- Results support BLA submission in 2024 using the accelerated approval pathway
- Primary endpoint of patients achieving reduction in CSF biomarker of MPS II disease was met with statistical significance (p value of 0.00016)
- Patients treated with RGX-121 have showed continued improvement in neurodevelopmental skill acquisition up to four years and discontinued intravenous enzyme therapy
- Company plans to discuss these results as part of a full rare disease program update on its conference call today, Wednesday, February 7, 4:30 p.m. ET
ROCKVILLE, Md., Feb. 7, 2024 /PRNewswire/ — REGENXBIO Inc. (NASDAQ:RGNX) today announced topline results from the Phase I/II/III CAMPSIITE® trial of RGX-121 for the treatment of patients up to 5 years old diagnosed with Mucopolysaccharidosis Type II (MPS II), also known as Hunter syndrome, demonstrating that the pivotal phase of the trial met its primary endpoint with statistical significance.
The results were presented at the 20th Annual WORLDSymposium™ by Paul Harmatz, M.D., UCSF Benioff Children’s Hospital and trial investigator.
“The data from this pivotal trial supports that RGX-121 changes the course of disease by restoring the gene missing in boys with Hunter syndrome and has the potential to significantly improve vital brain function for patients living with this debilitating disease,” said Kenneth T. Mills, President and CEO of REGENXBIO. “We are excited about these results and working quickly to complete activities to file the BLA this year. We have shared CAMPSIITE results with FDA leadership, and they have confirmed that, based on the totality of the evidence, they are open to accelerated approval if supported by review of the full data.”
“There is currently no treatment to address fatal neuronopathic CNS disease in MPS II, and I am encouraged by the topline data from the pivotal trial of RGX-121,” said Dr. Harmatz. “A one-time gene therapy that can help these boys develop beyond the natural history of the disease and may allow them to discontinue enzyme replacement therapy or remain ERT-naïve represents a meaningful breakthrough.”
Data Summary
In the pivotal phase, MPS II patients treated with RGX-121 achieved decreased cerebrospinal fluid (CSF) levels of D2S6, a key biomarker of brain disease activity, below maximum attenuated disease levels at 16 weeks (p value of 0.00016). Patients receiving RGX-121 demonstrated an 86% median reduction in D2S6, approaching normal levels.
Pivotal results were consistent with data from the dose-finding phase of CAMPSIITE. In the dose-finding phase, the majority of patients are exceeding expectations in neurodevelopmental function compared to natural history data up to four years. New long-term follow-up of patients treated with RGX-121 in the dose-finding phase also showed there was a high rate of patients for whom trial investigators chose to discontinue standard-of-care intravenous enzyme replacement therapy (ERT) or were allowed to remain ERT-naïve. At the pivotal dose level, 80% of patients were ERT-free at last time point.
As of January 3, 2024, RGX-121 continues to be well tolerated in 25 patients dosed across all phases of the CAMPSIITE trial.
Following an RMAT meeting held with FDA at the end of 2023, REGENXBIO continues with plans to use CSF levels of D2S6 as a surrogate endpoint for accelerated approval and is completing remaining activities in order to file a BLA in the second half of 2024. Based on an expected priority review, potential approval of the planned BLA could result in receipt of a Rare Pediatric Disease Priority Review Voucher in 2025.
Data presented is available on the “Publications” section of the REGENXBIO website at WWW.REGENXBIO.COM.
