FDA Approves Treatment for Rare Genetic Enzyme Disorder

NOVEMBER 15, 2017
Officials with the FDA today approved the first treatment for mucopolysaccharidosis type VII (MPS VII), a rare genetic enzyme disorder, also called Sly syndrome. Vestronidase alfa-vbjk (Mepsevii, Ultragenyx) is indicated to treat pediatric and adult patients with MPS VII.

Most patients with MPS VII have various skeletal abnormalities that become more pronounced with age, including short stature. Individuals with MPS VII can also develop heart valve abnormalities, enlarged liver and spleen, and narrowed airways that can lead to lung infections and trouble breathing. Heart disease and airway obstruction are major causes of death in those affected.

Vestronidase alfa-vbjk is an enzyme replacement therapy that works by replacing the missing enzyme, called beta-glucoronidase. MPS VII is caused by deficiency of this enzyme.

The approval is based on a clinical trial and expanded access protocols enrolling 23 patients, ranging from 5 months to 25 years of age, to evaluate the safety and efficacy of the treatment. Patients received treatment of the drug at doses up to 4 mg/kg once every 2 weeks for up to 164 weeks. The researchers assessed efficacy based on the 6-minute walk test in 10 patients who were able to perform the test. After 24 weeks of treatment, the mean difference in distance walked relative to placebo was 18 meters.

Follow-up for 12 weeks indicated continued improvement in 3 patients and stabilization in the others. Two patients experienced marked improvement in pulmonary function.

The most common adverse effects associated with vestronidase alfa-vbjk include infusion site reactions, diarrhea, rash, and anaphylaxis.


FDA approves treatment for rare genetic enzyme disorder [news release]. Gaithersburg, MD. FDA’s website. . Accessed November 15, 2017.