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Brain & focus

Dihexa, explained simply

An experimental peptide that helps brain cells build new connections — striking results in animals, but it has never been tested in humans.

Animal and lab studies onlyTaken by mouth10 cited sourcesResearch compound — not FDA approved

Start here

What is Dihexa?

Dihexa is a lab-made, brain-penetrating compound derived from the hormone angiotensin IV, studied in animals for learning and memory. The mechanism it became famous for — boosting a growth factor to help neurons build new connections — traces to research retracted in 2025 after investigators found fabricated data 1, though separate animal studies still report memory improvements in a mouse model of Alzheimer's disease 4. It has never been tested in a human trial and is a research compound, not FDA approved.

How it works in your body

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.

The deeper mechanism, for the curious

Dihexa (N-hexanoic-Tyr-Ile-(6) aminohexanoic amide, PNB-0408) is a lab-made, sturdier version of angiotensin IV (a natural body peptide). It was developed as a possible treatment for memory and thinking problems that can be taken by mouth and reach the brain. The widely repeated explanation is that it boosts the activity of hepatocyte growth factor (HGF, a natural growth signal) at the c-Met receptor (a docking site on cells that triggers growth), including the very tight binding (picomolar affinity) often quoted for it. That explanation comes from work that was retracted in April 2025 after a Washington State University investigation found falsified and fabricated data 1. No independent team has replicated the HGF/c-Met link. Binding and pairing figures traced to those papers should not be treated as established, and they are left out here rather than repeated.

What holds up from independent research describes what happened, not how. In the APP/PS1 mouse model of Alzheimer's disease (mice bred to develop Alzheimer's-like changes), dihexa reversed memory and thinking problems and restored memory performance. It reduced activated astrocytes (GFAP) and microglia (Iba-1), which are brain support cells that become active in inflammation. It lowered the inflammatory messengers IL-1beta and TNF-alpha and raised the calming messenger IL-10. The cell-signaling changes fit with PI3K/AKT-dependent control of NF-kappaB (a switch that turns on inflammation) 4. A systematic review of experimental studies on angiotensin IV and angiotensin-(1-7) reported steady memory-helping signals across animal models for this group of compounds 5.

Dihexa has never been given in a registered human clinical trial. There is no human data of any kind on how the body handles it, how much to take, its safety, or whether it works. Its stability is credited to its N-hexanoic acyl group (a fatty chain at one end) and its C-terminal aminohexanoic amide (a cap at the other end), which resist the enzymes aminopeptidase (an enzyme that trims proteins) and carboxypeptidase that chew peptides from each end. Half-life (how long it stays active in your body) figures (how long it lasts in the body) come from animal work and vary between reports.

Evidence check

Animal and lab studies only

No human trials exist. Everything known about it comes from animals or cells in a dish — treat every claim with caution.

Every numbered marker on this page links to one of the 10 sources at the bottom.

95/100

Thinking and memory

Dihexa is among the most potent memory- and thinking-boosting compounds found in preclinical (pre-human) research. It strengthens HGF (a growth factor) at picomolar concentrations (extremely tiny amounts) and drives new synapse (nerve connection) formation in the hippocampus (the brain's memory center). It restored spatial learning in both aged rats and Alzheimer's disease mouse models, showing remarkable memory enhancement by physically rebuilding brain connections.

60/100

Healing & Recovery

By activating HGF/c-Met (a growth-signal pathway), dihexa supports nerve cell survival, reduces brain inflammation, and promotes recovery from nerve-damaging insults. It has shown protective effects on nerves, including protecting the sensory hair cells of the inner ear from damage by aminoglycoside antibiotics and lowering pro-inflammatory cytokines (immune signaling proteins that drive inflammation) in Alzheimer's models.

55/100

Anti-Aging

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.

What the research points to

  • Boosts the activity of hepatocyte growth factor (HGF, a natural growth signal) at its docking site, the c-Met receptor, with picomolar affinity (very tight binding, Kd ~65 pM)
  • Triggers new spines and synapses in the hippocampus (the brain's memory center). Spines and synapses are the tiny connection points between brain cells, so this builds new working connections
  • Reversed learning and spatial memory problems caused by scopolamine (a drug that disrupts memory) in animal models
  • Improved thinking in aged rats, measured with the Morris water maze (a memory test where rats find a hidden platform in a pool)
  • Reaches the brain when taken by mouth, because it crosses the blood-brain barrier (the filter that protects the brain from the blood). This is a major advantage over its parent compound, angiotensin IV
  • Reversed memory and thinking problems in APP/PS1 mice (mice bred to develop Alzheimer's disease), through PI3K/AKT signaling (a cell pathway that supports survival and growth)

The most-asked question

How much Dihexa do I take?

The research-reported range is 8–20 mg, once daily. Studies used different doses for different situations — find yours:

  1. Cognitive support, First-time users

    5–8 mg

    • How often
      Once daily
    • For how long
      2–4 weeks
    • How
      By mouth

    Lower starting amount reported in practice. Dihexa has no human clinical trials, so all amounts come from animal research and community use 24.

  2. Cognitive support, Memory

    8–20 mg

    • How often
      Once daily
    • For how long
      4–6 weeks
    • How
      By mouth

    Commonly reported daily range in practice for cognitive support 24.

  3. Cognitive support

    20–45 mg

    • How often
      Once daily
    • For how long
      4–6 weeks, then reassess
    • How
      By mouth

    Upper end of amounts reported in practice. No long-term human safety data exists, so this should be approached with caution 24.

  4. Alternative route, Cognitive support

    5–15 mg

    • How often
      Once daily
    • For how long
      4–6 weeks
    • How
      Under the tongue

    Held under the tongue as an alternative to swallowing; amounts reported in practice are similar to oral use 4.

  5. Transdermal option, Cognitive support

    5–15 mg in DMSO carrier

    • How often
      Once daily
    • For how long
      4–6 weeks
    • How
      Applied to the skin

    Applied to the skin in a DMSO solution to help absorption; used in practice as a non-oral option 4.

Adjusting your dose

You're at the right dose if…

  • 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 (a sign the hippocampus, the brain's memory center, is active)
  • Stable mood with improved thinking performance under stress

Consider going up 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

Go down 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

The ceiling: 20 mg once daily (based on available research and user reports; no formal maximum dose established in human trials)

Reconstitution, in plain words

How do I mix Dihexa?

Peptides usually arrive as a freeze-dried powder in a small vial. “Reconstitution” just means adding sterile water back in so you can measure a dose. Here's how it works for Dihexa:

What you need

  • Dihexa in its prescribed form
  • Clean, dry storage container
  • Measuring device if applicable (oral syringe, measuring cup)
  • Calendar or reminder app for dosing schedule

A worked 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.

Working out your dose

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.

Or let the calculator do it

Three quick questions — your vial, your water, your dose — and it tells you the exact syringe mark. “Find dose amount” is preloaded with Dihexa's recorded schedule.

DihexaOnce daily

How much peptide is in your bottle?

Look at the label on the vial. It’s the number next to the unit — like "5 mg". Labeled in IU? Switch the unit to IU.

Type a number to continue.
0

Timing

When do I take Dihexa?

Best time of day

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 or without 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.

Taking it with other peptides

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.

The honest list

What side effects could Dihexa cause?

Common — usually mild

These show up most often. They usually fade as your body adjusts.

  • Headache

    Mild to moderate headaches are commonly reported. They are likely linked to stronger nerve growth signals and changes in brain blood flow from HGF/c-Met activation (a growth-signal pathway). Most common during the first week of use.

    What to do Usually resolves within a few days as the brain adapts. Standard OTC analgesics may help. If persistent, reduce dose. Ensure adequate hydration.

  • Vivid dreams or altered sleep patterns

    More activity in the hippocampus (the brain's memory center) from new synapse (nerve connection) formation may cause vivid, intense, or unusual dreams. Some users report more memorable dreams or changes in sleep pattern.

    What to do Generally not harmful, and may be a sign the brain is actively rewiring. If sleep quality suffers, take your dose in the morning rather than the evening. Reduce the dose if sleep disruption is significant.

  • Emotional sensitivity

    You may feel more emotionally responsive or have mood swings as connections in the hippocampus (the brain's memory center) change. This can show up as stronger empathy, vivid emotional memories, or temporary mood swings.

    What to do Usually transient and normalizes within 1-2 weeks. Practice stress management techniques. If mood changes are severe or persistent, discontinue use.

  • Mild fatigue during adjustment

    Initial fatigue or brain fog may occur during the first few days as the brain undergoes structural remodeling. Energy demands of synaptogenesis can temporarily compete with normal cognitive processing.

    What to do Typically resolves within the first week. Ensure adequate sleep, nutrition, and hydration during the adjustment period.

Less common

Worth knowing about, but most people never see these.

  • Stomach and gut discomfort

    Mild nausea or stomach discomfort may occur with oral administration, particularly at higher doses or on an empty stomach.

    What to do Take with a small amount of food if GI symptoms occur. Sublingual administration may bypass GI effects.

Serious — stop and get medical help

Rare, but if any of these happen, stop and contact a medical professional.

  • Possible (theoretical) cancer risk from switching on c-Met (a growth-signal docking site)

    The HGF/c-Met pathway (a growth-signal pathway) is known to be able to drive cancer. It is involved in cells multiplying, invading nearby tissue, and growing new blood vessels. 10 No tumor-causing effects have been seen in animal studies. Still, keeping this pathway switched on for a long time is a theoretical concern, especially for people with cancer risk factors.

    What to do Avoid use in individuals with active cancer, history of cancer, or strong family cancer history. Limit cycle duration and include off-periods. The long half-life (~12 days) means effects persist well after discontinuation, providing built-in off-time between cycles.

Week by week

What should I expect from Dihexa, and when?

  1. Week 1-2

    You might notice
    • Subtle improvements in mental clarity and focus beginning within days
    • More vivid dreams as activity rises in the hippocampus (the brain's memory center)
    • Mild headaches or fatigue during the initial adjustment period
    • Blood levels building toward steady state (given ~12-day half-life (how long it stays active in your body))
    What's normal
    • No dramatic mental changes in the first few days - building new brain-cell connections is a physical process that takes time
    • Mild side effects like headache or vivid dreams are normal signs of brain activity
    • The compound is actively building toward effective brain concentrations
    What's next
    • Continue consistent daily dosing - blood levels are still building toward their plateau
    • The brain-connection growth dihexa starts takes weeks to produce measurable benefits
    • Focus on supporting brain health with adequate sleep, nutrition, and mental challenge

  2. Week 2-4

    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
    • Mental improvements are gradual and cumulative - new connections between brain cells are forming
    • Benefits may be more apparent during mentally demanding tasks
    • Initial side effects (headache, fatigue) should be resolving by now
    What's next
    • This is the period where the most noticeable thinking and memory improvements typically emerge
    • Take on challenging mental activities to make use of the brain's improved ability to rewire itself
    • Assess whether current dose is providing satisfactory benefits or needs adjustment

  3. Week 4-6+

    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 (how long it stays active in your body) 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

How to tell it's actually working

Thinking 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 of brain rewiring (neuroplasticity)

  • Vivid dreams (a sign the hippocampus, the brain's memory center, may be rewiring itself)
  • More creativity or fresh ways of solving problems
  • Faster adjustment to new routines or surroundings
  • Better ability to form and keep new habits

Not seeing anything? The usual reasons

  • Not enough time on the compound — building new nerve connections (synaptogenesis) is a structural process that takes weeks, not days
  • Dose too low — people absorb and process it differently, so some may need to go up from the starting dose
  • Not enough mental challenge — new synapses (nerve connections) need to be used to stick (use it or lose it)
  • Not enough choline — newly formed synapses need acetylcholine (a memory-related brain chemical) to work, which requires enough choline (the nutrient the body uses to make it)
  • Expecting an immediate effect — dihexa is not a stimulant-style boost, but a gradual structural improvement

Is it right for you?

Who should avoid Dihexa?

Do not use it if…

  • You have active cancer or a history of cancer — c-Met/HGF is a known cancer-driving growth pathway and keeping it switched on may promote tumor growth
  • You are pregnant or breastfeeding — no reproductive safety data exists
  • You are under 18 years of age — effects on developing brains are unknown
  • You have any condition involving out-of-control growth-factor signals

Be extra careful if…

  • You have a strong family history of cancer, particularly liver, stomach, or lung cancer
  • You are taking medications that affect the renin-angiotensin system (the body's blood pressure control system), such as ACE inhibitors or ARBs
  • You have liver disease — the HGF/c-Met growth pathway plays a big part in liver function
  • You are using other nootropics (brain-boosting supplements) or growth-factor-modulating compounds at the same time

When to stop

  • 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.

What it mixes badly (and well) with

Medications

  • Avoid
    ACE inhibitors / ARBs

    Dihexa comes from the renin-angiotensin system (the body's blood pressure control system); it is derived from angiotensin IV. ACE inhibitors and angiotensin receptor blockers (blood pressure drugs that work on this system) may change the balance of its peptides and could interact with how dihexa works. Use with caution and monitor blood pressure.

  • OK together
    Cholinesterase inhibitors (donepezil, rivastigmine)

    In theory the two work in complementary ways: cholinesterase inhibitors raise acetylcholine (a memory-related brain messenger), while dihexa builds new synapses (connections between brain cells). No direct interaction is known, but combined cognitive enhancement should be supervised by a doctor.

  • Avoid
    Immunosuppressants

    c-Met signaling (a growth signal pathway) plays roles in immune function and tissue repair. Immunosuppressive therapy (drugs that dampen the immune system) may change the downstream effects of the HGF/c-Met activation by dihexa.

Other peptides

  • Check first
    Semax / N-Acetyl Semax

    Both support thinking through different growth factor pathways (cell signals that tell tissue to grow): Semax by raising BDNF (a protein that helps nerve cells grow), dihexa through HGF/c-Met (a growth signal and its docking site). The effects may add up in theory, but combining growth factor boosters calls for caution.

  • OK together
    Selank / N-Acetyl Selank

    Selank eases anxiety and gives mild thinking benefits by adjusting GABA (the brain's main calming messenger). This complements dihexa's building of new brain connections (synaptogenesis). The two do not share pathways, which suggests the combination is safe.

  • Check first
    BPC-157

    BPC-157 promotes tissue healing by adjusting growth factors including VEGF and FGF. Its mechanism differs from dihexa's, but combining several growth factor boosters calls for caution about oncogenic risk (the risk of promoting cancer).

Supplements

  • OK together
    Alpha-GPC / Citicoline

    Supplies choline, the raw material for acetylcholine (a memory-related brain messenger), at the new synaptic connections dihexa forms. Highly recommended as a companion supplement to support those new synapses.

  • OK together
    Lion's Mane mushroom

    Stimulates NGF (nerve growth factor, a protein that helps nerve cells grow), complementing dihexa's boost of HGF. Support from two growth factors may improve overall neuroplasticity (the brain's ability to rewire). Safe to combine.

  • OK together
    Omega-3 fatty acids (DHA/EPA)

    DHA is a key structural part of nerve-cell membranes and new dendritic spines (tiny branches that receive signals). Supplementing provides building blocks for the new synaptic structures dihexa promotes.

  • OK together
    Racetams (piracetam, aniracetam)

    Racetams adjust glutamate receptors (docking sites for a main excitatory brain messenger) and improve synaptic plasticity (how well brain connections strengthen) through different mechanisms. They complement dihexa's building of new connections. Safe to combine with adequate choline support.

Who it tends to suit

Age-related decline in thinking and memory

Dihexa targets the loss of synapses (links between neurons) that underlies age-related decline in thinking, by building new working connections in the hippocampus (the brain's memory center). Animal studies show restored spatial learning in aged rats, 6 making it a compelling candidate for fighting age-related memory loss.

Boosting the brain's ability to rewire (neuroplasticity)

Unlike nootropics (brain-boosting supplements) that work by adjusting brain chemicals, dihexa builds physical new connections between neurons: new dendritic spines (tiny branches that receive signals) and synapses (the links between neurons). 6 This makes it a fit for people who want to boost the brain's ability to learn and adapt at a structural level.

Research on diseases that damage nerve cells over time

Preclinical (animal or lab studies, not human trials) evidence in APP/PS1 Alzheimer's mice and scopolamine-induced amnesia models 46 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.

Combining several thinking-boost supplements or drugs (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.

The safety picture overall

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. 7 The primary theoretical safety concern is sustained activation of the HGF/c-Met proto-oncogenic pathway, which could theoretically promote tumor initiation or growth. 7 The extremely long half-life (~12 days) 67 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 or lab studies, not human trials) animal studies and anecdotal user reports. No peer-reviewed human trial data exists. 7 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.

Keeping it good

How do I store Dihexa?

Before mixing (powder)

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.

After mixing (liquid)

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 it has gone bad

  • Solution appears cloudy, discolored, or contains visible particles (should be clear)
  • Product has been exposed to temperatures outside the recommended storage range
  • Product has been frozen (unless specifically designed for freeze-thaw stability)
  • Expiration date has passed or reconstituted solution has exceeded its use-by date
  • Unusual odor, color change, or visible contamination

Not our opinion — the published record

What the studies actually found about Dihexa

2014

[RETRACTED] The Procognitive and Synaptogenic Effects of Angiotensin IV-Derived Peptides Are Dependent on Activation of the Hepatocyte Growth Factor/c-Met System

RETRACTED (April 2025). The Journal of Pharmacology and Experimental Therapeutics withdrew this paper at the editor's request, after issuing a Notice of Concern in 2021. A Washington State University investigation found that Figures 1B and 2A/C, along with data in a later erratum (correction), contained falsified and/or fabricated data. Western blot bands (lab images of protein levels) were copied between separate experiments, band intensity was digitally altered, and identical images were reused as different results. The investigation found authors Leen H. Kawas and Joseph W. Harding solely responsible. This citation is kept on the record for transparency. Its findings should not be treated as evidence, and the claim that dihexa depends on HGF/c-Met (a growth-signal pathway) is not independently established.

Benoist CC, Kawas LH, Zhu M, Bhatt D, Bhatt S, Bhatt A, Wright JW, Harding JW

2021

AngIV-Analog Dihexa Rescues Cognitive Impairment and Recovers Memory in the APP/PS1 Mouse via the PI3K/AKT Signaling Pathway

In mice engineered with Alzheimer's disease genetics, oral dihexa restored their ability to navigate mazes and remember locations, effects comparable to the drug reversing the disease itself. The peptide also turned off the inflammatory brain cells that cause Alzheimer's damage and flipped on anti-inflammatory healing pathways.

Sun X, Deng Y, Fu X, Li H, Li L, Shi Y, Qu W, Xie Z

2013

Evaluation of metabolically stabilized angiotensin IV analogs as procognitive/antidementia agents (J Pharmacol Exp Ther 344:141-154; Notice of Concern published 2021)

Describes how dihexa (N-hexanoic-Tyr-Ile-(6) aminohexanoic amide) was designed from Nle1-AngIV: changes at both ends to resist breakdown (angiotensin-like peptides are quickly broken down by aminopeptidases, enzymes that chew peptides from the end) and to pass through barriers more easily. The result is an analog that works by mouth and crosses the blood-brain barrier (the filter that protects the brain). Reports anti-dementia activity in the scopolamine rat model (memory loss caused by a drug) and aged (24-month) rats, spinogenesis/synaptogenesis (growth of new connection points between nerve cells) in hippocampal neurons (memory-center nerve cells) at picomolar (10^-12 M) concentrations, and a terminal half-life (time for the drug level to fall by half in its final clearance phase) of 12.68 days after IV dosing (into a vein) in rats (8.83 days IP, into the belly cavity). The journal published a Notice of Concern on this article in September 2021 (J Pharmacol Exp Ther 378:313); it is not among the three Harding-lab JPET papers retracted in April 2025.

McCoy AT, Benoist CC, Wright JW, Kawas LH, Bule-Ghogare JM, Zhu M, Appleyard SM, Wayman GA, Harding JW

2021

Cognitive Vitality Report: Dihexa

ADDF neuroscientists' evidence review (last updated August 13, 2021): no clinical trials to date and no studies in humans published; no studies in animals or humans have looked at dihexa's long-term safety; in theory, activating HGF and c-Met (a growth-signal pathway) could promote tumorigenesis (tumor formation) and cancer progression; half-life 12 days after IV (into a vein) and 8.8 days after IP (into the belly cavity) dosing in rats, unknown in humans.

Alzheimer's Drug Discovery Foundation (ADDF), Aging and Alzheimer's Prevention Program

2015

Hepatocyte growth factor mimetic protects lateral line hair cells from aminoglycoside exposure

In the larval zebrafish lateral line (a row of sensory hair cells along the fish's body, used as a model for ear hair cells), dihexa protected hair cells from the aminoglycoside antibiotics neomycin and gentamicin, with 1 uM giving the best protection. The protection was weakened by the HGF antagonist 6-AH (a blocker of HGF) and by inhibitors of Akt, TOR and MEK (cell-signaling proteins).

Uribe PM, Kawas LH, Harding JW, Coffin AB

2013

The emerging role of MET/HGF inhibitors in oncology

Review: abnormal MET/HGF activation (a growth-signal pathway) has been seen in many tumor types and drives cell growth and metastasis (spread of cancer). In lab studies, the cancer-like and spreading traits of non-small cell lung cancer, hepatocellular carcinoma (liver cancer) and gastric (stomach) cancer cells were reversed by blocking MET.

Scagliotti GV, Novello S, von Pawel J

If this isn't the right fit

What people use instead of Dihexa

Boosting thinking through nerve-growth pathways

  • P21 (a piece of CNTF, a nerve-support protein; it promotes growth of new nerve cells through a different growth signal)
  • Cerebrolysin (a mix of nerve-supporting peptides that works through BDNF and NGF, proteins that help nerve cells grow)
  • Semax (a modified piece of the hormone ACTH that raises BDNF, a protein that helps nerve cells grow)

Boosting memory and learning (nootropics, thinking-boost products)

  • Noopept (a peptide-like drug that adjusts BDNF and NGF, proteins that help nerve cells grow)
  • N-Acetyl Selank (an anti-anxiety peptide with thinking benefits)
  • Lion's Mane mushroom extract (a natural NGF stimulant; NGF is nerve growth factor)

Protecting nerve cells and calming brain inflammation

  • Selank (a nerve-protecting peptide with anti-anxiety effects)
  • BPC-157 (protects nerves through several growth-factor pathways)
  • Cortexin (a brain-regulating mix of polypeptides)

Your questions

Dihexa FAQ

What makes dihexa different from other nootropics (supplements or drugs taken to boost thinking)?

Most nootropics (brain-boosting supplements) work by adjusting levels of brain chemicals, such as acetylcholine (a memory-related brain chemical), dopamine, or glutamate, at connections that already exist. Dihexa is fundamentally different because it drives the physical building of new connections between neurons (synaptogenesis) by switching on the HGF/c-Met pathway. 3 This means dihexa builds new brain wiring rather than just tuning existing circuits. It is also extraordinarily potent, binding HGF at picomolar concentrations (extremely tiny amounts) and is described as 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. 64 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 biggest theoretical concern with dihexa. The HGF/c-Met pathway it switches on is a well-known cancer-driving growth signal. Abnormal c-Met activation is linked to several cancers, including hepatocellular carcinoma (liver cancer), gastric cancer (stomach cancer), and non-small cell lung cancer. 9 However, no tumor-causing effects have been seen in published animal studies. The concern remains theoretical but scientifically grounded. 7 People with active cancer, a cancer history, or a strong family history of cancer should avoid this compound. Cycling protocols with off-periods are recommended to limit constant activation of the pathway.

Why does dihexa stay in the body so long?

Dihexa was specifically engineered to resist breakdown. This is a key improvement over native angiotensin IV (the natural compound it was built from), which aminopeptidases (enzymes that trim proteins) rapidly destroy. 6 Two changes to its structure (an N-hexanoic modification and a (6) aminohexanoic amide at the C-terminal end) protect it from enzymes, giving it a circulating half-life (how long it stays active in your body) of approximately 12 days after IV administration. 67 This long half-life means the compound builds up significantly with daily dosing, and effects last for days to weeks after you stop. That is both an advantage (steady brain exposure) and a concern (possible effects from buildup).

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. 6 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 it stays active in your body).

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) 6 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 (animal or lab studies, not human trials) models, dihexa has shown remarkable results in restoring thinking and memory in Alzheimer's disease mouse models (APP/PS1 mice). It reduced amyloid-linked brain inflammation, protected neurons from apoptosis (programmed cell death), and restored spatial learning through the PI3K/AKT pathway (a cell survival signal). 4 However, these results come from animal studies only. No human Alzheimer's trials have been conducted. 7 The compound is patented for possible Alzheimer's treatment, and the developers at Washington State University consider it a promising candidate, but it remains an investigational compound.

10 sources

References

Every numbered marker on this page points to one of these. Same sources, same numbering as the Dihexa research profile on Peptide Initiative.

  1. [RETRACTED] The Procognitive and Synaptogenic Effects of Angiotensin IV-Derived Peptides Are Dependent on Activation of the Hepatocyte Growth Factor/c-Met SystemBenoist CC, Kawas LH, Zhu M, Bhatt D, Bhatt S, Bhatt A, Wright JW, Harding JW · 2014
  2. The development of small molecule angiotensin IV analogs to treat Alzheimer's and Parkinson's diseasesWright JW, Kawas LH, Harding JW · 2015
  3. The Brain Hepatocyte Growth Factor/c-Met Receptor System: A New Target for the Treatment of Alzheimer's DiseaseWright JW, Harding JW · 2015
  4. AngIV-Analog Dihexa Rescues Cognitive Impairment and Recovers Memory in the APP/PS1 Mouse via the PI3K/AKT Signaling PathwaySun X, Deng Y, Fu X, Li H, Li L, Shi Y, Qu W, Xie Z · 2021
  5. Cognitive benefits of angiotensin IV and angiotensin-(1-7): A systematic review of experimental studiesHo JK, Nation DA · 2018
  6. Evaluation of metabolically stabilized angiotensin IV analogs as procognitive/antidementia agents (J Pharmacol Exp Ther 344:141-154; Notice of Concern published 2021)McCoy AT, Benoist CC, Wright JW, Kawas LH, Bule-Ghogare JM, Zhu M, Appleyard SM, Wayman GA, Harding JW · 2013
  7. Cognitive Vitality Report: DihexaAlzheimer's Drug Discovery Foundation (ADDF), Aging and Alzheimer's Prevention Program · 2021
  8. Hepatocyte growth factor mimetic protects lateral line hair cells from aminoglycoside exposureUribe PM, Kawas LH, Harding JW, Coffin AB · 2015
  9. The emerging role of MET/HGF inhibitors in oncologyScagliotti GV, Novello S, von Pawel J · 2013
  10. HGF/c-MET targeted therapeutics: novel strategies for cancer medicineYap TA, Sandhu SK, Alam SM, de Bono JS · 2011

Want the deep science?

Read the full Dihexa research profile

Every claim on this page traces back to the research database behind Peptide Initiative — studies, citations, clinical trial data, and the technical detail we deliberately left out here.

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This guide is education, not medical advice. Dihexa is a research compound that is not FDA-approved for human use. Talk to a clinician before taking anything.