by Amirah Al Idrus
GlaxoSmithKline and Valeant marketed their epilepsy drug ezogabine for just six years before pulling it for “commercial reasons.” Now, Xenon Pharmaceuticals is taking a stab at repurposing the drug for a rare, difficult-to-treat form of pediatric epilepsy caused by a genetic mutation.
Ezogabine was originally approved in 2011 as an add-on treatment for adults with partial-onset, or focal, seizures. But the nod was limited; on the FDA’s recommendation, the drug, sold under the name Potiga in the U.S., was listed as a controlled substance. Reports soon emerged of skin discoloration and pigment changes in the eye, which could lead to vision loss. In 2013, the European Medicines Agency said the drug, marketed as Trobalt in the EU, should be restricted to patients for whom other anti-epileptic medicines did not work or who couldn’t tolerate them. That same year, the FDA added a black-box warning on the drug. Both agencies recommended patients undergo a comprehensive eye exam every six months while on the drug.
“We have done an immense amount of diligence leading up to the addition of XEN496 to our novel and robust pipeline of ion-channel, anti-epileptic drugs,” said Xenon CEO Simon Pimstone, Ph.D., in a statement. “Based on feedback from key opinion leaders, advocacy groups, pre-existing literature, and promising data generated to date, we believe there is tremendous support for us to vigorously pursue the development and commercialization of XEN496 in order to reach the pediatric KCNQ2-EE patient population as rapidly as possible.”
And Xenon is getting a leg up from the drug’s previous go-around: “We have already completed a number of critical steps to expedite our plans for XEN496. We have obtained a right of reference authorization from GSK so that the FDA can reference GSK’s regulatory filings to support Xenon’s own regulatory submissions,” Pimstone said.
The news comes shortly after a positive phase 1b readout of XEN1101, a potassium channel opener like ezogabine that was developed in-house. The trial enrolled 20 healthy volunteers and randomized them to receive a 20-mg dose of XEN1101 or placebo. After a washout period, the volunteers switched over to the other arm.
Patients who received XEN1101 had a statistically significant change in markers of corticospinal and cortical excitability over the following six hours. Increased excitability is thought to contribute to seizures, so the findings suggest that the drug may be able to help control forms of epilepsy. The company is conducting a phase 1 ascending-dose trial and is setting up for a phase 2 trial slated to start in the fourth quarter.