Comparison. Research use only.
Semax vs Selank
The two most-studied Russian-developed research peptides, frequently grouped together and rarely distinguished. Semax is an ACTH(4-7) fragment extended with Pro-Gly-Pro, studied mainly in neurotrophin expression and ischemia models. Selank is a tuftsin-derived heptapeptide investigated as a GABAergic modulator and enkephalinase inhibitor. Overlapping research framing, unrelated mechanisms.
What is the difference between Semax and Selank?
Semax is an ACTH(4-7) fragment extended with Pro-Gly-Pro, studied mainly for neurotrophin (BDNF, NGF) gene expression in rat brain ischemia models. Selank is a tuftsin analogue extended with the same Pro-Gly-Pro tail, studied as an enkephalinase inhibitor and positive allosteric modulator of GABA binding. Both evidence bases are largely preclinical and Russian, and neither Semax nor Selank is FDA-approved.
| Attribute | Semax | Selank |
|---|---|---|
| Parent molecule | ACTH(4-7), a melanocortin fragment | Tuftsin, an immune-signalling tetrapeptide |
| Sequence | Met-Glu-His-Phe-Pro-Gly-Pro (MEHFPGP) | Thr-Lys-Pro-Arg-Pro-Gly-Pro (TKPRPGP) |
| Molecular weight | 813.9 g/mol | 751.9 g/mol |
| Proposed mechanism | Specific binding sites in rat basal forebrain (Kd 2.4 nM); Bdnf and Ngf transcription changes (Dolotov 2006) | Enkephalinase inhibition (IC50 15 µM, Zozulya 2001); positive allosteric modulation of GABA binding (Vyunova 2018) |
| Typical research models | Rat cerebral ischemia (MCAO) and brain gene-expression studies | Rat frontal cortex gene expression; IMR-32 neuroblastoma cells |
| Human evidence | No human trials in our summary; mechanistic work from a few affiliated Russian institutions | No study registered on ClinicalTrials.gov; human literature unregistered and Russian-language |
| US regulatory status | Not FDA-approved; FDA bulk-substance Category 2 | Not FDA-approved; FDA bulk-substance Category 2 |
What is Semax?
Semax is a synthetic melanocortin derivative: the ACTH(4-7) fragment with the tripeptide Pro-Gly-Pro added at the C-terminus. That extension is generally described as making the peptide more resistant to enzymatic degradation than the unmodified ACTH fragment.
Read the full Semax research summary →What is Selank?
Selank is a synthetic heptapeptide analogue of tuftsin, a naturally occurring immune-signalling tetrapeptide, extended at the C-terminus with Pro-Gly-Pro. Two mechanistic lines dominate the literature.
Read the full Selank research summary →Semax and Selank specifications
Frequently asked questions
Are Semax and Selank related?
Only superficially. Semax and Selank are both short synthetic peptides ending in the same Pro-Gly-Pro tail, added for resistance to enzymatic breakdown, and both were developed in Russia. Their active cores come from unrelated parent molecules: Semax from the ACTH(4-7) melanocortin fragment, Selank from tuftsin, an immune-signalling tetrapeptide. Their published mechanisms differ accordingly.
Do Semax and Selank act on the same targets?
No. Semax showed specific, calcium-dependent binding in rat basal forebrain membranes (Dolotov et al., 2006), and its main downstream correlate is neurotrophin gene expression such as Bdnf and Ngf. Selank inhibited enzymatic breakdown of enkephalins (Zozulya et al., 2001) and has been described as a positive allosteric modulator of GABA binding (Vyunova et al., 2018). Neither compound's receptor has been definitively identified.
Have Semax or Selank been studied in humans?
Controlled human evidence is thin for both. Our Semax summary lists no human trials, and its in vivo mechanistic work comes mostly from a small number of affiliated Russian institutions. No Selank study is registered on ClinicalTrials.gov, and its available human literature is unregistered, Russian-language and generally lacks described blinding or placebo control. Semax and Selank are both reported to be registered medicines in the Russian Federation.
What is the US regulatory status of Semax and Selank?
Neither Semax nor Selank is approved by the FDA for any indication. FDA has placed both in Category 2 of bulk drug substances nominated under sections 503A/503B, the category for substances that may present significant safety risks, citing possible immunogenicity from aggregation and peptide-related impurities. Veridian supplies both strictly for in vitro and non-human laboratory research.
Other research peptide comparisons
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