What is Semax?
Semax is a synthetic seven-amino-acid peptide, Met-Glu-His-Phe-Pro-Gly-Pro, built from the ACTH(4-7) fragment of adrenocorticotropic hormone with a Pro-Gly-Pro tail added to resist enzymes. It was developed in Russia and is studied mainly in rat models of brain ischemia and gene expression. Here is its structure, origin, research record and status.
Semax in one table.
| Sequence | MEHFPGP (Met-Glu-His-Phe-Pro-Gly-Pro) |
|---|---|
| Length | 7 amino acids, a heptapeptide |
| Formula | C37H51N9O10S |
| Molecular weight | 813.9 g/mol (monoisotopic 813.3480) |
| PubChem CID | 9811102 |
| Parent peptide | ACTH(4-7), Met-Glu-His-Phe |
| Status | On Russia's list of vital and essential drugs; not approved by the FDA |
Formula and masses from Helion's peptide molecular weight calculator, matching PubChem.
A hormone fragment, made stable.
Semax starts from residues 4 to 7 of adrenocorticotropic hormone (ACTH) and adds Pro-Gly-Pro at the C-terminus, a tail included to make it resistant to peptidases. A 1991 study from the Institute of Molecular Genetics of the Russian Academy of Sciences found Semax more stable than ACTH(4-10) against blood enzymes, apart from aminopeptidases that still remove its first two residues. Despite its origin, it is described as having no hormonal activity. With nerve cells it breaks down into fragments including HFPGP and PGP.
Mostly rats.
Most published work on Semax is in rats. It raised levels of brain-derived neurotrophic factor (BDNF) in the rat hippocampus about 1.4-fold; after middle cerebral artery occlusion, the genes it changed were mostly immune and vascular; and in a rat model of cortical ischemia, infarcts were smaller. A 2025 study tested it in a transgenic mouse model of Alzheimer's disease. The human data are small Russian clinical studies in stroke, such as a 1997 study comparing 30 treated patients with 80 conventionally treated controls.
The modified version.
N-acetyl Semax amidate is Semax with an acetyl group on the N-terminus and an amide on the C-terminus, Ac-MEHFPGP-NH2: C39H54N10O10S, 855.0 g/mol. As of October 2026 we found no peer-reviewed study of that amidated form in PubMed; the closest work, from 2016, studied N-terminally acetylated Semax for its copper and zinc binding in cell culture. Check the calculator preloaded with the acetylated, amidated form.
Russia, not the FDA.
Semax is on Russia's list of vital and essential drugs and has no FDA approval; outside Russia it is a research compound. Helion supplies compounds for laboratory research use only.
The sister peptide.
Semax shares its Pro-Gly-Pro design with Selank, built from the immune peptide tuftsin. Selank vs Semax compares the two side by side.
Helion does not currently supply Semax.
Specs and storage by compound.
Questions (6)
What is Semax?
A synthetic seven-amino-acid peptide, Met-Glu-His-Phe-Pro-Gly-Pro: the ACTH(4-7) fragment with a Pro-Gly-Pro tail added to resist enzymes.
What is the Semax sequence?
MEHFPGP: methionine, glutamate, histidine, phenylalanine, proline, glycine, proline.
Is Semax a hormone?
No. It is built from a fragment of ACTH but is described as having no hormonal activity.
What is N-acetyl Semax amidate?
Semax with an N-terminal acetyl group and a C-terminal amide, Ac-MEHFPGP-NH2, 855.0 g/mol. We found no peer-reviewed study of that exact form.
What is the molecular weight of Semax?
813.9 g/mol (C37H51N9O10S).
Does Helion sell Semax?
Not currently.
Published studies (8)
- Semax, an analog of ACTH(4-10) with cognitive effects, regulates BDNF and trkB expression in the rat hippocampus
- The peptide semax affects the expression of genes related to the immune and vascular systems in rat brain focal ischemia: genome-wide transcriptional analysis
- Neuroprotective and antiamnesic effects of Semax during experimental ischemic infarction of the cerebral cortex
- Novel Insights into the Protective Properties of ACTH((4-7))PGP (Semax) Peptide at the Transcriptome Level Following Cerebral Ischaemia-Reperfusion in Rats
- N-terminal degradation of ACTH(4-10) and its synthetic analog semax by the rat blood enzymes
- The Potential of the Peptide Drug Semax and Its Derivative for Correcting Pathological Impairments in the Animal Model of Alzheimer's Disease
- Influence of the N-terminus acetylation of Semax, a synthetic analog of ACTH(4-10), on copper(II) and zinc(II) coordination and biological properties
- [Effectiveness of semax in acute period of hemispheric ischemic stroke (a clinical and electrophysiological study)]
Citations from PubMed for reference. They describe the compound in the literature, not any Helion lot, and nothing here is guidance on use.