Key Takeaways
- •Dihexa is a synthetic angiotensin IV-derived research compound studied in preclinical (cell culture and rodent) models for effects on cognition and synaptic plasticity.
- •No published human clinical trials are available. All evidence comes from in vitro and in vivo animal studies.
- •The proposed HGF/c-Met mechanism is partly affected by retracted literature. A key 2014 paper central to the mechanistic model was retracted in 2025.
- •The main rodent cognition study (McCoy et al., 2013) has a published notice of concern. It has not been retracted, but findings should be interpreted cautiously.
- •Safety in humans is unknown. No clinical pharmacokinetic, toxicology, or efficacy data exist.
- •Long-term c-Met activation raises theoretical safety questions, as the HGF/c-Met pathway is implicated in certain cancers.
Key Takeaways
- Dihexa is a synthetic angiotensin IV-derived research compound studied in preclinical (cell culture and rodent) models for effects on cognition and synaptic plasticity.
- No published human clinical trials are available. All evidence comes from in vitro and in vivo animal studies.
- The proposed HGF/c-Met mechanism is partly affected by retracted literature. A key 2014 paper central to the mechanistic model was retracted in 2025.
- The main rodent cognition study (McCoy et al., 2013) has a published notice of concern. It has not been retracted, but findings should be interpreted cautiously.
- Safety in humans is unknown. No clinical pharmacokinetic, toxicology, or efficacy data exist.
- Long-term c-Met activation raises theoretical safety questions, as the HGF/c-Met pathway is implicated in certain cancers.
Evidence Quality Summary
| Evidence Area | Strength | Notes |
|---|---|---|
| Rodent cognition | Low to moderate | Positive findings, but limited independent replication and notice of concern on key study |
| HGF/c-Met mechanism | Low | Key mechanistic paper retracted in 2025 |
| Human safety | Very low | No published human trials |
| Therapeutic use | Unsupported | No regulatory approval or clinical efficacy data |
| Question | Current Evidence | |
| Human trials? | No published human clinical trials found | |
| Main mechanism? | Proposed HGF/c-Met modulation (partly contested) | |
| Evidence type? | Cell culture and rodent models | |
| Safety established? | No | |
| Approved for human use? | No |
What Is Dihexa?
Dihexa (also known as PNB-0408; formal IUPAC name: N-(1-oxohexyl)-L-tyrosyl-N-(6-amino-6-oxohexyl)-L-isoleucinamide; molecular formula C₂₇H₄₄N₄O₅) is a synthetic peptide derived from angiotensin IV (Ang IV). It was developed as a metabolically stable analog of Ang IV, primarily investigated in preclinical models for effects on cognition and synaptic plasticity.
Dihexa has been reported to bind hepatocyte growth factor (HGF) and potentiate HGF-dependent signaling at the c-Met receptor, although this mechanistic model is partly based on literature that has since been retracted (see Evidence Limitations below).
All current evidence for Dihexa's effects is derived from in vitro (cell culture) and in vivo (animal model) studies. No human clinical trials have been published to date. Dihexa is classified as a research compound and is not approved for human consumption.
Proposed Mechanism of Action
The primary proposed mechanism of Dihexa involves the potentiation of HGF-dependent signaling at the c-Met receptor. Specifically, Dihexa has been reported to bind HGF and enhance its interaction with c-Met, rather than binding directly to the c-Met receptor itself. This potentiation is thought to activate downstream signaling cascades, including the PI3K/Akt and MAPK/ERK pathways, which are associated with neuronal survival, dendritic spine formation, and long-term potentiation (LTP) in preclinical models.
Important caveat: The mechanistic model linking Dihexa to HGF/c-Met-mediated synaptogenesis is substantially based on a 2014 paper (Benoist et al., Journal of Pharmacology and Experimental Therapeutics) that was retracted in 2025. Because this paper was central to the proposed mechanism, claims about Dihexa's c-Met-dependent effects should be interpreted cautiously and treated as provisional rather than established.
Dihexa was designed to be more lipophilic and metabolically stable than angiotensin IV, and preclinical studies report central nervous system activity consistent with brain penetration.
Preclinical Research Findings
Rodent Cognitive Studies
The most widely cited preclinical evidence for Dihexa comes from McCoy et al. (2013), published in the Journal of Pharmacology and Experimental Therapeutics (JPET). In this study, aged rats treated with Dihexa showed improvements in spatial memory performance in the Morris water maze task compared to controls. The study also reported increased hippocampal dendritic spine density, which the authors correlated with the cognitive improvements.
Note: This 2013 JPET paper has a published notice of concern. It has not been retracted, but readers should interpret findings from this research cluster cautiously and monitor for updates.
Context and Interpretation
Several points warrant caution when interpreting these findings:
- Single research group: Much of the published Dihexa literature originates from the laboratory of Dr. John W. Wright at Washington State University. Independent replication by other groups is limited.
- Animal models only: The Morris water maze and similar cognitive tasks in rodents have limited translational validity to human cognitive conditions.
- Doses and routes: The doses and routes of administration used in rodent studies may not translate to human physiology. No human pharmacokinetic data are available.
Wright and Harding (2015) published a review in the Journal of Alzheimer's Disease discussing the broader HGF/c-Met system in relation to Ang IV analogs and cognitive function. This review provides useful background context but does not represent new experimental data on Dihexa specifically.
Evidence Limitations and Retractions
The evidence base for Dihexa has several important limitations that researchers should consider:
Retracted literature: A key 2014 paper proposing that Dihexa's procognitive and synaptogenic effects depend on HGF/c-Met activation (Benoist et al., JPET, 2014) was retracted in 2025. Because this paper is central to the proposed mechanism, claims about Dihexa's c-Met mechanism should be interpreted cautiously and presented as provisional rather than established.
Notice of concern: A related 2013 JPET paper by McCoy et al., often cited for Dihexa's procognitive effects in aged rats, has a published notice of concern. It has not been retracted, but readers should interpret findings from this research cluster cautiously.
Limited independent replication: Most published studies come from a single research group. Independent confirmation of the key findings by other laboratories has not been widely reported in the peer-reviewed literature.
No human data: There are no published human clinical trials examining Dihexa's safety, pharmacokinetics, or efficacy. As of a July 2026 search, no registered human clinical trials for Dihexa were identified on ClinicalTrials.gov.
Small evidence base: The total number of published studies on Dihexa is small relative to more established research peptides. The depth of evidence does not support strong conclusions about therapeutic potential.
Safety Considerations
Dihexa is a research chemical and is not approved for human consumption. The safety profile in humans has not been established.
Potential safety concerns include:
- HGF/c-Met and cancer risk: The HGF/c-Met signaling pathway is implicated in cell proliferation and is dysregulated in certain cancers. Long-term activation of this pathway by an exogenous compound raises theoretical safety questions that have not been addressed in published Dihexa research.
- No toxicology data in humans: Without clinical trials, the metabolic pathways, half-life, organ-specific effects, and potential drug interactions in humans are entirely unknown.
- Preclinical toxicology limitations: The rodent studies that have been published were not designed to assess long-term safety, carcinogenicity, or reproductive toxicity.
Current Research Status
Dihexa remains at an early preclinical stage. No clinical development programs have been publicly announced. As of a July 2026 search, no registered human clinical trials for Dihexa were identified on ClinicalTrials.gov.
Research interest continues due to the compound's novel proposed mechanism of action (HGF/c-Met modulation) and its design for brain penetration, but the retraction of a key mechanistic paper in 2025 and the notice of concern on the main rodent cognition study have introduced additional uncertainty into the field.
Researchers working with Dihexa or related Ang IV analogs should closely monitor the publication and retraction status of cited literature and interpret all mechanistic claims in light of the current evidence base. For more context on how to evaluate peptide research, see our Research Disclaimer.
Frequently Asked Questions
What is the proposed mechanism of Dihexa?
Dihexa has been reported to bind HGF and potentiate HGF-dependent signaling at the c-Met receptor. However, the key paper proposing this mechanism was retracted in 2025, so the mechanistic model should be considered provisional.
Has Dihexa been tested in humans?
No. All published research on Dihexa has been conducted in cell culture and rodent models. There are no human clinical trials, and no clinical development program has been publicly announced.
What are the main limitations of the current evidence?
The evidence base is small, most studies originate from a single research group, independent replication is limited, a key mechanistic paper has been retracted, the main rodent study has a notice of concern, and there are no human safety or efficacy data.
Does Dihexa cross the blood-brain barrier?
Dihexa was designed to be more lipophilic and metabolically stable than angiotensin IV. Preclinical studies report central nervous system activity consistent with brain penetration, but direct BBB permeability data are limited.
Is Dihexa approved for any medical use?
No. Dihexa is not approved by any regulatory agency for medical, therapeutic, or veterinary use. It is available only for laboratory research purposes. For related context, see our Peptide Glossary.
References
- McCoy, A. T., et al. (2013). "Evaluation of metabolically stabilized angiotensin IV analogs as procognitive/antidementia agents." Journal of Pharmacology and Experimental Therapeutics, 344(1), 141–154. DOI: 10.1124/jpet.112.199430 [Notice of Concern]
- Benoist, C. C., et al. (2014). "The procognitive and synaptogenic effects of angiotensin IV-derived peptides are dependent on activation of the hepatocyte growth factor/c-Met system." Journal of Pharmacology and Experimental Therapeutics, 351(2), 390–402. [RETRACTED 2025]
- Wright, J. W., & Harding, J. W. (2015). "The brain hepatocyte growth factor/c-Met receptor system: A new target for the treatment of Alzheimer's disease." Journal of Alzheimer's Disease, 45(4), 985–1000.
- Wright, J. W., & Harding, J. W. (2011). "Brain renin-angiotensin — a new look at an old system." Progress in Neurobiology, 95(1), 49–67.
Research-Only Disclaimer
Dihexa is sold for laboratory research purposes only. It is not approved for human consumption, medical use, or veterinary use. This article is for informational and educational purposes and does not constitute medical advice. Researchers must handle this compound in accordance with institutional biosafety guidelines and applicable regulations. Volta Peptides does not promote or endorse the self-administration of research peptides. For more information, please read our [Research Disclaimer](https://voltapeptides.com/policies/research-disclaimer).
Reviewed by the Volta Peptides Research Team