Semax

Semax is a synthetic heptapeptide analog of adrenocorticotropic hormone (ACTH) fragment 4-10, developed at the Institute of Molecular Genetics of the Russian Academy of Sciences. It is approved in Russia as a prescription drug for stroke recovery, cognitive enhancement, and peptic ulcer treatment. Semax is considered one of the most potent nootropic peptides available.

Mechanism of Action

Semax is derived from ACTH(4-10) with a C-terminal Pro-Gly-Pro tripeptide extension that confers protease resistance and enhanced bioactivity. Despite being derived from ACTH, semax has no corticosteroid-stimulating activity — it retains only the neurotrophic and neuroprotective properties of the ACTH fragment.

Semax robustly increases brain-derived neurotrophic factor (BDNF), nerve growth factor (NGF), and TrkB receptor expression in the brain. It modulates dopaminergic and serotonergic systems, increases hippocampal acetylcholine levels, and enhances neuronal survival under conditions of oxidative stress, ischemia, and excitotoxicity. Its neuroprotective effects involve inhibition of nitric oxide synthase and modulation of inflammatory cytokines in brain tissue.

Clinical Evidence

Semax has undergone extensive clinical research in Russia spanning over 25 years. For acute ischemic stroke, clinical trials demonstrated that intranasal semax administered within 12 hours of stroke onset significantly improved neurological outcomes, reduced infarct volume, and accelerated functional recovery compared to standard care (Gusev et al., 1997, 2006).

For cognitive enhancement, studies in healthy volunteers demonstrated improved attention, memory consolidation, and learning efficiency. Eremin et al. (2004) showed that semax increased BDNF expression in rat hippocampus by 1.4-1.8 fold and BDNF mRNA levels remained elevated for up to 24 hours after a single administration, suggesting sustained neurotrophic effects.

The N-Acetyl-Semax modification (NASA, or Adamax) has been developed as an enhanced version with improved blood-brain barrier penetration and longer duration of action.