The US Food and Drug Administration has approved Acadia Pharmaceuticals’ Daybue Stix (trofinetide), a dye and preservative-free powder formulation of trofinetide, for oral solution, to treat Rett syndrome.

Rett syndrome is a rare neurodevelopmental disorder that progresses through four stages.

The formulation is intended to treat the condition in adult and paediatric patients aged two years and above, expecting to deliver the same efficacy and safety profile as Daybue oral solution.

It aims to offer both children and adults living with Rett syndrome more options regarding how their treatment is administered, particularly in terms of taste and dosage volume.

Daybue Stix’s efficacy and safety are supported by the outcomes from the LAVENDER study with Daybue oral solution in Rett syndrome patients.

Findings from a bioequivalence study support the new formulation’s approval, demonstrating that the original oral solution as well as the new powder formulation offer comparable exposure.

Daybue Stix will become available in limited quantities beginning in the first quarter of 2026, with wider distribution early in the second quarter.

The existing oral solution formulation will continue to be offered.

Trofinetide is a synthetic analogue of the N-terminal tripeptide of insulin-like growth factor 1.

Although the mechanism of action in patients with Rett syndrome is not known, animal studies have shown that trofinetide can increase dendritic branching and synaptic plasticity signals.

Acadia Pharmaceuticals CEO Catherine Owen Adams stated: “Daybue, the first and only approved treatment for Rett syndrome, has provided thousands of patients an important therapeutic option.

“With the approval of Daybue Stix, we are building on our commitment to turn scientific promise into meaningful innovation by introducing a new formulation informed by invaluable feedback from patients, caregivers and healthcare providers.”