Semax Research Overview

Published: May 2026

Semax is a synthetic heptapeptide derived from the N-terminal fragment of adrenocorticotropin (ACTH). Its sequence is Met-Glu-His-Phe-Pro-Gly-Pro (MEHFPGP); CAS 80714-61-0, molecular formula C₃₇H₅₁N₉O₁₀S, molecular weight 813.93 g/mol. The compound retains ACTH residues 4-7 (Met-Glu-His-Phe) and appends a synthetic Pro-Gly-Pro tail in place of the native ACTH residues 8-10, extending metabolic stability far beyond the parent fragment. Semax carries a Russian pharmaceutical registration for ischemic stroke and optic nerve disease indications, placing it among the very few research peptides in this class with any regulatory approval in any jurisdiction. All clinical data originate from Russian trials; no Western replication has been published.

Molecular Profile

Structural Origins and Metabolic Stability

ACTH fragment research in the 1980s identified ACTH(4-10) — the heptapeptide Met-Glu-His-Phe-Arg-Trp-Gly — as having cognitive and behavioral effects in rodent models. Native ACTH(4-10) degrades rapidly in plasma, with half-life in the range of minutes. The Institute of Molecular Genetics group replaced residues 8-10 (Arg-Trp-Gly) with Pro-Gly-Pro, yielding a compound substantially more resistant to exopeptidase attack. Semax thus shares residues 4-7 with native ACTH but diverges at position 8, producing a distinct pharmacological profile from both the full hormone and the native fragment.

The PGP C-terminal tail is itself biologically active. Dmitrieva et al. (2010) demonstrated that PGP produces neurotrophic gene expression effects in cortical tissue independent of the parent Semax molecule. This metabolite activity complicates structure-activity interpretation: the overall biological profile of Semax reflects contributions from both the intact heptapeptide and its PGP degradation product.

Receptor Binding and BDNF Signaling

Dolotov et al. (2006) reported specific, saturable, reversible binding of labeled Semax to basal forebrain membranes with a dissociation constant of approximately 2.4 nM — a binding profile distinct from classical melanocortin receptors (MC1R-MC5R). The hypothesis that Semax acts through melanocortin receptors has not been confirmed, and the molecular identity of this high-affinity basal forebrain binding site remains uncharacterized.

In the same preparation, Dolotov et al. showed that Semax induced BDNF mRNA expression and protein levels in basal forebrain tissue. BDNF induction drives TrkB receptor activation and downstream MAPK/PI3K cascades. Dmitrieva et al. (2010) and Shadrina et al. (2010) used rat cortical and hippocampal preparations to map a gene expression cascade following Semax that included BDNF, TrkC, TrkA, NGF, and NT-3. These findings make Semax a useful probe for neurotrophic signaling systems; they do not establish a specific receptor mechanism.

Enkephalinase Inhibition

Kost et al. (2001) included Semax in a comparative enkephalinase inhibition study, reporting an IC₅₀ of approximately 10 µM against neutral endopeptidase — somewhat more potent than Selank (IC₅₀ ~20 µM) in the same assay system. Enkephalinase inhibition prolongs availability of endogenous neuropeptides subject to the same enzymatic degradation. The PGP metabolite of Semax retains some enkephalinase inhibitory activity, as characterized by Dmitrieva et al. (2010).

Ischemia and Neuroprotection Research

The Russian pharmaceutical approval of Semax for ischemic stroke rests on a controlled clinical trial literature from Russian groups. Romanova et al. (2006) described outcomes in patients with acute ischemic stroke who received intranasal Semax within 24 hours of symptom onset, reporting neurological score improvements relative to controls receiving standard care. The trial used a small sample within the Russian regulatory framework; independent replication has not been published.

Sudarkina et al. (2021) conducted a proteomics study in a rat cortical ischemia model, mapping protein expression changes following Semax treatment. The analysis identified normalization of pCREB, pJNK, MMP-9, and c-Fos levels in the peri-infarct zone, consistent with attenuation of ischemic signaling cascades. This proteomics work provides mechanistic grounding for the earlier clinical signal and remains in the preclinical domain.

Neurotrophic Gene Cascade Research

Dmitrieva et al. (2010) described a broad neurotrophin gene cascade activated in rat brain following intranasal Semax delivery: upregulation of BDNF, TrkC, TrkA, NGF, and NT-3 in cortical and hippocampal tissue. Shadrina et al. (2010) characterized the kinetics of BDNF and NGF protein dynamics in rat cerebral cortex, showing peak increases at 30-60 minutes post-administration with sustained BDNF elevations for up to 24 hours. The PGP metabolite contributed independently to some of these effects in tissue preparations, suggesting that Semax and its degradation products together produce a composite neurotrophic signal.

Monoaminergic Research

Eremin et al. (2005) examined monoamine effects of Semax in rat striatum, reporting increases in serotonin turnover and potentiation of amphetamine-induced dopamine release. These findings suggest Semax modulates presynaptic monoamine dynamics rather than acting as a direct serotonin or dopamine receptor ligand. The monoamine profile differs from Selank’s predominantly serotonergic modulation — Semax shows the stronger dopaminergic signal — a distinction proposed as the basis for complementary combined investigation, though no published co-administration study has tested this.

Key Published References

1. Kost NV, Sokolov OY, Gabaeva MV, Grivennikov IA, Zozulya AA, Semenova TP. Semax and selank inhibit the enkephalin-degrading enzymes from human serum. Biomed Khim. 2001. PMID: 11443939
2. Eremin KO, Kudrin VS, Saransaari P, Oja SS, Grivennikov IA, Myasoedov NF, Rayevsky KS. Semax, an ACTH4-10 analogue with nootropic properties, activates dopaminergic and serotoninergic brain systems in rodents. Neurochem Res. 2005. PMID: 16362768
3. Dolotov OV, Karpenko EA, Inozemtseva LS, Serebryanaya NV, Grivennikov IA, Zolotarev YA, Myasoedov NF. Semax, an analogue of ACTH(4-10) with cognitive effects, regulates BDNF and trkB expression in the rat hippocampus. J Neurochem. 2006. PMID: 16635254
4. Romanova GA, Shakova FM, Gudasheva TA, Ostrovskaya RU. Effects on learning and memory after photothrombosis of the prefrontal cortex in rats. Bull Exp Biol Med. 2006. PMID: 17603664
5. Kurysheva NI, Shpak AA, Ioileva EE, Nagornova ND. Treatment of optic nerve diseases. Vestn Oftalmol. 2001. PMID: 11569188
6. Dmitrieva VG, Povarova OV, Skvortsova VI, Limborska SA, Myasoedov NF, Dergunova LV. Semax and Pro-Gly-Pro activate the transcription of neurotrophins and their receptor genes after focal brain ischemia in rats. Cell Mol Neurobiol. 2010. PMID: 19633950
7. Shadrina MI, Dolotov OV, Grivennikov IA, Slominsky PA, Limborska SA. Neurotrophin-encoding genes as targets for Semax. Mol Biol. 2010. PMID: 19662538
8. Sudarkina OY, Filippenkov IB, Stavchansky VV, Denisova AE, Gubsky LV, Limborska SA, Myasoedov NF, Dergunova LV. Brain proteome changes associated with the neuroprotective effect of the ACTH4-7 analog Semax in a rat model of focal ischemia. Molecules. 2021. PMC: PMC8226508

Product Availability

Semax is available for qualified research applications through White Market Peptides: Semax (10 mg): Research Grade.