FDA ALERT

FDA Approves Avlayah (Tividenofusp Alfa-Eknm) for Neurologic Manifestations of Hunter Syndrome in Pediatric Patients

Edited by:
Ashton L. Stahl

Key Highlights

  • Avlayah (tividenofusp alfa-eknm) was approved to treat neurologic manifestations of Hunter syndrome in presymptomatic or symptomatic pediatric patients weighing at least 5 kg before advanced neurologic impairment.
  • The accelerated approval was supported by a phase 1/2, multi-cohort, single-arm, open-label trial in 47 pediatric patients.
  • At week 24, patients with available measurements had a 91% average reduction from baseline in cerebrospinal fluid heparan sulfate, and 93% had levels below the upper limit of normal.

On March 25, the FDA approved Avlayah (tividenofusp alfa-eknm) to treat the neurologic manifestations of Hunter syndrome, also known as mucopolysaccharidosis type II, in presymptomatic or symptomatic pediatric patients weighing at least 5 kg who have not yet developed advanced neurologic impairment. According to the agency, tividenofusp alfa-eknm is administered as an intravenous infusion and is the first approved product to address neurologic complications of Hunter syndrome.

The approval was based on results from a phase 1/2, multi-cohort, single-arm, open-label trial that enrolled 47 pediatric patients, aged 3 months to 13 years, with Hunter syndrome. In the study, tividenofusp alfa-eknm significantly reduced cerebrospinal fluid heparan sulfate. Among the 44 patients with measurements at week 24, the average decrease from baseline was 91%, ranging from 72% to 98%. At baseline, no patients had cerebrospinal fluid heparan sulfate levels below the upper limit of normal, while 93% of treated patients with measurements were below that threshold at week 24.

“Today is a milestone day for children and their families battling Hunter syndrome,” Marty Makary, MD, MPH, FDA Commissioner, said in a press release.

The most common adverse events reported with tividenofusp alfa-eknm were upper respiratory tract infection, ear infection, fever, anemia, cough, vomiting, diarrhea, rash, COVID-19, runny nose, nasal congestion, fall, headache, skin abrasion, and hives. The labeling also includes a boxed warning for allergic reactions, including anaphylaxis.

The FDA said tividenofusp alfa-eknm is given once weekly by IV infusion. It also noted that patients should begin therapy in a health care setting with appropriate medical monitoring and support measures.

Reference

FDA approves drug to treat neurologic manifestations of Hunter syndrome [press release]. U.S. Food and Drug Administration. Published March 20, 2026. Accessed March 25, 2026. https://www.fda.gov/news-events/press-announcements/fda-approves-drug-treat-neurologic-manifestations-hunter-syndrome