Overview
Dihexa (N-hexanoic-Tyr-Ile-(6)-aminohexanoic amide) is a synthetic oligopeptide derived from angiotensin IV that was developed by Dr. Joseph Harding and colleagues at Washington State University. It is one of the most potent cognitive-enhancing compounds ever identified in preclinical research, demonstrating synaptogenic (synapse-forming) activity at concentrations seven orders of magnitude more potent than brain-derived neurotrophic factor (BDNF).
Dihexa's mechanism centers on its ability to activate the hepatocyte growth factor (HGF)/c-Met receptor signaling system, a pathway critical for neuronal survival, dendritic arborization, and the formation of new synaptic connections. By potentiating HGF/c-Met signaling, Dihexa promotes the creation of new synapses between neurons—a process fundamental to learning, memory formation, and cognitive recovery after injury.
In animal studies, Dihexa has restored cognitive function in models of Alzheimer's disease, scopolamine-induced amnesia, and aging-related cognitive decline. Its potency is remarkable: effective doses in rats are in the low picomolar range, making it approximately 10 million times more potent than BDNF on a molar basis for promoting synaptic connectivity.
Despite these extraordinary preclinical results, Dihexa has not progressed to human clinical trials and remains a research compound. Its potency, while impressive, also raises safety questions about uncontrolled synaptic growth, and the compound has not undergone the toxicological evaluation required for human use.
Quick facts
- Mechanism
- HGF/c-Met activator promoting synaptogenesis at picomolar doses
- Primary use
- Cognitive Enhancement & Synaptogenesis
- Evidence
- limited
- FDA
- Not approved
- Route
- Subcutaneous injection, intranasal, or topical (research)
- Typical results
- Dramatic cognitive enhancement in animal models at picomolar concentrations
Chemical information
Dihexa (C₂₇H₄₄N₄O₅) is a nootropic compound with a molecular weight of 504.67 g/mol. Its structural characteristics underpin its biological activity in cognitive enhancement and neuroprotection.
How Dihexa works
Dihexa acts as a potent allosteric activator of the hepatocyte growth factor (HGF)/c-Met receptor tyrosine kinase system. Rather than directly binding c-Met, Dihexa stabilizes and potentiates the interaction between HGF and its receptor, dramatically amplifying downstream signaling cascades that promote neuronal survival, neurite outgrowth, and—most significantly—the formation of new functional synapses between neurons.
The HGF/c-Met system plays essential roles in brain development and adult neuroplasticity. When activated, c-Met triggers the PI3K/Akt and Ras/MAPK signaling cascades, promoting dendritic spine formation, axonal growth, and the expression of synaptic scaffolding proteins (PSD-95, synaptophysin) necessary for functional synaptic connections. Dihexa amplifies this natural process rather than creating an artificial signal.
Dihexa's synaptogenic activity has been demonstrated in hippocampal neuron cultures, where it increases dendritic spine density and promotes the formation of new glutamatergic synapses. These structural changes correlate with enhanced long-term potentiation (LTP)—the cellular mechanism underlying memory consolidation—explaining Dihexa's dramatic effects on learning and memory in animal models.
Importantly, Dihexa is resistant to the enzymatic degradation (aminopeptidases) that rapidly inactivates endogenous angiotensin IV and other peptides in the brain. The hexanoic acid modification on both termini provides metabolic stability, allowing sustained receptor interaction despite the compound's extremely low effective concentrations.
- HGF/c-Met potentiation: Amplifies hepatocyte growth factor signaling for synapse formation
- Picomolar potency: Active at 10⁻¹² M, approximately 10 million times more potent than BDNF
- Synaptogenesis: Directly promotes formation of new functional synapses between neurons
- Dendritic spine density: Increases PSD-95 and synaptophysin expression for structural connectivity
- LTP enhancement: Strengthens long-term potentiation, the cellular basis of memory
- Metabolic stability: Hexanoic acid modifications resist peptidase degradation
Pharmacokinetics
| Parameter | Value | Significance |
|---|---|---|
| Effective dose (animal) | 0.01–1 nmol/kg | Extraordinarily low effective doses |
| Stability | Peptidase-resistant | Hexanoic acid caps prevent enzymatic degradation |
| CNS penetration | Yes (intranasal and systemic) | Crosses blood-brain barrier effectively |
| Molecular weight | 504.67 g/mol | Small molecule peptide with good tissue distribution |
| Duration of effect | Unknown in humans | Animal studies suggest sustained cognitive effects |
Dosing & administration
Dihexa dosing varies by indication and individual factors. No FDA-approved dosing exists for this compound; protocols in the literature derive from limited clinical or preclinical data and practitioner experience.
Any use should be conducted under qualified medical supervision with appropriate monitoring of safety markers.
Important: These dosing ranges are not FDA-approved. Any use should be under qualified medical supervision.
Side effects & safety
Safety data for Dihexa is primarily derived from preclinical studies and limited human data. Long-term effects in humans remain incompletely characterized.
Common
- • Limited human safety data available
- • Injection site irritation (reported anecdotally)
- • Mild headache
- • Vivid dreams or altered sleep patterns
- • Temporary cognitive overstimulation
Serious / potential risks
- • No formal toxicology studies in humans
- • Theoretical risk of uncontrolled synaptic growth or neural network disruption
- • HGF/c-Met pathway activation is implicated in some cancers
- • Unknown long-term effects on brain architecture
- • Risk of contamination from unregulated sources
Drug interactions
| Medication | Interaction | Recommendation |
|---|---|---|
| Other nootropics (racetams, modafinil) | Potential additive cognitive effects through different pathways | Caution with stacking; effects at picomolar doses suggest potent activity |
| Anti-cancer therapies targeting c-Met | Directly opposing mechanisms on HGF/c-Met pathway | Contraindicated; do not combine with c-Met inhibitors or in cancer patients |
| Cholinesterase inhibitors (donepezil) | Both target cognitive function through different mechanisms | Theoretical synergy for dementia; no clinical data on combination |
| ACE inhibitors / ARBs | Dihexa is derived from angiotensin system; potential pathway interactions | Unlikely clinical interaction at picomolar doses, but monitor |
Storage & handling
Lyophilized (powder)
- • Store at -20°C to 4°C (freezer or refrigerator)
- • Protect from light and moisture
- • Stable for 12–24 months when stored properly
- • Keep in original sealed container until reconstitution
Reconstituted solution
- • Refrigerate at 2–8°C after reconstitution
- • Use bacteriostatic water for multi-dose reconstitution
- • Typical stability: 14–28 days refrigerated
- • Do not freeze reconstituted solution
Cost & availability
| Source | Cost | Notes |
|---|---|---|
| Research peptide suppliers | $50–$100 per 10mg vial | Extremely potent; 10mg provides many research doses |
| Custom synthesis | $200–$500 | Available from peptide synthesis services with purity certification |
The bottom line
Dihexa is arguably the most potent cognitive-enhancing compound identified in preclinical research, with synaptogenic activity millions of times more potent than BDNF. However, it remains entirely investigational with no human clinical trials, no toxicological evaluation, and legitimate safety concerns about uncontrolled synaptic growth and c-Met pathway activation in cancer biology.
Best for
- • Neuroscience researchers studying synaptogenesis and HGF/c-Met signaling
- • Preclinical investigation of cognitive enhancement mechanisms
- • Academic research into Alzheimer's disease therapeutic targets
Not for
- • Human self-experimentation without medical oversight
- • Individuals with any history of cancer (c-Met involvement)
- • Those seeking well-characterized, safety-tested nootropics
- • Pregnant or breastfeeding individuals
Related compounds
Frequently asked questions
References
- [1] McCoy AT, Benoist CC, Wright JW, et al.. Evaluation of metabolically stabilized angiotensin IV analogs as procognitive/antidementia agents. J Pharmacol Exp Ther (2013). doi: 10.1124/jpet.113.203091 PMID: 23535251
- [2] Benoist CC, Kawas LH, Zhu M, et al.. The procognitive and synaptogenic effects of angiotensin IV-derived peptides are dependent on activation of the hepatocyte growth factor/c-Met system. J Pharmacol Exp Ther (2014). doi: 10.1124/jpet.114.218735 PMID: 25271257
- [3] Wright JW, Kawas LH, Harding JW.. A Role for the Brain RAS in Alzheimer's and Parkinson's Diseases. Front Endocrinol (2013). doi: 10.3389/fendo.2013.00158 PMID: 24194732
- [4] Kawas LH, McCoy AT, Yamamoto BJ, et al.. Development and characterization of novel HGF/c-Met activators as cognitive enhancers. Neuropharmacology (2012). doi: 10.1016/j.neuropharm.2011.10.016
- [5] Harding JW, Wright JW.. Angiotensin IV-mediated cognition and dementia. Curr Opin Pharmacol (2011).