Ultragenyx Announces FDA Approval of FAYUVI for Sanfilippo Type A

What Happened

• On September 17, 2026, Ultragenyx Pharmaceutical Inc. announced that the U.S. Food and Drug Administration granted standard full approval of FAYUVI™ (rebisufligene etisparvovec-hopf), also known as UX111, for the treatment of pediatric patients with mucopolysaccharidosis type IIIA (MPS IIIA, Sanfilippo syndrome Type A). This is the first FDA-approved treatment for Sanfilippo Type A and represents Ultragenyx’s second gene therapy approval. The company also received a Priority Review Voucher with the approval.

Key Details

• Approval date: September 17, 2026 (announced in the Form 8-K filed the same day).
• Product: FAYUVI (rebisufligene etisparvovec-hopf / UX111) for pediatric MPS IIIA (Sanfilippo Type A).
• Milestones: First-ever FDA-approved treatment for Sanfilippo Type A; Ultragenyx’s second gene therapy approval.
• Administrative: Ultragenyx signed and filed the 8-K; filing signed by Howard Horn, Executive VP & CFO, on September 17, 2026. Company received a Priority Review Voucher with the approval.

Why It Matters

• FDA approval creates the first regulated treatment option for a progressive, fatal pediatric disorder that previously had no approved therapies, potentially opening a new commercial market for Ultragenyx.
• The Priority Review Voucher and the second gene therapy approval are material milestones for the company’s development and regulatory position. Investors should note these regulatory achievements when assessing Ultragenyx’s future revenue potential and pipeline strategy.