EU Approves DAYBU as First Treatment for Rett Syndrome Neurobehavioral Symptoms

On August 24, 2026, the European Commission granted marketing authorization for DAYBU (trofinetide), according to Acadia Pharmaceuticals and the European Medicines Agency (EMA).

DAYBU is authorized to treat neurobehavioral symptoms of Rett syndrome in adults and children aged 5 years and older. These symptoms can include repetitive hand movements, restlessness, mood and anxiety problems, sleep difficulties, and communication problems.

The authorization makes DAYBU the first and only treatment specifically approved for Rett syndrome in the European Union for this indication.

Approval followed a June 2026 positive EMA recommendation after re-examination. The initial application had received a negative opinion in February.

The decision is based primarily on the Phase 3 LAVENDER study, which reported statistically significant improvements on the Rett Syndrome Behaviour Questionnaire and the Clinical Global Impression–Improvement scale.

The authorization applies across the 27 EU member states and, through the European Economic Area framework, Iceland, Liechtenstein, and Norway.

Acadia must still negotiate national pricing and reimbursement arrangements before the medicine becomes broadly available. DAYBU is prescribed by physicians experienced in treating Rett syndrome.