Semax vs Selank: Two Russian Peptides Compared

What are Semax and Selank?

Semax and Selank are both seven-amino-acid peptides made in Russia, and both carry the same stabilizing tail of proline, glycine and proline. What sits in front of that tail is different. Semax begins with a fragment of adrenocorticotropic hormone, the pituitary hormone that drives the adrenal glands; Selank begins with tuftsin, a small fragment of an antibody protein with effects on the immune system.

The marketing follows the parent molecules. Semax is sold as a nootropic for focus and memory, on the strength of animal work showing that it raises brain-derived neurotrophic factor, a protein that supports nerve cells, and its receptor in the rat hippocampus ^[1]. Selank was developed as an anti-anxiety drug meant to work without the sedation of benzodiazepines, and anxiety is what its Russian trials tested ^{[5, 6]}. The table sets the two records side by side.

What has each been tested for in people?

Semax has four trial-type records in PubMed, and all four are Russian-language: a 1997 study of 30 patients in the acute period of ischemic stroke compared with 80 on conventional therapy ^[3], a 2000 study in optic nerve disease ^[4], a 2007 study of 27 patients with motor neuron disease ^[2], and a 2018 study that followed 110 patients through stroke rehabilitation ^[2]. None enrolled healthy adults, and none measured memory or attention in people without a neurological diagnosis ^[2]. The nootropic claim is an inference from rat biology and from patients with brain injury.

Selank has three, all in Russian and all in one journal ^[5]. A 2008 study compared it with the benzodiazepine medazepam in 62 patients with generalized anxiety disorder or neurasthenia and reported similar anti-anxiety effects in the two groups ^[6]. A 2014 study compared it with phenazepam, another benzodiazepine, in 60 patients with anxiety and somatoform disorders and reported a pronounced anti-anxiety effect ^[7]. The third, from 2015, concerns optimizing the treatment of anxiety disorders with it ^[5].

The two records share one limit. No trial of either peptide appears in the English-language literature ^{[2, 5]}, and FDA has approved neither. The Semax evidence review reads the four Semax trials in detail, and the human trial record prints both counts beside every other molecule in the index.

What are the side effects of Semax and Selank?

No controlled study published in English reports them, and no FDA label exists for either, so there is no reliable side-effect list for either peptide. The 2014 Selank study names tolerability in its title, yet its abstract reports no adverse-event figures ^[7]; the 2008 study's abstract reports none either ^[6]. Any list of Semax or Selank side effects met online is therefore not drawn from a counted comparison with placebo.

What FDA has published is a statement of what it does not know. For Selank, the agency found that compounded drugs containing it may pose a risk of immunogenicity, an immune reaction against the peptide, because of aggregation and peptide-related impurities, and that it lacks important information about the safety of Selank in humans ^[9]. For Semax it recorded the same immunogenicity concern and wrote that it has no, or only limited, safety information for the proposed routes and therefore lacks enough information to know whether the drug would cause harm if given to people ^[9]. Both statements remain published among the substances whose nominations were withdrawn.

Is either one legal in the United States?

Neither is an approved drug, and no licensed pharmacy may lawfully compound either one as of September 2026. Drugs@FDA holds no application under the name Semax ^[14], and neither peptide appears in any category of the section 503A bulks list FDA published on May 14, 2026 ^[8]. Both were once in Category 2 of FDA's interim list, the category for substances that may present significant safety risks, and both now sit in the agency's table of nominations withdrawn ^[9].

The difference is the July 2026 advisory meeting. The Pharmacy Compounding Advisory Committee voted to recommend adding Semax to the 503A list, by a margin reported as 8 to 5 with one abstention in two independent law-firm accounts; FDA has published no vote record, and the vote is advisory until the agency issues a final rule ^{[10, 11]}. Selank was not among the seven substances voted on at that meeting ^[11]. The vote ledger carries the tallies, and the pending page explains what an advisory vote does and does not change.

Both peptides also appear in federal enforcement records. In April 2020 FDA warned a Kentucky compounding pharmacy that products it made with Selank and twenty-one other substances were not eligible for the compounding exemptions ^[12]. In October 2020 that pharmacy, Tailor Made Compounding, pleaded guilty to distributing unapproved new drugs from October 2018 to April 2020; the Justice Department's account of the plea agreement names both Semax and Selank among them, and the company agreed to forfeit $1,788,906.82, its 2019 sales of those products ^[13].

Semax or Selank: what the comparison shows

The two peptides invite comparison, one pitched for focus and one for calm, and the record pairs them too: similar size, the same origin, the same language barrier around their trials, and the same FDA finding that human safety information is lacking. What separates them in the United States is procedural rather than scientific. Semax has a recommendation from an advisory committee and awaits rulemaking; Selank has no pending nomination at all.

Product sold under either name to US buyers is research-use-only chemical supply or an import, made outside pharmacy licensure and with nothing independent confirming what a vial or spray contains. The neuropeptides class page files both beside the other brain-targeted peptides in the index, including DSIP, the one substance that committee voted against at the same meeting.

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