Semax is a synthetic neuropeptide that came out of Soviet and later Russian research into the brain-relevant effects of adrenocorticotropic hormone (ACTH), stripped of the hormone's steroid-stimulating action. Its backbone is the ACTH(4-10) fragment carrying an added proline-glycine-proline tail that slows enzymatic breakdown, and it was registered in Russia in the 1990s as an intranasal medicine. The N-acetylated form is a later chemical refinement that caps the peptide's terminus for greater stability, and it sits outside that approval as a research compound.
Semax is a synthetic ACTH(4-10) analog developed by Moscow research teams across the 1980s and 1990s and registered in Russia as an intranasal medicine, while its N-acetylated derivative remains an unapproved research compound outside that market.
Semax is built on ACTH(4-10), the region of adrenocorticotropic hormone linked in the literature to attention and memory rather than to stimulation of the adrenal cortex. Isolating that behaviorally active segment let the developers pursue the neural effects while leaving the endocrine ones behind, and a short proline-based tail was added to keep the fragment from being clipped apart within minutes.
Semax is a synthetic heptapeptide, Met-Glu-His-Phe-Pro-Gly-Pro, derived from the ACTH(4-10) fragment of adrenocorticotropic hormone with an added proline-glycine-proline tail that resists rapid enzymatic breakdown.
The peptide was not a single-lab product but the output of a multidisciplinary program centered in Moscow, most closely associated with the biology and chemistry faculties of Moscow State University working alongside institutes of the Russian Academy of Sciences. That collaboration ran from the late Soviet period into the post-Soviet 1990s, a stretch when Russian science held a strong tradition in regulatory-peptide research even as funding structures shifted.
Semax emerged from a multidisciplinary program centered on Moscow State University and Russian Academy of Sciences institutes, spanning the late Soviet 1980s into the post-Soviet 1990s, which is a large part of why the drug was registered domestically rather than through Western pipelines.
Laboratory synthesis of the Met-Glu-His-Phe-Pro-Gly-Pro sequence dates to the 1980s, when the Moscow teams first characterized its properties, and formal registration in Russia followed in the 1990s. The full arc from bench synthesis to registered product ran across roughly a decade, reflecting the usual sequence of chemistry, animal work, and human trials.
Laboratory synthesis of Semax dates to the 1980s and formal registration as an approved medicine in Russia followed in the 1990s, initially as a low-concentration intranasal solution cleared for cerebrovascular and cognitive indications.
The stated intent behind Semax was a treatment for the brain and cognition, particularly the aftermath of impaired blood flow such as ischemic stroke and transient ischemic attacks, along with disorders of attention, memory, and mental fatigue. The peptide-based strategy appealed to the developers because short regulatory peptides can influence neural signaling at very low doses and tend to carry a gentler side-effect profile than many small-molecule drugs, an attractive prospect for delicate brain tissue.
Semax was designed as a nootropic and neuroprotective treatment for ischemic stroke, transient ischemic attacks, and disorders of attention and memory, capturing ACTH's neural effects while deliberately discarding its corticotropic activity.
N-terminal acetylation attaches an acetyl group, a small two-carbon acyl fragment derived from acetic acid, to the free amino group at the head of the peptide chain. Applied to Semax it produces the derivative usually written as N-Acetyl Semax, frequently prepared together with a C-terminal amide, and the purpose is metabolic: the exposed N-terminus is the first point of attack for many degrading enzymes.
N-Acetyl Semax attaches an acetyl cap to the peptide's N-terminus, often paired with C-terminal amidation, to slow aminopeptidase and carboxypeptidase degradation and extend stability while leaving the active heptapeptide core unchanged.
Structurally the two share the identical Met-Glu-His-Phe-Pro-Gly-Pro core; the acetylated form simply adds protective end groups, capping the N-terminus and, in the amidated version, converting the C-terminal acid to an amide. The most consequential difference is metabolic stability, since blocking the termini denies aminopeptidases and carboxypeptidases their normal starting points, though the sharpest divergence is regulatory rather than chemical.
| Property | Original Semax | N-Acetyl Semax |
|---|---|---|
| Core sequence | Met-Glu-His-Phe-Pro-Gly-Pro | Identical heptapeptide core |
| Terminal groups | Free N- and C-termini | Acetyl cap, often a C-terminal amide |
| Metabolic stability | Baseline functional half-life | Longer expected functional half-life |
| Regulatory standing | Registered medicine in Russia | Unapproved research compound |
N-Acetyl Semax shares the identical Met-Glu-His-Phe-Pro-Gly-Pro core with the original but adds terminal caps that are expected to raise metabolic stability, and unlike the Russia-registered original it is generally handled as an unapproved research compound.
In the United States, the European Union, and most other major markets Semax has never received drug approval, so it is not sold or prescribed as a licensed medicine there, and clinical use stays concentrated in Russia and a handful of neighboring countries. Independent scientific interest outside Russia has grown, gradually building an English-language literature, even as the acetylated derivatives remain research-chemical designations carrying no assurance of pharmaceutical-grade purity or human safety review.
Outside Russia and a few neighboring countries Semax holds no drug approval in the United States, European Union, or other major markets, and its acetylated derivatives are treated as research chemicals not evaluated by the FDA or EMA.
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