Dihexa

Dihexa came out of Harding's angiotensin IV work at Washington State, engineered with an N-terminal hexanoic acid and a C-terminal aminohexanoic amide to survive metabolism and cross the blood-brain barrier. It does not act on angiotensin receptors in the way the parent does; instead it binds HGF and augments HGF/c-Met dimerisation and downstream signalling. In hippocampal culture the synaptogenic potency was reported at around seven orders of magnitude above BDNF, and orally dosed rats with scopolamine-induced or lesion-induced cognitive deficits recovered performance. The catch is the same as the promise: HGF/c-Met is one of the more thoroughly documented oncogenic drivers in human cancer biology, and nobody has run a human safety study on chronically potentiating it.

Targets: Hepatocyte growth factor (HGF), c-Met receptor, Dendritic spine / synaptogenesis pathways

• · There is no validated human dose. Grey-market protocols cluster at 5-15 mg daily, often dissolved in DMSO and applied transdermally because the compound is poorly water-soluble. For scale, rodent efficacy occurs around 0.25-2 mg/kg orally, which would extrapolate far lower than what people actually take.

Work out your exact syringe units →

• commonHeadache or a sensation of cranial pressure— The most consistently reported effect; dose-related.
• commonSkin irritation at the application site— Mostly from the DMSO vehicle rather than the peptide.
• uncommonAnxiety, agitation or overstimulation
• rareTheoretical promotion of occult tumour growth— Not observed in the short rodent studies, but HGF/c-Met potentiation is a known driver of tumour growth, invasion and metastasis. This is the single reason to be cautious with this compound.

• Any active or previously treated malignancy - c-Met potentiation is a recognised oncogenic pathway and this is not a theoretical quibble.
• Strong family history of cancer or known cancer-predisposition syndromes.
• Pregnancy and breastfeeding - it drives tissue growth signalling and has zero reproductive safety data.
• Proliferative retinopathy or other conditions driven by uncontrolled growth-factor signalling.

• synergyp21 — Both target neurogenesis and synaptic repair by different routes; occasionally stacked, with no data on the combination.
• cautionbpc-157 — Both push growth-factor and angiogenic signalling. If you are avoiding Dihexa for oncological reasons, the same logic applies to stacking it.

• · Get age-appropriate cancer screening up to date before using it, and stay current.
• · Investigate any new lump, unexplained weight loss or persistent pain rather than waiting it out.
• · No specific bloodwork tracks c-Met activity in a way that is useful to a consumer.

Not approved anywhere for human use. Sold as a research chemical.

• McCoy et al. 2013, evaluation of metabolically stabilised angiotensin IV analogues as procognitive agents, J Pharmacol Exp Ther (preclinical)
• Benoist et al., the procognitive and synaptogenic effects of angiotensin IV-derived peptides are dependent on activation of the HGF/c-Met system (preclinical)

Start with the fact that changes the reading of everything else: the two central papers underpinning the HGF/c-Met mechanism for this compound family have been retracted. The 2012 paper developing angiotensin IV analogues as HGF/Met modifiers and the 2014 paper showing the procognitive and synaptogenic effects depend on HGF/c-Met activation both received expressions of concern from the Journal of Pharmacology and Experimental Therapeutics in 2021 and were formally retracted in April 2025. The 2013 paper evaluating the metabolically stabilised analogues as procognitive agents - the one most often cited for Dihexa itself - carries a 2021 expression of concern and had not been retracted at the time of writing. That is not a technicality. The mechanism as usually described, in which Dihexa binds HGF and augments c-Met dimerisation and downstream signalling, rests principally on the retracted work. The synaptogenesis and cognitive-restoration observations may still be real - retraction of a mechanism paper does not automatically invalidate every behavioural finding in the literature - but the specific molecular story people repeat about this compound now has a hole in the middle of it. The frequently quoted claim that Dihexa is seven orders of magnitude more potent than BDNF at driving spinogenesis comes from a hippocampal culture assay in this same body of work. Treat it as a number from a compromised literature rather than an established fact. What has not changed is the safety logic: if the compound does potentiate HGF/c-Met, that is one of the best-documented oncogenic axes in human cancer biology, and no chronic toxicology package addressing it has ever been published. The uncomfortable position this leaves a user in is that the evidence for it working is now weaker than it looked, while the theoretical reason to worry is unchanged.

The first thing that goes wrong is intellectual: people take this compound on the strength of the seven-orders-of-magnitude-more-potent-than-BDNF claim, and that claim comes from a body of work that has now been partly retracted. Anyone deciding about Dihexa on the pre-2021 version of the story is working from a literature that no longer says what they think it says. The second is dosing arithmetic - grey-market protocols at 5-15 mg daily sit far above what allometric scaling from the rodent efficacy range would suggest, and the headache and cranial-pressure sensation that is the most consistent user report scales with that. Third is the DMSO vehicle: skin irritation attributed to the peptide is usually the solvent, DMSO is hygroscopic and quietly dilutes your solution over weeks as it pulls water from the air, and it carries contaminants through the skin. Fourth, and the one that matters most, is treating the absence of tumours in short rodent studies as reassurance about chronic use in a human with an unknown number of occult lesions. Nobody has run that experiment and nobody is going to.

1. 4 mgDays 1-5 — 4 mg once daily, orally with fat or transdermally in DMSO. The headache and cranial-pressure sensation that dominates the reported side-effect profile scales steeply with dose and shows up here if it is going to.
2. 8 mgDays 6-14 — 8 mg once daily. Grey-market protocols cluster between here and 15 mg. For scale, rodent efficacy was reported at roughly 0.25-2 mg/kg orally, and allometric scaling from that would put a human dose well below what people actually take.
3. 15 mgWeek 3-4, ceiling — 15 mg once daily is the top of the range people run. There is no evidence that more is better and no defensible reason to exceed it. Stop at four weeks regardless.

• Hepatocyte growth factor (HGF) — A picomolar binding affinity for HGF is widely quoted. The primary source for the HGF-binding claim is among the retracted papers, so I am not reproducing a number here

  Proposed to bind HGF and augment its dimerisation, potentiating rather than directly agonising the pathway. The mechanistic evidence is compromised.

• c-Met receptor tyrosine kinase — Not a direct ligand - the proposed action is indirect via HGF

  Downstream PI3K/Akt and MAPK signalling, dendritic spine formation and synaptogenesis in hippocampal culture. Also, unavoidably, the canonical proliferation, invasion and anti-apoptotic signalling that makes c-Met an oncology drug target in the opposite direction.

• Angiotensin IV receptor / IRAP (insulin-regulated aminopeptidase) — Dihexa was engineered away from the parent's IRAP interaction; it is not thought to act here in the way angiotensin IV does

  Minimal. This is a designed departure from the parent pharmacology rather than an incidental one.

There is no reliable timeline for this compound in humans. Rodent cognitive restoration in the published work emerged over days of repeated dosing rather than acutely. Human reports describe subjective changes over 1-2 weeks, and there is nothing rigorous to anchor that to. The headache and cranial-pressure sensation, when it happens, generally shows up within the first few doses and is the fastest and most reliable signal the compound produces. Anecdotal protocols run 2-4 weeks and stop; given the mechanism, short and infrequent is the only defensible approach, and no duration has been shown to be safe.

The stacking question for Dihexa is really a risk-aggregation question. If you are avoiding it because of the c-Met concern, then combining it with BPC-157, GHK-Cu, growth hormone secretagogues or anything else that pushes growth-factor and angiogenic signalling defeats the purpose - the mechanisms differ but the direction of travel is the same. The P21 pairing is sometimes run on the logic that the two hit neurogenesis by different routes, and there is no data on it in either direction. What is genuinely worth knowing is the vehicle interaction rather than the pharmacological one: Dihexa is poorly water-soluble and is usually carried in DMSO, and DMSO drives whatever else is on your skin through the barrier with it. Apply to clean skin, never over a topical medication, and never mix it into a carrier with another active compound. If you are using it at all, use it alone and use it briefly.

Against Semax or Selank: those are registered drugs in Russia with human clinical data, however imperfect. Dihexa has rodent work, part of which has been retracted, and zero human trials. The evidential gap is not close, and the risk profiles are not comparable either - Semax's worst realistic outcome is a wasted month and some irritability. Against P21: both are engineered for oral activity and blood-brain barrier penetration, both are rodent-only, and P21's literature is at least intact. If you want a neurogenesis-directed research compound and are choosing between them, P21's evidence base has not been withdrawn. Against BPC-157: often stacked, and the same growth-factor caution applies to both, but BPC-157's mechanism is angiogenic and local rather than a direct potentiation of a canonical oncogenic receptor axis. Against actually doing the things that raise BDNF with no oncological question attached - aerobic exercise, sleep, and treating whatever is disrupting either - the honest comparison is unflattering to Dihexa.

$60–$250/month. A 20 mg vial typically runs 60-120 USD, which at 8 mg daily is under three days of supply - this is one of the more expensive compounds in the class to run at the doses people actually use. A 30-day course at 8 mg/day needs roughly 240 mg of material. Anyone quoting a low monthly cost is either dosing far lower than the common protocols or buying something that is not Dihexa.

• ?Two of the foundational HGF/c-Met papers for this compound family were retracted in April 2025 and a third carries an expression of concern from 2021. The extent to which the behavioural and synaptogenesis findings survive that is not something I can resolve.
• ?No human pharmacokinetic, safety or efficacy data of any kind exists.
• ?The picomolar HGF binding affinity and the seven-orders-of-magnitude potency comparison against BDNF both originate in the compromised literature. I have deliberately not reproduced specific numbers.
• ?Oral bioavailability in humans is unknown; the transdermal route people use has never been characterised at all.
• ?Volume of distribution, clearance, protein binding, half-life and elimination route are all unmeasured.
• ?There is no chronic toxicology package addressing the c-Met oncological question in any species.
• ?The 5-15 mg daily grey-market dose range has no derivation I could trace to any study. It appears to be convention.
• ?Whether the compound retains any activity at the angiotensin IV/IRAP system of the parent molecule is not clearly established.
• ?The molecular weight of 504.7 Da in the Core record is plausible for the described structure but I did not verify it against a primary characterisation.

• Retraction notice to 'The Procognitive and Synaptogenic Effects of Angiotensin IV-Derived Peptides Are Dependent on Activation of the Hepatocyte Growth Factor/c-Met System' Benoist CC, Kawas LH, Zhu M, Tyson KA, Stillmaker L, Appleyard SM, Wright JW, Wayman GA, Harding JW, Journal of Pharmacology and Experimental Therapeutics, 2025 · PMID 40312093

  The formal 2025 retraction of the paper that established the HGF/c-Met mechanism for this compound family. This is the single most important thing to know about Dihexa's evidence base and it is almost never mentioned by vendors.

• The procognitive and synaptogenic effects of angiotensin IV-derived peptides are dependent on activation of the hepatocyte growth factor/c-met system (RETRACTED) Benoist CC, Kawas LH, Zhu M, Tyson KA, Stillmaker L, Appleyard SM, Wright JW, Wayman GA, Harding JW, Journal of Pharmacology and Experimental Therapeutics, 2014 · PMID 25187433

  The original mechanism paper, now retracted. Listed so you can see what was withdrawn rather than being told to trust a summary of it. PubMed carries both an expression of concern from 2021 and a retraction from 2025.

• Development of angiotensin IV analogs as hepatocyte growth factor/Met modifiers (RETRACTED) Kawas LH, McCoy AT, Yamamoto BJ, Wright JW, Harding JW, Journal of Pharmacology and Experimental Therapeutics, 2012 · PMID 22129598

  The companion medicinal-chemistry paper, also retracted in 2025 with a 2021 expression of concern. Between this and the Benoist paper, the core of the published HGF/c-Met story for these compounds has been withdrawn.

• Evaluation of metabolically stabilized angiotensin IV analogs as procognitive/antidementia agents McCoy AT, Benoist CC, Wright JW, Kawas LH, Bule-Ghogare JM, Zhu M, Appleyard SM, Wayman GA, Harding JW, Journal of Pharmacology and Experimental Therapeutics, 2013 · PMID 23055539

  The primary Dihexa paper, reporting oral activity and cognitive restoration in scopolamine-treated rats. It carries a 2021 expression of concern from the journal and had not been retracted as of this writing. Read it knowing that.