General Information

Daybue (trofinetide) is a novel synthetic analog of the amino‐terminal tripeptide of IGF-1.

Daybue is specifically indicated for the treatment of Rett syndrome in adults and pediatric patients 2 years of age and older.

Daybue is supplied as an oral solution. It should be administered orally twice daily, in the morning and evening, according to patient weight as shown below. Daybue can be taken with or without food.

Patient Weight

Daybue Dosage

Daybue Volume

9 kg to less than 12 kg

5,000 mg twice daily

25 mL twice daily

12 kg to less than 20 kg

6,000 mg twice daily

30 mL twice daily

20 kg to less than 35 kg

8,000 mg twice daily

40 mL twice daily

35 kg to less than 50 kg

10,000 mg twice daily

50 mL twice daily

50 kg or more

12,000 mg twice daily

60 mL twice daily

Mechanism of Action

The exact mechanism by which trofinetide exerts therapeutic effects in patients with Rett syndrome is unknown. Daybue (trofinetide) is a novel synthetic analog of the amino‐terminal tripeptide of IGF-1 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. In the central nervous system, IGF-1 is produced by both of the major types of brain cells – neurons and glia. IGF-1 in the brain is critical for both normal development and for response to injury and disease. Trofinetide has been shown to inhibit the production of inflammatory cytokines, inhibit the overactivation of microglia and astrocytes, and increase the amount of available IGF-1 that can bind to IGF-1 receptors.

Clinical Trial Results

The FDA approval of Daybue was based on results from the pivotal Phase 3 LAVENDER study evaluating the efficacy and safety of trofinetide versus placebo in 187 female patients with Rett syndrome five to 20 years of age. In the study, treatment with Daybue demonstrated statistically significant improvement compared to placebo on both co-primary efficacy endpoints, as measured by the change from baseline in Rett Syndrome Behaviour Questionnaire (RSBQ) total score and the Clinical Global Impression-Improvement (CGI-I) scale score at week 12. 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.