Abstract
Dihexa (PNB-0408; N-hexanoic-Tyr-Ile-(6)-aminohexanoic amide) is a synthetic oligopeptide derived from angiotensin IV (Ang IV) designed to act as a high-affinity hepatocyte growth factor (HGF) mimetic and potentiator at the c-Met receptor. It is orally active, blood–brain barrier permeable, and has shown robust procognitive, synaptogenic, and neuroprotective effects in rodent models of Alzheimer-like pathology, neurodegeneration, and ototoxic damage.PMC+4Wikipedia+4PubMed+4
Despite promising preclinical data, Dihexa has no approved clinical indication and no published human efficacy or safety trials. Its current status is strictly that of an experimental research tool. This review summarizes its chemistry, mechanism of action, preclinical efficacy, and limitations, and ends with a FAQ emphasizing that Dihexa is not for human use and should be handled exclusively in appropriate research settings.
1. Chemical Identity and Basic Properties
- Name: Dihexa
- Synonyms:
- PNB-0408
- N-hexanoic-Tyr-Ile-(6)-aminohexanoic amide
- Hexanoyl-Tyr-Ile-Ahx-NH₂Wikipedia+2ApexBio+2
- CAS Number: 1401708-83-5Pharmaffiliates+3Wikipedia+3MilliporeSigma+3
- Molecular formula: C₂₇H₄₄N₄O₅Wikipedia+2MilliporeSigma+2
- Molecular weight: ~504.7 g/molMilliporeSigma+2ApexBio+2
- Structural class: Angiotensin IV analog, small peptide/oligopeptide
- Key features:
- Orally bioavailable
- Blood–brain barrier permeable
- Designed as a HGF/c-Met system activatorMedKoo Biosciences+3PubMed+3OAE Publishing+3
Suppliers of analytical-grade Dihexa (e.g., MedChemExpress, Achemblock, research reagent vendors) uniformly label it as a research chemical with disclaimers such as “for laboratory research only; not for human use.”MedKoo Biosciences+3ApexBio+3MedChem Express+3
2. Mechanism of Action
2.1 HGF/c-Met Modulation
Preclinical work demonstrates that Dihexa:
- Binds with high affinity to hepatocyte growth factor (HGF).
- Potentiates HGF activity at the c-Met (HGFR) receptor, enhancing c-Met phosphorylation in the presence of low HGF concentrations.OAE Publishing+3PubMed+3PMC+3
This HGF-mimetic action drives:
- Spinogenesis and synaptogenesis in hippocampal neurons.
- Enhanced long-term potentiation (LTP) in hippocampal circuits.PubMed+2PMC+2
2.2 Relationship to Angiotensin IV Analogs
Dihexa belongs to the “6-AH family” of Ang IV analogs designed to:
- Cross the blood–brain barrier.
- Shift from classical renin–angiotensin targets to HGF/c-Met signaling as the primary functional pathway.PubMed+2PubMed+2
These analogs were developed following observations that Ang IV and certain analogs can modulate cognition via non-traditional angiotensin receptors and HGF/c-Met interactions.PubMed+1
3. Preclinical Evidence of Efficacy
3.1 Cognitive Enhancement and Synaptogenesis
Multiple rodent studies report that Dihexa:
- Improves performance in memory and learning tasks (e.g., Morris water maze, object recognition) in models of Alzheimer-like impairment.PubMed+4PubMed+4PubMed+4
- Enhances dendritic spine density and functional synapse number in hippocampal neurons ex vivo.PubMed+2PMC+2
- Facilitates memory consolidation and retrieval in animal models, consistent with long-term potentiation of synaptic circuits.PubMed+2OAE Publishing+2
Key PubMed-indexed references:
- Wright JW et al., Prog Neurobiol 2015 – development of small molecule Ang IV analogs including Dihexa for AD and PD models. (PMID: 25455861)PubMed+1
- Benoist CC et al., J Pharmacol Exp Ther 2014 – Dihexa’s synaptogenic and procognitive effects and c-Met-dependent mechanism. (PMID: 25187433)PubMed+1
- Kawas LH et al., J Pharmacol Exp Ther 2012 – characterization of 6-AH Ang IV analogs as HGF/Met modulators. (PMID: 22129598)PubMed
3.2 Alzheimer’s Disease Models
In APP/PS1 transgenic mice (a widely used Alzheimer’s model), Dihexa:
- Rescued cognitive impairment and improved memory performance.
- Showed efficacy after oral administration, consistent with its reported oral bioavailability.PubMed+2PMC+2
Reference:
- Sun X et al., Front Pharmacol 2021 – “AngIV-Analog Dihexa Rescues Cognitive Impairment and Memory Loss in an AD Mouse Model.” (PMID: 34827486)PMC+1
3.3 Neuroprotection in Hair-Cell Models
In zebrafish lateral line hair-cell assays, Dihexa:
- Protected sensory hair cells from neomycin-induced ototoxicity.
- The protective effect was blocked by HGF antagonism, implicating HGF/c-Met as the mediating pathway.PMC+1
Reference:
- Uribe PM et al., Front Cell Neurosci 2015 – HGF mimetic Dihexa protects lateral line hair cells via an HGF-mediated mechanism. (PMCID: PMC4309183)PMC
4. Safety, Toxicology, and Limitations
4.1 Short-Term Safety (Preclinical)
Patent and review literature claim that short-term animal studies with Dihexa did not show overt toxicity or tumor promotion despite chronic c-Met activation, although detailed toxicology data remain sparse and not independently replicated.Wikipedia+2PubMed+2
4.2 Oncogenic Concerns
Because c-Met is a recognized oncogene, chronic activation raises legitimate questions about long-term cancer risk.PubMed+2OAE Publishing+2
To date there is:
- No long-term carcinogenicity data for Dihexa.
- No human safety trials assessing cancer risk, cardiovascular effects, or systemic toxicity.
4.3 Lack of Human Data
Critically:
- There are no peer-reviewed human clinical trials establishing dosing, pharmacokinetics, safety, or efficacy in humans as of late 2025.American Medical Wellness+4PubMed+4OAE Publishing+4
- Any promotional or clinical-style discussion on commercial websites is speculative and not equivalent to regulatory approval or clinical evidence.Revolution Health & Wellness+2Holistic Medical Wellness+2
5. Regulatory and Practical Considerations
- Dihexa is not approved as a drug or dietary supplement by major regulatory bodies (FDA, EMA, etc.).
- Research-chemical vendors explicitly label it:
- “For laboratory research use only.”
- “Not for human or veterinary use.”MedKoo Biosciences+3ApexBio+3MedChem Express+3
Use outside of controlled laboratory environments (e.g., self-administration by individuals) falls well outside the available evidence base and may involve significant unknown risk.
6. Conclusion
Dihexa is a first-in-class angiotensin IV–derived small peptide with exceptional in vitro and in vivo neurotrophic potency, functioning as a high-affinity HGF mimetic that amplifies c-Met signaling. Preclinical data indicate robust synaptogenic, procognitive, and neuroprotective actions in models of Alzheimer’s disease and ototoxic injury.OAE Publishing+5PubMed+5PubMed+5
However, the absence of human clinical data, limited toxicological characterization, and theoretical oncogenic concerns mean that Dihexa should be regarded strictly as an experimental research tool, not as a therapeutic agent or nootropic for human use. Future work must prioritize rigorous safety evaluation, pharmacokinetics, and controlled clinical trials before any translation to clinical practice can be considered.
FOR RESEARCH USE ONLY. NOT FOR HUMAN OR VETERINARY USE. NOT A DRUG, DIETARY SUPPLEMENT, OR MEDICAL TREATMENT.
7. Frequently Asked Questions (FAQ)
1. What is Dihexa?
Dihexa (PNB-0408) is an angiotensin IV–derived small peptide that binds HGF and enhances c-Met signaling, leading to strong synaptogenic and procognitive effects in animal models.PMC+3Wikipedia+3PubMed+3
2. What is the CAS number and basic chemical information?
- CAS: 1401708-83-5
- Formula: C₂₇H₄₄N₄O₅
- Synonyms: N-hexanoic-Tyr-Ile-(6)-aminohexanoic amide, PNB-0408.Pharmaffiliates+3Wikipedia+3MilliporeSigma+3
3. Has Dihexa been tested in humans?
As of late 2025, there are no peer-reviewed human clinical trials on Dihexa’s safety or efficacy. All published work is in vitro or in animal models.American Medical Wellness+4PubMed+4OAE Publishing+4
4. What preclinical benefits have been observed?
Studies report:
- Improved memory and learning in Alzheimer-like mouse models.PubMed+2PubMed+2
- Increased hippocampal spine density and synapse formation.PubMed+2PMC+2
- Protection of sensory hair cells against aminoglycoside ototoxicity via HGF-dependent mechanisms.PMC
These are animal data, not confirmed in humans.
5. How does Dihexa differ from typical nootropics like racetams?
Racetams generally modulate glutamatergic and cholinergic signaling modestly. Dihexa, by contrast, directly potentiates the HGF/c-Met neurotrophic system, inducing robust structural synaptic changes and LTP at extremely low concentrations in preclinical models.OAE Publishing+3PubMed+3PubMed+3
6. Is Dihexa safe?
Short-term animal studies and some patent data report no obvious toxicity, but there is:
- No long-term toxicology
- No carcinogenicity data
- No human safety data
Because c-Met is an oncogene, chronic stimulation may theoretically increase cancer risk; this has not been adequately studied.PubMed+3PubMed+3OAE Publishing+3
7. Is Dihexa approved as a medication or supplement?
No. Dihexa is not approved by the FDA, EMA, or other major regulators as a drug or dietary supplement. It is sold only as a laboratory research reagent.Pharmaffiliates+3MedChem Express+3Achemblock+3
8. Can Dihexa be used by humans as a cognitive enhancer?
No. Any such use would be experimental, unsupported by clinical data, and potentially high-risk. Dihexa is not for human use and should not be self-administered under any circumstances.
FOR RESEARCH USE ONLY – NOT FOR HUMAN OR VETERINARY USE.MedKoo Biosciences+3ApexBio+3MedChem Express+3
9. What are typical research applications?
Current and potential research applications include:
- Mechanistic studies of HGF/c-Met signaling in the CNS
- Preclinical models of Alzheimer’s disease and cognitive impairment
- Synaptogenesis and neuroplasticity research
- Ototoxic injury and hair-cell protection modelsPMC+4PubMed+4PubMed+4
10. Where can I find primary literature on Dihexa?
Key PubMed/PMC entries include:
- Wright JW et al., Prog Neurobiol 2015 – Ang IV analogs including Dihexa (PMID: 25455861).
- Benoist CC et al., J Pharmacol Exp Ther 2014 – Procognitive/synaptogenic actions (PMID: 25187433).
- Kawas LH et al., J Pharmacol Exp Ther 2012 – Ang IV analogs as HGF/Met modulators (PMID: 22129598).
- Sun X et al., Front Pharmacol 2021 – Dihexa rescues cognition in APP/PS1 mice (PMID: 34827486).
- Uribe PM et al., Front Cell Neurosci 2015 – HGF mimetic Dihexa protects hair cells (PMCID: PMC4309183).
