Ultragenyx Analyst Day Presentation

GTX-102 for Angelman syndrome: Phase 1/2 showed meaningful and improving changes across multiple domains at longer timepoints¹ IIII & Quantitative improvements in Bayley-4 far exceeding natural history • • Cognition Receptive Communication Gross Motor Improvements in ASA show meaningful reductions in severity • Sleep • Behavior Supportive data from . EEG delta power and sleep spindle Enrollment in Phase 1/2 complete with 74 patients enrolled across Cohorts 1 to 7 and A through E 1: Data presented at the company's Analyst Day on October 16, 2023 12 Confidential and Proprietary ultragenyx

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