Semax vs Selank: What the Published Research Compares

Semax and Selank are two synthetic seven-amino-acid peptides developed at the Institute of Molecular Genetics of the Russian Academy of Sciences: Semax is built on a fragment of the hormone ACTH, and Selank on the immune peptide tuftsin. Semax has been studied mainly in stroke and cognition and Selank mainly in anxiety, and for both the evidence is largely animal work or small clinical studies published in Russian, with no FDA approval for either.

They are often discussed as a pair. The published record treats them as two molecules with two separate literatures.

At a glance

Origins

Both peptides come out of the same research tradition. A 2022 review of Russian peptide drugs (Deigin and colleagues, Pharmaceutics) records that Semax was synthesized at the Institute of Molecular Genetics under the academicians I. P. Ashmarin and N. F. Myasoedov. Selank was developed at the same institute together with the Zakusov Research Institute of Pharmacology, according to a 2017 paper from the group (Filatova and colleagues, Frontiers in Pharmacology).

The design logic is shared. Each takes a short fragment of a natural peptide and ends in the three-residue tail Pro-Gly-Pro, which the Selank group describes as providing metabolic stability.

Semax starts from ACTH(4-10), a fragment of adrenocorticotropic hormone. The FDA's 2026 review describes Semax as a synthetic heptapeptide analog of that fragment, differing from it in the last three amino acids, and describes the fragment itself as lacking the parent hormone's corticotropic activity.

Selank starts from tuftsin, the sequence Thr-Lys-Pro-Arg, which the Filatova paper describes as a fragment of the heavy chain of human immunoglobulin G.

What the animal and cell studies report

For Semax, the most cited mechanistic finding concerns brain-derived neurotrophic factor. Dolotov and colleagues (Brain Research, 2006) reported that a single intranasal application in rats raised BDNF protein in the hippocampus about 1.4 fold, along with activation of its receptor, trkB, and that treated animals performed better on a conditioned avoidance task. In a rat model of stroke, Medvedeva and colleagues (BMC Genomics, 2014) reported that Semax changed the expression of genes related to the immune and vascular systems in brain tissue after an artery was blocked.

For Selank, the mechanistic work points toward the GABA system, the target of benzodiazepines. Volkova and colleagues (Frontiers in Pharmacology, 2016) measured 84 genes involved in neurotransmission in the frontal cortex of rats and reported changes in 45 of them one hour after Selank was given. The result did not carry over cleanly to human cells: in a neuroblastoma cell line, the Filatova study found that Selank on its own did not change expression of the genes studied.

The FDA's reviewers summarized the Semax animal literature in cautious terms, writing that it acts through poorly understood mechanisms. They also flagged a mouse finding that Semax increased amphetamine-induced dopamine release, and noted that no published toxicity studies were identified for the route of administration that had been proposed.

The human record

Semax. The clinical literature is real and mostly out of reach for English-language readers. An early study (Gusev and colleagues, Zhurnal Nevrologii i Psikhiatrii, 1997) gave Semax to 30 patients in the acute phase of ischemic stroke and compared them with 80 patients on conventional therapy, reporting faster recovery of neurological function. A later one (Gusev and colleagues, same journal, 2018) followed 110 patients after stroke and reported higher plasma BDNF and better functional scores in those who received Semax. Both were published in Russian, and the English abstracts do not describe randomization or blinding.

In English, the human work is mostly in healthy volunteers. Lebedeva and colleagues (Bulletin of Experimental Biology and Medicine, 2018) scanned 24 volunteers with resting-state functional MRI, 14 given Semax and 10 placebo, and reported a difference in one brain network. That is an imaging finding, not a clinical outcome.

The FDA's briefing document for its July 2026 advisory meeting is the most thorough independent audit available. Across the references they could assess, reviewers counted between 33 and 47 healthy adults, 69 adults with medical conditions and 451 children who had received Semax, with several of those references available only as meeting abstracts. They could not find pharmacokinetic studies in humans. They set aside the Russian-language stroke papers because full texts were not available in English, and concluded that there was insufficient evidence of effectiveness and insufficient clinical information to characterize safety.

Selank. The main clinical paper (Zozulia and colleagues, Zhurnal Nevrologii i Psikhiatrii, 2008) studied 62 patients with generalized anxiety disorder and neurasthenia, 30 given Selank and 32 given the benzodiazepine medazepam. The authors reported similar effects on anxiety in the two groups. It was published in Russian, and the English abstract does not describe how patients were assigned. A 2021 review in the Journal of Clinical Pharmacology (Doyno and White) described Selank as poorly studied.

Together. The closest thing to a direct comparison is an imaging study (Panikratova and colleagues, Doklady Biological Sciences, 2020) in which 52 healthy participants received Semax, Selank or placebo and were scanned before and after. The authors reported that both peptides changed functional connectivity between the amygdala and the temporal cortex, with some effects in common and some specific to each. We found no clinical trial that compares the two on a patient outcome.

Regulatory status

Neither peptide is approved by the FDA for any use.

In Russia the picture is different. The FDA's review states that Semax is a registered drug there, and the Deigin review lists Selank among Russian peptide drugs as an anxiolytic. A registration in one country is not evidence the FDA has reviewed.

In US compounding policy the two have parted ways. Semax was one of seven peptides the FDA's Pharmacy Compounding Advisory Committee considered on July 23 and 24, 2026. FDA staff proposed against adding it to the 503A bulks list. The committee voted 8 to 5 to recommend it. That recommendation is not binding, and we could find no proposed or final rule as of this writing. Selank was nominated for the same list and the nomination was later withdrawn. The FDA's safety summary says the agency lacks important information about its safety in humans, and it was not on the July agenda. Our guide to FDA approval explains why a compounding recommendation is not an approval.

In sport, neither compound is named on the World Anti-Doping Agency's 2026 Prohibited List. We could not find a WADA statement addressing either one, so athletes should check with their own anti-doping organization.

For the wider argument about why this literature is hard to weigh, see our review of the cognitive peptides.

Frequently asked questions

Are Semax and Selank the same thing?

No. They share a three-residue tail and an institute of origin, but Semax is built on a fragment of ACTH and Selank on tuftsin, and they have been studied for different purposes.

Is Semax FDA-approved?

No. An FDA advisory committee recommended it for the compounding bulks list in July 2026, against the advice of FDA staff. That is not an approval and has not yet led to a rule.

Is Selank FDA-approved?

No. Its nomination for the compounding bulks list was withdrawn, and the FDA says it lacks important safety information on it.

Why is most of the research in Russian?

Both peptides were developed in Russia, and most of the clinical studies were published in Russian journals. The FDA's 2026 reviewers did not evaluate several of them because full English texts were not available.

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Sources:

• Deigin et al., Pharmaceutics, 2022 (review of peptide drug development in Russia)
• Filatova et al., Front Pharmacol, 2017 (Selank in human neuroblastoma cells; origin and structure)
• Dolotov et al., Brain Res, 2006 (Semax, BDNF and trkB in rat hippocampus)
• Medvedeva et al., BMC Genomics, 2014 (Semax, rat focal ischemia)
• Volkova et al., Front Pharmacol, 2016 (Selank, rat frontal cortex)
• Gusev et al., Zh Nevrol Psikhiatr, 1997 (Semax in acute ischemic stroke, in Russian)
• Gusev et al., Zh Nevrol Psikhiatr, 2018 (Semax after ischemic stroke, in Russian)
• Lebedeva et al., Bull Exp Biol Med, 2018 (Semax, resting-state fMRI in healthy volunteers)
• Zozulia et al., Zh Nevrol Psikhiatr, 2008 (Selank and medazepam in 62 patients, in Russian)
• Doyno and White, J Clin Pharmacol, 2021 (review including Selank)
• Panikratova et al., Dokl Biol Sci, 2020 (Semax and Selank, fMRI in 52 healthy participants)
• FDA briefing document, Semax-related bulk drug substances, PCAC, July 23 to 24, 2026
• FDA, July 23 to 24, 2026 meeting of the Pharmacy Compounding Advisory Committee
• RAPS, FDA advisory committee backs two more peptides, rejects one for compounding list, July 24, 2026
• FDA, Certain bulk drug substances for use in compounding that may present significant safety risks
• WADA 2026 Prohibited List, as published in the Dutch treaty series

No compound discussed in this review is FDA-approved. Nothing above is dosing guidance or a treatment claim. Research use only.