What it is
Semax is a synthetic peptide seven amino acids long, and it is built the way a lot of neurological peptides are built: take a fragment of a hormone that does something interesting in the brain, then bolt on a short tail to stop the body destroying it immediately.
The fragment is ACTH(4-7) — residues four to seven of adrenocorticotropic hormone. The tail is Pro-Gly-Pro, a tripeptide added to slow enzymatic breakdown.
One point of ordinary biology is worth making, because the parent hormone's name alarms people. Adrenocorticotropic hormone's own job is to tell the adrenal glands to release cortisol, the stress hormone. The four-residue fragment used in semax does not carry that function. Using a piece of a hormone rather than the whole thing is a deliberate way of keeping one property and discarding another.
What it is said to be good for
Internationally, semax is marketed for memory, focus and mental performance in healthy people.
In the country where it is an actual prescription medicine, it is used for something quite different: neurological injury and disease, stroke above all.
What the research shows
Semax is a genuinely awkward case, and the awkwardness is worth explaining rather than resolving in either direction.
There is real research, and there is quite a lot of it. PubMed indexed 207 records for semax on 2026-09-07, of which 46 are tagged as human research. That is not a compound somebody invented last year.
Almost none of it is the kind of trial the rest of the world reads. Exactly 1 of those records is indexed as a randomized controlled trial. The human studies are overwhelmingly published in Russian-language journals — principally the Korsakov Journal of Neurology and Psychiatry — and they study patients: efficacy at different stages of ischemic stroke, optic nerve disease, chronic partial denervation in motor neuron disease.
And it is completely absent from the international trial registry. A search of ClinicalTrials.gov on 2026-09-07 returns zero interventional studies naming semax. Not few. None.
That last figure deserves care, because it is easy to over-read in both directions. Registration on ClinicalTrials.gov is driven largely by US regulatory requirements and by journal publication policies, so a drug developed and used entirely within another medical system can be genuinely studied and still leave no trace there. Zero registered trials is not proof that nothing was studied.
What it does mean is practical and unavoidable: the ordinary way of checking a drug does not work here. A reader cannot look up who is testing semax, in how many people, against what comparator, with what pre-registered endpoint, or whether a trial that started ever reported. For most compounds in this library that check is available. For this one it is not, and no amount of published research in another language substitutes for it.
The marketed use is not the studied use. We found no randomized trial of semax for memory or focus in healthy adults. The human record is about patients with neurological conditions. A compound can be both a legitimately prescribed stroke medicine somewhere and an unevidenced nootropic everywhere else, and semax is the clearest example of that in this library.
Where it stands
Approved as a medicine: registered in Russia. Not approved in the United States, the European Union or the United Kingdom.
US compounding status: in a warning letter dated 2021-11-10, FDA stated that semax — along with cerebrolysin and selank — was not nominated for inclusion on the 503A bulks list, the list of substances that may lawfully be compounded into medicines in the United States. A substance never nominated is not on the list.
Available as: a prescription medicine in Russia; a research chemical elsewhere.
The other Moscow-developed compound sold as a nootropic peptide is noopept, and its record is thinner in one specific way worth comparing: it has no entry in the international trial registry at all.
Related entries in this library: Selank and Cerebrolysin sit in the same position — used clinically in Russia, absent from the international record, named in the same FDA letter. All three appear among the compounds sold for focus and mood.
Last checked
2026-09-07. The PubMed counts and the empty ClinicalTrials.gov result were produced on that date through the NCBI E-utilities and the registry API. The FDA statement is quoted from the agency's warning letter of 2021-11-10.