Pediatric Designation for Hunter Syndrome Gene Therapy Could Add Millions of $$$

James Radke, PhD

The FDA has given a pediatric disease designation to Regenxbio’s gene therapy to treat Hunter syndrome.

What is Hunter syndrome

Hunter syndrome, or mucopolysaccharidosis II (MPS II), is an X-linked lysosomal disorder caused by a deficiency or absence of iduronate-2-sulfatase, which leads to severe clinical complications and early mortality. Common symptoms may include stunted growth, coarse facial features, hearing loss, joint stiffness, sleep apnea, thickening of heart valves, obstructive airways, enlarged liver and spleen, and cognitive impairment.
Currently, the only approved treatment for patients with Hunter syndrome is the enzyme replacement therapy Elaprase (Elaprase). It only treats the peripheral aspects of the disease.

Pediatric designation = $$$

The rare pediatric disease designation means the FDA will give Regenxbio a pediatric priority review voucher if the therapy is approved for the pediatric indication. That voucher can then be used by the company for another drug—any drug—to be given a priority review. A priority review means the FDA will review the drug within 6 months instead of the standard 10 months.
The priority review voucher is also transferable and that is what many small biotech companies are doing. For example,  United Therapeutics sold their voucher to Abbvie for $350 million and Retrophin sold their priority review voucher to Sanofi for $245 million.

Rengenxbio focused on MPS diseases

Another gene therapy by Regenxbio, RGX-111 was given a pediatric designation last year for MPS I (Hurler syndrome).
In a news release, Kenneth T. Mills, President and Chief Executive Officer of Regenxbio said, "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.”  Mills added, “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.”
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