Enzyme Replacement Therapy

First Enzyme Replacement Therapy to Treat Rare Genetic Disorder Approved

Jessica Ganga

The FDA has approved the first enzyme replacement therapy for use in the United States, velmanase alfa, for the treatment of alpha-mannosidosis—a rare genetic condition where there is a lack of the alpha-mannosidase enzyme in the body. The new treatment will act the same way as the alpha-mannosidase enzyme, restoring normal cellular activity in patients

Alpha-mannosidosis presents with symptoms that vary but include mild-to-moderate intellectual disability, hearing loss, weakened immune system, distinctive facial features, skeletal abnormalities, and muscle weakness. Velmanase alfa is an injectable treatment that addresses the non-central nervous system symptoms.

The approval of velmanase alfa follows a phase 3 multicenter, randomized, double-blind, placebo-controlled, parallel group study where the treatment was evaluated in adults and pediatric patients. The efficacy was examined over 52 weeks where patients received a 1 mg/kg dose of velmanase alfa weekly as an intravenous infusion. In total, 25 patients were included in the study (13 adult patients, 12 pediatric patients). Of the total, 15 patients received the enzyme treatment and 10 patients received placebo.

The researchers tested the efficacy endpoints at 12 months where patients participated in a 3-minute stair climbing test, a 6-minute walking test, and forced vital capacity. Results from the tests favored the velmanase alfa group.

Adverse events observed were hypersensitivity reactions, including anaphylaxis. It is a recommended that if a severe hypersensitivity reaction occurs, the use of velmanase alfa should be discontinued.



FDA approves first enzyme replacement therapy for rare alpha-mannosidosis. News release. US Food and Drug Administration; February 17, 2023. Accessed March 17, 2023.