What Selank is
Selank is a seven-amino-acid synthetic peptide with the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro (abbreviated TKPRPGP, molecular weight 751.9 Da). It was created by extending tuftsin, a naturally occurring tetrapeptide fragment of human immunoglobulin G, with a Pro-Gly-Pro tripeptide at the C-terminus. That addition substantially increased metabolic stability compared to the parent compound, which is rapidly cleaved in plasma.
Development was carried out at the Institute of Molecular Genetics of the Russian Academy of Sciences, in collaboration with the V.V. Zakusov Research Institute of Pharmacology in Moscow. Selank received pharmaceutical registration in Russia, where it is prescribed as an anxiolytic nasal spray. Outside Russia, it has no approved medical use and is studied only in preclinical research settings.
Mechanism of action
Three distinct but overlapping pathways have been described in the literature to account for Selank's pharmacological profile.
Enkephalinase inhibition
Enkephalins are endogenous neuropeptides that bind opioid receptors and contribute to the brain's anxiety-buffering systems. Their activity is terminated by enkephalin-degrading enzymes in plasma and the central nervous system.
Zozulya et al. (2001, Bulletin of Experimental Biology and Medicine, PMID 11550013) showed that Selank dose-dependently inhibits the enzymatic hydrolysis of plasma enkephalin, with an IC50 of 15 micromolar. In the same study, patients with generalized anxiety disorder had shorter enkephalin half-lives and lower total enkephalinase activity in blood than controls. The authors proposed that a deficiency of endogenous enkephalinase inhibitors in GAD patients accelerates enkephalin breakdown, reducing opioidergic tone. In the in vitro assays, Selank outperformed both bacitracin and puromycin as enkephalinase inhibitors.
GABAergic neurotransmission
Volkova, Shadrina, Kolomin et al. (2016, Frontiers in Pharmacology, PMC4757669) examined gene expression in rat brain following Selank administration. The results showed changes in the expression of several genes involved in GABAergic neurotransmission, consistent with allosteric modulation at the GABA-A receptor complex. This is the same general mechanism through which benzodiazepines work, which explains why animal studies show behavioral overlap between Selank and diazepam: both suppress anxiety-like behavior, but Selank does this without the sedation typically associated with benzodiazepines at equipotent anxiolytic doses.
A follow-up paper from the same group (PMC5322660, 2017) reported additive anxiolytic effects when sub-threshold Selank doses were combined with sub-threshold diazepam in a rat model of unpredictable chronic mild stress. Neither compound at the lower dose reduced anxiety-like behavior on its own; together they did, consistent with activity at different modulatory sites on the GABA-A receptor complex.
BDNF modulation
A third line of research documents Selank's effects on brain-derived neurotrophic factor (BDNF), a protein important for neuron survival, synaptic plasticity, and memory consolidation. Kolik et al. (2019, Bulletin of Experimental Biology and Medicine, PMID 31625062) exposed rats to 10% ethanol for 30 weeks, producing spatial memory impairment and elevated BDNF in the hippocampus and prefrontal cortex. Selank prevented both effects: animals that received it showed no memory impairment, and BDNF levels in both brain regions returned to near-normal. The investigators attributed the mnemonic protection to Selank's ability to counteract neurotrophin dysregulation produced by chronic ethanol exposure.
Anxiolytic evidence from Selank research
The broadest body of evidence for Selank comes from rodent behavioral models. Across open-field tests, elevated plus maze assays, and forced-swim tests, Selank consistently reduces anxiety-like behavior compared to vehicle controls, and several studies compare it directly to diazepam.
Konstantinopolsky, Chernyakova, and Kolik (2022, Bulletin of Experimental Biology and Medicine, PMID 36322304) administered Selank at 0.3 mg/kg intraperitoneally to outbred rats in a naloxone-precipitated morphine withdrawal model. A single injection reduced the total withdrawal index by 39.6% and attenuated convulsive reactions, ptosis, and postural disorders. The tactile sensitivity threshold increased 9-fold versus controls. Diazepam at 2 mg/kg produced a somewhat larger total reduction, but Selank's effect was pharmacologically significant at a substantially lower milligram dose.
Across these studies, the compound does not appear to produce tolerance or physical dependence signs in the models used, which is consistent with the lack of physical dependence liability that characterizes benzodiazepines after chronic use. That said, long-term dependence studies in rodents for Selank specifically are limited, and no human data exists on this point.
Neuroprotection and cognitive effects
Beyond anxiety, several studies examined whether Selank preserves cognitive function under neurological stress. The ethanol model from Kolik et al. (2019) is the most directly relevant: 30 weeks of chronic ethanol produced spatial memory deficits that Selank prevented entirely, alongside BDNF normalization in hippocampus and prefrontal cortex.
Separate work published in Russian-language literature on antenatal hypoxia models has also been indexed on PubMed (PMID 17385425). English summaries report that Selank corrected biogenic amine imbalances and improved integrative brain activity scores in hypoxia-exposed rat pups. These models are not directly analogous to adult human anxiety conditions, but they suggest Selank affects broad neurochemical homeostasis rather than a single pathway.
For compounds with related mechanisms in the Russian neuropeptide research tradition, the Semax compound page and the detailed Semax research overview cover a structurally distinct but pharmacologically adjacent peptide developed by many of the same research groups.
Handling and storage in research settings
Selank is supplied as a lyophilized powder in sealed glass vials. The recommended storage condition for the intact vial is -20 degrees C, where the compound is stable for at least 24 months. Once reconstituted in bacteriostatic water, the solution should remain at 2-8 degrees C and be used within 28 days.
Researchers in Indonesia face a consistent practical constraint: ambient temperatures of 28-33 degrees C year-round mean that any break in cold chain during shipping or handling accelerates peptide degradation. For Selank, as for most reconstituted peptides, keeping the solution below 8 degrees C after the vial is opened is not optional. The lyophilized powder tolerates brief exposure to room temperature during transfer without significant loss, but repeated temperature cycling between freezer and warm ambient conditions should be avoided.
Before reconstituting, determine the exact volume of bacteriostatic water needed for the target concentration using the peptide dosing calculator, so the vial can be reconstituted and returned to cold storage in a single step rather than reopened multiple times.
Limitations of the current evidence base
The Selank literature has two constraints researchers should understand before designing studies around it.
First, almost all published work is animal-based. The human data consists primarily of observational clinical material from Russian pharmaceutical registration, which predates current standards for blinded, placebo-controlled trial design and is largely unavailable in English peer-reviewed journals. No published randomized controlled trial has evaluated Selank against validated human anxiety scales such as the Hamilton Anxiety Rating Scale or the GAD-7.
Second, most of the peer-reviewed English-language output comes from a small cluster of Russian institutions: the Institute of Molecular Genetics and the V.V. Zakusov Institute. Independent replication by external research groups, which is the standard confirmation step in pharmacological research, is sparse. The mechanistic proposals are plausible and internally consistent across studies, but they have not been widely tested outside the originating laboratories.
For a direct comparison of Selank's evidence profile against Semax, which shares the Russian neuropeptide origin and similar evidence constraints, see the Semax vs Selank comparison article.