The Food and Drug Administration (FDA) has approved Mepsevii (vestronidase alfa-vjbk) for the treatment of Mucopolysaccharidosis VII (MPS VII, Sly syndrome) in pediatric and adult patients. This enzyme replacement therapy is intended to replace the deficient lysosomal enzyme beta-glucuronidase in MPS VII patients.
The approval of Mepsevii was based on a clinical trial program that included 23 patients with MPS VII; the patients ranged in age from 5 months to 25 years. Patients received Mepsevii at doses up to 4mg/kg once every two weeks for up to 164 weeks. Efficacy was primarily assessed through the 6-minute walk test (6MWT) in 10 patients who could perform the test.
After 24 weeks, the mean difference in distance walked relative to placebo was 18 meters. Additional follow-up for up to 120 weeks suggested continued improvement in 3 patients and stabilization in the remaining 7 patients. After 120 weeks of exposure, 1 patient demonstrated a 21% improvement over baseline in forced vital capacity (FVC% predicted) on pulmonary function testing in addition to a 105 meter improvement in the 6MWT. Two other patients with baseline hepatosplenomegaly had reduction in liver volume (24% and 53%) and spleen volume (28% and 47%) after 36 weeks of Mepsevii treatment. The effect of Mepsevii on the central nervous system manifestations of MPS VII has not been determined.
The most common side of effects of treatment include infusion site reactions, diarrhea, rash, and anaphylaxis.
Mepsevii is supplied as a carton containing one 10mg/5mL single-dose vial. It is expected to be available later this month.
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