Semax Research

Semax research sits within a long-running effort to understand short regulatory peptides derived from adrenocorticotropic hormone (ACTH). The molecule at its center is a small synthetic peptide built from the neuroactive core of ACTH. It is studied mainly for how it influences neurotrophic factor signaling, and for its behavior in models of brain injury. This article summarizes what published preclinical studies show about Semax. The focus is [brain-derived neurotrophic factor](/glossary#term-bdnf-brain-derived-neurotrophic-factor) (BDNF) and related neurotrophic signaling, findings from cerebral ischemia models, and the peptide's reported effect on enkephalin-degrading enzymes. All of this is set against the clinical registration context in Russia. Each finding below is identified as coming from a cell culture (in vitro) or an animal model. Nothing here should be read as an outcome an individual should expect. Semax is a research compound. It is not characterized here for human use.

What Semax is

Semax is a synthetic heptapeptide with the sequence Met-Glu-His-Phe-Pro-Gly-Pro. It is built on the ACTH(4-7) core, Met-Glu-His-Phe, extended at the C-terminus by three additional residues, Pro-Gly-Pro. The addition is intended to slow enzymatic breakdown and give the molecule a longer duration than the rapidly degraded parent fragment.

The peptide is a synthetic analog of the N-terminal (4-10) region of ACTH rather than a fragment of it. ACTH residues 8 to 10, Arg-Trp-Gly, are absent from Semax and are replaced by Pro-Gly-Pro. That region carries the neurotropic and behavioral activity historically associated with ACTH, but Semax lacks the corticotropic hormonal action of the full hormone. It is therefore studied as a neuroactive peptide rather than an endocrine one. It was developed at the Institute of Molecular Genetics of the Russian Academy of Sciences, and across the research literature it is typically applied intranasally.

BDNF and neurotrophic factor research

The most developed strand of Semax research concerns neurotrophic factors, the proteins that support neuronal survival, growth, and plasticity. The earliest cellular evidence is in vitro. Shadrina and colleagues reported in 2001 that Semax rapidly induced the messenger RNAs for both nerve growth factor (NGF) and BDNF in rat glial cell cultures.^[1] The authors suggested that its effects on neuronal survival might be mediated through the regulation of neurotrophin expression.

Work then moved into the intact brain. Dolotov and colleagues reported in 2006 that intranasal Semax raised BDNF protein in the rat basal forebrain within 3 hours, though not in the cerebellum. They also reported that cell membranes isolated from that same region carried specific, reversible binding sites for radiolabeled Semax in an in vitro binding assay. The reported dissociation constant was about 2.4 nM.^[2] In a companion study, the same group found that a single application in rats increased BDNF protein in the hippocampus. In that region, the same application also raised phosphorylation of trkB, the receptor through which BDNF signals.^[3]

A further in vivo study by Agapova and colleagues in 2007 measured neurotrophin gene expression across brain regions. It found that Semax produced rapid, gene- and region-specific changes. Expression of both NGF and BDNF rose in the hippocampus, and BDNF also rose in the brainstem and cerebellum, while NGF expression fell in the frontal cortex.^[4] Taken together, these are in vitro and animal findings that point to modulation of neurotrophic signaling rather than a single uniform increase.

Ischemia model findings

A second strand has examined Semax in animal models of cerebral ischemia, where restricted blood flow drives neuronal injury and neurotrophic and vascular signaling become central.

Dmitrieva and colleagues reported in 2008 on rats subjected to experimental cerebral ischemia. In that model, they found that Semax and its C-terminal fragment Pro-Gly-Pro altered the expression of several growth factor genes and their receptors in the affected brain tissue.^[5] Medvedeva and colleagues extended this to the vascular side of the response, reporting in 2013 on a rat model of focal cerebral ischemia. In it, Semax and Pro-Gly-Pro influenced the expression of vascular endothelial growth factor (VEGF) family genes and their receptors.^[6]

Both are animal findings that characterize how the peptide interacts with the molecular response to ischemic injury. Neither predicts an outcome in an organism beyond the model.

Enkephalin system research

A distinct line of work concerns the endogenous opioid system. Kost and colleagues reported in 2001 that Semax, along with the related peptide Selank, dose-dependently inhibited enkephalin-degrading enzymes from human serum in vitro.^[7] By slowing the enzymatic breakdown of enkephalins, the peptide is thought to prolong endogenous enkephalin signaling rather than acting directly on opioid receptors.

Animal behavior is only partly consistent with an opioid-related action. Manchenko and colleagues reported in 2010 that intraperitoneal Semax produced an analgesic effect in rats in the Randall-Selitto paw-withdrawal test. The same study found that intranasal Semax, the route used in most Semax research, did not alter pain sensitivity at all. It nonetheless improved learning more than the intraperitoneal route. The authors took this dissociation as evidence that the nootropic and analgesic effects depend on different mechanisms and brain structures.^[8]

It is worth being precise about the evidence here. The enzyme inhibition is an in vitro biochemical finding, and the analgesia is an animal behavioral finding. The link between them, that inhibited enkephalin breakdown produces the observed analgesia, remains a proposed mechanism rather than a directly measured chain.

Human context

The directly relevant mechanistic and neurotrophic evidence on Semax is preclinical, drawn from cell and animal studies. Semax is also registered as a medicinal product in Russia and has been investigated in clinical settings there. That work includes early research by Miasoedova and colleagues on the mechanisms of its reported neuroprotective effect in the acute period of ischemic stroke.^[9] That clinical and regulatory context is specific to Russia and is distinct from the research-grade compound discussed here. No personal outcome should be inferred from it.

Limitations

Several limitations shape how this literature should be read. A large share of the work originates from a small network of affiliated Russian institutes, and much of it is published in Russian-language journals. This limits independent replication.

The proposed mechanisms are multiple, spanning neurotrophic, enkephalinergic, and vascular signaling. The neurotrophic effects themselves are region-specific rather than uniform, so a single unifying account is not yet settled. Human pharmacokinetic and long-term safety data available in the international literature are limited.

Conclusion

Semax is best understood as a metabolically stabilized ACTH(4-10) analog, an ACTH(4-7) core carrying a Pro-Gly-Pro extension. It is studied as a neuroactive peptide without the hormonal action of the parent hormone.

Its preclinical profile points to a multi-target picture. That picture includes modulation of NGF and BDNF signaling in cell and animal studies, along with altered growth factor and VEGF gene expression in animal ischemia models. It also includes inhibition of enkephalin-degrading enzymes in vitro alongside analgesic activity in animals. The findings above describe what has been investigated, not what any individual should expect.

References

1. 1

   Shadrina MI, Dolotov OV, Grivennikov IA, Slominsky PA, Andreeva LA, Inozemtseva LS, et al. Rapid induction of neurotrophin mRNAs in rat glial cell cultures by Semax, an adrenocorticotropic hormone analog. Neurosci Lett. 2001;308(2):115-118. PMID 11457573.
2. 2

   Dolotov OV, Karpenko EA, Seredenina TS, Inozemtseva LS, Levitskaya NG, Zolotarev YA, et al. Semax, an analogue of adrenocorticotropin (4-10), binds specifically and increases levels of brain-derived neurotrophic factor protein in rat basal forebrain. J Neurochem. 2006;97(s1):82-86. PMID 16635254.
3. 3

   Dolotov OV, Karpenko EA, Inozemtseva LS, Seredenina TS, Levitskaya NG, Rozyczka J, et al. Semax, an analog of ACTH(4-10) with cognitive effects, regulates BDNF and trkB expression in the rat hippocampus. Brain Res. 2006;1117(1):54-60. PMID 16996037.
4. 4

   Agapova TY, Agniullin YV, Shadrina MI, Shram SI, Slominsky PA, Lymborska SA, et al. Neurotrophin gene expression in rat brain under the action of Semax, an analogue of ACTH 4-10. Neurosci Lett. 2007;417(2):201-205. PMID 17353092.
5. 5

   Dmitrieva VG, Dergunova LV, Povarova OV, Skvortsova VI, Limborskaya SA, Myasoedov NF. The effect of semax and the C-terminal peptide PGP on expression of growth factor genes and receptors in rats under conditions of experimental cerebral ischemia. Dokl Biochem Biophys. 2008;422:261-264. PMID 19024553.
6. 6

   Medvedeva EV, Dmitrieva VG, Povarova OV, Limborska SA, Skvortsova VI, Myasoedov NF, Dergunova LV. Effect of semax and its C-terminal fragment Pro-Gly-Pro on the expression of VEGF family genes and their receptors in experimental focal ischemia of the rat brain. J Mol Neurosci. 2013;49(2):328-333. PMID 22772900.
7. 7

   Kost NV, Sokolov OYu, Gabaeva MV, Grivennikov IA, Andreeva LA, Myasoedov NF, et al. Semax and selank inhibit the enkephalin-degrading enzymes from human serum. Bioorg Khim. 2001;27(3):180-183. PMID 11443939.
8. 8

   Manchenko DM, Glazova NYu, Levitskaya NG, Andreeva LA, Kamensky AA, Myasoedov NF. Nootropic and analgesic effects of Semax following different routes of administration. Ross Fiziol Zh Im I M Sechenova. 2010;96(10):1014-1023. PMID 21268834.
9. 9

   Miasoedova NF, Skvortsova VI, Nasonov EL, Zhuravleva EY, Grivennikov IA, Arsenieva EL, Sukhanov I. Investigation of mechanisms of the neuroprotective effect of Semax in the acute period of ischemic stroke. Zh Nevrol Psikhiatr Im S S Korsakova. 1999;99(5):15-19. PMID 10358912.