Ultragenyx released new cognitive and safety data from its gene therapy program for Sanfilippo syndrome type A as part of a planned resubmission to the U.S. FDA. The company reported cognitive measures from 17 treated patients and is using the dataset to address prior regulatory concerns raised during an earlier review. Ultragenyx’s briefing highlights longitudinal assessments of cognition and developmental trajectories that the company believes support a favorable benefit–risk profile. The data package is intended to persuade regulators that the therapy delivers clinically meaningful effects in a rare, progressive neurodegenerative disorder with high unmet need. The resubmission will be closely watched by rare‑disease stakeholders because it could set precedents for evidentiary expectations in pediatric gene therapy reviews and for how regulators weigh small, open-label datasets in life‑threatening conditions.