FDA grants full approval to Ultragenyx gene therapy FAYUVI for Sanfilippo syndrome Type A

Ultragenyx Pharmaceutical Inc. disclosed in a September 17, 2026 regulatory filing that the FDA had cleared its gene therapy for a rare and severe pediatric condition. On that date the company announced that the FDA granted standard full approval of FAYUVI, generically named rebisufligene etisparvovec-hopf and also known as UX111, to treat pediatric patients with mucopolysaccharidosis type IIIA, also called Sanfilippo syndrome Type A.¹

Ultragenyx described the approval as notable on two counts. The company said FAYUVI is the first FDA-approved treatment for Sanfilippo syndrome Type A, which it characterized as a progressive and fatal neurodegenerative disease, and that this marks Ultragenyx's second approved gene therapy.¹

Alongside the approval, the company received a Priority Review Voucher.¹

The filing was submitted as an 8-K under Item 8.01, Other Events, and was signed by Howard Horn, Ultragenyx's Executive Vice President, Chief Financial Officer, Corporate Strategy. The company is headquartered in Novato, California, and trades on the Nasdaq Global Select Market under the ticker RARE.

The filing does not include details on the clinical trial data supporting the approval, pricing, or the timing of a commercial launch. Readers seeking those specifics should watch for a follow-on disclosure or investor materials from Ultragenyx.