Semax

Semax is a synthetic heptapeptide derived from the adrenocorticotropic hormone (ACTH) fragment 4-10, with the sequence Met-Glu-His-Phe-Pro-Gly-Pro. Developed by the Institute of Molecular Genetics of the Russian Academy of Sciences, Semax has been approved as a pharmaceutical agent in Russia and Ukraine for neurological applications. Research focuses on its ability to modulate brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF) expression, conferring neuroprotective properties particularly relevant to ischaemic brain injury research. Studies have documented its effects on dopaminergic and serotonergic neurotransmitter systems, suggesting broad neuromodulatory activity beyond simple ACTH fragment effects. Semax has been clinically documented in stroke rehabilitation literature, where its neuroprotective and neurorestorative properties have been examined in post-ischaemic recovery models. The peptide crosses the blood-brain barrier efficiently, enabling central nervous system activity following peripheral administration. Researchers in neuroscience and cognitive pharmacology consider Semax a significant tool for studying neuroplasticity, neurotrophic factor regulation, and cognitive enhancement mechanisms in preclinical and clinical contexts.

Structurally Semax is ACTH(4-10) carrying a Pro-Gly-Pro extension at the C-terminus, and that tripeptide tail is the functionally important part of the design rather than an inert addition. PGP resists aminopeptidase cleavage, which is what gives the molecule a usable duration where the bare ACTH fragment has almost none. Critically, Semax retains the neurotropic activity of the parent fragment while being devoid of its corticotropic activity, so it does not drive adrenal steroidogenesis the way ACTH itself does. That separation of activities is the single most important pharmacological fact about the compound.

The neurotrophic mechanism is the most studied. Dolotov and colleagues reported increased BDNF and TrkB expression in rat hippocampus following administration, and the wider literature describes effects on NGF signalling alongside modulation of dopaminergic and serotonergic transmission. Semax is registered as a pharmaceutical in Russia, where it is used in stroke and cognitive indications.

The limitation should be stated rather than glossed over. Almost the entire evidence base is Russian-language and originates from a small number of affiliated institutions, and independent replication in Western laboratories is sparse. Very few placebo-controlled trials are indexed in the major English-language databases. Semax holds no marketing authorisation in the UK, the EU or the US, and is supplied here as a lyophilised research chemical for in-vitro laboratory use only.