Dihexa is a synthetic, peptide-derived small molecule that came out of academic neuroscience work at Washington State University, built from a two-residue fragment of angiotensin IV and then chemically armored so it could survive digestion and reach the brain. Everything published about what it does in a living system comes from cell culture and rodent studies, and the paper anchoring its proposed mechanism was retracted in 2025. No regulatory agency has approved it for human use anywhere, and material sold under the name today circulates as a research chemical outside pharmaceutical manufacturing standards.
Dihexa is an unapproved research compound with the formula C27H44N4O5 and a molecular weight near 505 g/mol, developed at Washington State University in the early 2010s and supported only by preclinical evidence, part of which has since been retracted.
Dihexa is filed under peptides in most supplier catalogues, yet only one of its three amide linkages is a peptide bond between natural amino acids. Chemists generally describe it as a peptidomimetic: two real residues, tyrosine and isoleucine, carrying synthetic hydrocarbon scaffolding at both ends. That scaffolding is what makes the molecule fat-soluble rather than water-soluble, which governs both how it crosses a membrane and how a laboratory has to handle it.
Dihexa carries the formula C27H44N4O5 at roughly 504.7 g/mol and contains only one true peptide bond, which is why the published record classes it as a peptidomimetic rather than a peptide.
Dihexa was not a chance discovery. It closed out roughly two decades of angiotensin IV work run by Joseph W. Harding and John W. Wright in the neuroscience program at Washington State University in Pullman, with collaborators including Caroline Benoist and Leen Kawas. The founding literature no longer stands as originally issued, which changes how every secondary summary of that work has to be read.
The foundational dihexa literature now carries formal integrity actions against it, a Notice of Concern issued in 2021 against the 2013 paper and a 2025 retraction of the companion hepatocyte growth factor and c-Met report.
Angiotensin IV is a six-amino-acid fragment, Val-Tyr-Ile-His-Pro-Phe, clipped from angiotensin II, and in rodent work it did something almost no endogenous molecule does: injected directly into the brain, it reversed memory deficits caused by scopolamine, alcohol exposure, and physical lesions. The obstacle was never the pharmacology. It was the pharmacokinetics, and closing that gap is the entire reason the design campaign existed.
| Property | Angiotensin IV | Needed for an oral medicine |
|---|---|---|
| Plasma survival | Minutes; cleared by amino- and carboxypeptidases | Hours |
| Blood-brain barrier | Too polar and too large to cross in useful amounts | Passive entry at low dose |
| Oral activity | None; effects demonstrated only by direct brain injection | Active by mouth |
| Active portion | Six residues, most of them not required | Minimal core retained |
Truncation and substitution studies identified the tyrosine-isoleucine portion near the amino end of angiotensin IV as the fragment carrying most of the necessary activity, and that pair is the only natural amino acid content surviving in dihexa.
Three chemical moves separate dihexa from the fragile signaling peptide it came from, and each one blocks a specific route by which the body dismantles a small peptide. The reported result was a molecule active by mouth in rodents at microgram-per-kilogram doses with measurable brain exposure, which is the specific claim that made it notable, since orally active brain-penetrant peptides are rare.
Oral activity and brain penetration for dihexa are reported in rodents only, and with no published human pharmacokinetic dataset in existence, no oral dose in a person has been characterized for either effect or safety.
The mechanism most often attributed to dihexa is positive modulation of hepatocyte growth factor signaling at the c-Met receptor, meaning the compound is reported not to switch the receptor on by itself but to amplify growth factor already present. That claim now sits at the weakest standing available to a published result, because the paper establishing it was retracted in 2025. The same receptor is a well-characterized proto-oncogene, so the mechanism and the central safety objection are the same piece of biology.
The retraction in 2025 of the paper establishing dihexa's hepatocyte growth factor and c-Met dependence leaves the compound's proposed mechanism unconfirmed rather than under-replicated.
The target was dementia, Alzheimer's disease in particular, at a point when approved drugs offered modest symptomatic relief through cholinergic or glutamatergic tweaks and the dominant amyloid-clearing strategy had produced a long run of expensive clinical failures. Of all the pathological features of the disease, synapse loss tracks a patient's actual impairment most tightly, so a molecule that pushed neurons to build new functional connections was a bid to restore function in a damaged brain rather than slow further damage.
Procognitive, in the dihexa literature, is a technical claim about restoring impaired performance toward normal in animal models, not a claim of enhancement above baseline in healthy people.
Two afterlives ran in parallel. The licensed track carried the mechanism into real clinical trials but advanced a different molecule and reported no clear cognitive benefit on its primary endpoints. The unregulated track needed nothing beyond the published structure and the eye-catching potency figures to begin selling dihexa itself.
| Criterion | Licensed development track | Research chemical market |
|---|---|---|
| Holder | M3 Biotechnology, later renamed Athira Pharma, under a Washington State University license | Chemical suppliers, no license involved |
| Compound advanced | Fosgonimeton (ATH-1017), a related MET-modulating candidate | Dihexa itself |
| Human testing | Mid and late stage Alzheimer's disease trials | None on public record |
| Reported result | No clear cognitive benefit on primary endpoints | Nootropic marketing under a not-for-human-consumption disclaimer |
Dihexa has never entered a registered human trial under its own name, and the related compound that did reach mid and late stage Alzheimer's trials, fosgonimeton, failed to establish a clear benefit on its primary endpoints.
No regulatory authority anywhere has approved dihexa as a medicine, and no lawful route exists to sell it for human use in the United States. The research use only label attached to supplier listings is a commercial disclaimer rather than a regulatory category, and it certifies nothing about identity, purity, sterility, or toxicity.
Dihexa holds no marketing authorization from any regulator, cannot lawfully be sold as a dietary supplement in the United States, and falls under World Anti-Doping Agency category S0 as prohibited at all times.
There is effectively nothing to weigh. No completed controlled trial of dihexa in people appears in the peer-reviewed literature or in public trial registries, which leaves no established dose, no established route, no pharmacokinetic profile, and no safety database. What circulates instead is forum self-report and vendor testimonial, which cannot separate a real drug effect from expectation, from whatever else the person was taking, or from a vial that never contained the labeled compound.
Absence of reported harm from short-term self-experimentation is not a safety signal, because the hazard specific to amplifying c-Met signaling is growth in cells that already carry oncogenic potential, which would take years to surface.
Educational use only. This article describes what the published scientific and clinical literature reports about Dihexa. It is not medical advice, and it does not recommend, prescribe, or tell anyone to use anything described here. The regulatory status shown at the top of this page reflects what the record showed on the date given there and can change. mdpep.com does not sell any substance described here, does not endorse human use of it, and does not direct anyone to obtain it.
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