FDA Approves Avlayah for Hunter Syndrome Neurologic Manifestations

FDA Greenlights Avlayah: A New Era for Hunter Syndrome Treatment

The Food and Drug Administration has granted accelerated approval to Avlayah (tividenofusp alfa-eknm, Denali Therapeutics) for the treatment of neurologic manifestations of Hunter syndrome, likewise known as mucopolysaccharidosis type II. This marks the first treatment approved for this patient population in nearly 20 years, offering a beacon of hope for individuals and families affected by this rare genetic disease.

Breaking the Blood-Brain Barrier: The Enzyme TransportVehicle Platform

Avlayah’s approval hinges on its innovative delivery system – the Enzyme TransportVehicle (ETV) Platform. This platform is designed to deliver the therapeutic enzyme directly to both the brain and peripheral tissues, addressing a critical unmet need in Hunter syndrome. The ETV platform has been validated by the FDA’s approval, according to Denali Therapeutics.

Understanding Hunter Syndrome and the Need for Targeted Therapies

Hunter syndrome is caused by a deficiency in the iduronate 2-sulfatase enzyme, essential for breaking down complex sugars called glycosaminoglycans. The accumulation of these sugars leads to progressive damage to organs and tissues, impacting cognitive, behavioral, hearing, and motor functions. Current treatments often struggle to effectively reach the central nervous system, leaving a significant gap in care.

Phase 1/2 Trial Data: Promising Results in CSF and Biomarkers

The FDA’s decision was based on data from an international, multicenter, open-label phase 1/2 trial involving 47 boys with Hunter syndrome, aged up to 18 years. The trial included both treatment-naïve and previously treated patients, receiving Avlayah intravenously once a week.

Key findings from the trial include:

• A 91% reduction in cerebrospinal fluid heparan sulfate (CSF HS) levels at week 24.
• 93% of patients achieved CSF HS levels within the range of individuals without Hunter syndrome at week 24.
• Normalization of neurofilament light and urine HS levels, biomarkers of neuronal damage and peripheral disease progression, respectively.

Looking Ahead: The COMPASS Confirmatory Study

Denali Therapeutics is currently investigating Avlayah in a global phase 2/3 COMPASS confirmatory study, enrolling 63 young adults with Hunter syndrome. This head-to-head, randomized controlled trial will compare Avlayah to standard of care enzyme replacement therapy, evaluating both neurologic and somatic clinical outcomes.

Safety Profile and Manageable Adverse Events

The most frequently reported adverse event in the phase 1/2 trial was infusion-related reactions, experienced by 83% of patients at week 24. However, the incidence decreased over time, to 57% during the 80-week safety extension period and 41% during the 157-week open-label extension period. Researchers noted the safety profile was consistent with existing enzyme replacement therapies and manageable for chronic treatment.

Pro Tip:

Frequently Asked Questions (FAQ)

• What is Hunter syndrome? Hunter syndrome is a rare genetic disorder caused by a deficiency in the iduronate 2-sulfatase enzyme, leading to the buildup of harmful substances in the body.
• How does Avlayah perform? Avlayah delivers a therapeutic enzyme to the brain and periphery, helping to break down the accumulated substances and reduce disease progression.
• Is Avlayah safe? The most common side effect is infusion-related reactions, which generally decrease over time and are considered manageable.
• Who is eligible for Avlayah? Avlayah is approved for pediatric patients weighing at least 5 kg, with or without existing symptoms, before advanced neurologic impairment.