Selank: Tuftsin Analog for Anxiolytic and Immunomodulatory Research

What Is Selank?

Selank (TP-7) is a synthetic heptapeptide consisting of the endogenous immunomodulatory peptide tuftsin (Thr-Lys-Pro-Arg) extended with a Pro-Gly-Pro sequence at the C-terminus for metabolic stability. With a molecular weight of approximately 752 Da, Selank was developed at the Institute of Molecular Genetics of the Russian Academy of Sciences and is approved in Russia as an anxiolytic under the brand name Selank. Research interest spans both its anxiolytic properties and immunomodulatory activity, positioning it at a unique intersection of neuropharmacology and immunology.

The peptide sequence of Selank is Thr-Lys-Pro-Arg-Pro-Gly-Pro, which can be understood as tuftsin (positions 1-4) plus a stabilizing tripeptide extension (positions 5-7). This design significantly increases metabolic stability compared to parent tuftsin while preserving biological activity. The Pro-Gly-Pro extension protects the peptide from rapid enzymatic degradation and extends its functional half-life in biological systems.

Structure and Biochemistry

Molecular Architecture

Selank belongs to the structural class of peptide-based anxiolytics and immunomodulators. Its molecular formula is C₃₃H₅₇N₉O₈, with a molecular weight of 751.87 Da. The peptide is a heptapeptide (7 amino acids) and is administered intranasally in most research contexts, exploiting the direct olfactory pathway to bypass the blood-brain barrier.

The key structural features include:

• •Tuftsin core (residues 1-4): The Thr-Lys-Pro-Arg sequence is derived from the Fc region of IgG and confers innate immunomodulatory properties
• •Stabilizing extension (residues 5-7): Pro-Gly-Pro substantially increases resistance to peptidases and extends plasma half-life
• •Amphipathic character: The combination of charged residues (Lys, Arg) and hydrophobic/neutral residues enables both receptor binding and membrane interactions

Metabolic Stability

Unmodified tuftsin has an extremely short half-life in biological fluids due to rapid cleavage by serum peptidases. The Pro-Gly-Pro extension at the C-terminus creates steric hindrance that significantly reduces peptidase accessibility. In nasal mucosal secretions and cerebrospinal fluid, Selank demonstrates substantially greater metabolic stability than its parent compound, enabling sustained receptor engagement following intranasal administration.

Mechanism of Action

GABAergic Modulation

Selank's primary anxiolytic mechanism involves modulation of the GABAergic system — the main inhibitory neurotransmitter system in the central nervous system. In rat frontal cortex, a single dose of Selank changed the expression of 45 of 84 neurotransmission genes at one hour and 22 at three hours, with changes that correlated positively with those produced by GABA itself (PMID 26924987).

Radioligand work from the same institute found that Selank acts as a positive allosteric modulator of [3H]GABA binding, and that its joint action with diazepam is not additive, suggesting overlapping but distinct binding sites (PMID 30255741). This distinction is pharmacologically significant: benzodiazepines bind to a specific allosteric site on GABA-A receptors and are associated with tolerance, dependence, and withdrawal. Selank's GABAergic modulation appears to occur through a different mechanism, potentially explaining its lack of dependence-forming properties.

The main clinical comparison is a 2008 Russian study of 62 patients with generalized anxiety disorder and neurasthenia, in which Selank (30 patients) was compared with the benzodiazepine medazepam (32 patients) on the Hamilton, Zung, and CGI scales. Anxiolytic effects were similar; the Selank group also showed antiasthenic and psychostimulant effects, and serum leu-enkephalin half-life, which was reduced in the patients at baseline, rose during Selank treatment (PMID 18454096). The study is open-label and published in Russian, and has not been replicated outside Russia. The peptide appears to normalize anxiety-related behavioral disturbances without impairing cognitive function or producing motor incoordination — a key differentiation from classical anxiolytics.

Serotonergic System Interactions

Beyond GABAergic modulation, research has identified interactions between Selank and the serotonergic system. The peptide appears to influence gene expression of the serotonin transporter (SERT) and serotonin receptors in brain regions associated with anxiety regulation, including the hippocampus and prefrontal cortex. These serotonergic interactions may contribute to mood-stabilizing effects observed in research models.

In rats whose serotonin synthesis had been suppressed with p-chlorophenylalanine, Selank increased serotonin metabolism in the brainstem within 30 minutes, whereas the parent peptide tuftsin did not (PMID 19803361). This normalization effect positions Selank as a compound of interest for studying stress-related disorders.

BDNF and Neurotrophic Effects

Selank also acts on brain-derived neurotrophic factor (BDNF) expression. BDNF is a critical growth factor for neuronal survival, plasticity, and the formation of new synaptic connections. Reduced BDNF expression is associated with depression, anxiety, and neurodegenerative conditions.

Intranasal Selank altered BDNF expression in the rat hippocampus in vivo (PMID 18841804). The direction is not simply "up": in rats given ethanol for 30 weeks, Selank prevented the ethanol-induced rise in hippocampal and prefrontal BDNF while also preventing the memory deficits that developed during withdrawal (PMID 31625062), so "regulates" is the more accurate word than "increases". This neurotrophic effect may underlie some of the cognitive-enhancing and neuroprotective properties attributed to Selank in research contexts, and creates mechanistic overlap with peptides like Semax which also upregulate BDNF.

Enkephalinase Inhibition

Selank is thought to inhibit enkephalin-degrading enzymes rather than bind opioid receptors directly: in mice its suppression of apomorphine-induced behaviour was blocked by naloxone, yet radioreceptor assays showed no displacement of delta/mu opioid or D2 ligands (PMID 17415472). In the 2008 clinical study, serum leu-enkephalin half-life rose during Selank treatment (PMID 18454096). By prolonging the half-life of endogenous enkephalins, Selank may amplify their physiological effects on mu and delta opioid receptors. This indirect opioidergic mechanism could contribute to anxiolytic and mood-stabilizing effects observed in research models.

Immunomodulatory Properties

As a tuftsin analog, Selank retains and extends the immunomodulatory activity of its parent compound. Tuftsin (Thr-Lys-Pro-Arg) is a naturally occurring tetrapeptide derived from the Fc region of immunoglobulin G that stimulates phagocytic activity of macrophages and neutrophils by binding to a specific tuftsin receptor on phagocytic cells.

In mouse spleen, a single Selank injection changed the expression of 34 of 84 inflammation-related genes at 6 and 24 hours, with Bcl6 and its targets among the most responsive (PMID 21609736). In blood cells from patients with depression, Selank suppressed IL-6 gene expression in vitro, and patients with anxiety-asthenic disorders showed shifts in Th1/Th2 cytokine balance over 14 days of treatment (PMID 18577961). The pattern reported across these studies:

• •IL-6: Reduces excessive IL-6 production while preserving baseline immune function
• •Interferon-gamma (IFN-γ): Modulates IFN-γ expression in T-lymphocytes
• •Tumor necrosis factor (TNF-α): Influences TNF-α secretion from activated macrophages
• •Interleukin-2 (IL-2): Supports IL-2 signaling important for T-cell proliferation

This cytokine-modulating profile makes Selank of interest for research into immune-mediated neurological conditions and neuroinflammation, where excessive cytokine activity may drive pathological processes.

Research Applications

Anxiety and Stress Models

Selank has demonstrated anxiolytic effects across multiple validated behavioral paradigms for anxiety research:

Elevated Plus Maze (EPM): Selank significantly increases time spent in open arms and number of open arm entries — a behavioral signature of reduced anxiety — without impairing locomotor activity or exploration in the closed arms. This anxiolytic signature without motor impairment is critical for distinguishing anxiolytic from sedative effects.

Light-Dark Box: In this exploration-based anxiety paradigm, Selank-treated animals show increased time in the illuminated (aversive) compartment, indicating reduced anxiety-driven avoidance behavior.

Stress-Induced Hyperthermia: Selank attenuates stress-induced hyperthermia, a physiological readout of acute anxiety, suggesting action on autonomic stress responses in addition to behavioral effects.

Open Field Test: Selank normalizes freezing behavior and hyperlocomotion induced by stressors, with effects on anxiety-like behaviors that are distinguishable from non-specific sedation.

Neuroimmune Research

The dual neurotrophic-immunomodulatory profile positions Selank for research at the intersection of neuroscience and immunology. The neuroimmune interface — the bidirectional communication between the nervous and immune systems — is an area of growing interest for understanding conditions where immune dysregulation contributes to neurological dysfunction.

Key neuroimmune research questions that Selank helps explore:

• •How do peripheral immune signals (cytokines) influence central nervous system function and behavior?
• •What is the role of innate immune activation in anxiety and stress responses?
• •Can immunomodulatory peptides exert direct CNS effects, and through what mechanisms?
• •How does tuftsin-like activity in the CNS contribute to neuroprotection?

Cognitive Enhancement Research

Beyond anxiolysis, Selank has been investigated for cognitive effects in research models. The combination of BDNF upregulation, GABAergic modulation, and enkephalinase inhibition creates a neurochemical environment that may support attention, memory consolidation, and cognitive performance under stress.

Research in rodent models suggests Selank can improve performance in:

• •Reference memory tasks (Morris water maze performance)
• •Passive avoidance learning in stress conditions
• •Attention and concentration measures in chronic stress models

These cognitive effects are mechanistically plausible given Selank's effects on hippocampal BDNF and its normalization of stress-related neurochemical disruptions.

Alcohol and Substance Research

An intriguing area of Selank research involves its potential effects on alcohol intake and dependency models. Several studies in rodent models of alcohol preference have demonstrated that Selank administration reduces voluntary alcohol consumption. The proposed mechanisms involve:

• •Normalization of GABAergic tone disrupted by chronic alcohol exposure
• •Reduction in stress-driven alcohol seeking through HPA axis modulation
• •Enkephalinase inhibition increasing endogenous opioid tone, reducing reward-seeking

These findings position Selank as a research tool for studying the neurobiological basis of alcohol preference and potential pharmacological interventions.

Gene Expression Studies

Selank has emerged as a useful tool for studying gene expression changes in the central nervous system. Its well-characterized effects on multiple neurotransmitter systems make it valuable for:

• •Mapping anxiety-related gene networks in the hippocampus and amygdala
• •Studying stress-responsive gene expression changes
• •Investigating cytokine-CNS gene interactions
• •Examining BDNF-dependent neuroplasticity gene programs

Transcriptomic analyses following Selank administration have identified dozens of differentially expressed genes in brain regions including prefrontal cortex, hippocampus, and amygdala, providing a comprehensive molecular fingerprint of its CNS effects.

Pharmacokinetics and Administration

Intranasal Route in the Research Literature

Most Russian clinical and preclinical work on Selank used the intranasal route, and the registered Russian product is a nasal solution. Intranasal delivery is used because the heptapeptide is cleaved quickly in plasma; the olfactory route is intended to reach the CNS before degradation. Published pharmacokinetic parameters for the intranasal route in humans are sparse and mostly appear in Russian-language sources, so onset, peak, and bioavailability figures quoted on supplier sites should be treated as unverified.

Route Dependence

Preclinical studies have used intranasal, intraperitoneal, and subcutaneous administration, and the transcriptomic and behavioural readouts differ by route and by time after administration (the frontal-cortex gene-expression study, for example, found a different set of responsive genes at one hour versus three hours; PMID 26924987).

Stability in Solution

Selank in aqueous solution is less stable than the lyophilised powder. For laboratory storage, lyophilised material at -20°C, protected from light and moisture, is the standard; reconstituted solutions should be aliquoted to avoid repeated freeze-thaw cycles and used promptly.

Comparison with Related Peptides

Selank vs. Semax

Selank and Semax are frequently studied together as complementary nootropic/anxiolytic compounds. Despite both being synthetic peptides with CNS activity, their mechanisms and profiles are quite distinct:

Researchers sometimes combine Selank (anxiolytic, calming) with Semax (activating, nootropic) to study synergistic CNS effects, though combination research is more limited than individual compound studies.

Selank vs. Diazepam

The classical comparison in Selank research is with benzodiazepines (diazepam as prototype):

Research Considerations

Dose-Response Design

Selank studies report effects across a wide concentration range, and several groups describe non-monotonic (U-shaped) dose-response curves, which is common for neuroactive peptides. Any experimental design should establish the dose-response relationship for its own paradigm rather than assume linearity. This article does not provide dosing figures; the studies cited in the reference list report their own protocols.

Safety Profile in Research

The Russian literature reports that Selank produced anxiolytic effects without the sedation associated with benzodiazepines in the medazepam comparison study (PMID 18454096), and in a rat model of naloxone-precipitated morphine withdrawal a single anxiolytic dose reduced the withdrawal index by 39.6%, slightly less than diazepam (PMID 36322304). Claims that Selank produces no tolerance, no dependence, and no memory impairment come from the same body of Russian work and have not been tested in independent, blinded trials outside Russia; they should be read as preliminary.

Research Limitations

• •Most mechanistic studies come from the Institute of Molecular Genetics and allied Moscow groups, and many are published in Russian with English abstracts only
• •The clinical comparison with medazepam was open-label, and no Western double-blind trial exists
• •Intranasal pharmacokinetic data in humans are not available in the peer-reviewed English literature
• •CNS effects vary with baseline stress status of the animals, which complicates cross-study comparison

Research Specifications

• •Molecular weight: 751.87 Da
• •Molecular formula: C₃₃H₅₇N₉O₈
• •Sequence: Thr-Lys-Pro-Arg-Pro-Gly-Pro (TKPRPGP)
• •CAS number: 129954-34-3
• •Half-life: short in plasma (rapid proteolysis); not well quantified in the English-language literature
• •Available forms: Lyophilized powder; nasal solution (registered Russian product)
• •Reconstitution: Bacteriostatic water or sterile saline
• •Storage: -20°C (lyophilized), 2-8°C (reconstituted, use within 30 days)
• •Stability: pH 4-7 optimal; avoid alkaline conditions
• •Classification: For laboratory research use only (RUO)

Internal Research Context

Selank belongs to a broader category of neuroimmune peptides studied for their capacity to modulate both CNS and immune function simultaneously. Researchers interested in Selank may also explore:

• •Semax — complementary BDNF-upregulating nootropic peptide
• •Dihexa — HGF-mimetic cognitive enhancer targeting synaptic formation
• •P21 — CNTF-derived neurogenesis research peptide
• •Thymosin Alpha 1 — thymic immune peptide with neuroimmune applications
• •LL-37 — cathelicidin peptide with antimicrobial and immunomodulatory properties

Understanding Selank's mechanism within the broader landscape of immunomodulatory peptides provides context for its unique position as a compound operating at the neuroimmune interface.

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Further Reading:

• •PE-22-28: Complete Research Profile — Spadin Analog, TREK-1 Blocker, and Rapid-Onset Antidepressant Peptide for Nootropic Research (2026)
• •Thymosin Alpha 1: Immunomodulatory Peptide for Immune Function Research
• •Semax: ACTH(4-10) Analog for Neuroprotection and Cognitive Research
• •LL-37: The Human Cathelicidin Antimicrobial Peptide in Research
• •Reconstitution Calculator
• •Peptide Stack Builder

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Selank Pricing: What the Platform Shows (September 2026)

Computed from the peptides.so listings table on 20 September 2026 for the Selank product row (list prices of at least $5; vial sizes pooled because most feeds do not pin the mg amount in the product name):

Selank is one of the most widely listed research peptides on the platform; only BPC-157 (97 suppliers) has a broader supplier base among the compounds we track. Because vial sizes are pooled, compare offers per milligram on the Selank compound page, where each listing shows its stated size, or use the compare tool. Sub-dollar per-mg figures that circulate for Selank almost always come from feeds with a currency or unit error rather than from a real price; a 10 mg vial below about $15 should prompt a certificate of analysis request before ordering.

Frequently Asked Questions About Selank Research

Q: What distinguishes Selank from classical benzodiazepine anxiolytics in research models?

A: Selank modulates GABAergic transmission through an allosteric mechanism that differs from classical benzodiazepine binding. In research models, Selank produces anxiolytic effects in elevated plus maze and light-dark box paradigms without the sedation, motor incoordination, or tolerance-associated receptor downregulation observed with benzodiazepines. The enkephalinase inhibition mechanism adds an endogenous opioid component absent in benzodiazepine pharmacology.

Q: How does Selank's intranasal route affect CNS delivery compared to subcutaneous administration?

A: The intranasal route was chosen in the Russian programme because the heptapeptide is cleaved rapidly in plasma and the olfactory pathway offers a route to the CNS that does not depend on crossing the blood-brain barrier from blood. Quantitative human bioavailability figures for intranasal Selank are not available in the peer-reviewed English-language literature; percentages quoted on supplier sites are unsourced. Preclinical studies have used intranasal, intraperitoneal, and subcutaneous routes and report route- and time-dependent differences in gene-expression readouts.

Q: What is the mechanistic basis for Selank's effect on BDNF?

A: Intranasal Selank changes hippocampal BDNF expression in rats (PMID 18841804), and in a chronic-ethanol model it prevented the ethanol-induced rise in hippocampal and prefrontal BDNF alongside preventing withdrawal-related memory deficits (PMID 31625062). The intracellular pathway has not been mapped; the GABAergic and serotonergic effects described above are the candidate upstream mechanisms, but that link is inferred rather than demonstrated.

Q: How does Selank compare to Semax in the context of nootropic peptide stacking research?

A: Selank (anxiolytic, calming, immunomodulatory via tuftsin-derived mechanism) and Semax (activating, neuroprotective, BDNF-upregulating via MC4R/ACTH mechanism) represent complementary CNS profiles. Their mechanisms operate through distinct receptor systems, providing rationale for studying combined administration. Selank may attenuate any activating/stimulant-like effects of Semax while both contribute to BDNF upregulation through different pathways. See the nootropic peptides comparison guide for a detailed head-to-head analysis.

Q: How should Selank be stored and handled in the laboratory?

A: Lyophilised Selank is stored at -20°C, protected from light and moisture. Reconstituted solutions are less stable; aliquot to avoid freeze-thaw cycles and use promptly. See the peptide storage guide for general handling.

Q: What safety data exist for Selank?

A: The clinical data are Russian and open-label: the medazepam comparison reported anxiolytic effects without sedation (PMID 18454096), and the immunology study in the same patient group reported cytokine shifts over 14 days (PMID 18577961). No independent blinded trial, and no published carcinogenicity or reproductive toxicity data, exist in the English-language literature. Preclinical monitoring in the cited studies focused on behavioural endpoints (open field, object recognition) and, where relevant, immune gene expression.

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For research use only. Selank is not approved for human administration.

What to Look for in Selank COAs

Selank (Thr-Lys-Pro-Arg-Pro-Gly-Pro) is a heptapeptide with molecular weight 751.9 Da. Key COA checkpoints:

• •Expected molecular weight: 751.9 Da; the MS data should show this ion within ±1 Da
• •HPLC purity: ≥98% for research applications, ≥95% minimum for screening studies
• •Chromatogram: Single dominant peak, with known impurity peaks labeled if present
• •Storage confirmation: Selank is stable as lyophilized powder at -20°C; reconstituted solutions are less stable and should be aliquoted

Because Selank is not an FDA-approved drug, no compounding pharmacy or 503A/503B compounder may legally prepare it for human administration. All legitimate supplier sales are for research use only.

Internal Resources

• •Selank Compound Page, live pricing across 90 suppliers
• •COA Interpretation Guide, how to evaluate supplier documentation
• •Peptide Storage Best Practices, maintaining sample integrity
• •Neuroprotective Peptides Compared, Selank vs. Semax and other cognitive research peptides

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For research use only. Selank is not approved for human administration.

References

1. Zozulia AA, Neznamov GG, Siuniakov TS, et al. [Efficacy and possible mechanisms of action of a new peptide anxiolytic selank in the therapy of generalized anxiety disorders and neurasthenia]. Zh Nevrol Psikhiatr Im S S Korsakova. 2008;108(4):38-48. Russian. PMID 18454096

2. Volkova A, Shadrina M, Kolomin T, et al. Selank Administration Affects the Expression of Some Genes Involved in GABAergic Neurotransmission. Front Pharmacol. 2016;7:31. PMID 26924987

3. Vyunova TV, Andreeva L, Shevchenko K, Myasoedov N. Peptide-based Anxiolytics: The Molecular Aspects of Heptapeptide Selank Biological Activity. Protein Pept Lett. 2018;25(10):914-923. PMID 30255741

4. Inozemtseva LS, Karpenko EA, Dolotov OV, et al. Intranasal administration of the peptide Selank regulates BDNF expression in the rat hippocampus in vivo. Dokl Biol Sci. 2008;421:241-243. PMID 18841804

5. Kolik LG, Nadorova AV, Antipova TA, et al. Selank, Peptide Analogue of Tuftsin, Protects Against Ethanol-Induced Memory Impairment by Regulating of BDNF Content in the Hippocampus and Prefrontal Cortex in Rats. Bull Exp Biol Med. 2019;167(5):641-644. PMID 31625062

6. Semenova TP, Kozlovskii II, Zakharova NM, Kozlovskaia MM. [Comparison of the effects of selank and tuftsin on the metabolism of serotonin in the brain of rats pretreated with PCPA]. Eksp Klin Farmakol. 2009;72(4):6-8. Russian. PMID 19803361

7. Meshavkin VK, Kost NV, Sokolov OY, et al. Naloxone-blocked depriming effect of anxiolytic selank on apomorphine-induced behavioral manifestations of hyperfunction of dopamine system. Bull Exp Biol Med. 2006;142(5):598-600. PMID 17415472

8. Kolomin T, Shadrina M, Andreeva L, et al. Expression of inflammation-related genes in mouse spleen under tuftsin analog Selank. Regul Pept. 2011;170(1-3):18-23. PMID 21609736

9. Uchakina ON, Uchakin PN, Miasoedov NF, et al. [Immunomodulatory effects of selank in patients with anxiety-asthenic disorders]. Zh Nevrol Psikhiatr Im S S Korsakova. 2008;108(5):71-75. Russian. PMID 18577961

10. Konstantinopolsky MA, Chernyakova IV, Kolik LG. Selank, a Peptide Analog of Tuftsin, Attenuates Aversive Signs of Morphine Withdrawal in Rats. Bull Exp Biol Med. 2022;173(6):730-733. PMID 36322304