FDA Bumps Back PDUFA for REGENXBIO's MPS II Gene Therapy RGX-121
The new PDUFA date is set for February 8, 2026.
The FDA has extended the review timeline for REGENXBIO's biologics license application (BLA) for clemidsogene lanparvovec (RGX-121), an investigational adeno-associated virus (AAV) vector-based gene therapy intended to treat mucopolysaccharidosis type 2 (MPSII, also known as Hunter syndrome), setting a new Prescription Drug User Fee Act (PDUFA) goal date of February 8, 2026.1
The new PDUFA date is several months later than the original PDUFA date of November 9, 2025. REGENXBIO noted that the extended timeline came after the company responded to an FDA information request by submitting longer-term clinical data for all 13 patients treated in the pivotal phase 1/2/3 CAMPSIITE clinical trial (NCT03566043). REGENXBIO pointed out that the updated data are consistent with previously submitted biomarker and neurodevelopmental findings. The new data will be presented at the International Congress of Inborn Errors of Metabolism (ICIEM), which will be held in Kyoto, Japan, from September 2 to 6, 2025.
REGENXBIO also noted that a prelicense inspection and bioresearch monitoring information inspection has been carried out by the FDA for the RGX-121 BLA. The inspection, carried out in August 2025, yielded no observations. Furthermore, the agency has not brought up and safety concerns during the BLA review.
"Boys with this rare, devastating disease have no treatment options to address neurodevelopmental decline, and the Hunter syndrome community is in urgent need for a therapeutic option with the potential to improve these patients' lives," Curran M. Simpson, the president and chief executive officer of REGENXBIO, said in a statement.1 "We promptly provided the FDA with the information requested and expect the commercial launch plans remain on track."
The BLA for RGX-121 was originally accepted for review by the FDA in May 2025.2 RGX-121 has previously received orphan drug, rare pediatric disease, fast track, and regenerative medicine advanced therapy designations from the FDA and advanced therapy medicinal products classification from the European Medicines Agency. Notably, REGENXBIO has a strategic partnership in place with Nippon Shinyaku subsidiary NS Pharma, under which the latter company will carry out commercialization of RGX-121 if it is approved by the FDA.3 Under the same partnership, NS Pharma will also carry out commercialization activities for another of REGENXBIO’s investigational gene therapy products, RGX-111, which is in development for MPS I (also known as Hurler syndrome), pending that therapy’s approval by the FDA.
At the Society for the Study of Inborn Errors of Metabolism (SSIEM) Annual Symposium 2024, held September 3-6, in Porto, Portugal, REGENXBIO presented data from CAMPSIITE showing that among patients who received the pivotal dose level (dose level 3, DL3) in the study, a median reduction of 85% in heparan sulfate D2S6 levels was seen in the cerebrospinal fluid (CSF).4 The company noted that these levels of the biomarker approach normal levels and were sustained for up to 2 years.
"A potential one-time treatment that can allow these boys to exceed the natural history of this disease in their neurocognitive development, as well as the ability to remain off enzyme replacement therapy for multiple years represents a meaningful option for patients and their families," Roberto Giugliani, MD, PhD, a professor in the Department of Genetics, UFRGS, Medical Genetics Service, HCPA, Porto Alegre, Brazil, said in a September 2024 statement.4 "I continue to be very encouraged by the data supporting RGX-121 and look forward to the seeing this program advance towards potential approval for this community."
REFERENCES
1. REGENXBIO announces FDA review extension of BLA for RGX-121 to treat patients with MPS II. News release. REGENXBIO Inc. August 18, 2025. August 25, 2025. https://ir.regenxbio.com/news-releases/news-release-details/regenxbio-announces-fda-review-extension-bla-rgx-121-treat
2. REGENXBIO announces FDA acceptance and priority review of the BLA for RGX-121 for MPS II. News release. REGENXBIO Inc. May 13, 2025. August 25, 2025. https://ir.regenxbio.com/news-releases/news-release-details/regenxbio-announces-fda-acceptance-and-priority-review-bla-rgx
3. REGENXBIO and Nippon Shinyaku announce exclusive partnership to develop and commercialize RGX-121 and RGX-111 for MPS diseases. News release. REGENXBIO Inc. January 14, 2025. August 25, 2025. https://regenxbio.gcs-web.com/news-releases/news-release-details/regenxbio-and-nippon-shinyaku-announce-exclusive-partnership/
4. REGENXBIO announces positive data from pivotal dose level of RGX-121 demonstrating long-term systemic effect. News release. REGENXBIO Inc. September 3, 2024. August 25, 2025. https://ir.regenxbio.com/news-releases/news-release-details/regenxbio-announces-positive-data-pivotal-dose-level-rgx-121
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