Selank vs Semax: are they the same peptide?

Are Selank and Semax the same peptide?

Selank and Semax are not the same peptide. The two chains match at three of seven positions and differ at four (PubChem compound records 11765600 and 9811102, read 14 October 2026). Selank starts with threonine, lysine, proline and arginine, and Semax starts with methionine, glutamic acid, histidine and phenylalanine. Their molecular formulas differ as well. A molecular formula counts each kind of atom in one molecule, with C for carbon, H for hydrogen, N for nitrogen, O for oxygen and S for sulfur. Selank is C33H57N11O9, and Semax is C37H51N9O10S, the only one of the pair with a sulfur atom (PubChem).

A certificate of analysis (the supplier's per-batch test sheet) is explained in how to read a certificate of analysis. This site's catalogue lists both names in its research range, for example Semax reference material.

Where do the two sequences come from?

Selank is built on tuftsin and Semax is built on a fragment of ACTH, and each carries the same Pro-Gly-Pro ending. Tuftsin is a fragment of four amino acids, threonine-lysine-proline-arginine (Thr-Lys-Pro-Arg), of the human immunoglobulin G heavy chain, the larger protein chain of an antibody type (Volkova et al., Frontiers in Pharmacology, 2016). Selank is a synthetic analogue, a lab-made relative of that natural molecule, elongated at the finishing end of the chain, the C-terminus, with Pro-Gly-Pro to improve its metabolic stability, in that paper's wording (Volkova et al., 2016). Semax includes the Met-Glu-His-Phe fragment of ACTH and the C-terminal tripeptide Pro-Gly-Pro (Stavchansky et al., Genes, 2022), and PubChem lists it as ACTH(4–7) with Pro-Gly-Pro (record 9811102).

Volkova et al. state that Selank was designed and produced at the Institute of Molecular Genetics of the Russian Academy of Sciences, in cooperation with the V.V. Zakusov Research Institute of Pharmacology (Volkova et al., 2016). Each peptide also has its own starting-reference page: the Selank research guide and the Semax research guide.

What does the shared Pro-Gly-Pro tail do?

Both sequences end in Pro-Gly-Pro (PGP) (PubChem records 11765600 and 9811102, read 14 October 2026). A 2016 paper reports that PGP was added to Selank with metabolic stability (resistance to breakdown by the body's enzymes, proteins that cut other molecules) stated as a design aim, not a measured result reported here (Volkova et al., 2016). In a 2022 rat study, PGP alone showed effects unlike Semax's, predominantly leaving gene activity (how strongly genes are switched on) unchanged 24 hours after an induced stroke, a brain blood vessel blocked for a short time on purpose; the abstract gives no animal number, and this rat result does not establish a human result (Stavchansky et al., 2022).

The same rat study also tested Pro-Gly-Pro-Leu, a four-amino-acid relative of the tail that adds leucine (Leu), and again showed effects unlike Semax's, predominantly without changing gene activity 24 hours after the induced stroke; the abstract gives no animal number, and this rat result does not establish a human result (Stavchansky et al., Genes, 2022).

Which is better, Selank or Semax?

No source read for this page ranks Selank above Semax or the reverse, so neither can be called better. PubMed returned 11 records with both names in the title or abstract on 14 October 2026, and none tests the two against each other in patients. The closest designs tested both peptides in the same kind of subject: a 2020 resting-state brain-scan study of 52 healthy people compared Semax, Selank and placebo and reported connectivity differences between the right amygdala and a region of the right temporal cortex, a connectivity measure and not a clinical outcome (Panikratova et al., Doklady Biological Sciences, 2020), and a 2017 study of rats with induced Parkinson-like damage found that Selank decreased anxiety on a maze test while the abstract names no such change for Semax; the abstract gives no animal number, and this rat result does not establish a human result (Slominsky et al., Doklady Biological Sciences, 2017). A ranking would need a head-to-head study, and none was found in the sources searched.

The 11 records are a mix of reviews, rat and cell studies, an analysis of seized preparations, and biochemical work. The Selank study findings page lists the human-participant studies of Selank; the records there include trials with phenazepam, a benzodiazepine (a class of calming medicines), and a study of blood markers, and none of the 11 records compares Selank with Semax in patients.

What do studies show about Selank, Semax and anxiety?

No study compared Selank and Semax for anxiety in people in the sources searched. The authors of the 2020 scan study of 52 healthy people describe Selank as an 'anxiolytic' and Semax as a 'nootropic', a description and not a trial result (Panikratova et al., 2020). The Russian product label for Selank on the RLS drug encyclopaedia (page changed 15 July 2025, read 14 October 2026) lists anxiety states among its indications and places it in ATC group N05BX, 'other anxiolytics', a registration record reproduced on a medicines register site and not evidence of effect; the official Russian registration record was not opened for this page. In rats with toxic damage to dopamine neurons, Selank decreased anxiety on a maze test, and the abstract names no such change for Semax; the abstract gives no animal number, and this rat result does not establish a human result (Slominsky et al., 2017).

Semax is also registered in Russia, and the FDA briefing document on Semax for the 23–24 July 2026 Pharmacy Compounding Advisory Committee meeting says 'Semax is a registered drug in Russia' (FDA briefing document, read 14 October 2026). Neither record ranks the two peptides. The legal status page covers how regulators outside Russia treat Selank.

What are the differences between Selank and DSIP?

Selank and DSIP are different peptides of different length and origin. Selank has seven amino acids and is a synthetic analogue of tuftsin (PubChem record 11765600). Delta sleep-inducing peptide (DSIP) has nine, Trp-Ala-Gly-Gly-Asp-Ala-Ser-Gly-Glu, with the formula C35H48N10O15 (PubChem record 68816, read 14 October 2026). DSIP was isolated from rabbits and named for the brain-wave changes it produced: in a double-blind test of nine synthetic peptides in 58 rabbits including controls, only synthetic DSIP showed significant and specific enhancement of delta and spindle brain-wave patterns, an animal result that does not establish a human result (Schoenenberger and Monnier, PNAS, 1977). A 2006 review calls the hypothesis that DSIP is a sleep factor 'extremely poorly documented and still weak' (Kovalzon and Strekalova, Journal of Neurochemistry, 2006).

The FDA's compounding page (content current as of 22 April 2026, read 14 October 2026) lists both 'Selank acetate (TP-7)' and 'Emideltide (DSIP)' under 'Bulk drug substances nominated but withdrawn'. The sources searched did not find a study comparing Selank with DSIP. One PubMed record names both, a 2026 review of therapeutic peptides in orthopaedics that groups them under different headings.

Evidence limits

Can research on Selank and Semax be compared directly?

Animal and laboratory results do not establish a human result. On scheduling, a text search of the Poisons Standard (Australia's national list sorting medicines and poisons into schedules, tiers of control), the October 2026 instrument F2026L01327 dated 28 September 2026, read 14 October 2026, found no entry naming Semax or Selank. An absent name is not permission, and the search draws no conclusion on class membership, a named group of related substances. The research material is not a medicine and is not for human use.