Peptide profile · Cognitive
Dihexa
Angiotensin IV-derived oligopeptide that potentiates hepatocyte growth factor to drive synaptogenesis and cognitive enhancement with extraordinary potency
Written & reviewed by Michael Carroll · Research, Peptide Initiative
Typical dose
8–20 mg
Half-life
~12 days (following IV administration in rats)
Bioavailability
Orally active and blood-brain barrier permeable — specific oral bioavailability percentage not published
Molecular weight
504.7 g/mol
Evidence level
Preclinical only — animal and cell-culture studies; no human trials
01 · Compound profile
Scientific & efficacy data
Molecular formula
C27H44N4O5
Primary benefits
Dihexa is among the most potent procognitive compounds identified in preclinical research, potentiating HGF at picomolar concentrations and driving new synapse formation in the hippocampus. It restored spatial learning in both aged rats and Alzheimer's disease mouse models, demonstrating remarkable memory enhancement via structural neuroplasticity.
Through HGF/c-Met activation, dihexa supports neuronal survival, reduces neuroinflammation, and promotes recovery from neurotoxic insults. It has demonstrated neuroprotective properties including protection of sensory hair cells from aminoglycoside damage and reduction of pro-inflammatory cytokines in Alzheimer's models.
By addressing age-related synaptic loss — a hallmark of cognitive aging — dihexa promotes the formation of new dendritic spines and functional synapses in aged brains, potentially reversing structural deficits that underlie age-related cognitive decline.
Washington State University, Pullman, WA
Amino acid sequence
N-hexanoic-Tyr-Ile-(6) aminohexanoic amide (modified dipeptide)02 · Dosing
How much do I take?
8–20 mg · once daily
Oral: Taken by mouth as a capsule, tablet, or liquid.
Bioavailability Varies by compound — many peptides are largely broken down in the gut, so little reaches the blood intact; some small molecules absorb well.
Best time to take
Take Dihexa at the same time each day for consistent blood levels. Morning dosing with breakfast is often preferred, but follow your healthcare provider's specific instructions.
With food?
Dihexa can typically be taken with or without food. Taking it with a light meal may help reduce any GI discomfort. Avoid taking with grapefruit juice or high-fat meals unless specifically directed.
If stacking
Dihexa should be used as directed by your healthcare provider. If combining with other medications or supplements, discuss potential interactions with your provider. Avoid combining with compounds that have overlapping mechanisms unless specifically guided by a medical professional.
＋ Increase if
- +You have been at the starting dose for 2+ weeks with good tolerance and want enhanced cognitive effects
- +You are not experiencing noticeable cognitive improvements at the current dose after 3-4 weeks
- +You are an experienced nootropic user with established tolerance to neurotropic compounds
－ Decrease if
- −You experience persistent headaches or sleep disturbances
- −You notice excessive emotional sensitivity or mood instability
- −You want to maintain cognitive benefits while minimizing c-Met pathway activation
✓ Signs of right dose
- ✓Improved ease of learning new information and skills
- ✓Enhanced memory recall — both short-term and long-term
- ✓Better verbal fluency and word retrieval
- ✓Vivid but not disruptive dreams (indicating hippocampal engagement)
- ✓Stable mood with improved cognitive performance under stress
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03 · Suitability
Is this right for me?
Best for cognitive enhancement and memory consolidation in age-related decline & supporting neuroplasticity and new synaptic connection formation
Best for
Age-Related Cognitive Decline
Dihexa directly addresses the synaptic loss that underlies age-related cognitive decline by building new functional synaptic connections in the hippocampus. Animal studies demonstrate restored spatial learning in aged rats, making it a compelling candidate for combating memory loss associated with aging.
Neuroplasticity Enhancement
Unlike nootropics that work through neurotransmitter modulation, dihexa drives physical neuroplasticity — the formation of new dendritic spines and synapses. This makes it ideal for individuals looking to enhance their brain's capacity for learning and adaptation at a structural level.
Neurodegenerative Disease Research
Preclinical evidence in APP/PS1 Alzheimer's mice and scopolamine-induced amnesia models positions dihexa as a leading research compound for neurodegenerative disease. It is patented for potential use in Alzheimer's and Parkinson's diseases, with ongoing interest from the research community.
Advanced Nootropic Stacking
Dihexa's unique mechanism (HGF/c-Met potentiation) is complementary to most other nootropic mechanisms, making it an excellent addition to advanced cognitive enhancement protocols when combined with choline donors, racetams, or adaptogens.
Consider alternatives if
Do not use if
Use with caution if
Not sure?
Compare Dihexa with similar peptides to find the best fit for your goals.
04 · Administration
How do I use it?
Oral (capsule/tablet) · Sublingual
Reconstitution — what you need
Example
Dihexa comes in pre-measured doses or forms. Follow the exact dosing instructions on your prescription label. No reconstitution or mixing is typically required for this formulation.
Use Dihexa exactly as prescribed. Each unit contains the labeled amount. Your healthcare provider will determine the appropriate dose based on your individual needs and response.
Route
Dihexa is administered Oral (capsule/tablet)—no injection required
Best sites
Technique
- 01Follow the specific administration instructions for your Dihexa formulation
- 02Take or apply as directed by your healthcare provider
- 03Store properly between uses according to package instructions
Storage · before reconstitution
Store Dihexa in the refrigerator at 36-46°F (2-8°C) in its original packaging. Protect from light and moisture. Do not freeze. Check the expiration date before use. Some formulations may be stored at room temperature for limited periods—check your specific product labeling.
Storage · after reconstitution
Once reconstituted, Dihexa should be kept refrigerated at 36-46°F (2-8°C) and used within the timeframe specified on your product labeling (typically 14-28 days). Label the vial with the reconstitution date. Do not use if the solution appears cloudy, discolored, or contains particles.
Signs of degradation
Sample daily schedule
05 · Safety
Is it safe?
4 common side effects · 2 serious
Dihexa has demonstrated a favorable safety profile in published animal studies, with no reported tumorigenic effects or organ toxicity at cognitive-enhancing doses. However, the compound has not undergone formal human clinical trials, and long-term safety data does not exist. The primary theoretical safety concern is sustained activation of the HGF/c-Met proto-oncogenic pathway, which could theoretically promote tumor initiation or growth. The extremely long half-life (~12 days) raises additional concerns about compound accumulation with chronic daily dosing. Anecdotal reports from the nootropics community generally describe good tolerability at doses of 5-20 mg daily, with headaches and vivid dreams as the most commonly reported effects.
All efficacy and safety data comes from preclinical animal studies and anecdotal user reports. No peer-reviewed human trial data exists. The compound is designated as a research chemical and is not approved for human therapeutic use by any regulatory agency. Individuals considering use should weigh the strong preclinical cognitive enhancement evidence against the complete absence of controlled human safety data and the theoretical oncogenic concerns.
Common side effects · experienced by some users
Less common
These typically resolve with continued use or dose adjustment.
Stop and seek help if
- ×Persistent severe headaches that do not resolve with dose reduction
- ×Significant mood instability or personality changes
- ×Any suspicious lumps, unexplained weight loss, or other potential cancer symptoms
- ×Completion of planned cycle duration (4-6 weeks recommended maximum)
- ×Adverse interaction with other medications or supplements
Dihexa is a research compound with no FDA approval and limited human safety data. All use is at the individual's own risk. The long half-life (~12 days) means effects persist for weeks after discontinuation. Consult a healthcare provider before using any research peptide, and report any concerning symptoms immediately.
With other peptides
- ✓Semax / N-Acetyl Semax — Both enhance cognitive function through different growth factor pathways — Semax via BDNF upregulation, dihexa via HGF/c-Met. Theoretical synergy for cognitive enhancement but combined growth factor stimulation should be approached cautiously.
- ✓Selank / N-Acetyl Selank — Selank provides anxiolytic and mild cognitive benefits through GABAergic modulation, complementing dihexa's synaptogenic mechanism. No overlapping pathways suggest safe combination.
- ✓BPC-157 promotes tissue healing through growth factor modulation including VEGF and FGF. While mechanism differs from dihexa, combining multiple growth factor stimulants warrants caution regarding oncogenic risk.
With medications
- !ACE inhibitors / ARBs — Dihexa is derived from the renin-angiotensin system (angiotensin IV). ACE inhibitors and angiotensin receptor blockers may alter the balance of RAS peptides and potentially interact with dihexa's mechanism. Use with caution and monitor blood pressure.
- ✓Cholinesterase inhibitors (donepezil, rivastigmine) — Theoretical complementary mechanisms — cholinesterase inhibitors increase acetylcholine while dihexa builds new synapses. No known direct interactions, but combined cognitive enhancement should be medically supervised.
- !Immunosuppressants — c-Met signaling plays roles in immune function and tissue repair. Immunosuppressive therapy may alter the downstream effects of HGF/c-Met activation by dihexa.
With supplements
- ✓Alpha-GPC / Citicoline — Provides choline substrate for acetylcholine synthesis at the new synaptic connections formed by dihexa. Highly recommended complementary supplement to support new synapse function.
- ✓Lion's Mane mushroom — Stimulates nerve growth factor (NGF), complementing dihexa's HGF potentiation. Dual growth factor support may enhance overall neuroplasticity. Safe to combine.
- ✓Omega-3 fatty acids (DHA/EPA) — DHA is a critical structural component of neuronal membranes and new dendritic spines. Supplementation provides building blocks for the new synaptic structures dihexa promotes.
- ✓Racetams (piracetam, aniracetam) — Racetams modulate glutamate receptors and enhance synaptic plasticity through different mechanisms. Complementary to dihexa's structural synaptogenesis. Safe to combine with adequate choline support.
06 · Effectiveness
How do I know it's working?
Preclinical only — animal and cell-culture studies; no human trials · first signs week 1-2
Evidence level
Preclinical only — animal and cell-culture studies; no human trials
How it works
Dihexa is a synthetic, brain-penetrating peptide derived from angiotensin IV, studied in animals for learning and memory. The mechanism it became known for — amplifying a growth factor called HGF at its receptor to help neurons build new connections — traces back to research retracted in April 2025, after investigators concluded the underlying data had been fabricated [1]. That explanation is no longer supported and no independent study has reproduced it. Separate animal research does still report improved memory and reduced brain inflammation in a mouse model of Alzheimer's disease [4]. Dihexa has never been tested in a human clinical trial.
Dihexa (N-hexanoic-Tyr-Ile-(6) aminohexanoic amide, PNB-0408) is a metabolically stabilized angiotensin IV analog developed as an orally active, brain-penetrant candidate for cognitive impairment. Its widely repeated mechanism — allosteric potentiation of hepatocyte growth factor (HGF) at the c-Met receptor tyrosine kinase, including the picomolar binding affinity often quoted for it — originates in work retracted in April 2025 after a Washington State University investigation found falsified and fabricated data [1]. That HGF/c-Met dependency has not been independently replicated. Affinity and dimerization figures traceable to those publications should not be treated as established, and are omitted here rather than repeated. What survives from independent research is observational rather than mechanistic. In the APP/PS1 transgenic mouse model of Alzheimer's disease, dihexa rescued cognitive impairment and recovered memory performance, reduced activated astrocytes (GFAP) and microglia (Iba-1), lowered the pro-inflammatory cytokines IL-1beta and TNF-alpha, and raised anti-inflammatory IL-10, with signaling changes consistent with PI3K/AKT-dependent regulation of NF-kappaB [4]. A systematic review of experimental studies covering angiotensin IV and angiotensin-(1-7) reported consistent procognitive signals across animal models for this compound class [5]. Dihexa has never been given in a registered human clinical trial. There is no human pharmacokinetic, dose-response, safety, or efficacy data of any kind. The compound's metabolic stability is attributed to its N-hexanoic acyl group and C-terminal aminohexanoic amide, which resist aminopeptidase and carboxypeptidase degradation respectively; specific half-life values in circulation come from preclinical work and vary between reports.
What to expect
Week 1-2
What you might notice
- •Subtle improvements in mental clarity and focus beginning within days
- •Increased dream vividness as hippocampal activity increases
- •Mild headaches or fatigue during the initial adjustment period
- •Plasma levels building toward steady state (given ~12-day half-life)
What's normal
- •No dramatic cognitive changes in the first few days — synaptogenesis is a structural process that takes time
- •Mild side effects like headache or vivid dreams are normal indicators of neural activity
- •The compound is actively building toward effective brain concentrations
What's next
- →Continue consistent daily dosing — steady-state levels are still accumulating
- →The neural growth processes dihexa initiates take weeks to produce measurable cognitive benefits
- →Focus on supporting brain health with adequate sleep, nutrition, and cognitive engagement
Week 2-4
What you might notice
- •Improved ability to learn new information and consolidate memories
- •Enhanced spatial reasoning and pattern recognition
- •Greater ease in retrieving previously learned information
- •Improved conversational fluency and word recall
- •More vivid and emotionally rich experiences
What's normal
- •Cognitive improvements are gradual and cumulative — new synaptic connections are forming
- •Benefits may be more apparent during cognitively demanding tasks
- •Initial side effects (headache, fatigue) should be resolving by now
What's next
- →This is the period where the most noticeable cognitive improvements typically emerge
- →Engage in challenging cognitive activities to take advantage of enhanced neuroplasticity
- →Assess whether current dose is providing satisfactory benefits or needs adjustment
Week 4-6+
What you might notice
- •Sustained cognitive enhancement reflecting established new synaptic connections
- •Improved long-term memory formation and retrieval
- •Enhanced cognitive resilience under stress or fatigue
- •Benefits that may persist after discontinuation due to structural synaptic changes
What's normal
- •Cognitive benefits should be stable and sustained at this point
- •The structural nature of dihexa's effects means some benefits persist after stopping
- •The long half-life means the compound clears slowly — effects taper gradually
What's next
- →Consider cycling off after 4-6 weeks to assess baseline and allow the c-Met pathway to normalize
- →Benefits from new synaptic connections may persist for weeks to months after discontinuation
- →Plan next cycle if desired, with at least 2-4 weeks off between cycles
Signs it's working · Cognitive performance
- ✓Easier acquisition of new information and skills
- ✓Improved recall of names, facts, and details
- ✓Enhanced verbal fluency and conversational ease
- ✓Better spatial reasoning and navigation
- ✓Improved working memory capacity
Signs it's working · Neuroplasticity indicators
- ✓Vivid dreams (indicating active hippocampal remodeling)
- ✓Increased creativity or novel problem-solving approaches
- ✓Faster adaptation to new routines or environments
- ✓Enhanced ability to form and maintain new habits
Not seeing results? Common reasons
- •Insufficient time on compound — synaptogenesis is a structural process requiring weeks, not days
- •Dose too low — given inter-individual variation in absorption and metabolism, some may need to increase from starting dose
- •Lack of cognitive engagement — new synapses require activity-dependent consolidation (use it or lose it)
- •Inadequate choline intake — newly formed synapses need acetylcholine to function, requiring sufficient choline precursors
- •Expectations of immediate acute effects — dihexa does not provide stimulant-like cognitive boost but rather gradual structural enhancement
Key research
07 · Questions
Frequently asked
What makes dihexa different from other nootropics?+
Most nootropics work by modulating neurotransmitter levels — increasing acetylcholine, dopamine, or glutamate activity at existing synapses. Dihexa is fundamentally different because it drives the physical construction of new synaptic connections (synaptogenesis) through HGF/c-Met pathway activation. This means dihexa creates new neural infrastructure rather than simply optimizing existing circuits. It is also extraordinarily potent, binding HGF at picomolar concentrations — described as being effective at doses 10 million times lower than other cognitive enhancers.
Has dihexa been tested in humans?+
No, as of 2025, dihexa has not completed formal human clinical trials. All published efficacy data comes from animal studies, primarily in rats and mice. These include studies in aged rats with natural cognitive decline, scopolamine-induced amnesia models, and APP/PS1 transgenic Alzheimer's disease mice. The compound has been patented for potential human therapeutic use in Alzheimer's and Parkinson's diseases, but the development path to human trials has not been completed. User reports from the nootropics community provide anecdotal human experience data.
Is there a cancer risk from using dihexa?+
This is the most significant theoretical concern with dihexa. The HGF/c-Met pathway it activates is a well-known proto-oncogenic signaling axis — aberrant c-Met activation is implicated in various cancers including hepatocellular carcinoma, gastric cancer, and non-small cell lung cancer. However, no tumorigenic effects have been observed in published animal studies. The concern remains theoretical but scientifically grounded. Individuals with active cancer, cancer history, or strong family cancer history should avoid this compound. Cycling protocols with off-periods are recommended to limit sustained pathway activation.
Why does dihexa have such a long half-life?+
Dihexa was specifically engineered for metabolic stability — a key improvement over native angiotensin IV, which is rapidly degraded by aminopeptidases. The N-hexanoic modification and (6) aminohexanoic amide C-terminal protect against enzymatic degradation, resulting in a circulating half-life of approximately 12 days following IV administration. This long half-life means the compound accumulates significantly with daily dosing and effects persist for days to weeks after discontinuation. This is both an advantage (consistent brain exposure) and a consideration (potential for accumulation-related effects).
What is the best way to take dihexa?+
Oral administration in capsule or tablet form is the most practical and well-studied route. Dihexa was specifically designed to be orally active and blood-brain barrier permeable — these were the two key pharmacological goals its developers aimed to achieve. Sublingual administration is an alternative that may provide faster onset. Transdermal application in DMSO has been used by some researchers but is less practical for regular use. Take in the morning with or without food, and consider cycling protocols given the long half-life.
How long do the effects of dihexa last after stopping?+
Because dihexa works through structural changes — building new dendritic spines and synaptic connections — its benefits can persist well beyond the duration of active dosing. The new synapses formed during treatment don't disappear immediately when the compound is discontinued. Additionally, the extremely long half-life (~12 days) means the compound itself remains in circulation for weeks after the last dose. Users often report sustained cognitive benefits for weeks to months after completing a cycle, though the magnitude may gradually diminish as some newly formed synapses are pruned through normal brain maintenance processes.
Can dihexa help with Alzheimer's disease?+
In preclinical models, dihexa has shown remarkable efficacy in restoring cognitive function in Alzheimer's disease mouse models (APP/PS1 mice). It reduced amyloid-associated neuroinflammation, protected neurons from apoptosis, and restored spatial learning via the PI3K/AKT pathway. However, these results are from animal studies only — no human Alzheimer's trials have been conducted. The compound is patented for potential Alzheimer's treatment, and the developers at Washington State University consider it a promising candidate, but it remains an investigational compound.
08 · Further reading
History & related research
History · since 2012
A tiny peptide that rewires the brain by binding hepatocyte growth factor with extreme precision.
Dihexa is an orally active, blood-brain barrier permeable peptide that potentiates hepatocyte growth factor signaling. Derived from angiotensin IV, this compound promotes hippocampal synaptogenesis and spinogenesis with remarkable potency—roughly 10 million times more effective than BDNF at building new synapses.
Read the full history of Dihexa