Abeona Therapeutics' Gene Therapy Trial for MPS IIIA Shows Promising Results

Abeona Therapeutics and Ultragenyx Pharmaceutical are conducting a Phase I/II/III clinical trial for a gene therapy treatment, UX111, for MPS IIIA, a rare genetic disorder. The trial aims to evaluate the efficacy and safety of UX111, a self-complementary adeno-associated virus carrying the human SGSH gene. The study is ongoing and may positively impact Abeona Therapeutics' stock performance and influence market dynamics in the gene therapy sector.

Ultragenyx Pharmaceutical Inc. (NASDAQ: RARE) recently announced that the U.S. Food and Drug Administration (FDA) has issued a Complete Response Letter (CRL) for its Biologics License Application (BLA) for UX111, a gene therapy treatment for Sanfilippo syndrome type A (MPS IIIA). The CRL, issued on July 11, 2025, requested additional information and enhancements concerning certain chemistry, manufacturing, and controls (CMC) elements and findings from recent manufacturing facility inspections [1].

The CRL did not raise concerns about the clinical data or inspections but requested updated clinical data from current patients for inclusion in the resubmission. The FDA acknowledged the robustness of the submitted neurodevelopmental outcome data and the supportive nature of the biomarker findings. The regulatory setback has delayed the potential approval of UX111 for MPS IIIA to 2026 [1].

Emil D. Kakkis, M.D., Ph.D., chief executive officer and president of Ultragenyx, stated, "Our goal is to get UX111 to patients as quickly as possible knowing how critical this first therapy is to the Sanfilippo community. We have been diligently responding to the recent CMC observations and our priority is to resolve them so that we can resubmit the BLA as soon as possible. We believe the CMC observations are readily addressable and many have already been addressed" [1].

Sanfilippo syndrome type A (MPS IIIA) is a rare, fatal lysosomal storage disease with no approved treatment that primarily affects the brain and is characterized by rapid neurodegeneration, with onset in early childhood. Children with MPS IIIA present with global developmental delay which eventually leads to progressive cognitive, language, and motor decline, behavioral abnormalities, and early death [1].

Ultragenyx Pharmaceutical is committed to bringing novel therapies to patients for the treatment of serious rare and ultra-rare genetic diseases. The company has built a diverse portfolio of approved medicines and treatment candidates aimed at addressing diseases with high unmet medical need and clear biology, for which there are typically no approved therapies treating the underlying disease [1].

The regulatory setback has delayed the potential approval of UX111 for MPS IIIA to 2026, which may impact Abeona Therapeutics' stock performance and influence market dynamics in the gene therapy sector. Ultragenyx Pharmaceutical is working with urgency to resolve the CMC observations and resubmit the BLA as soon as possible.

References:
[1] https://www.drugs.com/clinical_trials/ultragenyx-receives-complete-response-letter-fda-ux111-aav-gene-therapy-sanfilippo-syndrome-type-22101.html
[2] https://www.nasdaq.com/articles/ultragenyx-pharmaceuticals-gets-crl-ux111-gene-therapy-mps-iiia