Selank vs Semax: Nootropic Peptide Comparison | Peptide Intel Hub

Selank is a synthetic heptapeptide derived from the immunomodulatory tetrapeptide tuftsin, with additional Pro-Gly-Pro C-terminal stabilisation. Its proposed research mechanism centres on GABAergic-axis modulation, BDNF-axis effects and downstream anxiolytic-profile signalling in preclinical models.

Semax is a synthetic heptapeptide derived from the 4–10 fragment of adrenocorticotropic hormone (ACTH), with Pro-Gly-Pro C-terminal stabilisation. Its proposed research mechanism centres on BDNF- and NGF-axis modulation and downstream cognitive- and neuroprotective-axis signalling in preclinical models.

Selank does not act through a single canonical receptor. Published research suggests indirect GABAergic-axis modulation and BDNF-axis effects, with a research profile centred on anxiolytic and immunomodulatory endpoints.

Semax likewise does not act through a single canonical receptor. Published research emphasises BDNF- and NGF-axis modulation, with a research profile centred on cognitive-axis and neuroprotective endpoints.

Both compounds are short heptapeptides with Pro-Gly-Pro stabilisation, and both are researched via intranasal administration as the primary route — a distinctive feature versus most other research peptides. Research cadences are typically daily.

The intranasal route is the reason both compounds are studied in CNS-axis research models — direct nose-to-brain delivery bypasses the substantial first-pass metabolism that would limit oral or subcutaneous administration of these short peptides.

Selank is used in anxiolytic-axis, immunomodulatory and GABAergic-axis research models. The tuftsin-derived structure gives it a research profile distinct from classical benzodiazepine-axis anxiolytic comparators.

Semax is used in cognitive-axis, neuroprotective and BDNF/NGF-axis research models. The ACTH-derived structure gives it a research profile distinct from classical nootropic small molecules.

Both Selank and Semax should only be sourced from suppliers that use independent third-party verification — Janoshik Analytical is the default verifier, with orthogonal independent laboratories used when batch chemistry calls for confirmation by a second method. Minimum release specification is ≥99.0% HPLC main-peak purity with matching mass-spectrometry molecular weight and water content within the published specification for the compound.

Batch COAs for both compounds should be published by the supplier so a researcher can audit the analytical detail. The /trust/how-to-read-a-coa reference walks through every field on a modern COA.

Both compounds ship as lyophilised research peptides. Hold at 2–8 °C; freeze at −20 °C for long-term storage. Reconstitution for intranasal-administration research is typically with sterile saline; bacteriostatic-water reconstitution is used for subcutaneous research protocols. Both compounds are sensitive to repeat freeze-thaw cycling — aliquot before any freeze.

Aliquot before any freeze. The single most common cause of measurable potency loss in research peptides is repeat freeze-thaw cycling — both Selank and Semax benefit from single-thaw aliquot workflows. Vortex gently, never shake aggressively, and keep reconstituted vials away from direct light. The /research/compound-storage-guide reference covers the per-compound stability windows in detail.

Researchers choose Selank when the protocol targets anxiolytic-axis or immunomodulatory endpoints, particularly where GABAergic-axis modulation is central to the experimental design. Researchers choose Semax when the protocol targets cognitive-axis or neuroprotective endpoints, particularly where BDNF- and NGF-axis signalling is the experimental focus. Matched panels sometimes include both compounds where a complete Russian-origin nootropic-peptide comparator is required.

For multi-compound comparator studies, reputable suppliers can often reserve matched-batch inventory of both Selank and Semax against a project timeline so the experimental panel is sourced under a single analytical specification window.

Selank is identified as a heptapeptide (Thr-Lys-Pro-Arg-Pro-Gly-Pro) (PMID 30255741), and a peptide analog of tuftsin (PMID 36322304, PMID 31625062). It is also described as a glyprolin neuropeptide drug (PMID 32621722). Semax is a synthetic heptapeptide (Met-Glu-His-Phe-Pro-Gly-Pro) (PMID 16635254) which is an analogue of the ACTH(4-10) fragment (PMID 40692165, PMID 16635254, PMID 33418449) and an ACTH(4-7) analogue (PMID 28255762). Both Selank and Semax are classified as neuroactive peptides that enhance brain-derived neurotrophic factor and HGF/c-Met pathways critical to neuroplasticity (PMID 41490200). They are also broadly categorized as therapeutic peptides (PMID 41490200, PMID 42021992).

Therapeutic peptides, including Selank and Semax, are emerging as promising adjuncts in various medical fields due to their ability to modulate molecular signaling networks central to cellular medicine (PMID 41490200). In gerontology, they are recognized for targeting fundamental hallmarks of aging such as metabolic dysfunction, telomere attrition, tissue repair impairment, and hormonal decline (PMID 42021992). Both peptides are noted for exhibiting neuroprotective and nootropic activities (PMID 33418449, PMID 35080861, PMID 16635254). Semax, specifically, has proved efficient in the therapy of brain stroke (PMID 24661604).

A human study involving 52 healthy participants assessed the effects of Selank and Semax on whole-brain resting-state functional connectivity (FC) (PMID 32342318). The predefined regions of interest (ROIs) included the amygdala, a key region for anxiety regulation, and the dorsolateral prefrontal cortex (DLPFC), which is crucial for executive functions including working memory, in both hemispheres (PMID 32342318). Resting-state fMRI scans were conducted before, and at 5 and 20 minutes after injection of Semax, Selank, or placebo (PMID 32342318).

This human study revealed between-group and between-condition differences in FC between the right amygdala and a region encompassing fusiform, inferior, and middle temporal as well as parahippocampal gyri in the right hemisphere (PMID 32342318). Post hoc analysis from this research allowed for the identification of both general and specific effects of Selank and Semax on FC between the right amygdala and the right temporal cortex for the first time (PMID 32342318).

In another human study, the effects of intranasal 1% Semax or placebo were investigated on the default mode network (DMN) of the brain in two groups of healthy volunteers (14 subjects for Semax, 10 for placebo, mean age 43.9±9.5 years) using resting state fMRI (PMID 30225715). This study found a greater volume of the rostral (medial frontal cortex) subcomponent of the DMN in the Semax group compared to controls (PMID 30225715). These results confirm Semax's effects on the neuronal network of the brain and demonstrate the topography of these effects (PMID 30225715).

Clinical studies have indicated that Selank exhibits an anxiolytic effect comparable to that of classical benzodiazepine drugs (PMID 28293190, PMID 30255741), suggesting a potentially similar basis for their mechanism of action (PMID 26924987, PMID 28293190). Anxiety and mood disorders are prevalent mental health problems globally, and traditional anxiolytics often target the brain's GABA receptor system, but can lead to issues such as dependence and memory impairment (PMID 30255741). Neuropeptides and bioactive lipids are gaining recognition as 'mild' agents in the pathophysiology of these disorders (PMID 30255741).

Heptapeptide Selank exhibits prolonged anti-anxiety and nootropic effects (PMID 30255741). Molecular studies using the radioligand-receptor method showed that Selank affects [3H]GABA binding as a positive allosteric modulator (PMID 30255741). The combined action of Selank and some benzodiazepines also regulates [3H]GABA binding activity in a specific manner, which is not cumulative and differs from either substance individually (PMID 30255741). Selank has been shown to block the modulatory activity of Diazepam and Olanzapine, suggesting their binding sites may not be identical but could partially overlap (PMID 30255741). Thus, one of Selank's anti-anxiety molecular mechanisms may involve subtype-selective, concentration-dependent allosteric modulation of GABA receptors (PMID 30255741).

Further supporting this, in-vitro experiments using neuroblastoma IMR-32 cells showed no direct effect of Selank on the mRNA levels of GABAergic system genes, but the combined effect of GABA and Selank nearly completely suppressed changes in gene expression that occurred with GABA alone (PMID 28280289). When Selank was used with olanzapine, more gene expression alterations were observed compared to olanzapine alone (PMID 28280289). These in-vitro results partially confirm the hypothesis that Selank may affect the interaction of GABA with GABAA receptors and could enhance olanzapine's effect on gene expression (PMID 28280289). In rats, Selank administration was found to affect the expression of some genes involved in GABAergic neurotransmission (PMID 26924987). One hour after administration, significant changes in the expression of 45 genes were found, and 22 genes showed altered expression after three hours (PMID 26924987). This suggests Selank has complex effects on nerve cells, with one possible molecular mechanism associated with allosteric modulation of the GABAergic system (PMID 26924987).

Both Selank and Semax are recognized as neuroactive peptides that enhance brain-derived neurotrophic factor (BDNF) and HGF/c-Met pathways, which are critical for neuroplasticity (PMID 41490200). Semax, an analogue of ACTH(4-10), has shown profound effects on learning and memory formation in rodents and humans, and exhibits marked neuroprotective effects (PMID 16635254). A molecular mechanism underlying its neurotropic action involves stimulating the synthesis of BDNF, a potent modulator of synaptic plasticity, in astrocytes cultured from rat basal forebrain (PMID 16635254).

In rats, intranasal application of Semax at doses of 50 and 250 microg/kg bodyweight resulted in a rapid increase in BDNF levels after 3 hours in the basal forebrain, but not in the cerebellum (PMID 16635254). Specific binding sites for Semax were found in rat basal forebrain cell membranes, with binding being time-dependent, specific, and reversible, requiring calcium ions (PMID 16635254). The dissociation constant (KD) was 2.4±1.0 nm and the BMAX value was 33.5±7.9 fmol/mg protein (PMID 16635254). These findings suggest that the cognitive effects of Semax might be partly associated with increased BDNF protein levels in this brain region (PMID 16635254).

In a human study of patients after ischemic stroke (IS), administration of Semax (6000 mcg/day for 10 days, two courses) increased BDNF plasma levels, which remained high throughout the study period, regardless of the timing of rehabilitation (PMID 29798983). Higher BDNF plasma levels were positively correlated with early rehabilitation in groups not receiving Semax, and administration of Semax along with high BDNF levels accelerated functional recovery and improved the final Barthel score index (PMID 29798983).

Selank also demonstrates neuroprotective and cognitive-stimulating effects related to BDNF. In outbred rats receiving chronic ethanol, Selank (0.3 mg/kg a day for 7 days, intraperitoneally) showed a cognitive-stimulating effect in 9-month-old rats not exposed to ethanol (p<0.05) and prevented ethanol-induced memory and attention disturbances during alcohol withdrawal (p<0.01) (PMID 31625062). Ex vivo experiments showed Selank prevented an ethanol-induced increase in BDNF content in the hippocampus and frontal cortex (p<0.05) (PMID 31625062). These results indicate positive effects of the tuftsin analog on age-related memory disturbances associated with chronic alcohol intoxication and confirm the involvement of the neurotrophin mechanism related to BDNF production in Selank's effect (PMID 31625062).

Selank, a peptide analog of tuftsin, has demonstrated anxiolytic and stress-protective effects in various rat models. In outbred rats undergoing naloxone-precipitated morphine withdrawal, a single intraperitoneal injection of Selank at an anxiolytic dose of 0.3 mg/kg reduced the total index of morphine withdrawal syndrome by 39.6% (p<0.0001) (PMID 36322304). It significantly attenuated convulsive reactions, ptosis, and posture disorders, and increased the tactile sensitivity threshold nine-fold in morphine-dependent rats compared to the active control group (PMID 36322304). While effective, Selank was slightly less potent than diazepam (2 mg/kg), which reduced the withdrawal syndrome by 49.3% and increased the sensitivity threshold thirteen-fold (PMID 36322304). This suggests Selank, similar to diazepam, weakens aversive signs of morphine withdrawal in rats with opiate dependence (PMID 36322304).

In Wistar male rats subjected to chronic foot-shock stress, Selank (injected intraperitoneally at 100, 300, and 1000 μg/kg 15 minutes before each stress session) reduced the intensity of stress-induced degenerative changes in liver morphological parameters (PMID 31243679). Chronic foot-shock stress caused hydropic degeneration of hepatocytes, an increased nucleus/cytoplasm ratio, focal necroses, and lymphohistiocyte infiltration (PMID 31243679). Selank at doses of 300 and 1000 μg/kg restored the nucleus/cytoplasm ratio in hepatocytes, with the maximum stress-limiting effect observed at 300 μg/kg (PMID 31243679).

Selank also exhibited stress-protective activity in white nonlinear rats under 'social' stress conditions (PMID 32621722). In a model of male confrontations, animals subjected to stress showed a statistically significant increase in IL-1β, IL-6, and TGF-β1 levels in serum (PMID 32621722). Intraperitoneal administration of Selank at 100 mcg/kg/day during 20 days of stress, indicated the presence of stress-protective activity, although the abstract details the increase in cytokines in stressed animals but does not explicitly state Selank's effect on these cytokine levels (PMID 32621722). Additionally, Selank was shown to enhance the anxiolytic effect of diazepam in rats under unpredictable chronic mild stress (PMID 28280289). While individual Selank administration was most effective in reducing elevated anxiety induced by a course of test substances, the combination with diazepam was most effective in reducing anxiety in chronic stress conditions (PMID 28280289). Peptide compounds of the tuftsin family and Selank were also shown to have positive emotional effects and antistress actions in male rats and mice (PMID 14969422).

Semax, a synthetic heptapeptide, has demonstrated neuroprotective properties and improved cognitive function (PMID 40692165, PMID 33418449). In a female C57BL/6 mouse model of spinal cord injury (SCI), Semax improved functional recovery and inhibited lysosomal membrane permeabilization (LMP)-related pyroptosis in SCI mice and neuroinflammation models by decreasing oxidative stress (PMID 40692165). RNA sequencing and other analyses found that Semax regulated the ubiquitin specific protease USP18, and network pharmacology and docking revealed the μ-opioid receptor as a Semax target (PMID 40692165). Semax promoted SCI functional recovery by targeting μ-opioid receptors, which regulated USP18 and subsequently deubiquitination of the fat mass and obesity-associated protein (FTO), suggesting its potential for SCI treatment in this animal model (PMID 40692165).

In rats with focal cerebral ischemia, genome-wide transcriptional analysis showed that Semax affected the expression of genes related to the immune and vascular systems (PMID 24661604, PMID 28255762). Three hours after permanent middle cerebral artery occlusion (pMCAO), Semax influenced genes affecting immune cell activity, and 24 hours after pMCAO, its effect on the immune response increased considerably, with over 50% of the total altered genes related to immune response (PMID 24661604). Notably, it enhanced the expression of genes encoding immunoglobulins and chemokines (PMID 24661604). Semax also increased expression of the gene encoding the immunoglobulin heavy chain, intensified ischemia's effect on interferon signaling pathways, and affected immunoglobulin synthesis processes (PMID 28255762). Additionally, 24 genes related to the vascular system showed altered expression 3 hours post-pMCAO, and 12 genes at 24 hours (PMID 24661604). These genes are associated with endothelial tissue development and migration, smooth muscle cell migration, hematopoiesis, and vasculogenesis (PMID 24661604). This suggests Semax's neuroprotective mechanism involves neuroimmune crosstalk and impacts the vascular system during ischemia in rats (PMID 24661604, PMID 28255762).

Semax also influences intracellular calcium dynamics. In rat brain neurons, application of Semax (1 μM) significantly increased the frequency of spontaneous intracellular calcium ion concentration ([Ca2+]i) fluctuations in pyramidal layer cells of the hippocampal CA1 field (PMID 41171324). However, it had no significant effect on proton-stimulated increases in [Ca2+]i in cerebellar granule cells (PMID 41171324). This provides insight into the localization of cellular targets and initial interaction dynamics between Semax and the hippocampal neuronal network (PMID 41171324). The primary mechanism of its neuroprotective effect appears unrelated to attenuating calcium entry through acid-sensing ion channels in cerebellar granule cells (PMID 41171324). As a therapeutic peptide in gerontology, Semax is identified for its neuroprotective potential in healthy aging and age-related conditions (PMID 42021992).

Furthermore, Semax has shown promise in addressing copper-induced Aβ aggregation, a characteristic of Alzheimer's disease. In artificial membrane models, Semax demonstrated anti-aggregating and protective properties, especially in the presence of Cu2+ ions (PMID 35080861). It was able to prevent the formation of Aβ:Cu2+ complexes and inhibited fiber formation by interfering with the fibrillogenesis of these complexes (PMID 35080861). This suggests Semax, which is known to form a stable complex with Cu2+ ions and has neuroprotective and nootropic effects, could be a multifunctional compound to inhibit fibrillogenesis and prevent Aβ:Cu2+ complex formation (PMID 35080861).

Early-life exposure to Selective Serotonin Reuptake Inhibitors (SSRI) like fluvoxamine (FA) can have long-term consequences on offspring brain development (PMID 33418449). In white rats, neonatal FA exposure (postnatal days 1-14) led to impaired emotional response to stress and novelty, and delayed acquisition of a food-motivated maze task in adolescent and young adult rats (PMID 33418449). This exposure also induced alterations in monoamine levels in the brains of 1- and 2-month-old rats (PMID 33418449).

Semax administration (postnatal days 15-28) after FA treatment reduced anxiety-like behavior, improved learning abilities, and normalized brain biogenic amine levels that were impaired by FA exposure (PMID 33418449). The results indicate that early-life FA exposure in rat pups causes long-term disturbances in anxiety-related behavior, learning abilities, and brain monoamines (PMID 33418449). Semax, a synthetic ACTH(4-10) analogue, exerted a favorable effect on the behavior and biogenic amine system of rats exposed to the antidepressant, suggesting its potential to prevent behavioral deficits caused by altered 5-HT levels during development (PMID 33418449).

While both Selank and Semax are recognized as therapeutic peptides with promising preclinical findings, the landscape of clinical evidence for them, particularly in orthopaedics and gerontology, is still developing. For therapeutic peptides generally, preclinical studies show promise, but there is a current lack of clinical trials (PMID 41490200). In the context of orthopaedics, therapeutic peptides are grounded in their ability to modulate molecular signaling networks, influencing tissue regeneration, inflammation resolution, and neuromuscular recovery by acting on pathways like PI3K/Akt, mTOR, MAPK, TGF-β, and AMPK (PMID 41490200). However, their integration into musculoskeletal care emphasizes the need for further evidence regarding safety, efficacy, and future directions (PMID 41490200).

In gerontological medicine, while FDA-approved agents demonstrate robust safety profiles from large-scale trials, non-approved peptides like Semax show promising preclinical and limited clinical evidence but lack long-term safety data and systematic validation (PMID 42021992). Significant knowledge gaps exist concerning optimal dosing regimens, combination therapy effects, and biomarkers for monitoring efficacy (PMID 42021992). This highlights the need for rigorous validation through well-designed clinical trials to establish safety and efficacy for healthspan extension with investigational peptides (PMID 42021992).

For Selank, clinical studies have shown its anxiolytic effect is comparable to classical benzodiazepine drugs (PMID 26924987, PMID 28293190, PMID 30255741). However, the detailed molecular mechanisms are largely derived from in-vitro and animal studies (PMID 26924987, PMID 28280289, PMID 30255741). For Semax, while human studies have investigated its effects on functional connectivity and the default mode network (PMID 32342318, PMID 30225715) and its impact on BDNF levels and functional recovery post-stroke (PMID 29798983), many of its proposed mechanisms (e.g., in SCI, neuroinflammation, Aβ aggregation) are based on animal models or in-vitro experiments (PMID 40692165, PMID 24661604, PMID 28255762, PMID 41171324, PMID 35080861, PMID 33418449). The potential for synthesis of peptide compounds with predictable pharmacological actions and safe for wide use is recognized, but also noted is the individuality of physiologically significant effects due to molecular structures (PMID 14969422).

• Functional Connectomic Approach to Studying Selank and Semax Effects. — Doklady biological sciences : proceedings of the Academy of Sciences of the USSR, Biological sciences sections (2020). PMID 32342318
• Therapeutic Peptides in Orthopaedics: Applications, Challenges, and Future Directions. — Journal of the American Academy of Orthopaedic Surgeons. Global research & reviews (2026). PMID 41490200
• Selank, a Peptide Analog of Tuftsin, Attenuates Aversive Signs of Morphine Withdrawal in Rats. — Bulletin of experimental biology and medicine (2022). PMID 36322304
• Effect of Selank on Morphological Parameters of Rat Liver in Chronic Foot-Shock Stress. — Bulletin of experimental biology and medicine (2019). PMID 31243679
• The Influence of Selank on the Level of Cytokines Under the Conditions of "Social" Stress. — Current reviews in clinical and experimental pharmacology (2021). PMID 32621722
• Selank, Peptide Analogue of Tuftsin, Protects Against Ethanol-Induced Memory Impairment by Regulating of BDNF Content in the Hippocampus and Prefrontal Cortex in Rats. — Bulletin of experimental biology and medicine (2019). PMID 31625062
• Selank Administration Affects the Expression of Some Genes Involved in GABAergic Neurotransmission. — Frontiers in pharmacology (2016). PMID 26924987
• GABA, Selank, and Olanzapine Affect the Expression of Genes Involved in GABAergic Neurotransmission in IMR-32 Cells. — Frontiers in pharmacology (2017). PMID 28293190
• Peptide Selank Enhances the Effect of Diazepam in Reducing Anxiety in Unpredictable Chronic Mild Stress Conditions in Rats. — Behavioural neurology (2017). PMID 28280289
• Peptide-based Anxiolytics: The Molecular Aspects of Heptapeptide Selank Biological Activity. — Protein and peptide letters (2018). PMID 30255741
• Selank and short peptides of the tuftsin family in the regulation of adaptive behavior in stress. — Neuroscience and behavioral physiology (2003). PMID 14969422
• Semax peptide targets the μ opioid receptor gene Oprm1 to promote deubiquitination and functional recovery after spinal cord injury in female mice. — British journal of pharmacology (2025). PMID 40692165
• Therapeutic peptides in gerontology: mechanisms and applications for healthy aging. — Frontiers in aging (2026). PMID 42021992
• The Effect of Peptide Semax, an ACTH(4-10) Analogue, on Intracellular Calcium Dynamics in Rat Brain Neurons. — Bulletin of experimental biology and medicine (2025). PMID 41171324
• Semax, synthetic ACTH(4-10) analogue, attenuates behavioural and neurochemical alterations following early-life fluvoxamine exposure in white rats. — Neuropeptides (2021). PMID 33418449
• Semax, a Synthetic Regulatory Peptide, Affects Copper-Induced Abeta Aggregation and Amyloid Formation in Artificial Membrane Models. — ACS chemical neuroscience (2022). PMID 35080861
• Semax, an analogue of adrenocorticotropin (4-10), binds specifically and increases levels of brain-derived neurotrophic factor protein in rat basal forebrain. — Journal of neurochemistry (2006). PMID 16635254
• Semax, an analog of ACTH(4-7), regulates expression of immune response genes during ischemic brain injury in rats. — Molecular genetics and genomics : MGG (2017). PMID 28255762
• Effects of Semax on the Default Mode Network of the Brain. — Bulletin of experimental biology and medicine (2018). PMID 30225715
• The peptide semax affects the expression of genes related to the immune and vascular systems in rat brain focal ischemia: genome-wide transcriptional analysis. — BMC genomics (2014). PMID 24661604
• [The efficacy of semax in the tretament of patients at different stages of ischemic stroke]. — Zhurnal nevrologii i psikhiatrii imeni S.S. Korsakova (2018). PMID 29798983

Both Selank and Semax are supplied strictly for in-vitro and preclinical research use. They are not medicines, are not approved for human consumption in Spain, the United Kingdom, the European Union or the United States, and are not dispensed against a prescription. The research-use declaration ships with every package alongside the independent third-party COA.

Comparison pages on Peptide Intel Hub exist for laboratory-research reference. Nothing on this page constitutes a recommendation for human use of either compound.