FDA Approves Drug for Mucopolysaccharidosis Type VII

Mepsevii replaces beta-glucuronidase, the deficiency of which causes an abnormal buildup of toxic materials in the body's cells.

Mepsevii™ (vestronidase alfa-vjbk; Ultragenyx Pharmaceuticals) has been approved by the US Food and Drug Administration (FDA) to treat pediatric and adult patients with mucopolysaccharidosis type VII (MPS VII), commonly known as Sly syndrome.1,2

MPS VII is a rare, progressive lysosomal storage disorder that affects less than 150 people worldwide. People with MPS VII experience skeletal abnormalities, heart valve abnormalities, enlarged liver and spleen, and narrowed airways that can predispose patients to lung infections. Developmental delay and progressive intellectual disability may also be associated with the condition.

Drug safety and efficacy were examined in clinical trials (ClinicalTrials.gov Identifiers: NCT02230566, NCT02432144, NCT01856218) and expanded access protocols that studied the effects of investigational agent UX003 in 23 patients. Efficacy was assessed via 6-minute walk test, and continued improvement was seen in patients over 120 weeks of follow-up. According to the FDA press release, “[T]he results observed would not have been anticipated in the absence of treatment.”

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. Mepsevii also received Orphan Drug designation.

Related Articles

The most common side effects of this treatment include infusion site reactions, diarrhea, rash, and anaphylaxis.

According to Ultragenyx, Mepsevii will be available to US patients later this month.


  1. FDA approves treatment for rare genetic enzyme disorder [news release]. Silver Springs, MD: US Food and Drug Administration. https://www.fda.gov/NewsEvents/Newsroom/PressAnnouncements/ucm585308.htm. Published November 15, 2017. Accessed November 15, 2017.
  2. Ultragenyx announces FDA approval of MEPSEVII™ (vestronidase alfa), the first therapy for progressive and debilitating rare genetic disease mucopolysaccharidosis VII [news release]. Novato, CA: Ultragenyx Pharmaceutical. http://ir.ultragenyx.com/releasedetail.cfm?ReleaseID=1048901. Published November 15, 2017. Accessed November 15, 2017.