Head to head
Selank vs Semax
Two Russian peptides, two different parents, one evidence problem.
Selank is a tuftsin analog registered in Russia as an anxiolytic; Semax is an ACTH fragment registered there for stroke and cognitive indications. Both carry the same Pro-Gly-Pro stabilizing tail and the same gap: a Western-indexed mechanism literature and clinical claims that rest on Russian studies no one has replicated abroad.
| Measure | SelankTuftsin-derived heptapeptide | SemaxACTH (4-10) analog |
|---|---|---|
| Best evidence | Emerging | Preclinical |
| Human-tested claims | 0 of 1 | 0 of 2 |
| Status | Approved abroad | Approved abroad |
| Cited sources | 2 | 2 |
Where the evidence lands
They are easy to confuse and should not be. Selank's story is GABA: a positive allosteric effect on GABA-A receptors, and small clinical reports of anxiety relief without sedation. Semax's story is BDNF: raised neurotrophin signalling in animals and in treated stroke patients. Both are prescription drugs in their home market and Tier 4 by our standard, because registration in Russia is a regulatory fact, not independent evidence of efficacy.
Where they differ
Each row cites a fixed record. Numbers from different trials are not directly comparable, and the rows say so where that applies.
| Aspect | Selank | Semax |
|---|---|---|
| Parent peptide[1] | Tuftsin (TKPR), an immune tetrapeptide, plus Pro-Gly-Pro. | ACTH(4-7), Met-Glu-His-Phe, plus Pro-Gly-Pro. |
| Proposed mechanism[2] | Allosteric modulation of GABA-A receptors. | Up-regulation of BDNF and its receptor TrkB. |
| Clinical use in Russia[3] | Anxiety disorders, including generalized anxiety and neurasthenia. | Ischemic stroke, cognitive and cerebrovascular indications, given intranasally. |
| Strongest evidence[4] | A small Russian study comparing it with a benzodiazepine (Tier 4). | Russian clinical series in stroke rehabilitation (Tier 4); mechanism in rats (Tier 3). |
| Status[1] | Registered in Russia; not approved by the FDA or EMA. | Registered in Russia; not approved by the FDA or EMA. |
What each is studied for
The efficacy claims from each monograph, with their tiers. Follow the entry for sources and safety.
Selank
- EmergingComparable anxiolytic effect to a benzodiazepine, with added anti-asthenic effects, in a small Russian study of generalized anxiety and neurasthenia.
Semax
- PreclinicalRegulated BDNF and TrkB expression in rat hippocampus – the mechanistic basis for its nootropic claims.
- EmergingNeuroprotective and pro-cognitive effects reported in Russian clinical studies; not independently replicated in Western RCTs.
Frequently asked
Are Selank and Semax the same drug?
No. They share a stabilizing tail and a country of origin. The active cores come from different hormones, the proposed mechanisms differ, and they are registered for different conditions.
References
The monographs
Written by Twenty Residues editorial. Medical review: pending; a named reviewer is being assigned.
Last updated October 1, 2026.
Tiers are explained in the Standard. Spot an error? Report a correction.