Shares of Ultragenyx Pharmaceutical RARE jumped 12.6% on Thursday after the FDA granted standard full approval to Fayuvi (rebisufligene etisparvovec-hopf), also known as UX111. The one-time gene therapy is approved for treating the neurologic manifestations of mucopolysaccharidosis type IIIA (MPS IIIA or Sanfilippo syndrome Type A) in pediatric patients with preserved neurodevelopmental function. The approval makes Fayuvi the first FDA-approved treatment for the rare and fatal neurodegenerative disorder.
The regulatory milestone also marks Ultragenyx’s second gene therapy approval and sixth FDA approval overall. The company additionally received a Priority Review Voucher upon this approval, which can be used to obtain an accelerated FDA review for a future eligible drug application or potentially sold or transferred to another company.
Ultragenyx in-licensed Fayuvi from Abeona Therapeutics in 2022 under an exclusive agreement for ABO-102, which RARE later developed as UX111. Under the deal, Ultragenyx assumed responsibility for the program and obtained exclusive rights to develop, manufacture and commercialize the therapy worldwide. In return, Abeona is eligible for tiered royalties ranging from mid-single-digit percentages to 8% of net sales, along with up to $30 million in commercial milestone payments following regulatory approval. Abeona shares rose 4.1% on Thursday following the approval.
Clinical Data Backs the FDA Approval of RARE’s MPS IIIA Drug
The FDA approval was supported by data from the pivotal Transpher A study and long-term follow-up studies. According to Ultragenyx, clinical data now extend to nearly eight years and show a durable treatment effect across multiple clinical assessments and biomarkers, while maintaining an acceptable safety profile. Biochemical efficacy was demonstrated through reductions in accumulated cerebrospinal fluid heparan sulfate levels, reflecting replacement of the deficient enzyme responsible for the disease throughout the study and across all age groups.
The key efficacy analysis compared 17 Fayuvi-treated patients in the modified intention-to-treat population with 27 untreated patients from an external natural-history cohort. Between 24 and 60 months of age, Fayuvi-treated patients demonstrated a 23.5-point higher mean change in Bayley-III Cognitive raw score compared with the natural-history group. The difference was statistically significant and provided the efficacy basis for the FDA’s standard full approval.
Year to date, shares of Ultragenyx have plunged 37% against the industry’s 5.8% growth.
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MPS IIIA is an ultra-rare lysosomal storage disorder caused by mutations that result in a deficiency of the sulfamidase enzyme. The resulting accumulation of heparan sulfate primarily damages the central nervous system, leading to progressive developmental delay and eventual loss of cognitive, language and motor abilities. Ultragenyx estimates that the disease affects approximately 3,000 to 5,000 patients across commercially accessible geographies, with a median life expectancy of about 15 years. The Fayuvi approval therefore introduces the first FDA-approved treatment option for an indication with substantial unmet medical need.
Fayuvi is designed as a single-dose intravenous AAV9 gene therapy that delivers a functional copy of the SGSH gene. This enables production of the sulfamidase enzyme that is deficient in patients with MPS IIIA and is intended to address the underlying cause of the disease. Ultragenyx expects the commercial product to be available for shipment to Qualified Treatment Centers within 30 to 60 days. The company will support treatment access through its UltraCare program, while manufacturing will be carried out in the United States.
Fayuvi Expands RARE’s Approved Product Portfolio
Ultragenyx’s portfolio of non-gene therapy drugs comprises four established products. Crysvita (burosumab-twza) is approved in the United States for X-linked hypophosphatemia in adults and pediatric patients and for tumor-induced osteomalacia. Mepsevii (vestronidase alfa-vjbk) is approved for mucopolysaccharidosis type VII, while Dojolvi (triheptanoin) is approved for long-chain fatty acid oxidation disorders. The fourth product, Evkeeza (evinacumab-dgnb), is indicated for homozygous familial hypercholesterolemia. Ultragenyx holds rights to develop, commercialize and distribute Evkeeza outside the United States, while Regeneron Pharmaceuticals commercializes the drug in the United States.
Last month, the FDA granted accelerated approval to DTX-401, an AAV8 gene therapy for glycogen storage disease type Ia (GSDIa). The therapy will be marketed in the United States as Genglycos (pariglasgene brecaparvovec-opnr) and is indicated to reduce daily cornstarch intake as an adjunct to nutritional management in adult and pediatric patients aged eight years and older with GSDIa. The approval made Genglycos the first FDA-approved treatment designed to address the underlying cause of GSDIa and Ultragenyx’s first gene therapy product.
Ultragenyx Pharmaceutical Inc. Price and Consensus
Ultragenyx Pharmaceutical Inc. price-consensus-chart | Ultragenyx Pharmaceutical Inc. Quote
RARE’s Zacks Rank & Stocks to Consider
Ultragenyx currently carries a Zacks Rank #3 (Hold).
Some better-ranked stocks in the biotech sector are Precigen PGEN, currently sporting a Zacks Rank #1 (Strong Buy), and AC Immune ACIU and Aldeyra Therapeutics ALDX, carrying a Zacks Rank #2 (Buy) each. You can see the complete list of today’s Zacks #1 Rank stocks here.
Over the past 60 days, estimates for Precigen’s 2026 bottom line have improved from a loss of 2 cents to earnings per share of 25 cents. Over the same period, earnings estimates for 2027 have risen from 25 cents to 86 cents. PGEN shares have increased 88.3% year to date.
Precigen’s earnings beat estimates in three of the trailing four quarters and missed in the remaining one, with the average surprise being 108.96%.
Over the past 60 days, estimates for AC Immune’s 2026 loss per share have narrowed from 84 cents to 60 cents. Over the same period, earnings estimates for 2027 remained unchanged at 17 cents. ACIU shares have lost 14.7% year to date.
AC Immune’s earnings beat estimates in each of the trailing four quarters, with the average surprise being 33.25%.
Over the past 60 days, loss per share estimates for Aldeyra Therapeutics have narrowed from 43 cents to 39 cents for 2026. Over the same period, estimates for 2027 loss per share have narrowed from 22 cents to 16 cents. ALDX shares have plunged 73.4% year to date.
Aldeyra Therapeutics’ earnings beat estimates in each of the trailing four quarters, delivering an average surprise of 29.25%.
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