Biohaven Ltd. (NYSE: BHVN) reported clinical trial data for opakalim, its experimental epilepsy treatment, showing seizure control benefits and a tolerability profile that differs from other investigational treatments in the same class.

In a randomized, placebo-controlled study of patients with idiopathic generalized epilepsy, the median time to a second generalized tonic-clonic seizure was 141 days for patients taking opakalim 75 mg once daily compared to 47 days for those on placebo. The study enrolled 27 patients but was closed before reaching its planned enrollment due to recruitment challenges and strategic portfolio decisions.

An ongoing open-label extension study in focal epilepsy showed 54% of patients on opakalim 75 mg once daily achieved at least a 50% reduction in seizure frequency over any consecutive six-month period compared to baseline. The company reported 95% completion rates for the double-blind portion of the study and 95% rollover rates to the extension phase.

In the idiopathic generalized epilepsy study, patients taking opakalim reported no cases of somnolence, dizziness, fatigue, or memory impairment. In the focal epilepsy extension study, rates of these central nervous system adverse events were 5% or lower for each symptom.

Biohaven also provided a six-month update on a pediatric patient with KCNQ2-Developmental and Epileptic Encephalopathy receiving compassionate use treatment. Overnight EEG monitoring showed a 50% reduction in seizure counts compared to pre-treatment baseline.

Opakalim is a selective Kv7.2/7.3 potassium channel activator that the company states is differentiated from other investigational treatments in this class by its selectivity profile and lack of GABA receptor activity. The company expects to announce results from the first of two pivotal Phase 2/3 studies in refractory focal epilepsy in the second half of 2026.