# Cognitive Peptide FAQ — Selank & Semax — Sigma A Peptides > Frequently asked questions about two Cognitive & Nootropic research peptides — Selank and Semax — answered from the peer-reviewed literature, with citations. Direct, citation-anchored answers to the questions readers most often bring to these two cognitive research peptides. ## What is Selank? Selank is a synthetic heptapeptide — seven amino acids — derived from tuftsin, a naturally occurring fragment of immunoglobulin G with immunostimulatory properties. The sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro is tuftsin extended at the C-terminus with Pro-Gly-Pro to slow enzymatic degradation and improve metabolic stability. It is catalogued as TP-7 and described as a *tuftsin analogue* in the literature [1]. It is not an approved drug in the US or Europe; outside Russia it is sold only as a research chemical [6]. ## What does Selank do? In animal and limited human research, Selank reduces anxiety, modulates mood, and may support cognition without the sedation or dependence associated with benzodiazepines [6]. Its mechanisms include positive allosteric modulation of GABA receptor binding [1], inhibition of enzymes that break down endogenous enkephalins [7], induction of BDNF expression in the hippocampus [4], and modulation of the Th1/Th2 cytokine balance [5]. A small Russian clinical study reported anxiolytic effects in patients with generalized anxiety disorder comparable to a benzodiazepine comparator [6]. Community users frequently describe reduced situational anxiety, calm without sedation, and a mild focus effect — though these are anecdotal, not clinical evidence. ## What is Selank peptide used for? In Russia, Selank has been used clinically for anxiety-related and neurasthenic disorders, and a clinical study specifically examined it in generalized anxiety disorder [6]. In research settings, it is studied for anxiolytic effects, mood modulation, immunomodulation, and cognitive support. Outside Russia it is not approved for any medical use and is classified as a research chemical. It is not a supplement, not an approved drug, and not intended for human consumption outside a research context. This site does not recommend or advise on any use. ## How does Selank work? Selank's anxiolytic effects are attributed to two primary non-benzodiazepine mechanisms. First, it acts as a positive allosteric modulator of GABA receptor binding — enhancing how GABA binds to its receptor in a subtype-selective, concentration-dependent way [1], and shifting gene expression in GABAergic-pathway genes in rat frontal cortex [3]. Second, it inhibits the enzymes (enkephalinases) that normally break down endogenous enkephalins in human plasma, thereby extending the half-life of those natural anxiety-calming opioid peptides [7]. It also modulates BDNF expression in the hippocampus [4] and the Th1/Th2 cytokine balance [5], suggesting effects beyond the purely anxiolytic. ## What is Semax? Semax is a synthetic heptapeptide with the sequence Met-Glu-His-Phe-Pro-Gly-Pro. It combines the ACTH(4-7) fragment of adrenocorticotropic hormone with a C-terminal Pro-Gly-Pro tail to slow degradation. Crucially, it lacks the steroidogenic (cortisol-releasing) activity of full-length ACTH. In the research literature it is also catalogued as ACTH(4-7)PGP and MEHFPGP [10]. It is a prescription medicine in Russia and Ukraine for ischemic stroke and cognitive impairment; in the United States it is an unscheduled research chemical [9]. ## What is Semax peptide used for? In Russian and Ukrainian clinical practice, Semax is used for ischemic stroke, transient ischemic attack, optic-nerve disease, and cognitive impairment. In research, it is studied primarily for neurotrophin upregulation (BDNF and NGF induction in rodent brain) [10][11], neuroprotection in cerebral ischemia models [9][12], and nootropic effects. A 2025 study documented protective effects in mouse spinal cord injury via an opioid-receptor-linked mechanism [8]. There are no published Western randomized controlled trials for any indication. Community users report focus, mental clarity, and mood lift — but these are anecdotal, not clinical evidence. ## Is Semax a peptide? Yes. Semax is a synthetic linear heptapeptide — a chain of seven amino acids: methionine, glutamic acid, histidine, phenylalanine, proline, glycine, and proline (one-letter code MEHFPGP). It is commonly supplied as the acetate salt. It is not a hormone, not a steroid, and not a growth factor; it is a small peptide that acts on neurotrophin signaling pathways and, in injury models, on immune and vascular gene expression [9][10][11]. As a synthetic research peptide it is not an approved drug in the United States or Europe. ## How does Semax work? The best-characterized effect of Semax in rodents is rapid, region-specific induction of the neurotrophins BDNF and NGF. A single intranasal dose raised NGF and BDNF mRNA in the hippocampus and BDNF in the brainstem, while NGF fell in frontal cortex — a pattern that is gene- and region-specific, not a global surge [10]. A companion study identified a specific, reversible, calcium-dependent binding site with KD 2.4 nM and confirmed a rapid rise in BDNF protein in rat basal forebrain [11]. In ischemia models, its protection is dominated by immunomodulatory and vascular gene-expression shifts [9]. It also inhibits enkephalin-degrading enzymes in human serum in vitro and modulates monoaminergic signaling in rodents [8]. ## Are Selank and Semax the same thing? No. Selank and Semax are distinct synthetic heptapeptides with different amino-acid sequences, different parent molecules, and different primary mechanisms. Selank (Thr-Lys-Pro-Arg-Pro-Gly-Pro) is a tuftsin analog whose primary documented effects are anxiolytic via GABAergic and enkephalin-stabilizing mechanisms [1][7]. Semax (Met-Glu-His-Phe-Pro-Gly-Pro) is an ACTH(4-7) analog whose primary documented effects are neurotrophin upregulation and neuroprotection in injury models [10][11]. They share only the C-terminal Pro-Gly-Pro metabolic stabilizer and their Russian research origin. Their pharmacology is categorically different. ## Is Selank or Semax FDA-approved? Neither compound is FDA-approved for any indication, and neither has EMA approval. Selank has regulatory registration in Russia only, where it has been used clinically for anxiety-related disorders [6]. Semax is a registered prescription medicine in Russia and Ukraine for ischemic stroke, TIA, and cognitive impairment; outside those jurisdictions it is a research chemical [9]. In the United States, both compounds are sold only as unscheduled research chemicals. They are not approved medicines, not dietary supplements, and not intended for human consumption outside a research context. ## What are the main differences between Selank and Semax in the research? Their research profiles reflect their different parent molecules. Selank's evidence concentrates on anxiety, mood, and immune modulation — it is described as an anxiolytic with GABAergic and enkephalin-based mechanisms, and it has a small human dataset in anxiety patients [6]. Semax's evidence concentrates on neurotrophin induction and neuroprotection in ischemia and injury models — its most replicated finding is rapid BDNF and NGF upregulation in specific brain regions [10][11]. In community use, Selank is more often taken for anxiety and social situations, while Semax is more often described as a focus and clarity nootropic. Neither characterization is clinically validated; both are anecdotal alongside a largely regional evidence base. --- A cross-referenced literature digest on cognitive research peptides — citations and context, not guidance and never a product for sale.