Collaboration Agreements	12 Months Ended
Dec. 31, 2025
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Collaboration Agreements	10. Collaboration agreements: Neurocrine Biosciences license and collaboration agreement In December 2019, the Company entered into the Neurocrine Collaboration Agreement with Neurocrine Biosciences granting the Company an exclusive license to NBI-921352 (formerly XEN901) and certain pre-clinical compounds for development (the “DTCs”). The agreement also includes a two-year research collaboration to discover, identify and develop additional novel Nav1.6 and Nav1.2/1.6 inhibitors (“Research Compounds”). The Company and Neurocrine Biosciences collaborated on the conduct of two collaboration programs: (a) a joint research collaboration to discover, identify and preclinically develop Research Compounds (the “Research Program”), which was completed in June 2022, and (b) a collaborative development program for NBI-921352 and two DTCs selected by the joint steering committee. Under the arrangement, the Company was entitled to funding for certain full-time equivalent and external costs incurred by the Company for the research and development services requested by Neurocrine Biosciences, and these services were priced at estimated fair value. The Company is eligible to receive pre-commercial and commercial milestone payments with respect to the licensed products totaling up to an additional $1,667,500, comprised of up to $1,067,500 in additional development and regulatory milestone payments related to NBI-921352 and other licensed Nav1.6 or Nav1.2/1.6 inhibitor products, and up to $600,000 in additional sales-based milestone payments for multiple products. In addition, the Company is eligible to receive royalties on net sales in and outside the U.S., ranging from (a) for NBI-921352, a low double-digit percentage to a mid-teen percentage and a high-single digit percentage to low double-digit percentage, respectively; (b) for DTCs, a high-single digit percentage to a low double-digit percentage and a mid-single digit percentage to a high-single digit percentage, respectively; and (c) for Research Compounds, a mid-single digit percentage to a high-single digit percentage and a tiered mid-single digit percentage, respectively. Royalty rates are subject to customary reductions. The Company has an option to co-fund 50% of the development costs of NBI-921352 or another product candidate in the U.S., exercisable upon achievement of certain milestones, in exchange for increased U.S. royalties. The Company has not exercised this option as of December 31, 2025. In February 2025, NBI-921355, a Nav1.2 and Nav1.6 sodium channel inhibitor in development for the potential treatment for certain types of epilepsy, progressed into a Phase 1 clinical study in healthy adult participants, triggering a $7,500 milestone payment to the Company, which was recognized as revenue for the year ended December 31, 2025.

Collaboration Agreements

12 Months Ended

Dec. 31, 2025

Organization, Consolidation and Presentation of Financial Statements [Abstract]

10.

Collaboration agreements:

Neurocrine Biosciences license and collaboration agreement

In December 2019, the Company entered into the Neurocrine Collaboration Agreement with Neurocrine Biosciences granting the Company an exclusive license to NBI-921352 (formerly XEN901) and certain pre-clinical compounds for development (the “DTCs”). The agreement also includes a two-year research collaboration to discover, identify and develop additional novel Nav1.6 and Nav1.2/1.6 inhibitors (“Research Compounds”). The Company and Neurocrine Biosciences collaborated on the conduct of two collaboration programs: (a) a joint research collaboration to discover, identify and preclinically develop Research Compounds (the “Research Program”), which was completed in June 2022, and (b) a collaborative development program for NBI-921352 and two DTCs selected by the joint steering committee. Under the arrangement, the Company was entitled to funding for certain full-time equivalent and external costs incurred by the Company for the research and development services requested by Neurocrine Biosciences, and these services were priced at estimated fair value.

The Company is eligible to receive pre-commercial and commercial milestone payments with respect to the licensed products totaling up to an additional $1,667,500, comprised of up to $1,067,500 in additional development and regulatory milestone payments related to NBI-921352 and other licensed Nav1.6 or Nav1.2/1.6 inhibitor products, and up to $600,000 in additional sales-based milestone payments for multiple products. In addition, the Company is eligible to receive royalties on net sales in and outside the U.S., ranging from (a) for NBI-921352, a low double-digit percentage to a mid-teen percentage and a high-single digit percentage to low double-digit percentage, respectively; (b) for DTCs, a high-single digit percentage to a low double-digit percentage and a mid-single digit percentage to a high-single digit percentage, respectively; and (c) for Research Compounds, a mid-single digit percentage to a high-single digit percentage and a tiered mid-single digit percentage, respectively. Royalty rates are subject to customary reductions.

The Company has an option to co-fund 50% of the development costs of NBI-921352 or another product candidate in the U.S., exercisable upon achievement of certain milestones, in exchange for increased U.S. royalties. The Company has not exercised this option as of December 31, 2025.

In February 2025, NBI-921355, a Nav1.2 and Nav1.6 sodium channel inhibitor in development for the potential treatment for certain types of epilepsy, progressed into a Phase 1 clinical study in healthy adult participants, triggering a $7,500 milestone payment to the Company, which was recognized as revenue for the year ended December 31, 2025.