Key Takeaways:
- Promising Results: REGENXBIO’s RGX-121 shows significant long-term reductions in a key biomarker for brain disease in MPS II patients, with sustained results for up to two years.
- Enzyme Replacement Therapy: 80% of patients treated with RGX-121 at the pivotal dose level discontinued intravenous enzyme replacement therapy, highlighting the potential of RGX-121 as a first-line treatment.
- Regulatory Progress: REGENXBIO is on track to submit a rolling Biologics License Application (BLA) for RGX-121 using the accelerated approval pathway by Q3 2024.
REGENXBIO Inc. has announced positive data from the pivotal dose level of its gene therapy, RGX-121, for treating Mucopolysaccharidosis Type II (MPS II), also known as Hunter syndrome. The results, presented at the 2024 SSIEM Annual Symposium, demonstrate long-term, sustained reductions in cerebrospinal fluid (CSF) levels of heparan sulfate D2S6, a key biomarker of brain disease activity in MPS II. This development marks a significant step forward in the treatment of this rare and debilitating condition.
In the ongoing Phase I/II/III CAMPSIITE® trial, RGX-121 has shown an 85% median reduction in CSF levels of heparan sulfate D2S6 at the pivotal dose level, with these reductions sustained for up to two years. This biomarker is closely linked to the neurocognitive decline seen in MPS II patients, and the ability of RGX-121 to reduce its levels to near-normal suggests a meaningful impact on disease progression.
Clinical Impact in Mucopolysaccharidosis II Trial
80% of patients who received the pivotal dose of RGX-121 discontinued their standard intravenous enzyme replacement therapy (ERT) or remained ERT-naïve for over 18 months post-treatment. This finding highlights RGX-121’s potential to serve as a first-line treatment for MPS II, offering a one-time therapeutic option that could alleviate the need for ongoing enzyme replacement therapy.
The CAMPSIITE trial continues to demonstrate that RGX-121 is well tolerated, with no significant safety concerns across the 25 patients treated in various phases of the trial. These encouraging results have set the stage for the planned submission of a rolling Biologics License Application (BLA) in Q3 2024, utilizing the accelerated approval pathway. Should the BLA be approved, REGENXBIO could receive a Priority Review Voucher in 2025, further accelerating the availability of this potentially transformative therapy.
Regulatory Pathway and Clinical Significance
REGENXBIO is moving forward with its plans to submit a rolling BLA for RGX-121, using the biomarker reduction of CSF D2S6 as a surrogate endpoint reasonably likely to predict clinical benefit under the FDA’s accelerated approval pathway. This approach underscores the therapy’s potential to address the significant unmet medical need for treatments that can halt or reverse neurocognitive decline in MPS II patients.
The CAMPSIITE trial, which is currently using commercial-scale cGMP material from REGENXBIO’s proprietary NAVXpress™ manufacturing process, will continue to collect data on neurodevelopmental outcomes and caregiver-reported experiences. The ongoing success of RGX-121 could establish a new standard of care for MPS II, offering hope to patients and families affected by this challenging condition.
As the trial progresses, REGENXBIO remains committed to advancing RGX-121 towards potential approval, with the ultimate goal of delivering a one-time treatment that not only improves brain function but also reduces the systemic effects of MPS II.
Resource: Regenxbio, September 03, 2024
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