Abstracts

Rationale: ,
Kv7 channels are voltage-gated potassium channels encoded by KCNQ genes that exert physiological control over excitable cells. In the CNS, the Kv7.2/7.3 channel subtype generates M-currents that represent a clinically validated drug target for treating seizures. Positive modulation of M-current facilitates normalizing the excitation/inhibition imbalance that occurs in epilepsy patients. There remains a high unmet medical need for increased efficacy and better anti-seizure medication tolerability in patients with refractory epilepsy.

Methods:
BHV-7000 was rationally designed from a novel Kv7 pharmacophore platform. Fluorescent and electrophysiological assays were employed to identify active compounds and characterize compounds for further development. Antiseizure efficacy was evaluated in rats in the maximal electroshock seizure (MES) model and tolerability was assessed by neurological score (NS) and rotarod assays. Cells transiently transfected with mutant (W236L) KCNQ2 were used to characterize BHV-7000 activity at Kv7.2 channels relative to WT channels. Standard ADME and toxicology assays were used for progressing BHV-7000 to Phase 1 trials.

Results:
Thallium flux screening identified active compounds that were confirmed for activity and further characterized by electrophysiology. BHV-7000 activates the Kv7.2/7.3 channel with an EC₅₀ value of 0.6 µM. At 1 µM, BHV-7000 slowed deactivation kinetics from 7.9 ± 1.9 ms to 32.3 ± 6.9 ms and shifted the half-maximal activation potential by -15.2 mV.  In rat primary cortical neuron cultures, BHV-7000 produced a concentration dependent hyperpolarization of the resting membrane potential.  Similar to other Kv7.2/7.3 activators, BHV-7000 does require the W236 amino acid for its activity. Further, BHV-7000 demonstrated little to no effect against the human α1β3ɣ2 GABA receptor at 10 µM and showed no significant activity in off-target pharmacology panel screens. In the MES model, BHV-7000 provides protection against seizures with a brain EC₅₀ of 0.12 µM and a TD₅₀ >20 by NS, a sensitive measure of tolerability. A standard rotarod assay demonstrated no motor effects across all doses further validating the wide tolerability index and the new behavioral measure of neurological score.

Conclusions:
BHV-7000 is a novel activator of heteromeric Kv7.2/7.3 potassium channels for the treatment of refractory focal seizures in epilepsy patients. BHV-7000 displays potent antiseizure activity in the rat MES model with no overt neurobehavioral or motor effects, favorable ADME parameters, a favorable toxicology profile, and thus represents a promising next generation antiseizure medication for clinical development.

Funding: This research was funded by Knopp (acquired by Biohaven) and Biohaven.