Ultragenyx Pharmaceutical RARE announced that the European Medicines Agency (EMA) has validated its Marketing Authorization Application (MAA) for the investigational gene therapy rebisufligene etisparvovec (also known as UX111) to treat mucopolysaccharidosis type IIIA (MPS IIIA), also known as Sanfilippo syndrome Type A. The validation marks a key regulatory milestone as the therapy advances toward formal review in Europe.
EMA validation confirms that the application is sufficiently complete for the agency to begin its scientific assessment. However, the validation does not indicate the therapy’s safety or efficacy, nor does it guarantee that the MAA will ultimately be approved. As an investigational advanced therapy, the MAA will undergo the EU’s Joint Clinical Assessment, which supports a coordinated clinical evaluation across EU member states as part of the broader pathway to patient access.
Last month, Ultragenyx received standard full FDA approval for rebisufligene etisparvovec to be marketed in the United States as Fayuvi for treating the neurologic manifestations of MPS IIIA in pediatric patients with preserved neurodevelopmental function. The approval made Fayuvi the first FDA-approved treatment for the rare and fatal neurodegenerative disorder. The approval marked Ultragenyx’s second gene therapy approval and sixth FDA approval overall.
Ultragenyx in-licensed the drug 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.
Clinical Data Backs the FDA Approval of RARE’s MPS IIIA Drug
The EMA validation of the MAA for rebisufligene etisparvovec in MPS IIIA is 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.
Year to date, Ultragenyx shares have plunged 33.8% against the industry’s 4% growth.
Image Source: Zacks Investment Research
The key efficacy analysis compared 17 rebisufligene etisparvovec-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, rebisufligene etisparvovec-treated patients demonstrated a 23.5-point greater 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.
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.
Ultragenyx’s rebisufligene etisparvovec 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.
Treatment options for children affected by MPS IIIA remain limited outside the United States, underscoring the significant unmet medical need in this patient population. Rebisufligene etisparvovec has received Priority Medicines (PRIME) and Orphan Drug designations from the EMA, reflecting the rarity and severity of MPS IIIA and the need for new treatment options. These designations support the development and regulatory evaluation of medicines for serious and rare conditions and do not imply that marketing authorization will ultimately be granted.
Ultragenyx is also engaging with health authorities across multiple regions, including initiating discussions with the regulatory bodies in the United Kingdom and Saudi Arabia, as it works toward potential geographic expansion.
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, each carrying a Zacks Rank #2 (Buy). 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 24 cents. Over the same period, earnings estimates for 2027 have risen from 25 cents to 73 cents. PGEN shares have increased 104.3% 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 13.2% 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 77.4% year to date.
Aldeyra Therapeutics’ earnings beat estimates in each of the trailing four quarters, delivering an average surprise of 29.25%.
Zacks' Research Chief Names "Stock Most Likely to Double"
Our team of experts has just released the 5 stocks with the greatest probability of gaining +100% or more in the coming months. Of those 5, Director of Research Sheraz Mian highlights the one stock set to climb highest.
This innovative software-as-a-service firm upped its user base +22% year over year. That rate is increasing and margins are expanding as AI efficiencies take effect. Of course, all our elite picks aren't winners, but this one could far surpass earlier Zacks' Stocks Set to Double like D-Wave Quantum, which shot up +680.1%.
Free: See Our Top Stock And 4 Runners UpWant the latest recommendations from Zacks Investment Research? Today, you can download 7 Best Stocks for the Next 30 Days. Click to get this free report
Ultragenyx Pharmaceutical Inc. (RARE): Free Stock Analysis Report
Aldeyra Therapeutics, Inc. (ALDX): Free Stock Analysis Report
AC Immune (ACIU): Free Stock Analysis Report
Precigen, Inc. (PGEN): Free Stock Analysis Report
This article originally published on Zacks Investment Research (zacks.com).