Cortexin vs Selank.

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.

Selank is a synthetic heptapeptide (Thr-Lys-Pro-Arg-Pro-Gly-Pro) developed at the Institute of Molecular Genetics of the Russian Academy of Sciences, with the laboratory designation TP-7. It is a stabilized analog of tuftsin, an endogenous immunomodulatory tetrapeptide (Thr-Lys-Pro-Arg) derived from the Fc region of immunoglobulin G; the added Pro-Gly-Pro tail confers resistance to enzymatic degradation. It is studied primarily as an anxiolytic and nootropic agent and is most associated with Russian neuropharmacology research.

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.

Selank's parent peptide tuftsin acts on immune cells, and Selank retains immunomodulatory activity while shifting toward neuromodulation. Proposed central mechanisms include modulation of monoamine systems (serotonin, dopamine, noradrenaline) and interaction with the GABAergic and enkephalin/opioid systems; Selank has been reported to inhibit enkephalin-degrading enzymes, prolonging the action of endogenous enkephalins. It has also been reported to influence expression of brain-derived neurotrophic factor (BDNF) and to alter cytokine balance (e.g., IL-6 and interferon-related signaling). These mechanisms are largely characterized in rodent and in vitro models rather than established in humans.

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.

The great majority of Selank evidence is preclinical (rodent and in vitro), covering anxiolytic-like behavior, stress models, immune/cytokine modulation, and tissue effects under chronic stress (e.g., Bull Exp Biol Med studies on rat intestine and liver under restraint/foot-shock stress, and a cytokine study under 'social' stress). Human clinical data are limited and come almost entirely from Russian-language trials and registry approval rather than large, independently replicated, placebo-controlled studies indexed in Western literature; reported uses include generalized anxiety disorder and asthenic/neurasthenic conditions. A frequently cited molecular review (Protein and Peptide Letters, 2018, PMID 30255741) summarizes the proposed biology. Overall, robust, independently replicated human efficacy data are thin, and mechanistic plausibility should not be read as proven clinical benefit.

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.

Published reports, mostly from the developing Russian groups, describe Selank as generally well tolerated with a notably low sedation, dependence, and withdrawal profile compared with benzodiazepines, but rigorous long-term and large-sample safety data from independent groups are lacking. Because much of the safety record comes from the originating institutions and small studies, the true adverse-event and long-term safety profile in humans is not well established. As a peptide typically administered intranasally in research, purity, contamination, and product-quality concerns apply to non-pharmaceutical material. It has not undergone the comprehensive safety review required for major regulatory approval outside its country of origin.

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.

Selank is reported to have been registered/approved in Russia (around 2009) for anxiety and asthenic conditions, marketed as an intranasal preparation. It is not approved by the US FDA and is not an approved drug in the EU; outside Russia it is effectively investigational and is widely sold as a research-use-only / not-for-human-consumption chemical. It is not a controlled substance and is not a standard WADA-prohibited agent, but its unapproved status means quality and legality vary by jurisdiction.