What is Semax?
Semax is a synthetic heptapeptide derived from the adrenocorticotropic hormone (ACTH) fragment 4-7, with a C-terminal Pro-Gly-Pro (PGP) extension that confers stability against enzymatic degradation. Its full sequence is Met-Glu-His-Phe-Pro-Gly-Pro (MEHFPGP).
Semax was developed by the Institute of Molecular Genetics of the Russian Academy of Sciences in the 1980s and 1990s as part of a research program focused on neuropeptides derived from ACTH. It has been the subject of preclinical studies examining neuroprotection, cognitive function, and neurotrophin regulation, and is registered as a drug in Russia and Ukraine (under the names Semax and Semaxin) for neurological indications, though this regulatory status does not apply to research use in other countries.
BDNF Modulation
One of the most studied aspects of Semax’s biological activity in preclinical models is its effect on Brain-Derived Neurotrophic Factor (BDNF) — a critical neurotrophin involved in neuronal survival, synaptic plasticity, and learning and memory processes.
Rodent studies have reported that Semax administration upregulates BDNF gene expression in the hippocampus and frontal cortex — brain regions central to memory formation and executive function. Additionally, research has documented increases in TrkB receptor expression (the primary BDNF receptor) in cortical tissue following Semax exposure in rat models.
Given BDNF’s established role in long-term potentiation (the cellular mechanism underlying memory consolidation) and adult neurogenesis, these preclinical findings have driven substantial interest in Semax as a research tool for studying neurotrophin signaling.
Neuroprotective Research
A meaningful portion of Semax preclinical research has focused on neuroprotection — the ability to preserve neuronal viability under conditions of injury or stress. Studies have examined Semax in models of:
- Ischemic stroke — rodent middle cerebral artery occlusion (MCAO) models have reported reduced infarct volume and improved functional recovery with Semax treatment
- Oxidative stress — in vitro neuronal culture studies showing reduced cell death under oxidative challenge
- Optic nerve lesion models — studies reporting preservation of retinal ganglion cell survival following optic nerve injury
Proposed neuroprotective mechanisms include anti-apoptotic signaling, upregulation of antioxidant defenses in neural tissue, and modulation of inflammatory cytokine production in microglial cells.
Cognitive Research in Animal Models
Behavioral studies in rodents have examined Semax’s effects on learning and memory tasks including:
- Morris Water Maze — a standard test of spatial learning and hippocampal-dependent memory
- Passive avoidance — evaluating associative memory formation
- Radial arm maze — measuring working memory in rodents
Several studies have reported improved performance on these tasks in Semax-treated animals compared to vehicle controls, particularly in models involving cognitive impairment induced by stress, cholinergic blockade, or aging.
Serotonergic and Dopaminergic Interactions
Preclinical studies have also investigated Semax’s interactions with monoamine neurotransmitter systems. Research has documented effects on serotonin receptor expression in limbic brain regions and modulation of dopaminergic neurotransmission in some models. These findings are of interest to researchers studying mood-related neural circuitry and attention pathways, though the mechanisms remain incompletely characterized.
Regulatory and Clinical Context
Semax is registered as a pharmaceutical in Russia for indications including stroke rehabilitation and cognitive impairment. However, it has not undergone evaluation by the FDA and is not approved for any human therapeutic use outside of registered clinical settings in countries where it holds authorization. Its regulatory status varies by jurisdiction, and researchers are responsible for verifying applicable regulations in their location.
Semax sold by Euno Labs is for in vitro and laboratory research use only.
Selected References
Dolotov OV, et al. (2006). Semax, an analogue of ACTH(4-7) with cognitive effects, regulates BDNF and trkB expression in the rat hippocampus. Brain Research, 1117(1), 54–60.
Shadrina MI, et al. (2010). Neuroprotective Effect of Semax in Rat Hippocampus after Global Ischemia. Journal of Molecular Neuroscience, 41(2), 276–281.
Gusev EI & Skvortsova VI. (2003). Semax in acute ischaemic stroke. Cerebrovascular Diseases, 15 (Suppl 2), 4 (Abstract).