Ultragenyx Resubmits Biologics License Application for UX111 AAV Gene Therapy to Treat Sanfilippo Syndrome Type A (MPS IIIA) to U.S. FDA

Core Viewpoint - Ultragenyx Pharmaceutical Inc. has resubmitted its Biologics License Application (BLA) for UX111, a gene therapy for Sanfilippo syndrome type A, to the FDA, aiming for accelerated approval based on new long-term clinical data demonstrating positive effects over 8.5 years [2][3][5]. Group 1: Product and Clinical Data - UX111 (rebisufligene etisparvovec) is an AAV9 gene therapy in Phase 1/2/3 development targeting Sanfilippo syndrome type A, a rare and fatal lysosomal storage disease with no approved treatment [6]. - The resubmitted BLA includes comprehensive responses to previous FDA observations and additional long-term clinical data, which support an intermediate clinical endpoint for accelerated approval [3][4]. - Updated clinical data show a durable treatment effect across multiple biomarkers and maintain an acceptable safety profile, with detailed updates to be presented at WORLDSymposium™ 2026 [4]. Group 2: Regulatory Process and Timeline - The FDA granted Priority Review for the UX111 BLA in February 2025, with a Prescription Drug User Fee Act (PDUFA) action date expected within a month of resubmission [5]. - The company anticipates a review period of up to six months from the resubmission date, with a PDUFA date expected in the third quarter of 2026 [5]. Group 3: Disease Background - Sanfilippo syndrome type A (MPS IIIA) is characterized by rapid neurodegeneration, with onset in early childhood, leading to cognitive, language, and motor decline, and has a median life expectancy of 15 years [7]. - The disease affects approximately 3,000 to 5,000 patients in commercially accessible geographies and is caused by biallelic pathogenic variants in the SGSH gene, leading to a deficiency in the sulfamidase enzyme [7][8]. Group 4: Company Overview - Ultragenyx is focused on developing novel therapies for serious rare and ultra-rare genetic diseases, with a diverse portfolio aimed at addressing high unmet medical needs [9]. - The company is led by a management team experienced in rare disease therapeutics, emphasizing time- and cost-efficient drug development [10].