The US Food and Drug Administration (FDA) has approved Ultragenyx’s gene therapy for Sanfilippo syndrome type A, marking the first treatment of its kind greenlit for children with the genetic neurodegenerative disorder.
The authorisation for Fayuvi (rebisufligene etisparvovec-hopf) marks a significant landmark for Sanfilippo syndrome type A, also known as mucopolysaccharidosis type IIIA (MPS IIIA). While current drugs and medical devices help manage daily symptoms, Ultragenyx’s gene therapy is the first disease-modifying treatment (DMT) approved for patients.
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Sanfilippo syndrome type A is a rare, inherited disease that progressively damages the brain and nervous system, causing children to lose cognitive, language and other developmental abilities over time. Patients with the syndrome have an average lifespan of around 15 years. Sanfilippo syndrome Type A is estimated to affect approximately 3,000 to 5,000 patients in commercially accessible geographies.
Fayuvi is a one-time gene therapy that is delivered via an adeno-associated virus serotype 9 (AAV9) vector to deliver a working copy of the SGSH gene into the patient’s cells. This enables the body’s cells to produce sulfamidase — the enzyme that is missing or deficient in MPS IIIA — allowing heparan sulfate to be properly broken down in lysosomes and reducing its harmful buildup throughout the body and brain.
A clinical trial demonstrated that one-time, intravenous administration with the gene therapy maintained or improved cognitive function compared to an untreated historical control cohort. This means that patients who take Fayuvi diverge from the expected natural disease course.
The FDA’s director of the Center for Biologics Evaluation and Research (CBER), Karim Mikhail, said: “Approval of Fayuvi is a meaningful step forward — not only for these children and their families, but for the promise of gene therapy to address rare and devastating diseases where the need for safe and effective treatment is the most urgent.”
Expensive gene therapies
On an investor call on the same day as the approval, Ultragenyx revealed the drug will have a US list price of $3.95m, making it one of the most expensive drugs in the world. Justifying the price tag, the company pointed to the lifetime cost of caring for a child with Sanfilippo syndrome Type A can exceed $8m. Gene therapies are often expensive due to small patient populations, high development costs, and complex manufacturing.
Fayuvi will be available through a network of qualified treatment centres (QTCs), which are places specifically trained to administer gene therapy.
Ultragenyx’s CEO, Emil Kakkis, said: “We recognise the profound urgency of making this therapy available to families, and our focus now is on supporting timely access in the US as we work closely with treatment centres and payers to support families on the gene therapy treatment journey.
As per the approval for a rare paediatric disease, Ultragenyx received a priority review voucher (PRV). This can be used to slash review time for another asset in the company’s pipeline or be sold for cash – vouchers are currently worth between $150m and 200m.
Fayuvi is Ultragenyx’s second approved gene therapy after Genglycos (pariglasgene brecaparvovec) for glycogen storage disease type Ia (GSDIa), which won FDA approval in August and has a list price of $2.7m.
Cell & Gene Therapy coverage on Pharmaceutical Technology is supported by Cytiva.
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