Angiotensin IV analog
Dihexa was designed as a metabolically stabilized analog of angiotensin IV. Its exact clinically relevant targets in humans remain unestablished.
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Experimental Cognitive Compound
Dihexa
PNB-0408 • Angiotensin IV–Derived Research Compound
Dihexa is an experimental angiotensin IV analog investigated in preclinical models of memory, neuroprotection, and synaptic function. No published human efficacy or safety studies exist, and a key 2014 mechanism paper was retracted in 2025.
At a glance
Dihexa Quick Reference
- Oral community range
- 5–30mg dailyCommunity-reported; no validated human dose
- SubQ community range
- 5–20mg dailyCommunity-reported; no route-comparison study
- Community cycle
- 4–8 weeksLong-term human safety is unknown
- Research target
- Cognitive modelsPreclinical evidence only; human benefit unproven
Overview
What Is Dihexa?
Dihexa is a synthetic, metabolically stabilized derivative of angiotensin IV developed by Joseph Harding and colleagues at Washington State University. It was investigated as a possible approach to cognitive decline and Alzheimer’s disease.
Early cell and animal research reported memory-task performance and markers related to dendritic spines and synapses. These findings do not establish cognitive benefit in people. No published human study has established efficacy, dosing, pharmacokinetics, or safety.
A foundational 2014 mechanism paper was formally retracted in April 2025 after findings of fabricated western-blot data. Independent behavioral studies are not automatically invalidated, but the HGF/c-Met and synaptogenesis story must be treated as proposed and uncertain.
Mechanism
Dihexa Mechanism of Action
Proposed synaptic effects
Early laboratory reports described changes in dendritic spines and synaptic markers; a central mechanism paper was later retracted.
HGF/c-Met hypothesis
The proposed growth-factor pathway remains uncertain for Dihexa. It should not be described as a confirmed human mechanism.
Evidence boundary
Rat and mouse memory-model findings do not establish cognitive efficacy or safety in people.
Research findings
Dihexa Benefits
All potential benefits below come from laboratory or animal research. No published human data demonstrates a Dihexa benefit.
Current evidence level: preclinical
Animal Memory Tasks
A 2013 rat study reported reversal of scopolamine-induced Morris water-maze deficits; a 2021 APP/PS1 mouse study reported improved spatial learning.
Synaptic Markers
Early laboratory work reported increased dendritic-spine and synaptic-marker activity. The retracted mechanism paper limits confidence in strong HGF/c-Met claims.
Neuroinflammatory Markers
The 2021 mouse study reported changes in glial activation and inflammatory markers. These were not reproduced in humans.
Neuronal Markers
The same mouse study reported reduced neuronal loss and improved tissue markers; therapeutic benefit remains unproven.
Protocol planning
Dihexa Dosing Protocol
Both oral and subcutaneous use appear in community discussions. No human dose-finding, route-comparison, efficacy, or safety study has established a validated Dihexa protocol; the route ranges should not be treated as interchangeable.
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Preparation
Dihexa Reconstitution
Example concentration
Example: 10mg vial + 2mL compatible diluent
Result5mg/mL
Reconstitution steps
1
Prepare
Wash your hands, clean the work surface, and wipe both vial stoppers with alcohol. Allow them to dry.
2
Add diluent slowly
Use a new sterile syringe and needle to direct the selected volume of compatible diluent down the inside wall of the vial.
3
Dissolve gently
Swirl or roll the vial until the contents dissolve; do not shake.
4
Store
Follow verified supplier storage instructions and protect the prepared vial from light. Record the reconstitution date in your research journal.
N=1 reports
Dihexa Community Experience
Self-reported anecdotal experiences from nootropic and peptide communities. These reports do not have the weight of published human research.
Positive Reports
- Some users report improved mental clarity, focus, or ability to process complex information.
- A smaller number report better recall of recently learned material.
- Some describe a subtle sense of being more mentally present.
Negative & Mixed Reports
- A significant portion report no noticeable effect.
- Some report headache, anxiety, or overstimulation, particularly at higher reported doses.
- A few report brain fog or cognitive dulling rather than improvement.
- Community discussion repeatedly raises the retracted paper and unresolved HGF/c-Met safety concern.
Stacking & synergy
Dihexa Stacking & Synergy
These pairings are community or mechanistic discussions, not studied Dihexa combination protocols. No published human interaction, efficacy, or safety data establish them.
Safety notes
Dihexa Side Effects & Safety
No published human safety profile exists. Animal observations are not a substitute for formal toxicity or long-term human safety testing.
Proposed HGF/c-Met activity raises an unresolved cancer-related concern. Dihexa has not been shown to cause cancer in humans, but carcinogenicity studies are absent.
Common User Reports
- Mild headache, especially early in use.
- Overstimulation or anxiety.
- Vivid dreams or disrupted sleep.
Less Common Reports
- Brain fog or cognitive dulling.
- Mood changes or irritability.
- Gastrointestinal discomfort with oral use.
Dihexa Precautions
Avoid or Discuss With a Clinician If
- Active cancer, a history of cancer, precancerous conditions, or an unresolved mass.
- Pregnancy or breastfeeding; safety data are absent.
Use Caution With
- Any use, given the absence of human safety data.
- Higher doses or extended cycles, because dose-response and long-term safety are unknown.
- Concurrent compounds that may affect growth-factor signaling.
Dihexa is not FDA approved for cognitive enhancement, Alzheimer’s disease, or another medical use.
Final verdict
Peptide Protocols Verdict on Dihexa
Not medical advice. This editorial is our own opinion piece based off the experience of our own lab rats.
Our opinionated opinion
Dihexa generates significant hype in certain corners of the community. Some users report fast improvements in focus, memory, and neurorecovery, particularly after head trauma or chronic stress. We are deliberately staying away from it and will not be testing Dihexa in-house at peptideprotocols.app.
A central paper supporting its proposed mechanism was retracted after data concerns. Long-term human safety is unknown, and results reported by users vary widely. For us, the risk/reward does not line up favorably.
We suggest skipping Dihexa until better, independent human data emerge. We would look to better-studied approaches for cognitive and neurological support.