On March 10, 2023, the U.S. Food and Drug Administration (FDA) approved Daybue^™ (trofinetide) oral solution. It is the first drug indicated to treat the underlying cause of Rett syndrome for patients at least two years old. Almost exclusively affecting girls, Rett syndrome is caused by random mutations on X chromosomes. A progressive neurodevelopmental disorder, it has a wide range of symptoms that can impact multiple organ systems. To treat it, Daybue is taken twice a day at doses determined by the patient’s weight. The manufacturer, Acadia Pharmaceuticals, plans to launch Daybue before May 1, 2023; its cost has not been announced. Complete prescribing information is here.

u  At a Glance

• Brand (Generic) Name: Daybue (trofinetide)
• Manufacturer: Acadia Pharmaceuticals
• Date Approved: March 10, 2023
• Indication: to treat Rett syndrome for patients two years of age and older
• Dosage Forms Available: 450mL bottles of an oral solution containing 200mg/mL
• Launch Date: by the end of April 2023
• Estimated Annual Cost: Not yet available
• As many as 9,000 American girls and women are believed to have Rett syndrome, but only around one-half have been diagnosed with the disorder. Symptoms vary from mild to disabling.
• Characterized by repeated involuntary movements of the hands, such as clapping or wringing, Rett syndrome also causes differing levels of incoordination, muscle weakness, and social withdrawal beginning when a girl whose development has appeared normal is approximately one year old. Often, symptoms start quite suddenly.
• A wide variety of breathing, gastrointestinal (GI), mental health, speech, and other problems develop. Some patients also experience seizures.
• By increasing amounts of insulin-like growth factor 1 (IGF), Daybue decreases the inflammation of neurons. In the brain, IGF helps to regulate development and disease response.
• In the phase III clinical trial that included 187 patients between five years old and 20 years old, those taking Daybue scored better on standard measures of Rett syndrome severity than patients using a placebo.
• Diarrhea, including some severe episodes, was experienced by 85% of patients in clinical trials. Other common side effects of Daybue are vomiting and weight loss.
• Previous treatment for Rett syndrome was limited to managing its symptoms. Daybue is the first drug to treat the cause of the condition.
• Daybue was approved under the FDA’s Fast Track and Priority Review programs. A designated Orphan Drug, it also was awarded a Rare Pediatric Disease Priority Review Voucher that Acadia can use to expedite a future FDA submission or sell to another company.