The US Food and Drug Administration (FDA) has approved trofinetide (Daybue) to treat persons with Rett syndrome who are two years of age and older. This the first and only drug approved for the treatment of Rett syndrome.

​​Rett syndrome is a rare progressive neurodevelopmental condition that primarily affects girls. These girls appear to have develop normally during the first 6 to 18 months of life, followed by a developmental “plateau,” and then rapid regression in language and motor skills as synaptic connections deteriorate over time. Common symptoms include hand-wringing, fits of screaming and inconsolable crying, autistic features, panic-like attacks, bruxism, episodic apnea and/or hyperpnea, gait ataxia and apraxia, tremors, seizures, and slowed head growth. Most patients with Rett syndrome live into adulthood but require round-the-clock care.

Trofinetide is a synthetic analog of the amino‐terminal tripeptide of IGF-1. It is designed to treat the core symptoms of Rett syndrome by potentially reducing neuroinflammation and supporting synaptic function. Trofinetide is thought to stimulate synaptic maturation and overcome the synaptic and neuronal immaturities that are characteristic of Rett syndrome pathophysiology.

The approval of trofinetide was largely based on data from the Phase 3 Lavender study (NCT04181723) involving 187 patients with Rett syndrome who received  trofinetide or placebo over a 12 week period. In that study,  the girls given trofinetide had statistically significant improvement over placebo in the Rett Syndrome Behavior Questionnaire (RSBQ) and the Clinical Global Impression of Improvement (CGI-I).

The RSBQ is a caregiver assessment that evaluates a range of symptoms of Rett syndrome including vocalizations, facial expressions, eye gaze, hand movements (or stereotypies), repetitive behaviors, breathing, night-time behaviors and mood. The CGI-I is a global physician assessment of whether a patient has improved or worsened.

The most common side effects were diarrhea (82%) and vomiting (29%).

The approval also provides the developers of trofinetide, Acadia Pharmaceuticals, with a Rare Pediatric Disease Priority Review Voucher, which can be used to obtain priority review for a subsequent application. In other words, the FDA will have to review the medicine within 6 months instead of 10 months. For small companies like Acadia Pharmaceuticals, this voucher is often sold to another company.  Bluebird bio recentlysold their review voucher for $95 million.

In clip below, Kathie Bishop, PhD, Chief Scientific Officer at Acadia Pharmaceuticals, describes the mechanism of action of trofinetide.

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For more information about Rett syndrome, visit our Rett Syndrome Learning page here: