Mucopolysaccharidosis VII is an extremely rare, autosomal recessive lysosomal storage disorder characterized by a deficiency of β-
glucuronidase activity, resulting in partial degradation and accumulation of GAGs in numerous tissues throughout the body, with consequent cellular damage and organ dysfunction.
Enzyme replacement therapy (ERT) with intravenous
vestronidase alfa (Mepsevii™), a recombinant form of human β-
glucuronidase, is the first disease-specific
therapy approved for the treatment of
mucopolysaccharidosis VII in pediatric and adult patients. In the pivotal, blind start, phase 3 trial, 24 weeks of
vestronidase alfa therapy significantly reduced urinary GAG (uGAG) excretion in patients with
mucopolysaccharidosis VII. Based on a Multi-Domain Responder Index (MDRI; comprises six clinically important morbidity domains, with prespecified minimally important differences for each domain), most evaluable patients experienced an improvement in ≥ 1 domain during the 24-week primary assessment period (overall positive mean change of 0.5 domains). The clinical benefits of
vestronidase alfa were sustained during longer-term treatment, as was the reduction in uGAG excretion.
Vestronidase alfa has a manageable tolerability profile, with most adverse reactions of mild to moderate severity. Given the lack of treatment options and the clinical benefits it provides, intravenous
vestronidase alfa is an important emerging ERT for patients with
mucopolysaccharidosis VII.