What is Semax? A plain-English explainer

Semax is a synthetic heptapeptide (seven-amino-acid chain) built from the ACTH(4-7) fragment of adrenocorticotropic hormone, the pituitary hormone that normally tells the adrenal gland to release cortisol^[1]. Researchers at the Institute of Molecular Genetics of the Russian Academy of Sciences developed it in the early 1990s by taking that ACTH fragment, which earlier work had shown carries cognitive and behavioural effects without adrenal-stimulating action, and adding a Pro-Gly-Pro tail at the chain's end to slow enzymatic breakdown. The result is sometimes written ACTH(4-7)PGP. It is administered as a nasal spray in its Russian-licensed form, and the intranasal route allows it to reach the brain without passing through the gut.

How semax works

Because the ACTH(4-7) fragment in Semax does not bind the adrenal melanocortin-2 receptor, it does not drive cortisol output. The mechanistic interest centres on the brain instead. Dolotov and colleagues (2006) administered Semax intranasally to rats and found that BDNF protein (brain-derived neurotrophic factor, a growth-and-survival signalling protein for neurons) rose in the basal forebrain within three hours, with regional specificity^[2]. The cerebellum did not respond in the same study, suggesting the effect is not a non-specific brain-wide event. Separately, Eremin and colleagues (2005) reported that Semax raised striatal serotonin metabolite levels and amplified the dopaminergic response to co-administered amphetamine in rats, though Semax alone did not shift baseline dopamine^[3]. More recent work from 2025 found that Semax targets the mu-opioid receptor gene Oprm1 in a mouse spinal-cord-injury model, adding another layer to the mechanistic picture. These are all rodent findings. The pathway from rat BDNF elevation to a measurable effect in a human brain has not been established by Western-standard controlled trials.

Where semax is approved

Russia is the only country where Semax holds a marketing authorisation. It was added to the Russian List of Vital and Essential Drugs on 7 December 2011 as a prescription intranasal nasal spray, with indications spanning ischemic stroke recovery, transient ischemic attack, and memory and cognitive disorders^[1]. A 2026 review of therapeutic peptides in gerontology classified Semax explicitly in the "non-approved" category, noting it has promising preclinical and limited clinical evidence but lacks long-term safety data to meet regulatory standards^[4]. The EMA has no marketing authorisation or EPAR entry for Semax. The FDA classifies it as unapproved. The MHRA has not licensed it for any indication. Online vendors sell Semax nasal sprays and powders through the same grey-market channel that supplies BPC-157 and ipamorelin. That supply sits outside any pharmaceutical quality framework we cover.

What the evidence shows

The most-cited Russian clinical study is Gusev and colleagues (2018), which enrolled 110 patients at different stages of ischemic stroke^[5]. The study reported increases in plasma BDNF, gains on the British Medical Research Council motor scale, and gains on the Barthel index of activities of daily living after the standard Russian regimen. Those are real measured outcomes. The limitation is methodological: the PubMed abstract does not describe the study as a fully randomised, placebo-controlled, double-blind trial, it is conducted by a small number of Russian academic groups, and it is published in a Russian-language journal. None of that makes the findings wrong, but it does mean the dataset sits well below what the FDA or EMA would require before granting marketing authorisation. There is no completed Western-standard phase-2 or phase-3 randomised controlled trial for any Semax indication.

What we still do not know

Several questions that matter for any non-Russian reader remain open. We do not know how the BDNF-elevating effect observed in rats translates to humans at the doses used in the Russian indications, or whether that elevation is what produces the motor-recovery signal Gusev measured. We do not have a characterised dose-response curve for cognitive endpoints in healthy adults. We do not know the chronic-dosing safety profile in months-to-years use outside the Russian post-marketing context. And the grey-market supply reality in the EU, UK and US means there is no way to confirm what is in a given vial without independent identity and purity testing. The Russian post-marketing record since 2011 is the strongest safety signal available; a Western regulator would want substantially more before drawing conclusions about long-horizon risk.

This article is for education and journalism only. We do not advise on starting, stopping, or sourcing Semax. Any decision about whether Semax is appropriate for a specific person belongs with a clinician who knows their medical history. For jurisdiction-specific supply and import rules, see the country pages. For the full evidence picture, see the Semax peptide page.