On this page
What it is
Dihexa, also called PNB-0408, is a small synthetic derivative developed from angiotensin IV research. It is often called a peptide, although its modified structure is designed to be more drug-like and orally available in animal experiments.
Most claims trace to one research program. Two influential papers supporting the HGF and c-Met synapse mechanism were retracted in 2025, and another key animal paper carries an Expression of Concern.
What people research it for
Animal cognition findings
Animal studiesOlder rodent studies reported improved maze performance in impaired animals.
Synapse mechanism is disputed
Preclinical / theorizedThe two central HGF and c-Met papers were retracted in 2025.
No demonstrated human benefit
Preclinical / theorizedNo controlled human trial has established memory, focus, or dementia benefit.
Research integrity is a major limitation
Preclinical / theorizedAn Expression of Concern also affects a key characterization paper.
How it works
The published hypothesis was that Dihexa enhances hepatocyte growth factor signaling through the c-Met receptor, promoting new synaptic connections. Retractions now mean that mechanism must be treated as unconfirmed.
Animal studies reported cognitive effects after brain injury or chemically induced impairment. Those models do not show that Dihexa improves memory in healthy people or treats dementia.
What the research actually shows
A 2013 paper described metabolically stabilized angiotensin IV analogs and reported cognitive effects in rodent models. The journal added an Expression of Concern in 2021, so its findings should not be treated as settled.
A 2014 paper reported HGF and c-Met-dependent procognitive and synaptogenic effects. The paper was formally retracted in April 2025 after an institutional investigation, removing a central pillar of the Dihexa story.
A related 2012 HGF paper was also retracted in 2025. The retraction notices say the articles are no longer reliable, which matters more than how often their claims are repeated on retail pages.
A separate zebrafish study reported protection of lateral-line hair cells from aminoglycoside exposure by an HGF mimetic. This is not evidence for memory improvement or human neuroprotection.
A systematic review of angiotensin IV and angiotensin-(1-7) found preclinical cognitive signals across experimental studies, but that broader literature does not validate Dihexa specifically.
No registered, peer-reviewed human trial has established Dihexa pharmacokinetics, effective exposure, cognitive benefit, interaction risks, or long-term safety.
Handling & storage
Storage at a glance
Vendor consensus- Lyophilized
- -20°C
- Keep sealed, dry, and protected from light and moisture.
- Reconstituted
- 2 to 8°C
- Use the product-specific laboratory instructions. No independently validated universal in-use period was found.
- Light
- Protect from light and moisture.
- Room temperature
- Brief shipping exposure is not a validated shelf life. Avoid sustained heat.
- Reconstitution
- product-specific laboratory solvent
- A research vial must not be assumed sterile or suitable for injection.
Basis: Vendor consensus. Sources: MedChemExpress Dihexa data sheet, MedKoo Dihexa technical page
Dihexa is poorly water-soluble and is sold in different chemical forms. MedChemExpress gives solvent-specific stock-solution storage, while another supplier lists dry, dark storage near -20°C. These instructions are not interchangeable with a sterile vial.
Use the exact analytical product instructions. No published clinical formulation or independently validated retail-vial shelf life was found.
Safety & cautions
There is no adequate human safety dataset. Because the proposed pathway involves HGF and c-Met, a signaling system involved in cell growth and cancer biology, uncontrolled stimulation is a theoretical concern, not a proven Dihexa outcome.
Unknowns include neurological effects, blood pressure, liver metabolism, cancer risk, reproductive safety, drug interactions, and cumulative exposure. Online products add identity, solvent, potency, and contamination risks.
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Frequently asked questions
Has Dihexa been tested in humans?
No controlled peer-reviewed human efficacy trial has established its benefits or safety.
Were Dihexa studies retracted?
Yes. Two central HGF and c-Met papers were retracted in April 2025, and another key paper carries an Expression of Concern.
Does Dihexa improve memory?
Some animal studies reported cognitive effects, but reliable human evidence is absent.
Is Dihexa approved for Alzheimer disease?
No.
Is the c-Met mechanism proven?
No. The papers that directly supported that mechanism were retracted.
How should laboratory Dihexa be stored?
Follow the exact supplier instructions for the chemical form and solvent. Technical pages commonly use cold, dry, dark storage, but no universal vial lifetime is validated.
Sources
- Expression of Concern paper on stabilized angiotensin IV analogs
- Retracted Dihexa mechanism paper
- Retraction notice for 2014 paper
- Retraction notice for related 2012 paper
- HGF mimetic hair-cell study
- Angiotensin cognition systematic review
- MedChemExpress Dihexa data sheet
- MedKoo Dihexa technical page
Last reviewed September 17, 2026. This guide is educational and research-focused, not medical advice. Dihexa products referenced on PeptidePub are sold by third parties as materials for laboratory research use only, not for human or animal consumption.
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