Cortexin vs PE-22-28.

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.

PE-22-28 is a synthetic seven-residue peptide corresponding to residues 22 to 28 of spadin, itself a fragment derived from the sortilin propeptide (also called neurotensin receptor-3). It was developed as a shortened, more stable analog of spadin intended to block the TREK-1 potassium channel. It has been studied as a fast-acting antidepressant candidate in rodent models. It is a preclinical research compound with no human data.

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.

PE-22-28 acts by inhibiting the TREK-1 two-pore-domain potassium channel, which is implicated in mood regulation and in resistance to conventional antidepressants. By blocking TREK-1, it is proposed to increase serotonergic neurotransmission and promote hippocampal neurogenesis. Reported potency is high, with a sub-nanomolar IC50 and improved metabolic stability compared with spadin. These effects are characterized in cell and animal systems.

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.

Evidence for PE-22-28 is preclinical only. In the foundational study, shortened spadin analogs including PE-22-28 showed stronger TREK-1 inhibition, longer in-vivo stability and antidepressant-like activity in behavioral tests such as forced swim and novelty-suppressed feeding, along with induction of neurogenesis after a short treatment course (Djillani et al., Frontiers in Pharmacology 2017). A review of TREK-1 blockers situates spadin and its analogs within antidepressant drug discovery (Djillani et al., Pharmacology and Therapeutics 2019). Related work describes the sortilin/NTSR3 origin of spadin and its role in the membrane expression of TREK-1, which supplies the mechanistic rationale for the shortened analogs (Frontiers in Pharmacology, 2018). Separate mouse work using genetic and pharmacological inhibition of TREK-1 reported changes in depression-related behavior and hippocampal neuronal plasticity (CNS Neuroscience and Therapeutics, 2021); that work supports the target as biologically interesting but does not test this peptide. The design of the supporting studies limits the conclusions available. They are rodent experiments run in academic laboratories, largely the group that originated spadin, over short treatment courses. The behavioral readouts are screening assays rather than models of depression: forced swim, tail suspension and novelty-suppressed feeding are sensitive to known antidepressants, which makes them useful filters, but a long list of compounds that performed well in them has failed in human trials. The reports are not blinded multi-centre studies, are not pre-registered, and have not been replicated head to head by an independent group. No completed or registered human clinical trial exists for PE-22-28. There is consequently no Phase 1 safety or tolerability dataset, no human pharmacokinetic profile, no measured central nervous system exposure in people, and no published toxicology package. This is a weaker position than that of compounds it is informally compared with: approved rapid-acting antidepressants such as esketamine were established through randomized, placebo-controlled trials with standard depression rating scales before approval, and even TREK-1 or novel-mechanism candidates that ultimately failed generally reached Phase 1 and produced human exposure and tolerability data. Antidepressant-like signals in rodents do not establish human efficacy or safety.

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 for PE-22-28; all information comes from short-term rodent studies. There is no published Phase 1 tolerability study, no human pharmacokinetic or elimination data, no immunogenicity assessment, and no repeat-dose or reproductive toxicology package in the public literature. Because TREK-1 is expressed in tissues outside the brain, including cardiovascular, smooth muscle and immune-related tissues, systemic and off-target effects are theoretically possible; the channel also contributes to cellular responses to mechanical and thermal stimuli, so blocking it chronically could have consequences that short rodent behavioral experiments were never designed to detect. Effects on mood-related circuitry are themselves a caution: psychoactive compounds acting on serotonergic signaling and neurogenesis can produce agitation, sleep disruption or worsening mood, and no monitored human exposure exists to characterize any of this. Purity, identity and long-term toxicology of material sold as a research chemical are not controlled. Such products are made outside pharmaceutical good manufacturing practice, carry no verified certificate of analysis for peptide content, impurity profile or endotoxin, and are labeled for laboratory use only. Buyers cannot confirm what the vial holds or whether a reconstituted solution is sterile. The lack of reported adverse events reflects the lack of supervised human use rather than a safety record. With no clinical trials, no pharmacovigilance reporting and no registry, harms occurring in unsupervised use would not be captured. It is not a medicine and is not intended for human use.

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.

PE-22-28 is not approved by the FDA or any other regulator and has no approved medical use. It exists only as a preclinical research compound. This summary is educational and includes no dosing guidance.