reviewed april 2026|next review october 2026|88 physicians psi has verified|1066 published studies
Trofinetide (Daybue)
Trofinetide (Daybue) is the first and only FDA-approved treatment for Rett syndrome, a rare genetic neurological disorder caused by methyl-CpG binding protein 2 (MECP2) mutations that primarily affects girls. It is a synthetic cyclic analog of GPE (glycine-proline-glutamate), a three-amino-acid fragment of IGF-1.
Evidence landscape: 1066 published studies
127 published items indexed. 12 human studies and 34 animal studies. A focused evidence base reflecting the rare-disease development pathway.
- 17 Human
- 170 Animal
- 13 Reviews
- 866 Other research
FDA-approved (March 2023) as Daybue for Rett syndrome in patients aged 2 years and older. First-in-class for this condition. A powder formulation (Daybue Stix) was approved in December 2025.
Derived from a three-amino-acid fragment of IGF-1 called GPE. Does not act through the IGF-1 receptor and does not have growth-promoting effects. Works by reducing neuroinflammation.
Diarrhea occurs in more than 80% of patients and is often severe enough to require dose modification. This is the primary treatment consideration for families and clinicians.
PSI Assessment
Until 2023, Rett syndrome had no approved treatment. Trofinetide, sold as Daybue, changed that. It is the first and only FDA-approved medication for this rare genetic neurological disorder, which primarily affects girls and causes progressive loss of motor skills, speech, and purposeful hand use. The Phase III pivotal trial (called LAVENDER) demonstrated measurable symptom improvement. The primary tolerability challenge is diarrhea, which occurs in more than 80% of patients.
First and only approved treatment for Rett syndrome. The LAVENDER Phase III trial demonstrated statistically significant improvement. Diarrhea in over 80% of patients is the primary tolerability challenge.
The mechanism is derived from an unexpected source: a three-amino-acid fragment of IGF-1 called GPE (glycine-proline-glutamate). Trofinetide does not act through the IGF-1 receptor and does not have growth-promoting effects. Instead, it reduces neuroinflammation by modulating glial cell activation, normalizes glutamate signaling, and reduces oxidative stress. In Rett syndrome, where the MECP2 mutation causes chronic brain inflammation and disrupted neural connections, this anti-inflammatory mechanism addresses downstream consequences of the genetic defect without correcting the mutation itself.
What the evidence supports
First and only FDA-approved treatment for Rett syndrome. The LAVENDER Phase III trial demonstrated statistically significant improvement on both caregiver and clinician endpoints.
What is not yet established
Long-term efficacy beyond the 12-week trial duration. Whether symptom improvement is sustained or progressive with continued treatment. Management strategies for the high diarrhea rate.
Research Evidence
The findings below cover what the LAVENDER trial established and the key tolerability considerations.
Evidence by condition
Evidence dimensions for trofinetide in Rett syndrome. The single approved indication has Phase III support. No other conditions have been studied in humans.
| Condition | Mechanism | Animal evidence | Human evidence | Replication |
|---|---|---|---|---|
| Rett Syndrome |
The Phase III LAVENDER trial (N=187) demonstrated statistically significant improvement on both the Rett Syndrome Behaviour Questionnaire (caregiver-assessed, p=0.018) and the Clinical Global Impression of Improvement (clinician-assessed, p=0.003) over 12 weeks.
For a condition that had no approved treatment, statistically significant improvement on both caregiver and clinician endpoints represents a meaningful clinical advance.
The Phase II dose-finding trial established the safety profile and dose-response relationship that guided the Phase III dose selection. Weight-based dosing was validated.
The Phase II trial was essential for identifying the therapeutic window. The Phase III dose was selected based on the balance of efficacy signal and tolerability.
Diarrhea occurred in over 80% of LAVENDER trial patients, with severity often requiring dose modification. Vomiting and decreased appetite were also common. Weight monitoring during treatment is required.
The high diarrhea rate is the defining tolerability challenge. Families and clinicians must weigh the symptom improvement against the gastrointestinal side-effect burden.
17 Human|170 Animal|13 Reviews
View all 1066 indexed studiesHow Trofinetide (Daybue) Works
Trofinetide is a synthetic cyclic analog of GPE (glycine-proline-glutamate), a naturally occurring IGF-1-derived tripeptide. It reduces neuroinflammation without acting through the IGF-1 receptor.
In Rett syndrome, a genetic mutation (MECP2) causes brain inflammation and disrupted neural connections. Trofinetide reduces brain inflammation and supports neural function. Not by fixing the genetic problem, but by calming the inflammatory response that damages the brain.
For a more detailed view of the biology, here is what researchers have observed at the molecular level.
Trofinetide is derived from GPE, the amino-terminal tripeptide cleaved from IGF-1. Unlike IGF-1, trofinetide does not bind the IGF-1 receptor and has no growth factor activity. Its mechanism involves modulation of glial cell (astrocyte and microglia) activation, reducing the chronic neuroinflammation characteristic of Rett syndrome. It normalizes glutamate signaling at N-methyl-D-aspartate (NMDA) receptors, reduces oxidative stress markers, and decreases elevated levels of inflammatory cytokines and matrix metalloproteinases. In Rett syndrome, MECP2 mutations cause widespread epigenetic dysregulation leading to microglial overactivation and synaptic dysfunction. Trofinetide addresses these downstream inflammatory consequences without correcting the underlying MECP2 mutation.
What is Trofinetide (Daybue) being studied for?
Researchers are studying Trofinetide (Daybue) across several health conditions. Each condition below is labeled with the strength of evidence that exists for that specific use, not for Trofinetide (Daybue) overall. This means a compound can have human studies for one condition but only animal data for another.
Rett Syndrome
·FDA ApprovedFDA-approved (2023) as the first and only treatment for Rett syndrome. The LAVENDER Phase III trial showed statistically significant improvement on both caregiver-assessed and clinician-assessed endpoints at 12 weeks.
Limitations: Diarrhea in over 80% of patients, often severe. Whether trofinetide modifies disease progression or only manages symptoms is not established. Long-term efficacy beyond 12 weeks is limited to extension study data.
Safety and Regulatory Status
FDA Status: FDA-approved (March 2023) as Daybue for Rett syndrome in patients aged 2 years and older. Powder formulation (Daybue Stix) approved December 2025.
Administration: Oral liquid solution administered twice daily based on body weight. Liver function and weight monitoring are recommended during treatment.
Diarrhea is the most significant side effect, occurring in over 80% of patients and often severe enough to require dose modification. Vomiting and decreased appetite are also common. Weight monitoring is required during treatment. Liver function monitoring is recommended.
Peptide Structure
Technical molecular data for researchers and clinicians.
Questions and Comparisons
Questions the evidence raises for a Trofinetide (Daybue) discussion.
Comparison and Related Research
Trofinetide has no direct comparator as the only approved Rett syndrome treatment.
Related compounds
Frequently Asked Questions
References
Each citation links to the original study on PubMed, the U.S. National Library of Medicine database.
- 1.The LAVENDER Phase III trial. 187 females with Rett syndrome aged 5-20, treated for 12 weeks. Statistically significant improvement on both caregiver-assessed (RSBQ) and clinician-assessed (CGI-I) endpoints. Basis for the 2023 FDA approval.Neul JL et al., 2023 in N Engl J Med. View on PubMed
- 2.Phase II dose-finding trial in Rett syndrome. Established safety profile and dose-response relationship across weight-based dosing tiers.Glaze DG et al., 2019 in Pediatr Neurol. View on PubMed
- 3.Phase II trial of trofinetide (then NNZ-2566) in traumatic brain injury. Safety and pharmacokinetic data. The TBI program was eventually deprioritized in favor of Rett syndrome development.Delanty N et al., 2007 in Br J Clin Pharmacol. View on PubMed
- 4.Trial design publication for the pivotal LAVENDER study. Describes the primary and secondary endpoints, statistical analysis plan, and inclusion criteria.Neul JL et al., 2021 in J Neurodev Disord. View on PubMed
Medical Disclaimer
This content is for educational and informational purposes only and does not constitute medical advice. The information presented reflects published research as indexed by PSI and should not be used to make treatment decisions. Always consult a qualified healthcare provider before starting, stopping, or modifying any treatment.