Selank

01Key questions

02Overview

Selank is a synthetic heptapeptide developed as an anxiolytic (anti-anxiety) agent by researchers at the Institute of Molecular Genetics of the Russian Academy of Sciences in Moscow. It is a structurally stabilized analog of tuftsin, a naturally occurring tetrapeptide produced by enzymatic cleavage of the Fc fragment of immunoglobulin G in the spleen. Selank's C-terminal Pro-Gly-Pro extension (the "glyproline" motif shared with Semax) protects the molecule from rapid aminopeptidase degradation and gives it a plasma half-life of 2–5 minutes (vs. seconds for native tuftsin) — long enough for intranasal delivery to engage CNS targets through olfactory/trigeminal pathways plus residual enkephalinase inhibitory activity downstream.

Selank is approved and used clinically in Russia and Ukraine for generalized anxiety disorder (GAD, neurasthenic presentations), asthenic syndromes, and as a nootropic adjunct. Its clinical positioning is anxiolytic efficacy comparable to benzodiazepines without sedation, cognitive impairment, tolerance, or dependence — a profile that remains unique in the anxiolytic drug class and continues to be cited in 2025-2026 peer-reviewed reviews of next-generation anxiolytic pharmacology.

Evidence Level: Moderate. Multiple 2008–2015 Russian RCTs (n=60–70, active-comparator vs. medazepam or phenazepam), extensive preclinical mechanistic work including gene-expression profiling (45 genes, 1 h post-administration; 22 genes at 3 h), functional connectomic fMRI comparisons with Semax, and two 2020–2024 clinical-practice reports in post-COVID asthenia. No FDA approval, no Western clinical trials, no PMC-indexed RCT outside Russian Federation journals.

03Mechanism of Action

Selank is genuinely polypharmacological — at least four mechanistic axes cooperate, which is what distinguishes it from benzodiazepines (single-receptor saturators) and explains the absence of dependence/tolerance signaling.

1. GABA-A Modulation (without benzodiazepine-site binding)

• Allosterically modulates GABA-A receptors via a site distinct from the benzodiazepine binding pocket — increases receptor sensitivity to endogenous GABA without direct occupancy (PMID 26924987, Kolomin 2016, Front Pharmacol)
• Result: anxiolysis at the efficacy level of medazepam and phenazepam (active comparators in 2008/2014 RCTs) with no sedation, no cognitive impairment, no psychomotor slowing
• Confirmed by gene-expression profiling: changes in 45 frontal-cortex ion-channel and receptor transcripts 1 hour post-administration overlap with—but are not identical to—direct GABA administration (PMC4757669)

2. Serotonergic Modulation (turnover enhancement, not reuptake block)

• Increases brain serotonin turnover (5-HIAA / 5-HT ratio) in amygdala, hippocampus, frontal cortex — measured directly in rodent brain regions mediating anxiety (PMID 15840402 cited in PMID 37242459)
• Pre-treatment with PCPA (a tryptophan hydroxylase blocker) abolishes Selank's anxiolytic effect, confirming serotonergic mediation as upstream of anxiolysis (Semenova 2009, Eksp Klin Farmakol, PMID 19803361)
• Counteracts experimentally induced serotonin syndrome in rats — bidirectional serotonergic stabilizer (PMID 15840402)
• This mechanism has overlap with SSRIs but is downstream of reuptake; theoretical SSRI+Selank combination requires clinical supervision (see #Drug Interactions)

3. Enkephalinase Inhibition (endogenous opioid stabilization)

• Inhibits enkephalin-degrading enzymes in human serum — first described in 2001 (Zozulya AA et al., Bull Exp Biol Med 131(4):315-7, PMID 11550013)
• This raises endogenous enkephalin levels and provides a non-addictive opioid-stabilizing action — the structural basis for Selank's lack of dependence liability despite engaging endogenous opioid tone
• Mechanism is shared with Semax — joint publication (Kost NV et al., ResearchGate 11897257)

4. BDNF Upregulation

• Rapidly elevates BDNF expression in hippocampus of rats — confirmed Kolik 2019 (Bull Exp Biol Med, PMID 31625062)
• Counteracts chronic-ethanol-induced memory impairment by restoring BDNF in hippocampus + prefrontal cortex
• This is the structural basis for Selank's nootropic + mood-stabilizing properties that benzodiazepines cannot deliver

5. Immune Modulation (tuftsin-derived)

• Binds tuftsin receptor on macrophages, microglia, and CNS-resident immune cells — bridging Selank's neurological and immunological activities
• Modulates IL-6 and Th1/Th2 cytokine balance (Wikipedia medical citation)
• Antiviral effects — independent of CNS activity; the Gly-Pro fragment of Selank is the minimum pharmacophore for viral inhibition (Kostenko et al., cited in SciRP review)

6. Enkephalinase → Withdrawal Resistance

• The 2022 rat study (Bull Exp Biol Med, PMID 36322304) showing Selank attenuates morphine-withdrawal aversive signs is consistent with its enkephalinase inhibitory profile — the drug acts on the same neuropeptide system that morphine disrupts, but as a stabilizer rather than an agonist

04Primary Uses & Applications

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05Clinical Evidence

Human Clinical Trials (Russian Federation)

Study 1 — Zozulya 2008 (n=62, GAD + neurasthenia) — Selank vs. medazepam - Equivalent Hamilton Anxiety Scale improvement - Selank-added antiasthenic (anti-fatigue) effects - Selank-added psychostimulant effects (without jitteriness, distinct from classic stimulants) - Source: PMID 18454096, Zh Nevrol Psikhiatr Im S S Korsakova

Study 2 — 2014 (n=60, phobic anxiety + somatoform disorders) — Selank vs. phenazepam - Anxiolytic effects comparable to phenazepam (benzodiazepine) - Effects persisted one week post-discontinuation — unique durability vs. benzodiazepines - No sedation, no cognitive impairment - Source: PMID 25176261

Study 3 — 2015 (n=70) — Selank combined with benzodiazepine - Better efficacy than benzodiazepine alone - Fewer side effects than benzodiazepine alone - Direct support for benzodiazepine-taper bridge use - Source: cited in 2017 PMC5322660 / Kasian 2017 review

Study 4 — Pogodina et al. 2024 (n=64, post-COVID asthenia) — NEW 2024 datapoint - Vrach ("Врач") Russian practice journal, no PMID yet (Russian-only literature) - 64 patients with post-COVID asthenia, decreased performance, emotional disorders - Group 1 (n=32): neuroprotective complex (cholitilin, mexidol, milgamma) + Selank 0.15% nasal drops, 2-3 drops 4×/day × 30 days (≈500 µg/dose) - Group 2 (n=32): same complex without Selank - Results: "Good effect in patients with asthenia and impaired mental performance. In parallel, relief of anxiety and depressive symptoms." - Source: Pogodina EA, Nikiforova DA. Vrach 2024. Eco-Vector DOI 10.29260/10.29260/vrach.2024.633315 (Russian Federation) - Caveat: Open-label, no Selank monotherapy arm, no anxiety rating scale reported in abstract. Replicates Russian clinical practice pattern more than it extends RCT evidence.

Western Peer-Reviewed Mentions (2024–2026)

Rahman et al. 2026 — Orthopedic Therapeutic Peptide Review - Published in Journal of the AAOS Global Research & Reviews (Wolters Kluwer, US), the first sustained Western orthopedic journal engagement with cognitive peptides - Cites Selank alongside Semax and Dihexa for neuroactive BDNF / HGF-c-Met axis modulation in musculoskeletal recovery context - Explicitly notes: "preclinical studies are promising, [but] there is a current lack of clinical trials" - Source: PMID 41490200, JAAOS Glob Res Rev 10(1):e25.00236, PMCID PMC12753158

Preclinical and Mechanistic Evidence

• Kolomin 2016 (Front Pharmacol) — 45-gene expression profile in rat frontal cortex at 1 h post-administration; 22 genes at 3 h. Genes include GABA-A subunits, serotonin receptor subtypes, dopamine receptor transcripts, and ion channels (PMC4757669)
• Kasian 2017 — Selank + diazepam combination most effective in unpredictable chronic mild stress (UCMS) rat model of depression-like behavior; full paper in Bull Exp Biol Med 162(4):510–513
• Kozhevnikov & Sotnikov 2020 — Functional connectomic fMRI comparison of Selank and Semax in rat brain; Selank and Semax show distinct, partially opposite resting-state network signatures (PMID 32342318). Implication: the two IMG RAS peptides are not interchangeable anxiolytic/nootropic siblings despite shared C-terminal glyproline motif
• Kolik 2019 — Selank protects against ethanol-induced memory impairment via hippocampal + prefrontal BDNF restoration (PMID 31625062)
• 2019 chronic-stress hepatoprotection — Selank prevented stress-induced liver damage in chronic foot-shock rats (PMID 31243679)
• Trofimova 2022 — Selank reduced aversive signs of morphine withdrawal in rats (PMID 36322304)

06Research Update 2024–2026

The pipeline had effectively stalled from 2020–2023 (no PubMed-indexed primary research in Title/Abstract). The 2024–2026 window shows modest, but real, signal of reactivation:

2024 — Russian clinical practice reports

• Pogodina 2024 (Vrach): First post-COVID asthenia clinical-practice report of Selank efficacy in n=64 cohort (see #Human Clinical Trials above). Note: this is the same pattern of Russian practice-level reporting that characterized pre-2020 publications — there is still no large, well-controlled Western-style RCT in any indication.
• This paper is not yet PMC-indexed; PMID search returns 0 results as of 2026-10-12.

2026 — Western peer-reviewed engagement begins

• Orthopedic therapeutics review (Rahman 2026, JAAOS): PMID 41490200 — first US orthopedic journal to systematically catalogue Selank alongside BPC-157, TB-500, GHK-Cu, Semax, Dihexa, Epitalon. This is a positioning shift: Selank is now appearing in condition-specific (orthopedic recovery) therapeutic peptide reviews, not just nootropic/bioregulator surveys.
• Peptide gerontology reviews (2025–2026): Both Semax and now Selank are increasingly cited in gerontology reviews, e.g. Front Aging 2026 (PMID 42021992) and Neuropeptides 2025 (PMID 41004910) — the geroprotective peptide category is gaining Western peer-reviewed coverage.

2024 — Receptor pharmacology clarification

• A 2024 acceptance-functional review (Peptidepedia, 2024) and the Behavioural Neurology-era pharmacology literature consolidate the four-axis mechanism (GABA-A / serotonin turnover / enkephalinase / BDNF) and clarify that Selank is mechanistically distinct from benzodiazepines at every layer (no benzodiazepine-site binding, no sedation, no tolerance, no dependence).

Overall assessment

• 2024–2026 evidence: clinical-practice consolidation, not therapeutic breakthrough. Selank is now embedded in (a) post-COVID fatigue clinical practice in Russia, (b) the Western therapeutic-peptide review literature (orthopedic, geriatric), and (c) mechanistic pharmacology reviews of next-generation anxiolytics — but no new randomized Phase II/III trials have emerged.
• Comparison with Semax: Semax received substantial 2025 Western attention (μ-opioid receptor in spinal cord injury, copper chelation in AD model — see Semax#Recent Research (2023–2026)) while Selank has not received equivalent Western mechanistic reactivation. Why: Semax's mechanism (BDNF + NGF) maps more obviously onto Western pain/neurodegeneration research priorities; Selank's GABA/serotonin mechanism competes with established SSRI/SARI pipelines where the marginal benefit of a Russian peptide is harder to argue.

07Uses

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Administration Notes

• Intranasal is the primary route in clinical practice; oral bioavailability is effectively zero (gastric peptidases destroy the molecule)
• Olfactory and trigeminal pathways provide partial direct nose-to-brain transport; remainder is absorbed systemically across nasal mucosa
• Plasma half-life is short (2–5 min); downstream pharmacodynamic effects (gene expression, enkephalinase inhibition, BDNF changes) persist for hours to days
• No titration required (unlike benzodiazepines)
• No withdrawal reported upon discontinuation

08Safety Profile

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Key Safety Distinction vs. Benzodiazepines

Selank's safety profile represents an unfilled clinical niche: benzodiazepine-comparable anxiolysis without ANY of the characteristic benzodiazepine liabilities. This is the foundation of its 16-year clinical use in Russia — but the absence of Phase III Western trials means the safety claim rests on Russian clinical experience, not on FDA-style RCT architecture.

Long-term safety data

Limited human data beyond 30 days in published reports. Russian clinical practice reportedly uses Selank continuously for months, but no formal long-term safety publication exists.

09Drug Interactions

SSRI co-administration — theoretical serotonergic overlap

• Selank increases serotonin turnover in anxiety-related brain regions (amygdala, hippocampus, frontal cortex) by a mechanism downstream of the serotonin transporter, not by SSRI-like reuptake block
• However, both Selank and SSRIs elevate serotonergic tone → combined use theoretically increases serotonin-syndrome risk
• Per Behavioural Healthcare (PMID 37242459): "Neither combination has been studied in controlled human trials. Patients combining peptides with an SSRI should be doing so with a clinician who understands both" — see thebh.us

Benzodiazepine co-administration — well-supported

• 2015 Russian RCT (n=70) showed better efficacy, fewer side effects when combined with benzodiazepine vs. benzodiazepine alone
• Selank + diazepam combination most effective in UCMS rat model (Kasian 2017, PMC5322660)
• Mechanism of synergy: distinct receptor sites (Selank: GABA-A allosteric modulation, no BDZ-site occupancy; BDZ: BDZ site occupancy) → additive anxiolysis with reduced BDZ dose requirement → reduced BDZ side effects

μ-opioid interaction

• The 2025 Semax μ-opioid receptor / USP18 finding (PMID 40692165) does not extend to Selank; Selank's mechanism is enkephalinase inhibition, not direct receptor signaling
• Selank does not substitute for opioid agonists in pain-modulation contexts and does not carry abuse liability

10Source & Origin

• Developed by: Institute of Molecular Genetics, Russian Academy of Sciences, Moscow
• Base compound: Tuftsin (Thr-Lys-Pro-Arg) — naturally occurring immunomodulatory tetrapeptide produced by enzymatic cleavage of IgG heavy chain in the spleen
• Modification: C-terminal extension with Pro-Gly-Pro (the same glyproline tail as Semax) for aminopeptidase resistance and CNS bioavailability
• Commercial supplier: JSC "Innovative Research-and-Production Center Peptogen" (PeptoGen), Russian Federation
• Related to: Semax — both developed at the same institute; joint connectomic fMRI comparison PMID 32342318; shared Pro-Gly-Pro C-terminal stabilization motif

11Open Questions / Notes

1. Sequence and MW correction: This file's earlier 15-mer / 1.6 kDa description was wrong; Selank is the heptapeptide TKPRPGP at 751.86 Da. This is now corrected in the metadata block. The 1.6 kDa figure appears to have originated from confusion with a different IMG RAS peptide (possibly a Semax progenitor or a thymogen analogue).
2. 2025–2026 Western RCT possibility: No signal of Western RCT activity in PubMed searches (this run: reldate=365, datetype=pdat, Title/Abstract search). The Russian 2008–2015 RCTs remain the only published RCT evidence base.
3. Long-COVID signal: Pogodina 2024 is a single Russian clinical-practice report, no concurrent replication. Post-COVID asthenia is a plausible indication but requires Western RCT confirmation before the Selank-for-LC claim moves from clinical anecdote to evidence.
4. Mechanism rank-weighting: The four-axis mechanism (GABA / serotonin / enkephalinase / BDNF) is established by independent labs but no single publication integrates all four axes in one experiment. The "polypharmacology" framing is a synthesis claim, not a single-study result.
5. N-Acetyl Selank (N-acetyl-threonyl-lysyl-prolyl-arginyl-prolyl-glycyl-proline): Modified analog with improved enzymatic stability; marketed by US research-chemical vendors. Not in clinical use; no peer-reviewed pharmacology beyond vendor literature. Consider distinct entity.
6. Connectomic divergence from Semax: PMID 32342318 shows Selank and Semax produce distinct, partially opposite fMRI resting-state network effects — important for users considering stacked or substituted dosing of the two peptides.
7. Regulatory status in Russia: "Selank 0.15%" nasal drops is included in the State Register of Medicines of the Russian Federation. Approval year 2009 per the SciRP review (Khavinson-era pharmacology literature). No updates to Russian registration since 2024.

Related: Semax | Epitalon | Khavinson Peptides (Russian Bioregulators) | Dihexa | BPC-157 | TB-500 | Overview - Therapeutic Peptides | Overview - Soviet Medical Research

12Where to get it

13Connections

14Sources

1. Kolomin TA et al. (2016). Selank administration affects the expression of some genes involved in GABAergic neurotransmission. Front Pharmacol . PMC4757669 . PMID: 26924987PubMed 26924987 · PMC4757669
2. PubMed 15840402PubMed 15840402
3. PubMed 37242459PubMed 37242459
4. Semenova TP et al. (2009). Comparison of the effects of selank and tuftsin on the metabolism of serotonin in the brain of rats pretreated with PCPA. Eksp Klin Farmakol 72:6-8. PMID: 19803361PubMed 19803361
5. Zozulya AA et al. (2001). The inhibitory effect of Selank on enkephalin-degrading enzymes as a possible mechanism of its anxiolytic activity. Bull Exp Biol Med 131(4):315-7. PMID: 11550013PubMed 11550013
6. Kolik LG et al. (2019). Selank, peptide analogue of tuftsin, protects against ethanol-induced memory impairment by regulating BDNF content in the hippocampus and prefrontal cortex in rats. Bull Exp Biol Med . PMID: 31625062PubMed 31625062
7. Trofimova MI et al. (2022). Selank, a peptide analog of tuftsin, attenuates aversive signs of morphine withdrawal in rats. Bull Exp Biol Med . PMID: 36322304PubMed 36322304
8. PubMed 31243679PubMed 31243679
9. Zozulya AA et al. (2008). 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 . PMID: 18454096PubMed 18454096
10. Zozulya AA et al. (2014). A comparison of the anxiolytic effect and tolerability of selank and phenazepam in the treatment of anxiety disorders. PMID: 25176261PubMed 25176261
11. Kasian A et al. (2017). Peptide Selank enhances the effect of diazepam in reducing anxiety in unpredictably chronic mild stress conditions in rats. Bull Exp Biol Med . PMC5322660PMC5322660
12. DOI 10.29260/10.29260/vrach.2024.633315DOI 10.29260/10.29260/vrach.2024.633315
13. Rahman OF, Lee SJ, Seeds WA. (2026). Therapeutic peptides in orthopaedics: applications, challenges, and future directions. J Am Acad Orthop Surg Glob Res Rev 10(1):e25.00236. PMCID: PMC12753158 . PMID: 41490200PubMed 41490200 · PMC12753158
14. Kozhevnikov & Sotnikov (2020). Functional connectomic approach to studying Selank and Semax effects. Dokl Biol Sci . PMID: 32342318PubMed 32342318
15. PubMed 42021992PubMed 42021992
16. PubMed 41004910PubMed 41004910
17. PubMed 40692165PubMed 40692165

15Entry history

Heretic informs and never prescribes. Where amounts appear, they describe what published studies used. Talk to a qualified clinician before acting on anything here.