Trofinetide: earlier development programs before the Rett approval
Clinical review pending
What earlier trofinetide studies in fragile X syndrome and traumatic brain injury showed, and where their limits lie. It has no FDA approval for these uses.
Before it was approved for Rett syndrome, trofinetide was also studied in fragile X syndrome and in traumatic brain injury. It did not receive approval for either of these uses. A short study in fragile X syndrome did give early signs of possible efficacy, but the results were limited and were never confirmed.
What is trofinetide?
Trofinetide is a synthetic variant of a small fragment of insulin-like growth factor 1 (IGF-1). Neuren Pharmaceuticals originally developed it as a drug taken by mouth. The US Food and Drug Administration (FDA) has approved it under the brand name DAYBUE to treat Rett syndrome. Rett syndrome is a rare neurodevelopmental disorder.
Before that, researchers studied trofinetide mainly in fragile X syndrome and traumatic brain injury. Both uses remained experimental.
How does trofinetide work?
The IGF-1-related peptide is thought to support the maturation of synapses (1), the contact points where nerve cells pass signals to one another. Trofinetide is also believed to reduce inflammatory processes in the nervous system and dysfunction of glial cells. These cells support the nerve cells in the brain.
These ideas about the mechanism were one reason for testing trofinetide in various neurodevelopmental disorders. On their own, however, they cannot show whether treatment helps people with a particular condition. In the earlier development programs, the results in humans were not enough for approval.
Is trofinetide FDA-approved?
The FDA has approved trofinetide for Rett syndrome. There is no FDA approval for fragile X syndrome or traumatic brain injury.
| Development program | FDA status |
|---|---|
| Rett syndrome | Approved as DAYBUE |
| Fragile X syndrome | Not approved for this indication |
| Traumatic brain injury | Not approved; the development program was unsuccessful |
The approval for Rett syndrome therefore does not extend to the other conditions studied.
What does the research show?
In fragile X syndrome, a short double-blind, placebo-controlled phase 2 study (1) gave early signs of possible efficacy. The participants were adolescent and adult males with fragile X syndrome. The study compared trofinetide with a dummy preparation (placebo); during the study, neither the participants nor the study team caring for them knew who was getting which.
At the higher dose, the results over 28 days met prespecified criteria for early signs of efficacy. This held for several measures designed specifically for fragile X syndrome. The authors interpreted the findings as a preliminary signal. As a short, exploratory study, it could offer hints but could not confirm efficacy.
These results were not followed by a successful pivotal trial. Trofinetide is not approved for fragile X syndrome. The earlier studies in traumatic brain injury did not lead to approval for that use either. Given the limited and unconfirmed results, it remains open whether trofinetide offers a reliable benefit in these conditions.