FDA Approves MPS VII Treatment

Mathew Shanley

Today, the U.S. Food and Drug Administration (FDA) approved Mepsevii (vestronidase alfa-vjbk) for use in pediatric and adult patients with mucopolysaccharidosis type VII (MPS VII), often referred to as Sly syndrome.

MPS VII is a hereditary metabolic disorder resulting from the deficiency of an enzyme called beta-glucuronidase, which is required for the breakdown of glycosaminoglycans (GAGs) including: dermatan sulfate, chondroitin sulfate, and heparin sulfate. Mepsevii is an enzyme replacement therapy that operates by replacing the missing enzyme.

The “Sly Syndrome” nickname comes from William Sly, M.D. of St. Louis University, who described the first patient with MPS VII and worked with a team at The Jackson Laboratory to develop and characterize a mouse model for the disease.

The condition affects less than 150 patients worldwide and is characterized by an array of skeletal abnormalities, including short stature.

“This approval underscores the agency’s commitment to making treatments available to patients with rare diseases,” said Julie Beitz, M.D., director of the Office of Drug Evaluation III in the FDA’s Center for Drug Evaluation and Research (CDER) in the official FDA press release. “Prior to today’s approval, patients with this rare, inherited condition had no approved treatment options.”

The approval was based on data from a clinical trial that enrolled a total of 23 patients ranging from 5 months to 25 years of age and evaluated Mepsevii’s safety and efficacy. Patients treated in the trial received Mepsevii at doses up to 4 mg/kg once every 2 weeks for up to 64 weeks. The drug exhibited clinical benefit as seen via a completion in the 6-minute walk test (6MWT) by 10 patients, and additional follow-up for up to 120 weeks implied a continued improvement in three patients and stabilization in others.

It was concluded that these results would not have been seen without treatment in this cohort of patients.

The drug, developed by Ultragenyx Pharmaceutical, Inc., had previously received Fast Track and Orphan Drug designations from the FDA. Additionally, Ultragenyx is receiving a Rare Pediatric Disease Priority Review Voucher for Mepsevii, which can be used on any future drug, allowing its FDA review time to be reduced by 4 months. It can also be sold to other pharmaceutical companies; Earlier this year, Sarepta sold its voucher to Gilead Sciences for $125 million.

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