Peptide Graded

Trofinetide (predecessor programs)

Does Trofinetide (predecessor programs) work?

Partly: some human trials, with gaps: one 72-person fragile X trial for 28 days; brain injury work is in rats.

BSome human evidenceFDA approvedas of 2026-10-26

This page covers trofinetide's development outside Rett syndrome. The fragile X program produced one randomized placebo-controlled phase 2 trial in 72 adolescent and adult males, which reported an efficacy signal at the higher trial dose over 28 days on a novel composite analysis; the published brain injury work is in rats. A single small, short randomized trial makes the fragile X use B; the Rett syndrome use, graded on its own page, has a 187-patient phase 3 trial. 125

The fragile X phase 2 trial randomized 72 adolescent and adult males. They got one of two trofinetide doses or placebo for 28 days. Both doses were well tolerated. The higher dose met the trial's pre-set criteria for whether it works, on a new analysis that combined several symptom areas. It also improved three fragile X-specific measures. Trofinetide has not been approved for fragile X. 13

The published brain injury work is in animals. In rats with a penetrating ballistic-like brain injury, NNZ-2566 reduced brain inflammation and pro-inflammatory cytokine expression. Trofinetide has no approval for brain injury. 53

Evidence checklist

  • Randomised controlled trial Phase 2 fragile X and TBI trials
  • Human study over 100 people Non-Rett trials were small
  • More than one research group Sponsor programs; limited outside data
  • Clinical outcomes, not surrogate markers Exploratory measures; programs dropped
  • Human safety data beyond case reports Short trials; diarrhea common in Rett phase 3

Read the full Trofinetide (predecessor programs) page

More on Trofinetide (predecessor programs)

Citations

  1. Berry-Kravis 2020, Pediatric Neurology: randomized placebo-controlled phase 2 trial of trofinetide in fragile X syndrome doi.org
  2. Neul 2023, Nature Medicine: Trofinetide for the treatment of Rett syndrome, phase 3 LAVENDER trial doi.org
  3. FDA 2023: Daybue (trofinetide) approval label accessdata.fda.gov
  4. DailyMed: Daybue (trofinetide) current prescribing information dailymed.nlm.nih.gov
  5. Wei 2009, J Neuroinflammation: NNZ-2566 inhibits neuroinflammation after penetrating ballistic-like brain injury in rats pubmed.ncbi.nlm.nih.gov

Reference information only, not medical advice. Drawn from the Trofinetide (predecessor programs) article, fact-checked against the cited sources. No dosing anywhere on this site.