# Semax vs Selank: Comparing the Research > Semax vs Selank, compared from the literature: two Russian peptides, one a neurotrophic nootropic, the other a tuftsin-based anxiolytic. What each does, and where they overlap. Cited. Two Russian regulatory peptides, two different jobs — read against the studies, not the forum lore. ## The short version Semax vs Selank is the most common comparison in this corner of the literature, and the two are genuinely different compounds — they should never be treated as the same thing. Semax is a synthetic ACTH(4-7) peptide best known for raising brain growth factors and protecting brain tissue in stroke models, with a nootropic, focus-leaning reputation [1][4]. Selank is a different synthetic peptide, based on a fragment of a natural immune molecule called tuftsin, registered in Russia mainly as an anti-anxiety compound. They share a Russian research origin and one in-vitro property — both inhibit the same enkephalin-degrading enzymes — but their primary effects, structures, and reputations diverge. This page compares only what the studies support, and it makes no claim that either treats any disorder. ## Different molecules, different jobs Semax is the heptapeptide Met-Glu-His-Phe-Pro-Gly-Pro — built from the ACTH(4-7) hormone fragment with a stabilizing Pro-Gly-Pro tail (a three-amino-acid cap that slows the body's enzymes from breaking the peptide down) [16]. Its characterized actions are neurotrophic and neuroprotective: it raises the growth factors BDNF and NGF [1][2] and reduces infarct volume — the size of the dead-tissue zone — in rodent stroke models [4]. Selank is a distinct heptapeptide derived from tuftsin, a fragment of a natural immune protein, and is studied principally as an anxiolytic (an anti-anxiety agent) in Russian practice. Conflating the two is a common error — they are separate peptides with separate sequences, separate registrations, and separate primary uses. Semax leans cognitive and protective; Selank leans calming. Neither is FDA-approved, and both are research chemicals outside Russia and Ukraine. ## Why people compare them The two get paired constantly because they come from the same place and rhyme structurally. Both are short Russian regulatory peptides developed out of the same institutional research tradition, both are seven amino acids long, both are typically used intranasally, and both turn up in the same nootropic and peptide communities. People shopping for a cognitive or mood effect tend to weigh them side by side: Semax for the focus-and-clarity angle, Selank for the calm-and-anxiety angle. That framing is a reasonable starting point, but it flattens real differences — the structures are unrelated beyond length, and the best-characterized mechanisms diverge. A modern resting-state functional-connectivity study even examined both together as a pair [19], which is part of why they are so often discussed in the same breath. ## Where they overlap The clearest measured overlap is enzymatic. In human serum in vitro, both peptides inhibited enkephalin-degrading enzymes — Semax with an IC50 of about 10 microM and Selank around 20 microM, with Semax the more potent of the two [3]. Prolonging endogenous opioid signaling is one shared route by which each could influence mood and stress. They also share a research lineage from the same Russian institutional tradition, and a modern resting-state functional-connectivity study examined the effects of both Selank and Semax together [19]. Beyond that enzyme target, their mechanisms are more distinct than alike. ## Which the research supports for what For neuroprotection and cognition, the Semax record is deeper: a reproduced reduction in cortical infarct volume [4], an immune-gene-dominated transcriptional shift behind that protection [5], and rapid neurotrophin upregulation [1][2]. For anxiety, Selank is the compound with the relevant Russian registration — though, as with Semax, there are no published Western randomized controlled trials, so neither should be described as a proven treatment for any condition. Community comparisons often run the two together or stack them, and reported effects (and non-responses) for Semax are on the [Semax effects](/effects) page. The right summary is that they are complementary in reputation and distinct in mechanism, with the human evidence thin on both sides. ## On stacking the two Because the reputations are complementary — Semax for focus, Selank for calm — community discussion often pairs them, and the obvious appeal is wanting both effects at once. The research cannot endorse that. There is no controlled study of the two peptides taken together, so any combined effect, benefit, or risk is unmeasured. What the literature does flag is relevant: Semax modulates monoaminergic and endogenous-opioid signaling [20][3], and both peptides act on the same enkephalin-degrading enzyme target [3], so combining them — or combining either with stimulants or serotonergic drugs — has additive effects that no study has characterized. The honest position is that stacking is a community practice, not an evidence-based protocol, and this site describes it without recommending it. ## The bottom line on Semax vs Selank If you take one thing from this comparison, take this: they are not interchangeable, and the choice is about which mechanism you are asking about, not which is "stronger." The Semax case rests on a reproducible preclinical neuroprotection record and clear neurotrophin upregulation, with a focus-and-clarity community reputation [4][1]. The Selank case rests on its anxiolytic registration and tradition. The one hard, measured point of contact is the shared inhibition of enkephalin-degrading enzymes in human serum, where Semax is roughly twice as potent (IC50 ~10 microM versus ~20 microM) [3]. Both are unapproved outside Russia and Ukraine, both lack Western trials, and neither is a treatment for any diagnosed condition. This page compares the literature, not products, and nothing here is medical advice or a recommendation to use either compound. --- Filed from the published record on Semax like a front-page dispatch — the rodent neuroprotection and BDNF findings set in plain ink, the Russia-and-Ukraine-only registration and the missing Western trials printed in the same column, with no clinic behind the masthead and nothing here dosed, sourced, or sold.