# Compare Selank and Semax — Sigma A Peptides

> A side-by-side comparison of two Cognitive & Nootropic research peptides — Selank and Semax — across peptide class, most-studied application, evidence base, administration, regulatory status and key caution.

Where Selank and Semax converge, where they diverge, and — most importantly — how far the evidence behind each one actually reaches.

## The short version

This page lines up [Selank](/selank) and [Semax](/semax) on the dimensions that matter most when reading cognitive research peptides: what kind of molecule each one is, where it has been studied most, how strong that evidence is, how it was given in studies, its regulatory standing, and its single biggest caution. The headline is simple. Both are synthetic heptapeptides with a Russian origin, both lack Western regulatory approval, and both carry a largely regional evidence base. But they approach cognitive biology from different directions: Selank via anxiety reduction and GABAergic modulation, Semax via neurotrophin upregulation and neuroprotection in injury models. Neither is an approved medicine, and neither is presented here with a human dose.

## The comparison matrix

| Dimension | Selank | Semax |
| --- | --- | --- |
| Peptide class | Synthetic anxiolytic heptapeptide (tuftsin analog, 7 aa) | Synthetic neuropeptide / ACTH(4-7) analog (7 aa) |
| Most-studied in | Anxiety, mood, enkephalin stabilization, immune modulation | Neurotrophin upregulation (BDNF/NGF), neuroprotection in ischemia, nootropic |
| Evidence base (model) | Rat models + 1 small Russian clinical study in GAD [6] | Rat/mouse models + Russian/Ukrainian clinical practice [9][12] |
| Administration studied | Intranasal (primary); IV in some animal work [6][7] | Intranasal (primary); IP in animal work [10][11] |
| Regulatory status | Not approved (FDA/EMA); Rx in Russia only; sold as research chemical in US | Not approved (FDA/EMA); Rx in Russia and Ukraine for stroke/TIA; research chemical in US |
| Key caution | Single-region clinical evidence; GABAergic/opioid/immune interaction unknowns [1][6] | Regional evidence only; neurotrophin effects powerful and incompletely understood in long-term healthy-brain use [9][10][11] |

## Peptide class

Both Selank and Semax are synthetic heptapeptides — seven amino acids — built by extending an endogenous parent sequence with a C-terminal Pro-Gly-Pro tail to slow enzymatic degradation. But their parentage is completely different. Selank is a tuftsin analog: tuftsin (Thr-Lys-Pro-Arg) is an endogenous immune-regulatory tetrapeptide derived from immunoglobulin G, giving Selank its immunomodulatory character alongside its anxiolytic one [1]. Semax is an ACTH(4-7) analog: that parent fragment (Met-Glu-His-Phe) is from the pituitary hormone adrenocorticotropin, but Semax has been stripped of cortisol-releasing activity — so it engages the neurotrophin and neuroprotective axis of ACTH without the hormonal consequences of the full molecule [10].

## Most-studied in

Each peptide has a home territory. Selank's research is most consistent in anxiety models — it is described in the literature as an anxiolytic that reduces anxiety-related behavior in rodents, shifts GABAergic gene expression in frontal cortex, and produced a clinically comparable anxiolytic effect in a small study of patients with generalized anxiety disorder [1][3][6]. Semax is studied most for neuroprotection and neurotrophin biology: its most replicated finding is rapid, region-specific induction of BDNF and NGF in rodent brain, and its protective effects in focal ischemia models are documented across several studies [9][10][11][12].

## Evidence base (model)

This is where the two genuinely differ in character. Selank has a small human dataset — a Russian clinical study in generalized anxiety disorder patients [6] and a human plasma in vitro assay [7] — alongside its animal work, giving it a thin but real human signal for an anxiety indication. Semax's human evidence is largely clinical-practice based, drawn from Russian and Ukrainian use in stroke, TIA, and cognitive-impairment patients, with no published placebo-controlled Western trial for any indication [9][12]. The 2025 spinal cord injury study [8] is rodent work. Both are essentially preclinical from a Western regulatory standpoint.

## Administration studied

Both compounds are studied and used primarily via the intranasal route — a delivery approach that bypasses the blood-brain barrier by passing the peptide through the olfactory mucosa into the brain. For Selank, the intranasal route is the one used in the clinical study [6], and enkephalin inhibition was documented in human plasma in vitro [7]. For Semax, the published rodent dosing studies used intranasal delivery at 50 and 250 microg/kg [10][11], and the neuroprotective studies used intranasal administration over 6 days [12]. Neither compound has a validated human pharmacokinetic profile from the intranasal route outside the Russian clinical context.

## Regulatory / WADA status

Neither compound is approved by the FDA or EMA for any indication. Selank has regulatory registration essentially only in Russia, where it has been used clinically for anxiety-related disorders; in the United States it is sold as a research chemical [6]. Semax is a registered prescription medicine in Russia and Ukraine for ischemic stroke, transient ischemic attack, and cognitive impairment; outside those jurisdictions it is also handled as a research chemical. Neither compound is specifically named on the 2025 WADA Prohibited List, but as non-approved substances they may fall under the catch-all S0 category — athletes subject to anti-doping rules should consult GlobalDRO and relevant authorities before any use.

## Key caution

Each compound carries a defining caveat. For Selank it is the narrow regional evidence base and the interaction unknowns: its mechanisms span GABAergic, opioid, monoaminergic, and immune systems, and the consequences of combining it with medications acting on those same axes are essentially unstudied in humans [1][6]. For Semax it is that rapidly driving neurotrophin expression (BDNF, NGF) and large-scale immune and vascular gene-expression shifts in a healthy human brain over months is a powerful intervention whose long-term consequences are not characterized [9][10][11]. Reading them together, the common thread is a mechanistically interesting signal from a single research region, with limited independent replication and genuine interaction unknowns.

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A cross-referenced literature digest on cognitive research peptides — citations and context, not guidance and never a product for sale.