Families affected by Hunter syndrome, a rare and progressive genetic disorder, have received a significant boost of hope with the recent approval of a groundbreaking new drug by the Food and Drug Administration (FDA).

Understanding Hunter Syndrome

Elizabeth Chuck is a reporter for NBC News who focuses on health and mental health, particularly issues that affect women and children. Hunter syndrome, also known as mucopolysaccharidosis type II (MPS II), affects approximately 500 people in the U.S., predominantly boys. The condition stems from a deficiency in an enzyme needed to break down certain molecules, leading to a buildup of toxins that damage organs, including the heart and brain.

A Mother's Long Wait

Kim Stephens of Carrboro, North Carolina, has been waiting for a breakthrough since her 15-year-old son, Cole, was diagnosed with Hunter syndrome at age two. She worried about Cole losing his ability to walk, his cognitive skills, and ultimately, his life, as the disease often proves fatal before age 21. “I’ve been in fight-or-flight mode since his diagnosis,” Stephens said, adding that the FDA approval allows her “to breathe.”

The New Treatment: Avlayah

The newly approved drug, Avlayah, manufactured by Denali Therapeutics, is an intravenous enzyme replacement therapy. Experts believe it will be a “game changer” because, unlike current treatments that primarily address physical symptoms, Avlayah also targets cognitive decline. Dr. Joseph Muenzer of the Muenzer MPS Research and Treatment Center at the University of North Carolina at Chapel Hill explained, “If we take a child, very young, and can treat them prior to damage, now the potential is almost unlimited.”

Impact on Patients

While Avlayah won’t reverse existing regressions, it could significantly extend children’s lives and prevent further symptom development with early intervention. Stephens notes that Cole, who once spoke in full sentences, is now developmentally similar to a 3-year-old. The drug’s ability to penetrate the blood-brain barrier is a key advancement, addressing the neurological complications of the disease.

FDA Approval Amidst Scrutiny

The FDA’s approval of Avlayah was particularly welcomed given recent criticism regarding rejections of treatments for rare diseases. Patient advocates had even staged a protest outside agency headquarters. The FDA stated that approval and rejection rates remain consistent with historical data. FDA Commissioner Dr. Marty Makary called the approval a “milestone day” and pledged continued efforts to accelerate treatments for rare diseases.

A Wider Impact on the Rare Disease Community

Families like Kylie Jaskulski’s, whose 6-year-old son Roran was diagnosed with Hunter syndrome at age four, are hopeful. Jaskulski worries about Roran’s inability to communicate and the potential for others to underestimate his value. Christina Coldwell, whose 3-year-old grandson Kashton has a less severe form of the disease, is also eager to start him on the new treatment to prevent future health problems.

Looking Ahead

Denali Therapeutics has stated that the list price for Avlayah is $5,200 per 150-milligram vial and is working with payers to ensure access for families. The company also plans to expand clinical evidence for young adults and explore the use of its blood-brain barrier technology for other neurodegenerative diseases. Stephens, now the executive director at Muenzer’s MPS research center, expressed gratitude, stating, “My hope is he stays stable. Stable with a progressive disease is a win.”