# Dihexa: Evidence, Mechanism, Dosing & Legal Status

> A clinical monograph on dihexa — the angiotensin IV-derived nootropic peptide promoted for cognition. Its evidence is preclinical only, its foundational mechanism papers were retracted for fraud, and its clinical prodrug failed an Alzheimer's trial.

*Published 2026-06-30 · Updated 2026-07-01 · By Marcus Feld, PharmD, BCPS*

The short answer
Dihexa produced striking memory-rescue and synaptogenesis signals in *rodent* dementia models, but it has **never been tested in humans**, and several foundational mechanism papers were **retracted in 2025 for falsified data** — so its highest evidence grade is **C (preclinical only)**. Its clinical prodrug, fosgonimeton, was safe but failed its Alzheimer's trial. Dihexa is not FDA-approved, not legally compoundable, and prohibited in sport.[2](https://peptidevox.com/#r2)[8](https://peptidevox.com/#r8)

Dihexa (PNB-0408; *N*-hexanoic-Tyr-Ile-(6)-aminohexanoic amide) is a synthetic peptide derived from angiotensin IV, developed at Washington State University and promoted in nootropic and anti-aging circles as a potent cognitive enhancer.[15](https://peptidevox.com/#r15) Its popularity rests on dramatic preclinical claims; its proof in humans is nonexistent, and a core part of its scientific foundation has collapsed. This monograph separates the two.

*This article is informational and editorial content for research and educational purposes only. It is not medical advice, not a protocol to follow, and not a sourcing guide. Dihexa is not an FDA-approved drug; it is sold as a "research chemical not for human consumption" and is prohibited in sport. Dosing figures are reported strictly as seen in the published literature and anecdotal community reports for completeness — not as recommendations. Consult a licensed clinician before any health decision.*

## What is dihexa and how does it work?

Dihexa is an oligopeptide with the systematic name *N*-hexanoic-tyrosine-isoleucine-(6)-aminohexanoic amide, molecular formula C₂₇H₄₄N₄O₅ and molecular weight roughly 504.67 g/mol.[15](https://peptidevox.com/#r15) Native angiotensin IV is rapidly degraded by peptidases and does not cross the blood-brain barrier; dihexa was engineered with N-terminal hexanoyl and C-terminal aminohexanoic-amide modifications to increase hydrophobicity, confer metabolic stability and enable brain penetration.[4](https://peptidevox.com/#r4) It emerged from the angiotensin-IV cognition program of Joseph Harding and John Wright at Washington State University, which since the 1990s explored Ang IV analogs that reversed scopolamine-induced memory deficits in rats.[3](https://peptidevox.com/#r3)

The dominant published mechanism — all of it preclinical — is that dihexa binds hepatocyte growth factor (HGF) and acts as an allosteric potentiator or dimerization mimetic, augmenting HGF's ability to activate its receptor tyrosine kinase c-Met (MET) at otherwise subthreshold HGF concentrations. c-Met activation then engages downstream PI3K/AKT and MAPK/ERK cascades that drive neuronal survival, dendritic arborization and synapse formation.[15](https://peptidevox.com/#r15) A critical caveat applies: the widely cited binding affinity (around 65 picomolar) and the central c-Met phosphorylation and synaptogenesis data derive from Benoist and colleagues 2014, which was formally retracted in April 2025 for falsified figures — so the quantitative mechanism and potency claims cannot be relied upon.[1](https://peptidevox.com/#r1)[2](https://peptidevox.com/#r2) An earlier, competing framework proposed Ang IV analogs act via IRAP (insulin-regulated aminopeptidase, the AT4 site); this debate was never definitively resolved.[5](https://peptidevox.com/#r5) No formal human pharmacokinetic profile for dihexa exists; commonly repeated figures such as "38% oral bioavailability" appear only in secondary and vendor sources and are not anchored to a verifiable peer-reviewed study.[3](https://peptidevox.com/#r3)

## What is the evidence by indication?

Every indication below is animal-model or cell-system evidence, graded C. There are no human efficacy data for dihexa itself, and the most-cited mechanistic study is retracted.[2](https://peptidevox.com/#r2)

  Dihexa evidence by indication

    IndicationBest evidenceGrade

    Cognition / memory (dementia models)Oral dihexa reversed spatial-learning deficits in scopolamine-amnesia and aged rats (Morris water maze)C (preclinical)
    Synaptogenesis / dendritic spinesIn-vitro spine density increases on CA1 neurons — from the retracted 2014 studyC / unreliable
    Alzheimer's neuroprotectionIntragastric dihexa preserved cognition and reduced neuronal loss in APP/PS1 miceC (preclinical)
    Alzheimer's (human, via prodrug)Fosgonimeton Phase 2/3 LIFT-AD — failed primary endpointB safety, no efficacy

The cognition signal is the most cited. In a scopolamine-amnesia model and in aged Sprague-Dawley rats, oral dihexa reversed spatial-learning deficits, with brain levels reported sufficient for a therapeutic effect after oral dosing; notably, dihexa did not improve cognition in animals with normal baseline cognition, so the effect was deficit-specific.[3](https://peptidevox.com/#r3) In APP/PS1 transgenic Alzheimer's mice, intragastric dihexa over roughly three months was reported to restore declining brain Ang IV, preserve cognition, reduce neuronal loss and dampen neuroinflammation.[6](https://peptidevox.com/#r6) The now-retracted Benoist 2014 study reported that dihexa increased dendritic spine density on hippocampal neurons and that oral dihexa reversed scopolamine deficits via a central HGF/c-Met-dependent mechanism — findings that are retracted and should not be cited as established.[1](https://peptidevox.com/#r1)[2](https://peptidevox.com/#r2)

The one rigorous human test of the underlying HGF/MET-cognition thesis came through a separate prodrug. Dihexa itself never entered clinical trials; M3 Biotechnology, later Athira Pharma, developed fosgonimeton (ATH-1017), a subcutaneously injected molecule rapidly cleaved in plasma to a dihexa-related active metabolite.[9](https://peptidevox.com/#r9) In Phase 1 ([NCT03298672](https://clinicaltrials.gov/study/NCT03298672), 88 subjects) it was generally safe and well tolerated, with mainly injection-site pain and pruritus.[7](https://peptidevox.com/#r7) But the Phase 2/3 LIFT-AD trial in roughly 315 patients with mild-to-moderate Alzheimer's failed its primary endpoint (Global Statistical Test; -0.08, P=0.70) and key secondaries, with only numerical, non-significant trends favoring treatment.[8](https://peptidevox.com/#r8)

Proven vs hyped
Proven in humans: nothing for dihexa. Hyped: "seven orders of magnitude more potent than BDNF," picomolar synaptogenesis, and a precise 65-picomolar HGF affinity — all traceable to retracted or unverified sources. Even the optimized clinical prodrug failed in a well-powered Alzheimer's trial.[8](https://peptidevox.com/#r8)

## What doses appear in the literature?

Reported strictly as information, not a protocol. Dihexa has no approved human use and no validated human dose.[6](https://peptidevox.com/#r6) In preclinical rodent work, oral dosing was around 2 mg/kg in rats (scopolamine and aged-rat cognition studies) and 1.44 to 2.88 mg/kg intragastric in APP/PS1 mice over weeks to months.[3](https://peptidevox.com/#r3) In-vitro synaptogenic activity was reported at picomolar concentrations, but this comes from the retracted study and is not reliable.[1](https://peptidevox.com/#r1) Anecdotal human use — with no clinical basis — describes roughly 5 to 50 mg per day taken orally or applied transdermally, often dissolved in a carrier such as DMSO and sometimes cycled; these reports are unvalidated, unsupervised, and carry unknown bioavailability and safety.[6](https://peptidevox.com/#r6) For context, the clinical prodrug fosgonimeton was dosed at 40 mg once-daily subcutaneously in LIFT-AD — a different molecule, not dihexa.[8](https://peptidevox.com/#r8) Dihexa is poorly water-soluble by design, which is itself a practical liability and one reason a water-soluble prodrug was developed.[9](https://peptidevox.com/#r9)

## How safe is dihexa?

Human safety of dihexa itself is essentially unknown; no completed human trials of dihexa exist and there are no long-term human safety data.[6](https://peptidevox.com/#r6) The dominant theoretical risk is mechanistic and serious: c-Met is a well-characterized oncogene, and HGF/c-Met signaling drives tumor growth, invasion, metastasis and angiogenesis. A systemic agent that potentiates this pathway raises a credible cancer-promotion concern, especially with chronic, unsupervised dosing — a risk repeatedly flagged by the Alzheimer's Drug Discovery Foundation.[6](https://peptidevox.com/#r6) Short-duration animal studies were reported to show no apparent toxicity, but these are brief, animal-only, and partly drawn from the same compromised research program.[15](https://peptidevox.com/#r15) Theoretical contraindications include active, prior or strong family-history cancer, uncharacterized precancerous lesions, and pregnancy or breastfeeding given the absence of reproductive data. For the prodrug, human adverse events were mainly mild injection-site reactions with occasional transient eosinophil rises.[7](https://peptidevox.com/#r7) The research-integrity problem compounds the safety picture: because the foundational binding-affinity and mechanism data were falsified and retracted, any effective-dose and safety-margin extrapolations built on them are unreliable.[2](https://peptidevox.com/#r2)

## What is the FDA and WADA status in 2026?

Dihexa is not an FDA-approved drug; there is no NDA or BLA, and it is sold only as a research chemical labeled not for human consumption.[6](https://peptidevox.com/#r6) Dihexa acetate was moved into 503A Category 2 (significant safety concerns, not permitted in compounding) in September 2023, and it was never in Category 1, so it has never been legally usable in 503A compounding.[10](https://peptidevox.com/#r10) Under the January 7, 2025 final interim guidance, the FDA stopped placing newly nominated substances into Categories 2 and 3.[12](https://peptidevox.com/#r12) In April 2026 the FDA announced it would remove dihexa acetate from Category 2 within seven calendar days and convene a second Pharmacy Compounding Advisory Committee (PCAC) meeting before the end of February 2027 to review it alongside GHK-Cu, Melanotan II, LL-37 and PEG-MGF.[11](https://peptidevox.com/#r11) The critical legal point: removal from Category 2 is not approval, the PCAC recommendation is non-binding, formal notice-and-comment rulemaking would still be required, and dihexa remains not legally compoundable as of mid-2026.[11](https://peptidevox.com/#r11)

For athletes the picture is unambiguous. As a non-approved pharmacological substance, dihexa is prohibited at all times under WADA category S0 (non-approved substances) on the 2026 Prohibited List that came into force on January 1, 2026; its HGF and growth-factor mechanism also falls within the spirit of the S2 growth-factor prohibitions.[13](https://peptidevox.com/#r13) It is not currently listed explicitly by name, but S0 captures it regardless of naming, and no Therapeutic Use Exemption is available for a substance with no approved medical use.[14](https://peptidevox.com/#r14) Dihexa is not a DEA-controlled substance.

**Bottom line.** Dihexa pairs genuinely striking rodent memory-rescue signals with a near-total absence of human proof and a foundation partly destroyed by research fraud. From a functional, root-cause standpoint, supporting synaptic health through validated levers — metabolic health, sleep, exercise, omega-3s and cognitive engagement — is far better evidenced than an unapproved, fraud-tainted, untested-in-humans research chemical that activates an oncogenic pathway. Graded C, legally unsettled, and banned in sport. Regulatory facts here are current as of June 2026; the PCAC review (before February 2027) was pending at the time of writing and should be re-verified after that date.

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Source: https://peptidevox.com/peptide-encyclopedia/dihexa
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