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How the two peptides differ · Updated October 13, 2026
Semax is an ACTH-fragment analogue, while Selank is a tuftsin analogue. Both have seven amino acid residues and the same Pro-Gly-Pro tail, but their parent sequences and research questions differ. A ClinicalTrials.gov search checked October 13, 2026 found no Semax intervention records and two unrelated brain-stimulation records for Selank, rather than a registered peptide-intervention program.
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The Semax vs Selank difference is the parent peptide: ACTH(4-7) for Semax, tuftsin for Selank. Both add the same Pro-Gly-Pro tail.
Both are registered prescription medicines in Russia. Neither is approved by FDA.
FDA lists both among Category 2 nominations that the nominators withdrew. Only Semax was on the July 2026 advisory committee agenda.
The cited human studies are small and mainly from Russian research groups. The ClinicalTrials.gov search results do not identify a relevant Semax or Selank intervention study.
Both peptides came out of the Institute of Molecular Genetics, part of the Russian Academy of Sciences. The shared design idea was to take a short natural regulatory peptide and add Pro-Gly-Pro, a tail that slows breakdown by enzymes. The peptides differ in the natural sequence each one starts from.
Semax has the sequence Met-Glu-His-Phe-Pro-Gly-Pro. Its first four residues match positions 4 to 7 of ACTH, so it is often called an ACTH(4-10) analogue. It lacks the hormone's own corticotropic activity. Its formula is C37H51N9O10S, with a mass of about 813.9 g/mol.
Selank has the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro. Its first four residues are tuftsin, taken from the heavy chain of immunoglobulin G. Its formula is C33H57N11O9, with a mass of about 751.9 g/mol.
See the longer side-by-side article on the two peptides for additional context.
No. FDA has approved neither Semax nor Selank for any use. Both are registered prescription medicines in Russia, and that registration carries no US status.
FDA's Category 2 bulk substances page lists "Semax (heptapeptide)" and "Selank acetate (TP-7)" under nominations withdrawn by the nominators. The page shows content current as of April 22, 2026. A withdrawn nomination is not an approval.
Semax appeared on the July 23 and 24, 2026 committee agenda; Selank did not. The FDA staff briefing document found insufficient evidence for the three Semax uses it evaluated. Contemporaneous Hyman, Phelps & McNamara reporting on the committee vote gives 8 yes, 5 no and one abstention for recommending each Semax form. A committee recommendation is advisory and does not itself approve a drug product or add a substance to the 503A list.
The Semax 10 mg research material and Selank 10 mg research material listings provide examples to compare with the corresponding lot certificates. Their laboratory-research designation does not make them approved drug products.
Semax rodent studies measured BDNF and its receptor TrkB and examined neurotrophin, immune, vascular and stress-signaling pathways in ischemia models. The FDA's 2026 Semax scientific review identifies the experiments and their limits. A 2006 labeled-peptide study in rats examined Semax penetration into brain and blood. These animal findings do not establish effects in people.
Semax human research includes reports on cerebrovascular insufficiency, optic nerve disease, glaucoma and stroke, as well as healthy volunteers. FDA's linked scientific review evaluates the human literature and found insufficient evidence for its three assessed indications. Study design and the population actually analyzed matter when reading an individual report.
Selank's proposed mechanisms include changes in neurotransmission and immune signaling. A 2016 rat study of GABAergic gene expression measured changes in the frontal cortex after Selank or GABA. It supports a research hypothesis about GABA-related signaling, rather than a confirmed single target or a clinical outcome. The human-cell and clinical immune findings are described in the separate 2008 paper below.
A 2008 randomized Selank-medazepam comparison enrolled 62 participants with generalized anxiety disorder or neurasthenia, 30 in the Selank arm and 32 in the medazepam arm. A separate 2008 immune-signaling study examined interleukin-6 expression in cultured blood cells and Th1/Th2 cytokine balance in participants with those diagnoses. Later reports compared Selank with phenazepam in 60 participants and Selank added to phenazepam in 70 participants. These are distinct designs, and an add-on result should not be presented as a Selank monotherapy finding.
Checked October 13, 2026, the ClinicalTrials.gov Semax intervention search returned no records. The Selank intervention search returned NCT01747200 and NCT05832060, both brain-stimulation studies whose intervention descriptions do not administer Selank. A search result is not automatically a peptide trial; the published studies linked above form a separate evidence source.
A 2020 resting-state functional MRI study in 52 healthy participants compared Semax, Selank and placebo in separate groups. It reported connectivity differences between the right amygdala and the right temporal cortex. The study measured brain connectivity; it did not test a combined Semax-Selank formulation or establish a clinical benefit.
Semax and Selank reports should match the named compound and the exact lot. The COA reading guide explains how identity evidence differs from HPLC purity. The lot report library provides the corresponding certificates for its listed research materials.
The main Semax vs Selank difference is the parent peptide. Semax derives from the hormone ACTH. Selank derives from tuftsin, an immune peptide that comes from an antibody heavy chain. Both end in Pro-Gly-Pro and come from the same Russian institute. Their published research asks different questions: ischemia and stress models for Semax, anxiety and immune models for Selank.
No. As of October 2026, FDA has not approved Selank for any use. FDA lists Selank acetate (TP-7) among Category 2 nominations that the nominators withdrew, and the July 2026 advisory committee agenda did not include it. Selank is registered as a prescription medicine in Russia, which carries no US status.
The cited 2020 functional MRI study included Semax and Selank in separate groups against placebo, with 52 healthy participants in total. It did not test the peptides combined. The ClinicalTrials.gov searches checked October 13, 2026 found no relevant Semax or Selank intervention study; the two Selank search matches concern brain stimulation.
Both are registered prescription medicines in Russia, with nasal formulations described in Russian prescribing information cited in the research literature. Neither is approved in the United States. FDA's July 2026 advisory vote on Semax is a recommendation about compounding, not an approval.
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