Dihexa

Overview

Dihexa is a small oligopeptide derived from angiotensin IV by the Wright/Harding lab at Washington State University, designed to potentiate hepatocyte growth factor (HGF) signaling at the c-Met receptor with the explicit goal of inducing dendritic spine formation (synaptogenesis) and rescuing cognitive function in animal models of Alzheimer's disease. The evidence base looks larger than it is. The foundational rodent work (McCoy 2013, Benoist 2014, and a series of supporting papers from the same lab) was produced in the same period during which Athira Pharma's former CEO and lab trainee Leen Kawas admitted — through a January 2025 ~$4 million False Claims Act settlement with the U.S. Department of Justice — to systematically falsifying and manipulating scientific images in her doctoral dissertation and published research between 2008 and 2012, in work directly supporting dihexa's procognitive claims. Benoist 2014 was retracted in April 2025; other Kawas-co-authored papers have not been formally retracted but are tainted by the same data-integrity finding. The strongest independent preclinical evidence is Sun 2021, a transgenic APP/PS1 mouse study from Chinese investigators with no lab overlap with the Wright/Harding/Kawas group — meaningful but a single independent replication. There are no completed published human trials of any phase. The Alzheimer's Drug Discovery Foundation's Cognitive Vitality assessment characterizes dihexa as preclinical-only and requiring substantial additional research.

Mechanism

Acts as a positive allosteric modulator / mimetic of hepatocyte growth factor (HGF) at its receptor c-Met (MET). c-Met activation drives PI3K/AKT and MAPK signaling and, in central neurons, can promote dendritic spine formation and synaptogenesis. Sun 2021 specifically traced the procognitive effect in APP/PS1 mice through PI3K/AKT activation, with the PI3K inhibitor wortmannin reversing the anti-inflammatory and anti-apoptotic effects. The mechanism framing is broadly supported by the wider c-Met / HGF literature; dihexa-specific mechanism claims that originated solely from the Wright/Harding/Kawas lab during 2008-2014 should be treated cautiously given the documented integrity findings on that lab's output. The proposed safety concern is not theoretical: HGF/c-Met signaling is a known oncogenic driver in multiple epithelial cancers (gastric, certain lung, hepatocellular), and any chronic systemic c-Met agonist carries that risk profile.

Evidence by indication

We classify each indication separately. The same peptide can be Tier 1 for one use and Tier 4 for another. Tiers reflect the published literature, not the strength of community framing.

Studied dose ranges

The ranges below come from published trial protocols where available, and from documented self-experimenter consensus where the literature does not include human dose-finding work. The notes flag which is which.

Contraindications

• Any active or prior malignancy (HGF/c-Met signaling drives tumor invasion in many cancer types — this is a real, mechanistic safety concern, not theoretical)
• Family history of c-Met-driven cancers (gastric, certain lung, hepatocellular)
• Pregnancy and breastfeeding
• Use during chemotherapy or immunotherapy (interaction with cancer biology unknown)
• Known hypersensitivity

Reported side effects

• Unknown in humans — no published human safety data
• Theoretical: tumor promotion via c-Met signaling (the most serious uncharacterized risk)
• Theoretical: off-target effects on systemic c-Met-expressing tissues (liver, kidney, vascular endothelium)
• Anecdotal community reports: headache, anxiety, sleep disturbance — uncontrolled

Reconstitution & storage

Most community use is oral or sublingual — no reconstitution. The hexanoyl modification was designed for oral bioavailability and BBB penetration; vendor preparations vary in quality.

Storage. Vendor-dependent. Powder forms typically refrigerated; oral capsules at room temperature, dry, protected from light.

Open the peptide calculator → to compute exact draw volumes for your specific vial and BAC water choice.

Editorial note

DRAFT — Wayne-direction call (2026-05-05). overall_tier = 3 reflects Wayne's editorial direction; the evidence-tier-classifier skill's default reading on this corpus would be Tier 4 because of the Athira / Kawas data-integrity findings affecting the foundational Wright/Harding-lab papers. Tier 3 is defensible if anchored on Sun 2021 (independent transgenic-AD mouse replication) + Ho & Nation 2018 (class-level systematic review) + the c-Met mechanism story + the FDA direction-of-travel as soft signal — that is the rationale held in the indication's `rationale` field. Key facts the editorial reader needs to hold simultaneously: (1) The April 2026 FDA 503A Category 2 removal IS real, with PCAC review scheduled by/before Feb 2027 — that is a *scheduling of formal scientific evaluation by an advisory committee*, not approval, and compounding pharmacies still cannot legally compound dihexa today. (2) The foundational Wright/Harding-lab work has documented integrity problems: $4M DOJ settlement (Jan 2025), CEO admission of systematic image fabrication 2008-2012, Benoist 2014 retraction (April 2025). The fraud context never disappears; it lives openly in this entry. (3) Sun 2021 is the only genuinely independent dihexa-specific preclinical replication. (4) Zero human trials. The oncology contraindication is non-negotiable — c-Met / HGF signaling is a known oncogenic driver, and that is the safety concern that should never be softened. Lessons-learned for the editorial process: a paper retraction in a compound's foundational lab should always trigger a deeper integrity review of the wider corpus, not just exclusion of the single retracted paper. If a future reviewer disagrees with the Tier 3 call, this note is here to make the decision auditable.

Citations

1. [1]

   AngIV-Analog Dihexa Rescues Cognitive Impairment and Recovers Memory in the APP/PS1 Mouse via the PI3K/AKT Signaling Pathway

   Sun X, Deng Y, Fu X, Wang S, Duan R, Zhang Y, et al. · Brain Sciences · 2021 · PMID 34827486

   Genuine independent rodent replication (China Pharmaceutical University / Nanjing Medical University; no overlap with the Wright/Harding/Kawas lab). Transgenic APP/PS1 model, PI3K/AKT mechanism trace. The strongest single piece of dihexa-specific preclinical evidence not entangled with the Athira fraud history. Anchor for the Tier 3 preclinical-AD-cognition indication.

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2. [2]

   Cognitive benefits of angiotensin IV and angiotensin-(1-7): A systematic review of experimental studies

   Ho JK, Nation DA · Neuroscience & Biobehavioral Reviews · 2018 · PMID 29733881

   Systematic review of 32 animal studies establishing the class-level cognitive signal for angiotensin IV and analogs. Class-level support for the Tier 3 preclinical indication; not a dihexa-specific replication.

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3. [3]

   Stem cell, Granulocyte-Colony Stimulating Factor and/or Dihexa to promote limb function recovery in a rat sciatic nerve damage-repair model: Experimental animal studies

   Weiss JB, Phillips CJ, Malin EW, Gorantla VS, Harding JW, Salgar SK · Annals of Medicine and Surgery (Lond) · 2021

   Single-lab rat model on peripheral nerve regeneration. Includes Harding (the dihexa originating-lab senior author) — partial overlap with the lab orbit that produced the fraud-tainted work, so cited with that caveat.

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4. [4]

   Dihexa — Cognitive Vitality assessment

   Alzheimer's Drug Discovery Foundation · ADDF Cognitive Vitality (alzdiscovery.org) · 2021

   Independent expert assessment confirming the absence of human trial data and characterizing dihexa as preclinical-only. Anchors the Tier 4 framing for the human-applicable indications.

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5. [5]

   Athira Pharma Inc. Agrees to Pay $4M to Settle False Claims Act Allegations Related to Scientific Research Misconduct

   U.S. Department of Justice, Office of Public Affairs · DOJ press release · 2025

   Documents the January 2025 $4M settlement and the underlying admission by former Athira CEO Leen Kawas of systematic image manipulation between 2008-2012 in dihexa-supporting research. The single most important editorial-context citation for this entry.

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6. [6]

   The procognitive and synaptogenic effects of angiotensin IV-derived peptides are dependent on activation of the hepatocyte growth factor/c-met system — RETRACTED 2025

   Benoist CC, Kawas LH, Zhu M, Tyson KA, Stillmaker L, Appleyard SM, Wright JW, Wayman GA, Harding JW (RETRACTED) · Journal of Pharmacology and Experimental Therapeutics · 2014

   Cited as a record of the retracted foundational mechanistic paper, NOT as supporting evidence. Retracted April 2025 following image-manipulation investigation tied to the Athira / Kawas DOJ settlement. Listed here so the editorial context is visible; should never be used to support an indication tier.

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7. [7]

   FDA Announces Removal of 12 Peptides from 503A Category 2 and Schedules PCAC Meetings

   U.S. Food and Drug Administration / PCAC · FDA notice / industry coverage (Frier Levitt, Orrick, RAPS) · 2026

   Documents the April 15, 2026 removal of dihexa acetate (plus 11 other peptides) from 503A Category 2 and the PCAC review schedule. Anchors the fda_status field. NOT evidence of safety or efficacy — just regulatory scheduling.

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