Also known as: tuftsin analogue · Thr-Lys-Pro-Arg-Gly-Pro-Pro · TP-7 · Cеланк
| Parameter | Value | Source |
|---|---|---|
| Elimination Half-Life (Intranasal) | ~minutes (estimated; proteolytic) | Animal study data; Zozulya AA et al. 2001 |
| Tmax (Intranasal) | ~5–15 min (animal data) | Animal pharmacokinetic studies |
| Route(s) of Administration | Intranasal spray (0.15% solution) | Russian approved formulation |
| CNS Penetration (Intranasal) | Documented via olfactory route in animal models | Animal study data |
| Plasma Protein Binding | No published data | — |
| Full Clearance (5 half-lives) | ~60–90 min estimated | Inferred from heptapeptide proteolytic kinetics |
| Anxiolytic Effect Duration | ~4–6 hours (animal models) | Semenova TP et al. 2010 |
| Standard Dosing | 250–500 µg intranasal daily (Russian clinical practice) | Zozulya AA et al. 2001 |
| Data Quality | Animal Study + limited Russian human trials — No English-language human PK study published (as of May 2026) | |
Selank (synthetic tuftsin analogue; sequence Thr-Lys-Pro-Arg-Gly-Pro-Pro) has a plasma half-life estimated at minutes after intranasal administration, based on animal pharmacokinetic data and the known rapid proteolytic degradation of heptapeptides in nasal mucosal tissue and plasma.[1] No formal human pharmacokinetic study has been published in PubMed-indexed English-language peer-reviewed literature as of May 2026. Available data is from Russian-language clinical literature and animal studies.
Selank was developed at the Institute of Molecular Genetics, Russian Academy of Sciences, as a synthetic analogue of the endogenous immunomodulatory tetrapeptide tuftsin (Thr-Lys-Pro-Arg). The Gly-Pro-Pro tripeptide extension was added to improve metabolic stability by slowing aminopeptidase cleavage — but plasma half-life remains in the minutes range.[1] It was approved in Russia in 2009 as an anxiolytic agent and is not approved by the FDA in the United States.
The ~minutes half-life estimate is inferred from: (1) animal pharmacokinetic studies in rodents showing rapid plasma clearance of heptapeptides after intranasal administration; (2) the known susceptibility of the Thr-Lys-Pro-Arg-Gly-Pro-Pro sequence to nasal mucosal aminopeptidases despite the Gly-Pro-Pro stabilizing extension; and (3) structural analogy with tuftsin and related neuropeptides, which have rapid plasma turnover after systemic administration.[1][2] A formal two-compartment model or terminal half-life derived from human plasma concentration-time data does not exist in published English-language literature.
Selank's ~minutes plasma half-life contrasts with its reported anxiolytic effect duration of 4–6 hours in animal models and in Russian clinical use. This PK/PD dissociation — rapid plasma clearance with prolonged pharmacodynamic effect — is documented in rodent behavioral studies.[2][3] Proposed mechanisms include GABAergic receptor potentiation, serotonergic pathway upregulation (particularly 5-HT1A), and enkephalin-degrading enzyme inhibition — all mechanisms that produce lasting downstream effects independent of ongoing plasma drug levels.
Based on the estimated minutes-range plasma half-life, Selank is expected to reach pharmacologically negligible plasma levels within approximately 60–90 minutes of intranasal dosing (5× estimated t½). This is an inferred estimate, not a measured human value. The Gly-Pro-Pro extension provides some resistance to aminopeptidase cleavage compared to native tuftsin — which has near-zero plasma stability — but the added stability is modest and plasma clearance remains rapid.
| Phase | Approximate Time | Plasma Status | Note |
|---|---|---|---|
| Tmax (peak plasma) | ~5–15 min post-dose | Peak | Animal data; intranasal absorption via olfactory route |
| 50% decline | ~10–20 min | 50% of Cmax | Estimated from heptapeptide proteolytic kinetics |
| Near-complete plasma clearance | ~60–90 min | ~3% of Cmax | Estimated; no published human measurement |
| Anxiolytic effect duration | ~4–6 hours (animal) | Plasma < detection | Effects outlast plasma presence via GABAergic/serotonergic mechanisms |
Selank's primary anxiolytic mechanism is GABAergic potentiation — specifically, modulation of GABA-A receptor function — documented in rodent behavioral assays and electrophysiological studies.[1][3] Selank also modulates serotonergic signaling (particularly 5-HT1A pathways), which contributes to the anxiolytic and mood-stabilizing profile without sedation at standard doses.
Beyond anxiolysis, Selank inhibits enkephalin-degrading enzymes (including enkephalinase), prolonging endogenous opioid peptide activity. This enkephalinase inhibition is hypothesized to contribute to both anxiolytic and nootropic effects. The parent tuftsin sequence (Thr-Lys-Pro-Arg) has immunomodulatory properties at neutrophil Fc receptors — these are preserved in Selank's structure and may contribute to its immune-adjuvant effects documented in animal models.[2]
The Halflife app calculates your real-time plasma curve and dosing window based on half-life estimates — useful for timing repeat intranasal doses relative to the anxiolytic effect window.
Download for iOSGiven the minutes-range plasma half-life and the 4–6 hour anxiolytic effect window in animal models, Russian clinical protocols typically use once or twice daily intranasal dosing at 250–500 µg per dose.[1] This dosing interval is consistent with the behavioral effect duration — the anxiolytic effects substantially outlast plasma presence, so frequent dosing is not required to maintain effect throughout a clinical session. Once-daily morning dosing is commonly used for generalized anxiety applications in Russian clinical practice.
| Route | Typical Dose | Onset | Effect Duration | CNS Penetration |
|---|---|---|---|---|
| Intranasal spray | 250–500 µg | ~15–30 min | ~4–6 hr (animal) | Via olfactory/trigeminal route |
| Subcutaneous injection | 250–500 µg (some protocols) | ~20–40 min | ~4–6 hr (animal) | Systemic; CNS penetration uncertain |
Intranasal is the approved and most-studied route in Russian clinical literature. Subcutaneous use is documented in some protocols but no comparative human PK study between routes has been published in English-language literature.[1]
| Compound | Class | t½ (Intranasal) | Primary Mechanism | Regulatory |
|---|---|---|---|---|
| Selank | Tuftsin analogue (anxiolytic) | ~minutes | GABAergic, serotonergic (5-HT1A), enkephalinase inhibition | Russia-approved 2009; not FDA |
| Semax | ACTH(4-10) analogue (nootropic) | ~minutes | BDNF upregulation, monoaminergic modulation, enkephalinase inhibition | Russia-approved 1996; not FDA |
| DSIP | Delta sleep-inducing peptide | ~minutes | Sleep regulation; serotonergic, opioid modulation | Not approved (research) |
Selank and Semax are the two most studied intranasal nootropic peptides in Russian clinical literature, often positioned as anxiolytic (Selank) vs. cognitive-activating (Semax). Both share the rapid plasma clearance characteristic and the PK/PD dissociation between plasma half-life and behavioral effect duration.[1]
In animal studies and Russian clinical literature, Selank is characterized as having a low side effect burden at standard doses — no sedation, no physical dependence, and no withdrawal syndrome, distinguishing it from classical benzodiazepine anxiolytics that act on the same GABAergic system.[1] These properties are attributed to its partial agonist / modulator mechanism at GABA-A, rather than direct agonism.
However, the clinical safety database is limited to Russian-language literature and small trial sizes. No Phase II or Phase III randomized controlled trial conducted to FDA or EMA evidentiary standards has been published in English-language literature. In the United States, Selank is a research compound with no approved clinical use.
Track intranasal timing, dose, and subjective response data. The app's PK curve visualization shows estimated plasma activity relative to the anxiolytic effect window.
Download for iOSThis page is for informational and research purposes only. Selank is not FDA-approved and is not a licensed medicine in the United States. Nothing on this page constitutes medical advice. Consult a qualified healthcare provider before using any research compound.