Benzinga | Apr 14, 2021 04:15PM EDT

REGENXBIO Reports Dosing Of First Patient In Cohort 3 Of Phase 1/22 Trial Of RGX-121 For Treatment Of Mucopolysaccharidosis Type II

REGENXBIO Inc. (NASDAQ:RGNX) today announced that it dosed the first patient in Cohort 3 of the ongoing Phase I/II trial of RGX-121 for the treatment of Mucopolysaccharidosis Type II (MPS II), also known as Hunter Syndrome, in patients up to five years old. RGX-121 is an investigational one-time gene therapy designed to deliver the gene that encodes the iduronate-2-sulfatase (I2S) enzyme using the AAV9 vector. RGX-121 is administered directly to the central nervous system (CNS).

"We are pleased with our continued progress in the Phase I/II trial of RGX-121 as we increase the dose level to further our understanding of the potential treatment effects, including potential systemic benefit for patients," said Steve Pakola, M.D., Chief Medical Officer of REGENXBIO. "We are encouraged by the positive interim data we've reported previously from the first two cohorts, including signals of I2S enzyme activity in the CNS, continued neurocognitive development, and evidence of I2S enzyme activity in plasma and urine following administration of RGX-121. We look forward to further program updates later this year."

The Phase I/II trial of RGX-121 in patients with MPS II up to five years old is an open-label, dose escalation trial. RGX-121 is administered directly to the cerebrospinal fluid (CSF) and the study is designed to evaluate three dose levels, ranging from 1.3x1010 GC/g of brain mass to 2.0x1011 GC/g of brain mass. The primary endpoint of the study is safety and tolerability of RGX-121. Additional endpoints include the effect of RGX-121 on biomarkers of I2S enzyme activity in the CSF, serum and urine; neurocognitive development; and other outcome measures. The trial is being conducted at four leading clinical centers in the United States and Brazil.