Reportable segment disclosure - Schedule of Segment Reporting Information, by Segment (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2026	Sep. 30, 2025	Sep. 30, 2026	Sep. 30, 2025
Segment Reporting [Line Items]
Research and development expense	$ 47.0	$ 28.6	$ 111.6	$ 83.8
Sales & Marketing	5.3	1.2	15.7	1.9
General & Administrative	14.0	7.3	39.1	21.3
Total expenses	66.3	37.1	166.4	107.0
VIASKIN® Peanut
Segment Reporting [Line Items]
Sales & Marketing	5.3	1.2	15.7	1.9
General & Administrative	14.0	7.3	39.1	21.3
Total expenses	66.3	37.1	166.4	107.0
VIASKIN® Peanut \| Clinical studies
Segment Reporting [Line Items]
Research and development expense	16.8	10.1	38.0	33.2
VIASKIN® Peanut \| BLA & Regulatory
Segment Reporting [Line Items]
Research and development expense	11.2	3.3	23.1	7.0
VIASKIN® Peanut \| Medical Affairs & Other Medical
Segment Reporting [Line Items]
Research and development expense	6.3	2.3	16.3	6.2
VIASKIN® Peanut \| Research & Innovation
Segment Reporting [Line Items]
Research and development expense	0.5	0.4	1.6	1.4
VIASKIN® Peanut \| Manufacturing & Supply and Quality
Segment Reporting [Line Items]
Research and development expense	$ 12.3	$ 12.6	$ 32.6	$ 35.9

The aggregate total of expenses of managing and administering the affairs of an entity, including affiliates of the reporting entity, which are not directly or indirectly associated with the manufacture, sale or creation of a product or product line.

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