Evidence Grade A — Regulatory approved. 76 published studies. 13 registered clinical trials.
Medically reviewed by a licensed medical professional
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Trofinetide (sold as Daybue) is the first and only treatment ever approved for Rett syndrome — a rare genetic neurological disorder that primarily affects girls, causing severe impairments in communication, hand function, and movement. Taken as an oral liquid twice daily, it does not cure Rett syndrome but helps manage symptoms and improve quality of life for patients and their caregivers.
Trofinetide is also known by these brand and alternate names:
76 published studies: 47 human, 1 animal, 4 in-vitro, 25 reviews
Trofinetide is marketed as Daybue (Acadia Pharmaceuticals, approved March 2023). It is the first FDA-approved treatment for Rett syndrome, a condition that affects an estimated 15,000–20,000 individuals in the US. Previously, treatment was limited to managing individual symptoms.
In the LAVENDER trial, trofinetide showed significant improvement on both a clinician-assessed severity scale and a caregiver-assessed behaviour questionnaire compared to placebo. The most common side effects are diarrhoea (approximately 80%) and vomiting. While the improvements are meaningful to patients and families, trofinetide does not cure Rett syndrome — it is a symptom management treatment that requires ongoing daily dosing.
Trofinetide is based on a tiny three-amino-acid fragment that is naturally cleaved from IGF-1 in the brain. Despite this origin, it does not work through IGF-1 receptors. Instead, it appears to reduce neuroinflammation and normalise the abnormal brain signalling caused by mutations in the MECP2 gene that underlie Rett syndrome. The exact molecular targets are not fully characterised, but the compound modulates pathways related to inflammation, excitotoxicity, and synaptic function in the brain.
The LAVENDER trial showed significant improvement on both a clinician-assessed severity scale and a caregiver-assessed behaviour questionnaire compared to placebo. The effect sizes are modest, but for a condition that previously had no pharmacological treatment at all, any measurable improvement is meaningful to families. The most challenging side effect is diarrhoea, which occurs in approximately 80% of patients, though it is typically manageable. Vomiting is also common. An open-label extension study shows sustained benefit through 32 months of treatment. Rett syndrome affects an estimated 6,000–9,000 individuals in the US. Gene therapy approaches targeting restoration of the underlying MECP2 gene defect represent the next frontier for this condition.
PeptideTrace tracks 13 registered clinical trials for Trofinetide sourced from ClinicalTrials.gov.
Cognitive Function in Rett Syndrome During Trofinetide Treatment
An Open-Label Study of Trofinetide for the Treatment of Girls Two to Five Years of Age Who Have Rett Syndrome
Open-Label Extension Study of Trofinetide for Rett Syndrome
Open-Label Extension Study of Trofinetide for the Treatment of Girls and Women With Rett Syndrome
Study of Trofinetide for the Treatment of Girls and Women With Rett Syndrome (LAVENDER™)
FDA ORIG 1
FDA SUPPL 3
FDA SUPPL 1
Health Canada Market Authorisation
FDA SUPPL 7
FDA SUPPL 6
FDA ORIG 1
Trofinetide is a synthetic analogue of glycine-proline-glutamate (GPE), the N-terminal tripeptide naturally cleaved from insulin-like growth factor 1 (IGF-1). Despite its IGF-1 derivation, trofinetide does NOT act through the IGF-1 receptor. It is an oral solution administered twice daily with weight-based dosing.
Trofinetide's mechanism involves modulation of neuroinflammation, reduction of excitotoxicity (via glutamate pathway modulation), and normalization of synaptic function. The exact molecular targets are not fully characterized, but preclinical data suggest effects on microglial activation, astrocyte function, and neuronal connectivity relevant to the MECP2 deficiency underlying Rett syndrome. It does not stimulate growth or have metabolic effects associated with IGF-1 signaling.
Trofinetide is marketed as Daybue (Acadia Pharmaceuticals, FDA approved March 10, 2023—the first-ever FDA-approved treatment for Rett syndrome). The LAVENDER trial (N=187; 12 weeks) demonstrated significant improvement on the RSBQ (Rett Syndrome Behaviour Questionnaire): change of −4.9 versus −1.7 with placebo (difference −3.1; P=0.0175; Cohen's d=0.37). CGI-I: 3.5 versus 3.8 (P=0.003; d=0.47). Major adverse event: diarrhea in 80.6% (mostly mild/moderate). Daybue Stix powder formulation approved December 2025 for improved palatability.
Cerebrolysin has been studied in over 200 clinical trials involving more than 15,000 patients, primarily for stroke and Alzheimer's disease. The largest stroke trial (CASTA, 1,070 patients) showed no significant benefit on its primary endpoint. A Cochrane systematic review concluded that evidence was insufficient to support its routine use in stroke or dementia. Cerebrolysin is approved in some non-FDA/non-EMA jurisdictions for neurological conditions. Its clinical evidence base, despite being extensive in volume, has not met the standards required for FDA or EMA approval. The undefined molecular composition makes batch-to-batch consistency and quality standardisation inherently challenging compared to defined single-entity pharmaceuticals.
FGL has no marketing authorisation. A Phase I trial (24 healthy volunteers) of intranasal FGL demonstrated tolerability with only mild adverse events. Preclinical studies reported effects on memory in animal models. The compound has progressed further through formal development than many research peptides, having completed a Phase I safety study. However, no efficacy trials have been conducted in patients, and clinical development beyond Phase I has not been reported.
P21 has no marketing authorisation. No human clinical trials have been conducted. The evidence base consists entirely of studies in transgenic Alzheimer's disease mouse models, conducted primarily by a single research group. Animal studies reported behavioural and biochemical changes in AD mouse models following chronic oral administration. The translation of results from transgenic mouse models of Alzheimer's disease to human disease has historically been extremely poor — the vast majority of compounds showing efficacy in such models have failed in human trials. Products available through unregulated channels lack pharmaceutical quality assurance.
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