FDA grants rare pediatric disease label to gene therapy for Hunter syndrome

The FDA has issued rare pediatric disease designation to an investigational gene therapy product candidate for the treatment of infants with Hunter’s syndrome, also known as mucopolysaccharidosis type II, according to the drug’s manufacturer.

Hunter’s syndrome is a form of mucopolysaccharidoses (MPS) characterized by developmental delays and eventual regression in children. In severe forms of the disease, while early developmental milestone may be met, developmental delay is evident at 18 to 24 months. Patients with severe Hunter’s syndrome generally plateau in their developmental progression between 3 and 5 years, with developmental regression reported at 6 years.

RGX-121 (RegenXBio Inc.) is an investigational gene therapy product candidate for the treatment of Hunter’s syndrome that may help address developmental and neurological complications patients experience by using an adeno-associated virus gene therapy to administer the iduronate-2-sulfatase gene to the central nervous system.

Due to an estimate that Hunter’s syndrome affects approximately 500 to 1,000 newborns worldwide each year, there are no therapies currently approved for the disease.

“Along with RGX-111 for the treatment of MPS I, this is our second MPS program to achieve a Rare Pediatric Disease Designation and builds upon the Orphan Drug Designation granted to RGX-121 at the end of 2015 by the FDA, underscoring the therapy’s potential to provide meaningful benefit to children struggling with this severely debilitating disease,” Kenneth T. Mills, president and CEO of RegenXBio, said in a press release.

“Both of these programs use our NAV AAV9 vector and we plan to file Investigational New Drug applications for RGX-111 and RGX-121 in the first half of 2017. We look forward to working with the FDA to advance this platform of gene therapies for MPS to patients in need.”

The FDA has defined a “rare pediatric disease” as a disease that affects fewer than 200,000 individuals in the U.S., primarily aged from birth to 18 years. Under the FDA’s Rare Pediatric Disease Priority Review Voucher program, a sponsor who receives an approval of a new drug application or biologics license application for a rare pediatric disease may be eligible for a voucher which can be redeemed to obtain priority review for a subsequent marketing application for a different product.