FDA Approves New Treatment for Rare Hunter Syndrome

On March 25, 2026, the FDA granted accelerated approval to a new treatment called Avlayah (tividenofusp alfa-eknm) for Hunter syndrome, a rare genetic disorder.

Hunter syndrome, which mostly affects males, involves a dangerous buildup of substances in cells that leads to severe cognitive and motor decline.

Previously available therapies could not reach the brain, but Avlayah is specifically engineered to cross the blood-brain barrier using a special delivery technology.

The FDA's decision to grant accelerated approval was based on a reduction of certain markers in the cerebrospinal fluid, a move that highlights the agency's willingness to use surrogate endpoints when dealing with rare diseases.

While this approval is a significant win for biotechnology and patient advocacy groups, it also sparks discussion about regulatory standards.