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FDA Approves Keveyis for Primary Hyperkalemic and Hypokalemic Periodic Paralysis

Orphan drug is first approved treatment for patients with rare debilitating disease

The FDA has approved dichlorphenamide (Keveyis, Taro Pharmaceutical Industries Ltd.) 50-mg tablets for the treatment of primary hyperkalemic and hypokalemic periodic paralysis, a group of rare hereditary disorders that cause episodes of muscle weakness or paralysis. Keveyis is the first medicine approved by the FDA for the treatment of primary periodic paralysis, which is estimated to affect approximately 5,000 people in the U.S.

Taro expects Keveyis will be available for patients during the third quarter of 2015. The company has created the Keys2Care program, which will provide a suite of patient support services to ensure people diagnosed with periodic paralysis can receive treatment with Keveyis as soon as possible. Taro is working with Diplomat Pharmacy, Inc., a specialty pharmacy, to offer access and support to patients who are prescribed Keveyis and their caregivers.

“Because of the very rare nature of periodic paralysis, it is not unusual for patients to go years before receiving an accurate diagnosis,” says Robert Griggs, MD, principal investigator and professor, Department of Neurology, University of Rochester Medical Center. The symptoms are often debilitating.

Periodic paralyses are a group of rare hereditary disorders that cause episodes of muscle weakness or paralysis. Types of periodic paralyses are differentiated by criteria including underlying genetic mutations and changes in blood potassium levels during attacks. Hypokalemic and hyperkalemic are two common types of periodic paralyses. Keveyis is indicated for the treatment of primary hyperkalemic periodic paralysis, primary hypokalemic periodic paralysis, and related variants.

The efficacy of Keveyis was evaluated in two clinical studies. In the first, a nine-week, double-blind, placebo-controlled multicenter study,  patients with hypokalemic periodic paralysis treated with Keveyis (n = 24) had 2.2 fewer self-reported attacks of muscle weakness per week over the final eight weeks of the trial than patients (n = 20) treated with placebo. Patients with hyperkalemic periodic paralysis treated with Keveyis (n = 12) had 3.9 fewer attacks per week than patients (n = 9) treated with placebo.

The second study was a 35-week, double-blind, placebo-controlled, multicenter, two-period crossover study that included 31 patients with hyperkalemic periodic paralysis and 42 patients with hypokalemic periodic paralysis. Hyperkalemic periodic paralysis patients treated with Keveyis had 2.3 fewer attacks per week than those on placebo. Acute intolerable worsening necessitating withdrawal was observed in two hypokalemic periodic paralysis patients on Keveyis versus 11 patients on placebo.

In clinical studies, the most common side effects of Keveyis were a burning or pricking sensation, difficulty thinking and paying attention, changes in taste, and confusion. Keveyis may cause a drop in the amount of potassium in the body, which can lead to heart problems. The body may produce too much acid or may not be able to remove enough acid from body fluids while taking Keveyis. Keveyis may also increase the risk of falls, especially in elderly patients and patients taking high doses of Keveyis. 

Dichlorphenamide tablets, an oral carbonic anhydrase inhibitor that has been used to treat glaucoma, received initial U.S. approval in 1958 . The precise mechanism by which dichlorphenamide exerts its therapeutic effects in patients with periodic paralysis is unknown.

Sources: Taro Pharmaceutical Industries Ltd.; August 10, 2015; and Keveyis prescribing information, August 2015.

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