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Semax vs Selank: Differences, FDA Status and Price

· Education

Semax and Selank are synthetic peptides seven amino acids long, both developed at the Institute of Molecular Genetics of the Russian Academy of Sciences. Each was built the same way: a short fragment of a peptide the body makes, extended with the same three amino acids, Pro-Gly-Pro, to slow its breakdown by enzymes. Semax starts from a fragment of adrenocorticotropic hormone (ACTH), and Selank from tuftsin, a fragment of the immunoglobulin G (IgG) antibody.

Both are registered as medicines in Russia, where they are sold as nasal drops. Neither is approved by the U.S. Food and Drug Administration (FDA). In 2026 their U.S. paths split. An FDA advisory committee recommended Semax for pharmacy compounding in July, and in October the Department of Health and Human Services (HHS) said it does not intend to take enforcement action against pharmacies compounding Semax under set conditions. Selank was not before the committee and is not in the HHS policy.

Two fragments with the same tail

The different starting fragments set the two research programs apart. Semax's literature centers on cerebral ischemia, the loss of blood flow to brain tissue, and Selank's on anxiety.

What the laboratory research reports

The two share one reported mechanism. Kost and colleagues reported in 2001 that both Semax and Selank inhibit the enzymes in human serum that break down enkephalins, the body's own opioid peptides.

Past that, the preclinical work diverges. In rats, Dolotov and colleagues reported in 2006 that Semax raised expression of brain-derived neurotrophic factor (BDNF) and its receptor TrkB in the hippocampus. Selank's work points to the GABA system, the brain's main inhibitory signaling pathway. Volkova and colleagues reported in 2016 that Selank and GABA shifted the expression of related genes in the rat frontal cortex in correlated ways, and a 2018 study on isolated brain membranes by Vyunova and colleagues described Selank as a positive allosteric modulator of GABA binding.

These are animal and laboratory findings, and none establishes an effect in people. Each compound's page covers its mechanism in more detail.

The clinical record

Controlled human data for both peptides are small and come from Russia, mostly published in Russian.

FDA's 2026 review evaluated Semax for cerebral ischemia, migraine and trigeminal neuralgia. The cerebral ischemia references FDA found were published in Russian, and because the full texts were not available in English, the agency did not consider them.

Selank's main studies compare it with benzodiazepines and appeared in Zhurnal Nevrologii i Psikhiatrii. Zozulya and colleagues set it against medazepam in generalized anxiety disorder and neurasthenia in 2008, and Medvedev and colleagues against phenazepam in 2014. As of October 2026, ClinicalTrials.gov lists no registered study of either peptide.

Where FDA and HHS stand

Section 503A of the Federal Food, Drug, and Cosmetic Act governs compounding by state-licensed pharmacies. A bulk substance with no United States Pharmacopeia (USP) monograph and no place in an approved drug, as with both peptides, can be compounded only from FDA's 503A bulks list, and FDA sorts nominated substances into categories while that list is built. Category 2 holds substances FDA considers may present significant safety risks. Both peptides were placed in it in September 2023.

Semax since then:

Selank since then:

FDA's Category 2 page still lists both in its table of withdrawn nominations, with the same concern for each: a risk of immunogenicity, an unwanted immune response, from aggregation and peptide-related impurities. The committee vote is advisory, and the 503A list changes only through notice-and-comment rulemaking. Our post on the HHS policy covers its terms, and the July 2026 vote post covers the committee meeting.

Salt forms, N-acetyl versions and other names

FDA's documents name salt forms. Semax acetate and Selank acetate are the unmodified peptides paired with acetic acid, and the HHS policy covers Semax free base alone. Vendors also sell modified versions that are separate molecules:

What they cost

As of October 30, 2026, 38 vendors in our index list Semax and 36 list Selank. Median price per milligram for a single vial, one price per vendor:

At 10mg, the size most vendors carry, the two medians are identical, and most vendors charge the same for both. Of the 29 vendors that sell both at 10mg, 20 charge the same price for each, 7 charge more for Selank and 2 charge more for Semax. Thirteen vendors also sell each peptide as a premixed nasal spray, priced per bottle and left out of these figures. Prices compare milligrams as listed, whichever salt form each vendor counts. Definitions are on the methodology page, and blends vs separate vials compares blend and single-vial pricing.

Sources

Prices are as of October 30, 2026, computed from the PeptideScouter index. Sources checked October 30, 2026.

PeptideScouter indexes vendor prices for research chemicals sold for laboratory use only, not for human consumption. Nothing here is medical, legal, or investment advice. We earn affiliate commissions on some outbound vendor links - see our disclosure.