Trofinetide

Summary

Trofinetide is a synthetic tripeptide analogue of the glycine‑proline‑glutamate segment of insulin‑like growth factor‑1. It is approved in the United States for the treatment of Rett syndrome, a rare neurodevelopmental disorder, and is administered orally twice daily to address core behavioural and communication deficits.

Mechanism of Action

Trofinetide mimics the N‑terminal tripeptide of IGF‑1, a molecule involved in neuronal growth and synaptic modulation. By reproducing this short peptide fragment, it is thought to engage downstream IGF‑1‑related pathways that influence neurodevelopment, synaptic plasticity, and neuroinflammation, thereby improving behavioural and cognitive function in Rett syndrome. The precise cellular targets have not been detailed in the published trials.

What the Research Shows

A randomized, double‑blind phase 3 trial (LAVENDER) enrolled 187 females with Rett syndrome and compared twice‑daily oral trofinetide for 12 weeks with placebo. The study met both coprimary endpoints: the Rett Syndrome Behaviour Questionnaire improved by –4.9 versus –1.7 points (P=0.0175) and the Clinical Global Impression‑Improvement score improved by 3.5 versus 3.8 (P=0.0030). A key secondary endpoint, a social‑communication scale, also favoured trofinetide (P=0.0064). The most common adverse event was diarrhea (80.6%). An open‑label 40‑week extension (LILAC) involving 154 participants showed continued improvement in the same behavioural scores and a safety profile similar to the short‑term trial, with diarrhea (74.7%) and vomiting (28.6%) remaining the predominant side effects. Reviews cite trofinetide as a promising targeted therapy for neurodevelopmental disorders, but clinical data are confined to Rett syndrome.

Reported Benefits

Phase 3 data demonstrate modest but statistically significant improvements in core Rett symptoms, including behaviour, global clinical impression, and social‑communication abilities, with effect sizes ranging from 0.37 to 0.47. The open‑label extension suggests these benefits are maintained for at least 40 weeks. Trofinetide therefore offers the first disease‑specific pharmacologic option for Rett syndrome, addressing symptoms that behavioral therapies alone cannot fully manage.

Limitations of the Evidence

Evidence is limited to Rett syndrome; no controlled trials have been published for autism or other neurodevelopmental conditions. The phase 3 trial enrolled fewer than 200 participants, and the extension study lacked a control arm, limiting conclusions about long‑term efficacy. Effect sizes are small to moderate, and the high incidence of gastrointestinal side effects may limit tolerability. Data beyond 40 weeks and comparative effectiveness versus other interventions are not yet available.

Safety Considerations

Diarrhea is the most frequent adverse event, occurring in over three‑quarters of participants and leading to treatment discontinuation in about one‑fifth of cases in the extension study. Vomiting and, less commonly, COVID‑19 infection were also reported. Most gastrointestinal events were mild to moderate, but clinicians should monitor patients for dehydration and consider dose adjustments or supportive care if symptoms become severe.

How It Is Administered

Trofinetide is supplied as oral tablets taken twice daily. The formulation is designed for systemic absorption; no injection or inhalation routes are reported. Dosing specifics are defined in the prescribing information and should be followed according to the approved label.

Routes of Administration

Goals & Uses

• Fragile X syndromeNeurological DisorderLow
• Improvement of synaptic functionNeuroscienceModerate
• Rett syndromeNeurodevelopmental DisorderHigh
• Treatment of Rett syndromeNeurodevelopmental DisorderHigh
• Traumatic brain injuryNeuroprotectionLow
• Reduction of neuroinflammationNeurologyModerate

Contraindications

• Hypersensitivity to trofinetide or excipientsAllergic/immunologicHigh
• Hypersensitivity to trofinetideAllergyHigh
• Severe renal impairmentOrganModerateKidney function concerns

Adverse Effects

• NasopharyngitisInfectiousCommon
• HeadacheNeurologicCommonPain in the head or upper neck
• Weight loss / decreased appetiteMetabolicCommon
• NauseaGastrointestinalCommonFeeling of sickness or urge to vomit
• FatigueGeneralUncommonLow energy or tiredness
• VomitingGastrointestinalCommonForceful expulsion of stomach contents
• DiarrheaGastrointestinalCommonLoose or frequent stools
• DehydrationFluid BalanceUncommonLoss of body water or inadequate hydration
• Abdominal painGastrointestinalCommonPain or discomfort in the abdomen

Drug Interactions

• Oral contraceptivesModerateDelayed gastric emptying may affect absorption timing
• none identifiedLow
• CYP3A4 substrates (sensitive)Moderate

Population Constraints

• PregnancyReproductive SafetyRelative
• Age ≥5 yearsAgeAbsolute
• Children under 2 years of agePediatricAbsolute
• BreastfeedingReproductiveRelative
• Severe renal impairment (eGFR <30 mL/min)RenalRelative

Regulatory Status

• European UnionInvestigationalSubmitted for marketing authorization; pending
• United StatesApprovedApproved: Rett syndromeApproved as Daybue for patients ≥5 years
• United KingdomUnknown

FDA approved in August 2023 (brand name Daybue) as the first therapy for Rett syndrome; under regulatory review in the EU.

Evidence & Sources

• Trofinetide for the treatment of Rett syndrome: a randomized phase 3 study
  Journal ArticleModerateNeul JL, et al.2023-01-01T00:00:00.000000Z
• An Update on Psychopharmacological Treatment of Autism Spectrum Disorder
  Journal ArticleModerateAishworiya R, et al.2022-01-01T00:00:00.000000Z
• Rett Syndrome: The Emerging Landscape of Treatment Strategies
  Journal ArticleModeratePercy AK, Ananth A, Neul JL2024-01-01T00:00:00.000000Z
• Trofinetide for the treatment of Rett syndrome: Results from the open-label extension LILAC study
  Journal ArticleModeratePercy AK, et al.2024-01-01T00:00:00.000000Z
• [Autism. Pharmacological treatment]
  Journal ArticleModerateRuggieri V2023-01-01T00:00:00.000000Z

Frequently Asked Questions