CHMP Backs Antiarrhythmic for Muscle-Contraction Disorders

Deborah Brauser

October 19, 2018

The European Medicines Agency's (EMA's) Committee for Medicinal Products for Human Use (CHMP) has recommended marketing authorization for the antiarrhythmic drug mexiletine hydrochloride (NaMuscla, Lupin Neurosciences) for adults with nondystrophic myotonia (NDM), a group of inherited muscle contraction disorders.

This would be the first treatment authorized EU-wide for this rare condition that is characterized by chronic pain, fatigue, and muscle stiffness resulting in frequent falls and disability. In 2010, the active substance mexiletine was approved in France to treat these disorders.

"Today's positive CHMP opinion...is a very positive step towards meeting the significant unmet medical needs of this patient group across the European Union," Benedikt Schoser, MD, Department of Neurology, University of Munich, Germany, said in the manufacturer's press release.

"Untreated myotonia in NDM patients can lead to significant lifetime disability," Schoser added. "Access to a consistent mexiletine formulation is the first step in removing barriers and optimizing care for these patients."

The full indication for the capsules is "symptomatic treatment of myotonia in adult patients" with NDM disorders. In addition, the CHMP notes in their summary opinion that the drug should be prescribed only by physicians who have experience treating these disorders.

Safety Concerns

Today's recommendation is based on one phase 3 clinical trial, "as well as data from the literature," the agency noted in a press release. Together, the findings showed that patients with NDM treated with mexiletine experienced significant relief in muscle stiffness.

In addition, "the medicine's safety profile is well-established," CHMP reports. Common side effects include nausea, heartburn, vomiting, abdominal pain, insomnia, and diarrhea. Less common adverse events include drug reactions with eosinophilia and systemic symptoms and the triggering of new or aggravating existing arrhythmia.

"The CHMP therefore agreed on specific measures to minimize this risk such as certain contraindications and cardiac monitoring," they write.

The cause for NDM is traced to abnormalities in ion channels. Mexiletine, which was first authorized in Europe in the 1970s to restore normal heart rhythm, blocks channels for sodium ions in muscle cells, leading to a reduction in muscle contraction rate and stiffness.

In November 2014, the drug was designated as an orphan medicinal product.

"With this positive CHMP opinion we are now one step closer to offering NaMuscla to patients with NDM for whom there are currently no licensed treatment options available across all EU countries," Thierry Volle, president, Europe, Middle-East, and Africa (EMEA), Lupin, said in a statement.

"We eagerly await the next step," he added.  

The opinion from CHMP will now be sent to the European Commission for a decision on EU-wide marketing authorization.

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