Semax is a seven-residue synthetic peptide built from a fragment of adrenocorticotropic hormone (ACTH). Its first four amino acids are the ACTH(4-7) sequence, and a Pro-Gly-Pro tail was added to the C-terminus to slow enzymatic breakdown. The result is a short, linear peptide that keeps none of ACTH’s ability to drive adrenal steroid release, which is why investigators have studied it mainly as a probe of brain neurochemistry.
Almost all of the published work on Semax comes from Russian laboratories, much of it in rat brain tissue. This overview covers how the peptide was designed, the neurotrophin and monoamine findings that make up the core of its literature, the stability and enzyme studies, and the limits of what those studies can tell us.
At a glance
- Class: Synthetic heptapeptide; ACTH(4-10) analogue (melanocortin-derived)
- Origin: Designed in Russia from the ACTH(4-10) fragment and studied there since the 1980s
- Structure: Met-Glu-His-Phe-Pro-Gly-Pro; C37H51N9O10S; MW 813.9 g/mol; CAS 80714-61-0
- Main research areas: BDNF and TrkB signaling, dopamine and serotonin systems, peptide stability, peptidase inhibition, rodent ischemia models
- Regulatory status: Not approved by the FDA; a prescription medicine in Russia; sold here as a research reagent only
Structure and origin
The starting point for Semax was the observation, made in the mid-20th century, that short fragments of ACTH could act on the nervous system without stimulating the adrenal cortex. ACTH(4-10), Met-Glu-His-Phe-Arg-Trp-Gly, became a model fragment for that idea. Its weakness was speed of degradation: in blood and tissue it is cut apart within minutes.
Semax keeps the first four residues of that fragment and replaces the rest with Pro-Gly-Pro. Proline-rich C-terminal sequences resist many peptidases, and the Pro-Gly-Pro motif later reappeared in Selank, a related peptide from the same research tradition. The name itself is a contraction referring to the seven amino acids in the chain. Even so, the change did not make Semax fully stable. Potaman and colleagues incubated ACTH(4-10) and Semax with rat blood enzymes and found that both were cleaved from the N-terminus, with Semax persisting longer than the natural fragment (Potaman et al., 1991). That study set the template for later work on Semax metabolites, several of which are themselves biologically active in assays.
Mechanism: what the research shows
No single receptor has been identified as the target of Semax, and the mechanism remains a matter of active study. Several lines of evidence point in different directions.
The best-documented findings involve brain-derived neurotrophic factor (BDNF). Using membrane preparations from rat basal forebrain, Dolotov and colleagues reported specific, saturable binding of labeled Semax, and they measured higher BDNF protein levels in that region after exposure to the peptide (Dolotov et al., 2006a). A follow-up study in the rat hippocampus examined both BDNF and its receptor TrkB and reported changes in their mRNA and protein expression (Dolotov et al., 2006b).
A second line concerns the monoamine systems. Eremin and colleagues measured dopamine, serotonin and their metabolites in rodent striatum and other brain regions, and reported that Semax shifted these markers in both systems (Eremin et al., 2005). Because Semax is a melanocortin fragment, it has also been tested at melanocortin receptors; receptor assays reported competitive antagonism of α-MSH at the MC4 and MC5 subtypes. Finally, enzyme assays showed that Semax inhibits enkephalin-degrading peptidases in human serum, which would raise local levels of endogenous opioid peptides in a test tube (Kost et al., 2001).
Key areas of study
Neurotrophin signaling
BDNF work is the most cited part of the Semax literature. The basal forebrain binding study and the hippocampal BDNF/TrkB expression study used rat tissue, radioligand binding and immunoassays, and they are the reason Semax is often grouped with other compounds that modulate neurotrophin pathways (Dolotov et al., 2006a; Dolotov et al., 2006b). The binding site itself has not been isolated or cloned.
Dopamine and serotonin systems
Rodent neurochemistry studies have measured tissue levels of monoamines and their metabolites by HPLC after Semax exposure. The findings suggest that the peptide modulates dopaminergic and serotonergic activity rather than acting as a direct agonist at monoamine receptors, but the pathway linking the two has not been mapped (Eremin et al., 2005).
Peptide stability and enzyme interactions
Semax is also a case study in peptide design. Degradation work in rat blood identified its main cleavage pattern (Potaman et al., 1991), and serum enzyme assays showed that both Semax and Selank inhibit the enzymes that break down enkephalins (Kost et al., 2001). These experiments matter for anyone interpreting in vivo results, because the parent peptide and its fragments may both be present in a sample.
Ischemia models and brain network studies
Gene-expression studies in rat models of focal brain ischemia have examined how Semax exposure shifts transcription of genes tied to inflammation, vascular function and neurotrophins. More recently, a functional connectivity study compared the two related peptides, Semax and Selank, using imaging methods (Panikratova et al., 2020). Work of this kind is descriptive and comes from a small number of groups.
What the evidence does not show
The Semax literature has clear limits. The molecular target is unknown: the BDNF, monoamine, melanocortin and peptidase findings have not been tied together into one mechanism. Most studies come from a few institutes in Moscow, many are published in Russian-language journals, and independent replication outside that network is sparse. Sample sizes in rodent studies are often small. Because Semax breaks down into active fragments, it is not always clear whether an effect comes from the parent peptide or its metabolites. None of the animal or cell findings establishes any effect in people, and nothing in this literature describes the research material sold here.
Regulatory status
Semax is used as a prescription medicine in Russia and appears on the Russian List of Vital and Essential Drugs. It is not approved by the FDA and has not been approved in most other countries. The material sold by Rogue Compounds is a research reagent, not an approved drug product.
Handling and storage in the lab
Lyophilized Semax should be kept sealed and refrigerated at 2–8°C (36–46°F), protected from light. The N-terminal methionine can oxidize, so keeping the vial closed and dry until use helps preserve the material.
Sourcing and documentation
Rogue Compounds has Semax made in small batches. Every vial carries a batch number and a QR code that opens the independent U.S. testing lab’s own report for that batch. The same batch COA is posted on the product page and in the COA Library.
References
- Potaman VN, et al. N-terminal degradation of ACTH(4-10) and its synthetic analog semax by the rat blood enzymes. Biochem Biophys Res Commun. 1991;176(2):741-746. PMID 1851003
- Dolotov OV, 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(Suppl 1):82-86. PMID 16635254
- Dolotov OV, 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
- Eremin KO, et al. Semax, an ACTH(4-10) analogue with nootropic properties, activates dopaminergic and serotoninergic brain systems in rodents. Neurochem Res. 2005;30(12):1493-1500. PMID 16362768
- Kost NV, et al. Semax and selank inhibit the enkephalin-degrading enzymes from human serum. Bioorg Khim. 2001;27(3):180-183. PMID 11443939
- Panikratova YR, et al. Functional connectomic approach to studying Selank and Semax effects. Dokl Biol Sci. 2020;490(1):9-11. PMID 32342318
Research use only. Rogue Compounds products are sold strictly for laboratory research. They are not for human or veterinary use, and nothing in this article is medical advice. The studies cited here describe published research, not this product or any use of it.