MPS 1 Treatment, RGX-111, Receives FDA Fast Track Designation

Today, June 13, 2018, the US Food and Drug Administration (FDA) granted Fast Track designation to REGENXBIO Inc for its product, RGX-111, a novel, single-dose investigational treatment for mucopolysaccharidosis type I (MPS I).

RGX-111 is engineered to distribute the human iduronidase (IDUA) gene directly to the central nervous system (CNS) by utilizing the NAV AAV9 vector, an adeno-associated virus (AAV) vector.

Kenneth T. Mills, president and chief executive officer of REGENXBIO, expressed his excitement over the FDA’s recognition, in a recent statement.

"Fast Track designation represents another positive step for the development of RGX-111 as we seek to address the unmet needs of people living with MPS I,” Mills said. “We continue to engage the MPS community as we seek to provide innovative solutions to people with MPS 1 and their families. We look forward to working closely with the FDA to facilitate the development of RGX-111 and expect to begin the Phase I trial in the coming months."

A phase 1, multi-center, open-label, multiple-cohort, dose-escalation study will assess RGX-111 in children and adult subjects with MPS I. Inclusion criteria for the study involves documented evidence of early-stage neurocognitive deficit caused by MPS. In 2 dose cohorts (2 × 10⁹ GC/g brain mass and 1 × 10¹⁰ GC/g brain mass), approximately 5 MPS subjects will be administered 1 single dose of RGX-111 via injection directly in the cerebrospinal fluid (CSF).

For the first year post-RGX-111 administration, participating patients will be administered immunosuppression. Assessment of the safety and tolerability of RGX-111 at 24 weeks serves as the primary purpose of the study. Adverse events, certain laboratory measures (including immunologic parameters), and neurological examinations include the primary endpoints.

Biomarkers related to IDUA protein activity within the CSF, serum, and urine will also be assessed. For a total of 104 weeks following treatment with RGX-111 and completion of the primary study period, participants will continue to be assessed.

Long-time board member of the National MPS Society and father to 3 children with MPS I, Steve Holland reiterated the significance of the FDA Fast Track designation for RGX-111. "There are limited treatment options that address the CNS symptoms of MPS I. Having experienced firsthand the debilitating effects that MPS I can have on children living with this condition, we are encouraged to see the FDA recognize important research that explores new treatment options for people with MPS I,” he stressed.