Cortexin vs Dihexa.

Cortexin is a low-molecular-weight polypeptide preparation extracted from the cerebral cortex of cattle and calves. It contains a mixture of short water-soluble peptides (roughly 1 to 10 kDa), amino acids and trace elements, and is supplied as a lyophilized powder reconstituted for intramuscular injection. Developed and marketed primarily in Russia by GEROPHARM, it is positioned as a neurotrophic and neuroprotective agent. It is used clinically within Russia and several neighboring countries for a range of neurological conditions.

Dihexa (N-hexanoic-Tyr-Ile-(6)-aminohexanoic amide; also referenced as PNB-0408) is a small, orally active peptidomimetic derived from angiotensin IV (Ang IV), a C-terminal fragment of the renin-angiotensin system. It was designed at Washington State University by chemically modifying Ang IV to increase lipophilicity and metabolic stability, yielding a brain-penetrant molecule investigated as a procognitive / antidementia research agent. It is a research chemical, not a drug; it has never been an approved medicine.

Like other brain-tissue peptide preparations, Cortexin is a complex mixture, so its activity is attributed to the combined effect of many peptide-protein interactions rather than a single molecular target. Proposed mechanisms include support of neuronal energy metabolism, antioxidant and anti-apoptotic effects, and modulation of neurotrophic factors and neurotransmitter systems such as GABA and dopamine. Its low-molecular-weight peptides are claimed to cross the blood-brain barrier. These mechanisms are largely inferred from preclinical models.

Dihexa was developed from Ang IV, whose procognitive effects were originally studied at the AT4/IRAP site, but its proposed primary mechanism is potentiation of hepatocyte growth factor (HGF) signaling through its receptor tyrosine kinase c-Met, which drives dendritic spine formation (spinogenesis) and synaptogenesis in hippocampal neurons. Activating HGF/c-Met is thought to remodel synaptic connectivity rather than act as a classical neurotransmitter. Important caveat: the central biochemical evidence that dihexa works by binding HGF and augmenting HGF/c-Met activation came from a paper that has since been retracted for data fabrication, so the molecular mechanism should be treated as unproven. The downstream behavioral phenotype (improved spatial learning in rodents) was reported in separate, non-retracted work.

The evidence base for Cortexin comes predominantly from Russian-language studies and preclinical models, with limited independent Western validation. A recent preclinical study (Kurkin et al., Biomedicines 2025) reported neurotropic effects in rat models of toxic and traumatic developmental delay. Clinical use is widespread in Russia across pediatric neurology, stroke rehabilitation and cognitive disorders, but large, blinded, international randomized trials indexed in mainstream databases are scarce. As a result, Cortexin has not been subjected to the RCT and Cochrane-level scrutiny applied to Cerebrolysin. Its efficacy claims should therefore be read with caution. The human literature is dominated by multicenter observational programs rather than randomized comparisons: the CORNELia program in chronic cerebrovascular disease with cognitive impairment and the CORTEX program in post-COVID neurological complaints are both described as observational, meaning they lack a concurrent randomized control arm, blinding, and placebo control, so improvement over time cannot be separated from natural recovery, regression to the mean or expectation effects. Comparative studies do exist within the same national literature, for example a comparison with another peptide preparation in the early recovery period after ischaemic stroke, but these are typically single-country, modest in size and published in one journal, Zhurnal Nevrologii i Psikhiatrii imeni S.S. Korsakova, closely associated with the domestic market for the drug. Preclinical support includes rodent work on antioxidant effects in chronic cerebrovascular insufficiency and a cell-culture study reporting protection of cultured rat sensory neurons from high-glucose injury. Nearly all of this literature originates in the country where the product is registered and marketed, and the manufacturer's involvement in the observational programs is a relevant consideration. What is missing is specific: no independent multinational randomized trial, no Cochrane or comparable systematic review, no published characterization of which peptides in the extract are active, and no external regulatory assessment of the manufacturing and potency standards. Cortexin sits alongside thymalin, vilon and epitalon in resting on single-country literature, while Cerebrolysin, despite its own unresolved questions, has at least been tested in independently reviewed randomized trials.

There is NO human data on dihexa: no completed clinical trials, no published human pharmacokinetics or safety. The non-retracted foundational study (McCoy et al., J Pharmacol Exp Ther 2013, PMID 23055539) reported that orally administered dihexa reversed scopolamine-induced learning deficits and improved Morris water maze performance in aged (24-month) rats, and induced spinogenesis in cultured hippocampal neurons at picomolar concentrations. Later angiotensin-IV-analog work continued in disease models (e.g., a 2024 study of an Ang IV analog in a 3-nitropropionic-acid Huntington's-like rat model, PMID 38489193). Crucially, the most-cited mechanistic paper tying dihexa's cognitive effects to HGF/c-Met (Benoist et al., J Pharmacol Exp Ther 2014, PMID 25187433) was RETRACTED in 2025 (retraction notice PMID 40312093) after a Washington State University investigation found falsified/fabricated figure data; the widely repeated "thousands of times more potent than BDNF" claim derives from this now-discredited line of work and should not be cited as established fact. The honest summary: rodent behavioral evidence exists, but the headline mechanistic and potency claims rest partly on retracted literature, and human efficacy is entirely unestablished.

Cortexin is generally described in its clinical literature as well tolerated when given intramuscularly, with hypersensitivity and allergic reactions being the main labeled concern. As a parenteral bovine-derived biological, theoretical risks include allergic reactions and injection-site effects, and the same category concerns apply that attach to any animal-tissue extract given by injection: immunogenicity on repeated courses, dependence on the source herd and purification process for freedom from adventitious agents, and the practical difficulty of proving batch equivalence for a mixture whose active constituents are not defined. Independent long-term safety data from outside its region of use are limited, and the observational design of most human reports means adverse events were collected without a comparator, so background rates cannot be separated from drug-related events. Use in children, which is common in the Russian pediatric neurology setting, has not been evaluated in independently reviewed controlled trials, and pediatric exposure is precisely the situation where an external safety assessment would ordinarily be required. Product acquired outside licensed pharmacy channels carries additional contamination and counterfeit risk, since injectables demand verified sterility and endotoxin control that unregulated supply cannot demonstrate. A trial-grade safety evaluation would include prospective adverse-event capture against a control arm, hypersensitivity monitoring, hepatic and renal laboratory follow-up, and anti-drug antibody testing on repeat courses. It is a prescription clinical product, not a dietary supplement.

No human safety data exist; there is no published clinical adverse-event profile, and dihexa is sold only as a research chemical of variable purity. The principal theoretical concern follows directly from its proposed mechanism: c-Met is a validated oncology target because aberrant HGF/c-Met signaling promotes tumor proliferation, invasion, angiogenesis, and metastasis, so a chronic c-Met potentiator raises an unresolved oncogenic-risk question that no human study has addressed. Its reported long circulating half-life and high lipophilicity also mean tissue accumulation and off-target effects are poorly characterized. Because foundational mechanistic data were retracted for fabrication, even the basic biology underlying any risk assessment is uncertain.

Cortexin is not FDA-approved and is not marketed in the United States or the European Union. It is a registered prescription medicine in Russia and several post-Soviet states. This summary is educational and includes no dosing information.

Dihexa is investigational/research-use-only: it is not approved by the FDA or any major regulator for any indication, has no DailyMed monograph, and has not completed human clinical trials. It is not a dietary supplement and is widely sold only as a "research chemical." It is not a WADA-listed named substance, though non-approved experimental compounds are broadly disallowed in sport.