The FDA has approved Mepsevii (vestronidase alfa-vjbk) for an ultra rare genetic enzyme disorder called MPS VII, and the OK comes with a priority review voucher that could easily be worth more than $125 million.
Affecting fewer than 150 people worldwide, the extremely rare disorder typically causes various skeletal abnormalities that worsen with age, including short stature. A majority of patients with MPS VII die from heart disease and airway obstruction, according to the release.
"Prior to today's approval, patients with this rare, inherited condition had no approved treatment options", said Julie Beitz, MD, director of the Office of Drug Evaluation III in the FDA's Center for Drug Evaluation and Research.
The FDA reports that the life expectancy varies based on symptoms, with some patients not living past infancy and others surviving to adulthood. Affected individuals may have developmental delay and progressive intellectual disability, although intelligence is unaffected in some people with this condition.
Mepsevii works by replacing the deficient lysosomal enzyme beta-glucuronidase in MPS VII patients.
Data supporting the approval came from a clinical trial and also individual patients receiving the product through the FDA's expanded access program - 23 patients in all. Patients received Mepsevii at doses up to 4mg/kg once every two weeks for up to 164 weeks. A six-minute walk test assessed efficacy in 10 patients who could perform the test. The novel enzyme therapy, to be sold by Ultragenyx Pharmaceutical, is a recombinant version of the missing enzyme.
After 24 weeks, the mean difference in distance walked relative to placebo was 18 meters. Longer treatment resulted in additional gains or stabilization. Overall, the results observed would not have been anticipated in the absence of treatment.
Ultragenyx has cautioned that the effect of Mepsevii on the central nervous system manifestations of MPS VII has not been determined.
Mepsevii was granted FDA Fast Track designation, which expedites the development and review of drugs used to treat serious conditions with an unmet medical need.
The most common side effects after treatment with Mepsevii include infusion site reactions, diarrhea, rash, and anaphylaxis. The rare pediatric disease review voucher program is created to encourage development of new drugs and biologics for the prevention or treatment of rare pediatric diseases.
The California-based biopharmaceutical company plans to make Mepsevii available in the United States later this month.