Semax

It is like a home-town remedy that has sat on the local pharmacy shelf for thirty years in one country. Plenty of people there swear by it and there is a plausible scientific story for why it might help, but the wider medical world has never put it through the rigorous, independent testing that would turn 'we use it and it seems to work' into 'we know it works'.

Semax is an analogue of the ACTH(4-10) fragment of adrenocorticotropic hormone, stabilised against breakdown by a C-terminal Pro-Gly-Pro tail. In animal models it rapidly upregulates brain-derived neurotrophic factor (BDNF) and increases phosphorylation of its TrkB receptor in the hippocampus, engaging the BDNF–TrkB neurotrophic signalling pathway, and also increases nerve growth factor (NGF). It additionally modulates dopaminergic and serotonergic systems and shows antioxidant, anti-inflammatory and anti-excitotoxic effects relevant to ischaemia. The precise receptor-level target in humans is not firmly established. Proposed routes include melanocortin receptor activity and inhibition of enkephalin-degrading enzymes. As a peptide it is given intranasally or by injection rather than orally.

Research contexts. Not proven uses, and not recommendations.

Real human use exists. Semax is an approved prescription medicine in Russia (and used across the CIS) and has been administered to stroke and cognitive-disorder patients for decades, with studies such as Gusev/Martynov et al. (2018) reporting improved neurological and functional recovery alongside raised plasma BDNF. However, the human evidence base is weak by modern standards: it is overwhelmingly Russian-language, often single-centre, small, open-label or otherwise methodologically limited, and has not been independently replicated in large, well-controlled, blinded Western randomised trials. Evidence for benefit in healthy people seeking cognitive enhancement is essentially absent. A genuine clinical tradition and a plausible mechanism exist, but thin reproducible proof of efficacy.

• !Not a licensed medicine in the UK, US or EU. Sold online as an unlicensed 'research chemical' / 'not for human consumption', outside any pharmaceutical quality control.
• !Almost all efficacy evidence is Russian-language and has not been independently replicated in large blinded Western RCTs; meaningful risk of publication and methodological bias.
• !Grey-market products carry purity, sterility, dosing-accuracy and contamination risks, especially for injectable or intranasal use.
• !Long-term safety data, particularly in healthy users taking it for cognitive enhancement, are limited.
• !Mechanism in humans is incompletely characterised, so off-target or chronic-use effects are poorly mapped.
• !Marketing routinely overstates 'BDNF-boosting' nootropic benefits by extrapolating from animal data to healthy humans.

Not a licensed medicine in the UK. Semax has never been evaluated or authorised by the MHRA and holds no UK marketing authorisation. It is not an approved treatment for stroke, cognition or any other indication here. Under the Human Medicines Regulations 2012, a product making medicinal claims would require authorisation, so Semax is sold only as an unlicensed substance, typically labelled a 'research chemical' or 'not for human consumption'. It is not a controlled drug under the Misuse of Drugs Act, but supplying it for human medicinal use without authorisation would breach medicines law. Anyone obtaining it does so outside regulated pharmaceutical supply and quality control.

1. 01
   Semax, an analog of ACTH(4-10) with cognitive effects, regulates BDNF and trkB expression in the rat hippocampus — Dolotov OV, Karpenko EA, Inozemtseva LS, et al., Brain Research (2006)

   Landmark preclinical (rat) paper showing Semax upregulates hippocampal BDNF and increases TrkB phosphorylation, the core mechanistic rationale. Animal data, not human.

2. 02
   The efficacy of semax in the treatment of patients at different stages of ischemic stroke — Gusev EI, Martynov MYu, Kostenko EV, Petrova LV, Bobyreva SN, Zhurnal Nevrologii i Psikhiatrii imeni S.S. Korsakova (2018)

   Representative Russian-language human stroke study; open-label, single-centre, illustrative of both the clinical literature and its methodological limitations.

3. 03
   Semax (overview of structure, Russian regulatory status and indications), Wikipedia (2024)

   Background summary only (structure, Russian Vital and Essential Drugs listing, lack of Western approval); not a primary source, used as an orientation pointer to its primary citations.