Cortagen peptide: what the rat and cell studies show, and what is missing

Cortagen is a four-amino-acid synthetic peptide, Ala-Glu-Asp-Pro, from the series of peptide bioregulators developed by Vladimir Khavinson and colleagues at the St Petersburg Institute of Bioregulation and Gerontology. The group states that it was obtained by directed synthesis based on the amino-acid analysis of cortexin, a polypeptide preparation extracted from the brain cortex of cattle that is used as a medicine in Russia ^[3]. In the same way, the pineal extract epithalamin gave rise to epitalon (Ala-Glu-Asp-Gly), and the thymus extract thymalin gave rise to the dipeptides thymogen and vilon.

Cortagen differs from epitalon by a single amino acid: proline replaces glycine at the end of the chain. That small difference matters in the group’s own experiments. In neonatally hypophysectomised chickens and in old birds, epitalon corrected changes in red blood cells, immunity and blood clotting, while cortagen, distinguished only by that terminal residue, did not affect the same parameters ^[12]. Cortagen is also distinct from pinealon (Glu-Asp-Arg), the group’s other brain-directed peptide, and from semax and selank, which are Russian neuropeptide drugs of a different origin.

As with every peptide in this family, the research base is narrow: nearly all of it comes from the developers and their collaborators, much of it in Russian-language journals such as Advances in Gerontology and Experimental and Clinical Pharmacology, with English-language reports concentrated in the Bulletin of Experimental Biology and Medicine. Replication by unconnected groups is rare, and there is no controlled trial in people. The name is sometimes spelled cortagene in older translations ^[12], and sellers describe it as the cortagen bioregulator for the brain and nervous system.

The Khavinson group’s general model is that short peptides enter cells and the nucleus and change gene expression, partly by loosening tightly packed chromatin. In a 2004 study, lymphocytes from people aged 75 to 88 were cultured with vilon, epitalon, livagen, prostamax or cortagen. All five peptides activated ribosomal genes and decondensed densely packed chromatin, releasing genes that the authors described as repressed by age-related condensation; epitalon, livagen and prostamax also decondensed the pericentromeric heterochromatin of chromosome 1, while cortagen did not ^[7]. A 2023 study from Tbilisi repeated this approach with epitalon, livagen, cortagen and vilon in lymphocytes from 75 to 88-year-olds, reporting that each peptide acted on different chromosome regions ^[13]. These are cell-culture experiments on blood cells, and they do not show that cortagen taken by a person has any effect on the brain.

A 2020 review by the group places the AEDP peptide alongside AEDG (epitalon) as peptides that induce differentiation of pluripotent cells towards epidermis, mesenchyme and nervous tissue ^[15]. In mouse spleen cells, cortagen activated interleukin-2 mRNA synthesis without a specific inducer, but less strongly than vilon or epitalon ^[8]; in mouse thymocytes, vilon had a strong co-mitogenic effect, epitalon a weaker one and cortagen none ^[9]. After injection into rats, cortagen, vilon and epitalon changed IL-2 gene expression in cells of some hypothalamic structures depending on the route and timing ^[10], and the three peptides had opposite effects on the production of lymphocyte-activating factors by macrophages from young and old mice ^[11]. The pattern across these studies is that cortagen is consistently the least active of the group’s peptides on immune cells.

A 2004 microarray study is often cited as evidence for cortagen’s molecular effects. Six-month-old female mice were injected with cortagen for five days and the expression of 15,247 transcripts in the heart was measured; 234 clones, 1.5% of the total, matching 110 known genes changed significantly, with the largest change a 5.4-fold increase. The authors compared the profile with those of vilon, epitalon and melatonin and found both shared and cortagen-specific effects ^[3]. A change in 1.5% of transcripts after five days of injections does not by itself indicate benefit or harm; it shows the peptide, or the injection regime, did something measurable to gene expression in heart tissue.

Claims about cortagen benefits centre on nerve repair, protection of the brain from ischaemia and reduced oxidative damage. The studies behind them are in rats.

Nerve regeneration: in the first English-language cortagen paper, rats had the sciatic nerve cut and sutured and then received intramuscular cortagen at 10 µg/kg for 10 days. The growth rate of regenerating nerve fibres increased by 27% and their conduction velocity by 40% compared with controls ^[1]. A 2002 follow-up from the same team examined the delayed effect of cortagen on the recovery of function in the injured nerve ^[2]. Cortagen nerve regeneration data are the most specific results the peptide has, and they are the basis for the developers’ statement that in humans it produced a pronounced therapeutic effect on structural and functional recovery of injured peripheral nerves ^[3]; we could not find the human study itself in PubMed.

Brain ischaemia: pharmacologists at the Military Medical Academy in St Petersburg reported that cortexin and cortagen accelerated the recovery of disturbed behaviour in rats with chronic brain ischaemia, in both hypoxia-resistant and hypoxia-sensitive animals, and prevented excessive lipid peroxidation and loss of antioxidant activity in brain tissue ^[6]. In a 2016 study of ischaemic preconditioning, the same authors found that neurospecific peptide preparations reduced neurological deficit and restored individual behaviour during chronic ischaemic brain damage, with antioxidant effects ^[5].

Oxidative stress: injections of epitalon and cortagen into rats reduced lipid peroxidation products and oxidative modification of proteins in serum and cerebral cortex, alongside a fall in antioxidant activity, which the author interpreted as the peptides reducing the oxidative load rather than acting as antioxidants themselves ^[4].

Immunity and blood clotting: as noted above, cortagen did not correct the anaemia, immune deficiency and hypercoagulation seen in hypophysectomised chickens, whereas epitalon did ^[12]. Cortagen should not be assumed to share the properties claimed for epitalon.

We found no randomised controlled trial of cortagen in PubMed and no entry on ClinicalTrials.gov. The developers write that cortagen showed a therapeutic effect on post-traumatic recovery of peripheral nerve tissue in humans, with additional effects on cardiovascular and cerebrovascular parameters ^[3], and a 2013 Russian-language review from the group describes the clinical use of cortagen, semax and pinealon in elderly people alongside the polypeptide complexes cortexin and cerebrolysin ^[14]. Neither source gives the design, numbers or controls of the underlying clinical work in its English abstract.

The human material that does exist in English is laboratory work on cells taken from people: the chromatin studies in lymphocytes from very old donors ^{[7] [13]}. These show that cortagen changes chromatin packing in cultured blood cells at the concentrations used. They say nothing about whether a dose taken by mouth or injection reaches the nervous system, or about any clinical outcome.

In the sciatic nerve study, cortagen was given for 10 days after injury and the effect on regeneration was measured over the following weeks ^[1]; the 2002 paper specifically examined a delayed effect on functional recovery ^[2]. The microarray study used five daily injections ^[3]. There is no human timescale, because there is no controlled human study. Sellers in Russia market Khavinson-series peptides as courses of 10 to 30 days, which is a marketing convention rather than a finding.

These are laboratory doses, and none is a recommendation. In rats with a sutured sciatic nerve, cortagen was injected intramuscularly at 10 µg/kg daily for 10 days ^[1]. In mice, cortagen was injected for five consecutive days before heart gene expression was profiled ^[3]. In cultured lymphocytes and splenocytes, the peptides were added to the medium at concentrations that the abstracts do not specify ^{[7] [8]}. No dose for people has been published in a controlled study, and there is no pharmacokinetic study showing how much of a dose reaches the brain or peripheral nerves.

Research suppliers sell cortagen as a freeze-dried powder, typically in 10 mg or 20 mg vials, and sometimes as capsules. To convert vial contents to a concentration, use the peptide calculator or its cortagen page. For context, the 10 µg/kg rat dose is very small: scaled by body weight to a 70 kg adult it would be 0.7 mg, though rat-to-human dose scaling is not that simple and no human dose has been established.

In the animal studies cortagen was given by intramuscular injection ^[1] or by injection into mice ^[3], and the hypothalamic IL-2 study found that the route and timing of administration changed the result ^[10]. In Russia, Khavinson-series short peptides are sold mainly as oral capsules marketed as food supplements; research suppliers elsewhere sell mainly lyophilised powder for injection. Whether a tetrapeptide survives digestion and is absorbed intact is not known for cortagen. The group’s 2020 review argues that short peptides penetrate cell and nuclear membranes ^[15], which is a different question from absorption from the gut.

There is no systematic record of cortagen side effects because there are no controlled human trials. The developers’ reviews describe short peptides as free of side effects, but that reflects an absence of reporting rather than evidence from adverse-event monitoring. The animal papers do not report toxicity at the doses used, and a peptide of four common amino acids is unlikely to be acutely toxic; the uncertainties are about long-term effects, which have not been studied for cortagen.

The chromatin studies deserve a specific comment. Cortagen is claimed to loosen tightly packed chromatin and release repressed genes in cells from old people ^{[7] [13]}. If that is true in the body, it is not obviously benign: heterochromatin also keeps some genes and repetitive DNA elements silenced for good reasons. No study has examined cortagen and cancer incidence, in contrast to the long-term rodent studies that exist for epitalon and thymogen. There are no data on use in pregnancy, in children or alongside medicines.

For products bought online, the practical risks are identity, purity and sterility. Our guides to third-party testing and how to read a certificate of analysis cover what a test report should show.

Cortagen is not an approved medicine in the UK, US, EU, Canada or Australia, and, unlike cortexin and thymalin, it is not a registered medicine in Russia either; there it is sold as a supplement. Products sold as cortagen elsewhere are research chemicals whose sale for human use is not lawful. It is not named on the WADA Prohibited List. See our legal status overview and the pages for the UK, the US and Europe.

Cortagen is supplied as a freeze-dried powder to be kept cold, dry and away from light; short peptides are relatively stable in this form. Reconstituted solutions are refrigerated and used within a limited period. See how to store peptides and our guide to bacteriostatic water.

A tetrapeptide is inexpensive to synthesise, so cortagen should be among the cheaper products a supplier lists, and the main question is whether the vial contains it. Compare cortagen prices across suppliers, including listings in the UK and the US. A certificate of analysis should show a measured mass close to 430.4 g/mol and an HPLC purity figure; our lists of third-party tested suppliers and suppliers that publish COAs, and our guide to spotting a fake supplier, explain what to look for. Because cortagen and epitalon differ by one amino acid, a mass of about 390 g/mol on a certificate would indicate epitalon rather than cortagen.