Selank (TP-7) is a synthetic linear heptapeptide analog of the endogenous immunopeptide tuftsin, developed by Russian research institutes in the 1990s and studied as a regulatory peptide. Across the published record it has been examined primarily for anxiolytic-like and stress-modulating activity, nootropic/cognitive effects, and immunomodulation. The peer-reviewed literature describes a multi-target mechanism involving GABAergic modulation, enkephalinase inhibition, BDNF regulation, and cytokine balance. This monograph summarizes that literature for laboratory and research use only and makes no claims regarding human safety or efficacy.

Background & Discovery

Selank is a synthetic linear heptapeptide (Thr-Lys-Pro-Arg-Pro-Gly-Pro) developed in the 1990s at the V.V. Zakusov Research Institute of Pharmacology in collaboration with the Institute of Molecular Genetics of the Russian Academy of Sciences, under a program led by N.F. Myasoedov and S.B. Seredenin. It was originally designated TP-7. The molecule was engineered as an analog of tuftsin, an endogenous immunomodulatory tetrapeptide (Thr-Lys-Pro-Arg) that corresponds to residues 289-292 of the heavy chain of immunoglobulin G. Researchers appended a C-terminal Pro-Gly-Pro tripeptide to the tuftsin sequence, a modification that published literature associates with markedly increased metabolic stability against exopeptidase cleavage while retaining biological activity.

Selank is studied within the broader category of ‘regulatory peptides’ — short, endogenously-inspired sequences investigated for central nervous system and immune activity. It is frequently discussed alongside Semax (an ACTH(4-10) analog from the same Russian research lineage). The research interest in Selank arose from observations that tuftsin itself displayed both immunostimulatory and behavioral effects; the Pro-Gly-Pro extension was intended to yield a more stable, pharmacologically tractable molecule. In its country of origin, Selank was subsequently characterized in clinical pharmacology studies as a peptide anxiolytic and, per published reports, entered regulated use there for generalized anxiety and asthenic (neurasthenic) presentations.

Across the peer-reviewed record, Selank has been examined primarily in three overlapping domains: anxiolytic-like and stress-modulating activity, nootropic/cognitive effects (learning, memory, attention), and immunomodulation (cytokine balance, inflammation-related gene expression). It is important to note that the bulk of the primary literature originates from a small number of Russian research groups and is heavily weighted toward rodent models and in-vitro systems, with a smaller number of human clinical pharmacology reports. This monograph is provided strictly for laboratory and research use; it summarizes what the published literature reports and does not constitute medical guidance.

Chemical Identity

Structure & Physicochemical Properties

Selank is a water-soluble, linear heptapeptide with a free N-terminal threonine and a C-terminal proline carboxyl group. Its molecular formula is C33H57N11O9 (molecular weight ~751.9 g/mol; PubChem CID 11765600), and it contains basic residues (lysine and arginine) that render the molecule cationic at physiological pH and contribute to good aqueous solubility. The sequence is notable for its high proline content (three of seven residues), which imposes conformational constraint on the backbone and is generally associated in peptide chemistry with resistance to certain proteolytic enzymes and a propensity for polyproline-type local structure rather than classical alpha-helix or beta-sheet folding.

A key physicochemical rationale reported for the Pro-Gly-Pro C-terminal extension of the parent tuftsin sequence is enhanced enzymatic stability; the proline-rich C-terminus is described as slowing exopeptidase-mediated degradation relative to unmodified tuftsin. Published pharmacology work with Selank has commonly used intranasal administration in both animal and human studies, consistent with a small, hydrophilic peptide that is not orally bioavailable in intact form. As with most short peptides, the lyophilized (freeze-dried) solid is the typical reference form for handling and storage, and reconstituted aqueous solutions are treated as susceptible to hydrolysis, oxidation, and microbial degradation over time.

Mechanism of Action — as described in the literature

The mechanism of Selank characterized in the literature is multi-target rather than attributable to a single receptor. A recurring theme in mechanistic reviews is modulation of the GABAergic system. Vyunova and colleagues describe Selank interacting with the GABA/benzodiazepine receptor complex in a manner consistent with positive allosteric modulation of GABA-receptor binding, distinct from direct benzodiazepine-site agonism. This framing is offered as a rationale for reported anxiolytic-like activity that authors contrast with the classical dependence and cognitive-impairment profile of benzodiazepines. Importantly, in-vitro gene-expression work suggests the GABAergic influence may be indirect: in IMR-32 neuroblastoma cells, Selank alone did not directly change GABAergic gene mRNA levels but modulated the transcriptional response when co-applied with GABA.

A second, well-developed mechanistic strand concerns the endogenous opioid (enkephalinergic) system. Zozulya and colleagues reported that Selank inhibits enkephalin-degrading enzymes in human plasma/serum, dose-dependently slowing enzymatic hydrolysis of Leu-enkephalin. By reducing enkephalinase activity, Selank is proposed to prolong the half-life of endogenous enkephalins, and this enkephalinase-inhibition mechanism is advanced as a possible molecular basis for its anxiolytic activity. Clinical-biological data extended this idea, associating generalized anxiety states with shortened enkephalin half-life and reporting increases in serum enkephalin stability under Selank that correlated with symptom dynamics.

A third strand involves neurotrophic and neuroplasticity signaling, particularly brain-derived neurotrophic factor (BDNF). Rodent studies report that Selank administration alters BDNF content and expression in the hippocampus and prefrontal/frontal cortex — brain regions central to emotional regulation and memory. The directionality of the BDNF effect is context-dependent in the literature: some intranasal-administration studies describe upregulation of hippocampal BDNF, whereas in a chronic-ethanol model Selank was reported to prevent an ethanol-induced increase in cortical/hippocampal BDNF while protecting against memory impairment, indicating a normalizing (homeostatic) rather than uniformly stimulatory action.

The immunomodulatory mechanism reflects Selank’s tuftsin lineage. Studies report that Selank shifts cytokine balance and modulates inflammation-related gene expression. In mouse spleen, Selank produced rapid, wave-like changes in immune genes (for example, a several-fold early decrease in complement C3 mRNA), and broader panels of inflammation-related genes (chemokines, cytokines, and their receptors) were shown to change over time, consistent with a role in maintaining immunological balance. Under experimental ‘social’ stress in rats, Selank was reported to attenuate stress-induced elevations of pro-inflammatory cytokines (IL-1β, IL-6, TNF-α) and to restore anti-inflammatory IL-4.

Taken together, published literature characterizes Selank as acting through convergent pathways — allosteric/indirect GABAergic modulation, stabilization of endogenous enkephalins via enkephalinase inhibition, regulation of BDNF and monoaminergic (serotonin/dopamine turnover) systems, and cytokine/immune-gene modulation. Reviews emphasize that these mechanisms are still being delineated and that no single dominant receptor target has been established; the peptide is better described as a pleiotropic regulatory molecule than as a selective ligand.

Key Published Findings

• Anxiolytic mechanism / GABAergic modulation. A molecular-mechanism review by Vyunova et al. characterizes the heptapeptide Selank as interacting with the GABA-receptor system in a manner consistent with positive allosteric modulation of GABA binding, offered as a rationale for anxiolytic-like activity distinct from direct benzodiazepine-site agonism.[1]
• Enkephalinergic system (enkephalinase inhibition). Zozulya et al. reported that Selank dose-dependently inhibits enkephalin-degrading enzymes in human plasma, slowing Leu-enkephalin hydrolysis more effectively than reference peptidase inhibitors, and proposed this stabilization of endogenous enkephalins as a possible molecular basis for its anxiolytic activity.[2]
• Human clinical pharmacology. In a comparative clinical study of patients with generalized anxiety disorder and neurasthenia, Zozulya et al. reported that intranasal Selank produced anxiolytic effects broadly comparable to the benzodiazepine medazepam with an additional antiasthenic component, alongside changes in serum enkephalin half-life that tracked with symptom dynamics.[3]
• Neurotrophic signaling (BDNF). In a chronic-ethanol rat model, Kolik et al. reported that Selank protected against ethanol-induced memory impairment while normalizing BDNF content in the hippocampus and frontal cortex, indicating a context-dependent regulatory effect on neurotrophin levels.[5]
• Immunomodulation / inflammation-gene expression. Kolomin et al. found that a single intraperitoneal Selank injection produced rapid, time-dependent (‘wave-like’) changes in inflammation-related genes in mouse spleen, including an early several-fold decrease in complement C3 mRNA, consistent with the peptide’s tuftsin-derived immunomodulatory lineage.[9]
• Interaction with benzodiazepines under chronic stress. Kasian et al. reported that in a rat unpredictable chronic mild stress model, co-administration of Selank with diazepam produced the most pronounced reduction in anxiety-like behavior, with combined-treatment indicators approaching pre-stress baseline values.[4]

Research Applications

• Investigated in rodent models of anxiety-like behavior and unpredictable chronic mild stress as a peptide anxiolytic candidate
• Examined in learning and memory paradigms (e.g., conditioned active avoidance) as a nootropic-type modulator of cognition
• Studied in chronic-ethanol and alcohol-related cognitive-impairment rodent models in relation to BDNF regulation
• Investigated in opioid (morphine) withdrawal models for effects on aversive withdrawal signs
• Used in immunopharmacology research probing cytokine balance (IL-1β, IL-6, TNF-α, IL-4) and inflammation-related gene expression
• Applied in molecular studies of GABAergic neurotransmission and neuroreceptor gene expression in neuronal cell lines and brain tissue
• Examined in stress-physiology research addressing HPA-axis reactivity and stress-induced neuroinflammation
• Studied in human clinical pharmacology of generalized anxiety and asthenic (neurasthenic) states as a comparator to benzodiazepine therapy

Related & Comparator Compounds

Selank is most directly compared to its parent peptide tuftsin (Thr-Lys-Pro-Arg), the endogenous immunomodulatory tetrapeptide from which it is derived; the literature distinguishes Selank by its C-terminal Pro-Gly-Pro extension, which is reported to confer greater enzymatic stability while broadening the behavioral/anxiolytic activity profile. Within the same Russian regulatory-peptide research program, Selank is frequently studied in parallel with Semax, an analog of the ACTH(4-10) fragment; Semax is characterized more as a neuroprotective/nootropic and neurotrophic (NGF/BDNF-related) peptide, whereas Selank is framed primarily as an anxiolytic and immunomodulator, and the two have been co-examined for shared enkephalinase-inhibiting activity in human serum. Selank is also contrasted mechanistically with classical benzodiazepines (e.g., diazepam, medazepam): comparative animal and clinical reports position Selank as achieving anxiolytic effects without the sedation, motor impairment, and dependence/withdrawal signature associated with GABA-A benzodiazepine-site agonists. An N-acetylated variant (N-acetyl-Selank / Selank amidate forms) also appears in commercial and some research contexts as a stability-modified analog, and should not be conflated with the parent heptapeptide when interpreting data.

Handling, Reconstitution & Storage

In research settings, Selank is typically supplied as a lyophilized (freeze-dried) white powder and is described as handled under conditions that minimize peptide degradation. Published and reference-database handling practice for such short peptides generally involves storing the lyophilized solid desiccated at low temperature (commonly -20°C or colder for long-term storage; short-term refrigeration at 2-8°C) and protecting it from light, moisture, and repeated freeze-thaw cycles. For laboratory reconstitution, the water-soluble, cationic heptapeptide is generally dissolved in sterile water or buffered aqueous vehicle; reconstituted solutions are treated as less stable than the dry solid and are commonly aliquoted and kept cold, with freeze-thaw cycling avoided to limit hydrolysis, oxidation, and aggregation. All such handling is described here strictly in a research (in-vitro/preclinical) context and does not constitute human administration guidance.

Analytical & Quality Considerations

For a research-grade heptapeptide such as Selank, analytical quality control conventionally centers on reversed-phase high-performance liquid chromatography (RP-HPLC) to assess chromatographic purity (commonly reported as ≥95-98% area), paired with mass spectrometry (ESI-MS or MALDI-TOF) to confirm identity against the expected monoisotopic/average mass (formula C33H57N11O9, ~751.9 g/mol). Amino acid analysis and/or sequencing can corroborate the Thr-Lys-Pro-Arg-Pro-Gly-Pro sequence, while techniques such as Karl Fischer titration (water content), counterion/acetate determination, and endotoxin testing further characterize a lot. Because peptides are frequently supplied as acetate or trifluoroacetate salts, net-peptide content versus gross mass matters for quantitative in-vitro work. Independent third-party certificates of analysis (COA) are important because purity, correct sequence, counterion identity, and absence of deletion/truncation byproducts or residual solvents materially affect experimental reproducibility; verifying HPLC and MS data against a stated reference rather than relying on label claims alone is standard practice in rigorous research procurement.

Frequently Asked Research Questions

Q. What is Selank and where did it come from?
A. Selank is a synthetic linear heptapeptide (Thr-Lys-Pro-Arg-Pro-Gly-Pro), originally designated TP-7, developed by Russian research institutes in the 1990s as a more metabolically stable analog of the endogenous immunopeptide tuftsin. It is studied as a regulatory peptide with reported anxiolytic-like, nootropic, and immunomodulatory activity. It is intended for laboratory and research use only.

Q. How is Selank related to tuftsin?
A. Tuftsin is the endogenous tetrapeptide Thr-Lys-Pro-Arg, derived from immunoglobulin G and known for immunomodulatory activity. Selank consists of the tuftsin sequence extended at the C-terminus with a Pro-Gly-Pro tripeptide; published literature associates this modification with increased resistance to enzymatic degradation while retaining and broadening biological activity.

Q. What mechanisms does the published literature attribute to Selank?
A. Reviews and primary studies describe a multi-target profile: modulation of the GABAergic system (consistent with positive allosteric modulation rather than direct benzodiazepine-site binding), inhibition of enkephalin-degrading enzymes that stabilizes endogenous enkephalins, regulation of BDNF and monoamine turnover, and modulation of cytokines and inflammation-related gene expression reflecting its tuftsin lineage.

Q. Is there human clinical research on Selank?
A. Yes. A comparative clinical study by Zozulya and colleagues in patients with generalized anxiety disorder and neurasthenia reported anxiolytic effects broadly comparable to the benzodiazepine medazepam, with an additional antiasthenic component and changes in serum enkephalin half-life. This is summarized here as published scientific literature and is not medical advice or a treatment claim.

Q. How does Selank differ from benzodiazepines in the literature?
A. Comparative animal and clinical reports position Selank as producing anxiolytic-like effects without the sedation, motor impairment, and dependence/withdrawal profile characteristic of benzodiazepines. Mechanistically this is linked to indirect/allosteric GABAergic modulation and enkephalinergic effects rather than direct GABA-A benzodiazepine-site agonism.

Q. What analytical checks are relevant for research-grade Selank?
A. Standard QC includes RP-HPLC for purity, mass spectrometry to confirm identity against the expected mass (C33H57N11O9, ~751.9 g/mol), and sequence/amino-acid analysis. Independent third-party certificates of analysis, counterion (salt) identity, and net-peptide content are important for reproducible in-vitro and preclinical work.

Peer-Reviewed References

1. Vyunova TV, Andreeva L, Shevchenko K, Myasoedov N. Peptide-based Anxiolytics: The Molecular Aspects of Heptapeptide Selank Biological Activity. Protein & Peptide Letters. 2018. PubMed →
2. Zozulya AA, Kost NV, Sokolov OYu, Gabaeva MV, Grivennikov IA, Andreeva LN, Zolotarev YA, Ivanov SV, Andryushchenko AV, Myasoedov NF, Smulevich AB. The inhibitory effect of Selank on enkephalin-degrading enzymes as a possible mechanism of its anxiolytic activity. Bulletin of Experimental Biology and Medicine. 2001. PubMed →
3. Zozulia AA, Neznamov GG, Siuniakov TS, Kost NV, Gabaeva MV, Sokolov OYu, Serebriakova EV, Siranchieva OA, Andriushenko AV, Telesheva ES, Siuniakov SA, Smulevich AB, Miasoedov NF, Seredenin SB. Efficacy and possible mechanisms of action of a new peptide anxiolytic selank in the therapy of generalized anxiety disorders and neurasthenia. Zhurnal Nevrologii i Psikhiatrii imeni S.S. Korsakova. 2008. PubMed →
4. Kasian A, Kolomin T, Andreeva L, Bondarenko E, Myasoedov N, Slominsky P, Shadrina M. Peptide Selank Enhances the Effect of Diazepam in Reducing Anxiety in Unpredictable Chronic Mild Stress Conditions in Rats. Behavioural Neurology. 2017. PubMed →
5. Kolik LG, Nadorova AV, Antipova TA, Kruglov SV, Kudrin VS, Durnev AD. 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. PubMed →
6. Kozlovskii II, Danchev ND. The optimizing action of the synthetic peptide Selank on a conditioned active avoidance reflex in rats. Neuroscience and Behavioral Physiology. 2003. PubMed →
7. Volkova A, Shadrina M, Kolomin T, Andreeva L, Limborska S, Myasoedov N, Slominsky P. Selank Administration Affects the Expression of Some Genes Involved in GABAergic Neurotransmission. Frontiers in Pharmacology. 2016. PubMed →
8. Filatova E, Kasian A, Kolomin T, Rybalkina E, Alieva A, Andreeva L, Limborska S, Myasoedov N, Pavlova G, Slominsky P, Shadrina M. GABA, Selank, and Olanzapine Affect the Expression of Genes Involved in GABAergic Neurotransmission in IMR-32 Cells. Frontiers in Pharmacology. 2017. PubMed →
9. Kolomin T, Morozova M, Volkova A, Shadrina M, Andreeva L, Slominsky P, Limborska S, Myasoedov N. The temporary dynamics of inflammation-related genes expression under tuftsin analog Selank action. Molecular Immunology. 2014. PubMed →
10. Yasenyavskaya AL, Samotrueva MA, Tsibizova AA, Bashkina OA, Myasoedov NF, Andreeva LA. The Influence of Selank on the Level of Cytokines Under the Conditions of ‘Social’ Stress. Current Reviews in Clinical and Experimental Pharmacology. 2021. PubMed →
11. Konstantinopolsky MA, Chernyakova IV, Kolik LG. Selank, a Peptide Analog of Tuftsin, Attenuates Aversive Signs of Morphine Withdrawal in Rats. Bulletin of Experimental Biology and Medicine. 2022. PubMed →

For laboratory and research use only. Not for human or veterinary use, diagnosis, or treatment. This overview summarizes published scientific literature for informational and educational purposes and is not medical advice; no claims are made regarding safety or efficacy in humans.

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