Xenon Pharmaceuticals Inc. announced the launch of its XEN1101 Phase 3 program with the initiation of the X-TOLE2 clinical trial, which will examine XEN1101 administered as an adjunctive treatment for adult patients with focal epilepsy. XEN1101 is a differentiated Kv7 potassium channel opener being developed for the treatment of epilepsy and major depressive disorder. In October 2021, Xenon announced positive results from its Phase 2b X-TOLE clinical trial, which evaluated the clinical efficacy, safety and tolerability of XEN1101 administered as an adjunctive treatment for adult patients with focal epilepsy.

In June 2022, Xenon announced the successful completion of an End-of-Phase 2 meeting with the U.S. Food & Drug Administration (FDA). Based on the EOP2 meeting, Xenon and the FDA aligned on key elements of the Phase 3 program to support a New Drug Application (NDA) submission. Xenon plans to submit an NDA upon completion of the first XEN1101 Phase 3 clinical trial (X-TOLE2), if successful, and use the existing data package from the Phase 2b X-TOLE clinical trial along with additional safety data from other clinical trials to meet regulatory requirements.

Xenon has initiated its XEN1101 Phase 3 development program, which includes two identical Phase 3 clinical trials to be run in parallel, called X-TOLE2 and X-TOLE3, that are designed closely after the Phase 2b X-TOLE clinical trial. These multicenter, randomized, double-blind, placebo-controlled trials will evaluate the clinical efficacy, safety, and tolerability of XEN1101 administered as adjunctive treatment in approximately 360 patients per study with focal onset seizures (FOS). The primary efficacy endpoint is the median percent change (MPC) in monthly seizure frequency from baseline through the double-blind period (DBP) of XEN1101 compared to placebo.

On completion of the DBP in X-TOLE2 and X-TOLE3, eligible patients may enter an open-label extension (OLE) study for up to three years. In addition, the ongoing X-TOLE OLE also continues to generate important long-term data for XEN1101 in FOS. Xenon also intends to initiate a Phase 3 clinical trial, called X-ACKT, to support potential regulatory submissions in an additional epilepsy indication of primary generalized tonic clonic seizures (PGTCS).

This multicenter, randomized, double-blind, placebo-controlled study will evaluate the clinical efficacy, safety, and tolerability of XEN1101 administered as adjunctive treatment in approximately 160 patients with PGTCS. The primary efficacy endpoint is the MPC in monthly PGTCS frequency from baseline through the DBP of XEN1101 compared to placebo. On completion of the DBP in X-ACKT, eligible patients may enter an OLE study for up to three years.