Ultragenyx Receives Complete Response Letter from FDA for UX111 AAV Gene Therapy to Treat Sanfilippo Syndrome Type A (MPS IIIA)

Core Viewpoint - The FDA issued a Complete Response Letter (CRL) for Ultragenyx's Biologics License Application (BLA) for UX111, a gene therapy for Sanfilippo syndrome type A, citing specific chemistry, manufacturing, and controls (CMC) observations that are resolvable [1][2] Group 1: Company Overview - Ultragenyx Pharmaceutical Inc. is focused on developing therapies for rare and ultra-rare genetic diseases, with a diverse portfolio aimed at addressing high unmet medical needs [6] - The company is led by a management team experienced in rare disease therapeutics, emphasizing time- and cost-efficient drug development [7] Group 2: Product Information - UX111 is an in vivo gene therapy in Phase 1/2/3 development for Sanfilippo syndrome type A (MPS IIIA), a rare fatal lysosomal storage disease with no approved treatment [4] - The therapy targets the SGSH enzyme deficiency, which leads to the accumulation of heparan sulfate in the brain, causing neurodegeneration [4] - UX111 is administered via a one-time intravenous infusion using a self-complementary AAV9 vector to deliver a functional copy of the SGSH gene [4] Group 3: Regulatory Status - The FDA's CRL did not raise any issues regarding the clinical data package or clinical inspections, acknowledging the robustness of the neurodevelopmental outcome data and supportive biomarker data [3] - The company plans to address the CMC observations and resubmit the BLA, anticipating a review period of up to 6 months post-resubmission [2][3] Group 4: Disease Context - Sanfilippo syndrome type A (MPS IIIA) affects approximately 3,000 to 5,000 patients in commercially accessible areas, characterized by rapid neurodegeneration and a median life expectancy of 15 years [5] - The disease is caused by biallelic pathogenic variants in the SGSH gene, leading to a deficiency in the sulfamidase enzyme [5]