	(8,346)			(6,840)			(29,187)	(20,529)
Dividend income	6,933			5,793			20,845	16,977
Income tax (provision) benefit	1,424			0			(6,397)	0
Net income (loss)	(7,280)			(52,956)			110,475	(141,327)
KER-065 program expenses | Reportable Segment
Segment Reporting Information [Line Items]
Research and development	(1,345)			(4,935)			(4,293)	(12,225)
Elritercept program expenses | Reportable Segment
Segment Reporting Information [Line Items]
Research and development	(3,341)			(13,576)			(37,872)	(33,161)
Cibotercept program expenses | Reportable Segment
Segment Reporting Information [Line Items]
Research and development	(1,218)			(8,618)			(11,185)	(20,820)
Preclinical & development expenses | Reportable Segment
Segment Reporting Information [Line Items]
Research and development	$ (1,700)			$ (4,206)			$ (5,425)	$ (10,322)

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