Vestronidase alfa, sold under brand name Mepsevii, is a drug for the treatment of Sly syndrome.[2] It is a recombinant form of the human enzyme beta-glucuronidase. It was approved in the United States in November 2017, to treat children and adults with an inherited metabolic condition called mucopolysaccharidosis type VII (MPS VII), also known as Sly syndrome.[3][4] MPS VII is an extremely rare, progressive condition that affects most tissues and organs.[3]
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The most common side effects after treatment with vestronidase alfa include infusion site reactions, diarrhea, rash (urticaria) and anaphylaxis (sudden, severe allergic reaction).[3][5]
The U.S. Food and Drug Administration (FDA) considers it to be a first-in-class medication.[6] It was approved for use in the European Union in August 2018.[5]
The safety and efficacy of vestronidase alfa were established in a clinical trial and expanded access protocols enrolling a total of 23 participants ranging from five months to 25 years of age.[3] Participants received treatment with vestronidase alfa at doses up to 4 mg/kg once every two weeks for up to 164 weeks.[3] Efficacy was primarily assessed via the six-minute walk test in ten participants who could perform the test.[3] After 24 weeks of treatment, the mean difference in distance walked relative to placebo was 18 meters.[3] Additional follow-up for up to 120 weeks suggested continued improvement in three participants and stabilization in the others.[3] Two participants in the vestronidase alfa development program experienced marked improvement in pulmonary function.[3] Overall, the results observed would not have been anticipated in the absence of treatment.[3] The effect of vestronidase alfa on the central nervous system manifestations of MPS VII has not been determined.[3]
The FDA approved vestronidase alfa-vjbk based primarily on evidence from one clinical trial (NCT02230566) of 12 participants with mucopolysaccharidosis VII. The trial was conducted at four sites in the United States.[4]
The benefit and side effects of vestronidase alfa were based primarily on one trial.[4] Participants were randomly assigned to four groups.[4] Three groups of participants received placebo treatment before starting vestronidase alfa treatment and one group received vestronidase alfa only.[4] vestronidase alfa or placebo were given once every two weeks as intravenous (IV) infusions.[4] Neither participants nor healthcare providers knew which treatment was given until after the trial was competed.[4]
The benefit of 24 weeks of vestronidase alfa treatment was primarily evaluated by the 6-minute walking test (6MWT) and compared to placebo treatment in ten participants who could perform the test.[4] The 6MWT measured the distance a patient could walk on a flat surface in 6 minutes.[4] An additional follow-up using 6MWT was done for up to 120 weeks.[4]
The application for vestronidase alfa was granted fast track designation, orphan drug designation, and a rare pediatric disease priority review voucher.[3] This was the twelfth rare pediatric disease priority review voucher issued.[3]
The U.S. Food and Drug Administration (FDA) granted approval of Mepsevii to Ultragenyx Pharmaceutical, Inc,[3] and required the manufacturer to conduct a post-marketing study to evaluate the long-term safety of the product.[3]
