Dihexa

What it is

Dihexa is a lab-built compound with a small chemical structure; its backbone comes from a handful of amino acids chemically linked and then altered, unlike a large natural protein. It was developed by researchers at Washington State University out of work on angiotensin IV, a fragment of a larger hormone system usually associated with blood pressure control, as part of a search for compounds that support brain-cell health.

Researchers who developed dihexa proposed that it binds to a receptor called c-Met, which normally responds to a natural growth factor, and that this lets it trigger synapse-building signaling at very small amounts. Two of the papers making that specific mechanism claim were retracted by their journal in 2025 after a research-integrity review, so the receptor mechanism itself is no longer treated as established. Independent research using the compound has still reported memory benefits in mice, and dihexa is reported to get past the blood-brain barrier, the tissue layer that ordinarily keeps large molecules from reaching the brain.

How it is studied

Nearly all published research on dihexa comes from rodent studies, mostly mice or rats given a substance called scopolamine to temporarily impair memory, or bred to model Alzheimer disease, plus laboratory experiments on cells grown in a dish. There is no published human clinical trial of dihexa. Researchers have tested it by mouth and by injection in these animal models, typically measuring learning and memory tasks such as maze performance. Two papers from the compound's discovering laboratory describing its molecular mechanism were retracted in 2025, and a separate paper from that laboratory on its antidementia effects carries an unresolved editorial expression of concern issued in 2021.

What studies report

• In young rats given scopolamine to temporarily impair memory, dihexa reversed the resulting deficit on a water-maze memory task and raised markers of fresh brain-cell connections forming, in the paper that first described the compound; that paper carries an editorial expression of concern issued by the journal in 2021 that has not been resolved. [mccoy-2013]
• In mice bred to develop Alzheimer's-like brain changes, an independent research group found that dihexa restored performance on a spatial memory test, increased a marker of nerve-cell connections, and lowered markers of brain inflammation compared with untreated mice. [sun-2021]

What is not known

Two 2014 papers from dihexa's discovering laboratory that proposed its molecular mechanism, including the claim that its synapse-building action was many times stronger than that of BDNF, the body's own comparable growth factor, were retracted by their journal in 2025; no verified paper establishes that specific mechanism or potency comparison, so this profile does not repeat those figures. A separate 2013 paper from the same laboratory reporting dihexa's memory effects in rats carries an unresolved expression of concern. Because no human trial has been conducted, how the compound behaves in people, including whether it is safe at any amount, is entirely unknown. A concern raised in the wider literature is that the growth-factor receptor dihexa was proposed to act on is also involved in some cancers, though this has not been studied directly for dihexa itself.

Regulatory status

No national medicines regulator anywhere, the United States Food and Drug Administration included, has approved Dihexa for any use in people, and it has no history of human clinical testing. It does not show up on the roster of substances banned by the World Anti-Doping Agency.