Selank: a Russian anti-anxiety peptide built from an immune fragment

Anxiety relief from an immune peptide

Benzodiazepines, the best-known anti-anxiety drugs, came out of synthetic chemistry. Selank came from a different direction entirely: the immune system. Its starting point was tuftsin, a four-amino-acid fragment of an antibody that stimulates immune cells to engulf microbes ^[2,3]. Russian researchers lengthened it, tested it in stressed animals and ended up with a licensed medicine for anxiety ^[2,11].

Its developers report that it calms like a low-dose tranquilliser without benzodiazepine side effects such as amnesia, withdrawal and dependence ^[2]. Outside Russia, the picture is much less settled. A 2021 review from the University of Connecticut described Selank, together with phenibut, as a "poorly studied" Russian drug with a GABA-related mechanism ^[4]. This article sets out what each line of evidence actually shows.

From tuftsin to Selank

In 1970, Victor Najjar and Kenji Nishioka described tuftsin, a natural peptide that stimulates phagocytosis, the process by which immune cells swallow and destroy bacteria ^[3]. Tuftsin is the short sequence Thr-Lys-Pro-Arg, cut from the heavy chain of human immunoglobulin G ^[2].

To make tuftsin more durable, researchers at the Institute of Molecular Genetics of the Russian Academy of Sciences, working with the V.V. Zakusov Research Institute of Pharmacology, extended it at the end with three more amino acids, Pro-Gly-Pro, to improve its metabolic stability ^[2]. The result, Thr-Lys-Pro-Arg-Pro-Gly-Pro, is Selank ^[1,2]. The same Pro-Gly-Pro tail appears in the institute's other licensed peptide, Semax.

At the Zakusov Institute, scientists compared Selank with ten tuftsin-family peptides in rats and mice exposed to a conflict situation and reported anti-stress and positive emotional effects ^[5]. Selank was registered in Russia as a medicine in 2009 (registration number LSR-003338/09), and re-registered in 2025 ^[11].

Selank's ancestor, tuftsin, is a fragment of an antibody molecule that stimulates immune cells to engulf bacteria ^[2,3].

How Selank is thought to work

No single mechanism has been established. Three main ideas run through the literature.

Enkephalins. Enkephalins are the body's own calming, pain-dampening peptides, and enzymes break them down quickly. In a 2001 test-tube study, Selank inhibited the breakdown of enkephalin in human plasma, with half-maximal inhibition at 15 micromolar, and the authors proposed this as a possible anti-anxiety mechanism ^[6]. In a later clinical study, patients with generalised anxiety and neurasthenia had a shortened half-life of leu-enkephalin in their blood, which rose during Selank treatment ^[7]. An analogy: rather than adding more calming signal, Selank may stop the cleaning crew from sweeping it away so fast.

GABA. GABA is the brain's main inhibitory messenger and the target of benzodiazepines. In the frontal cortex of rats, 45 of 84 nerve-signalling genes changed expression one hour after Selank or GABA was given, and 22 after three hours, with the changes after Selank correlating with those after GABA ^[2]. The authors suggested Selank might act as an allosteric modulator of the GABA system, but this was a gene-expression study, not a direct receptor-binding measurement ^[2].

Immune signals. True to its tuftsin roots, Selank altered immune messengers. In a small Russian study, it suppressed interleukin-6 gene expression in blood cells from patients with depression in the lab, and shifted the balance between Th1 and Th2 immune messengers in patients with anxiety disorders treated for 14 days ^[9].

What the research shows

Animal studies

Beyond the early stress experiments ^[5], a 2017 rat study examined Selank with the benzodiazepine diazepam under unpredictable chronic mild stress ^[10]. Selank alone was the most effective at reducing anxiety induced by a course of injections, while the combination of Selank and diazepam worked best under chronic stress, according to the authors ^[10]. Like most Selank research, these studies came from the institute that developed it ^[2,10].

Clinical studies in anxiety

These studies are informative but limited. They are small, published in Russian, and their abstracts do not describe placebo control or blinding ^[7,8]. Neither abstract reports a placebo group, so neither study can show how much of the improvement is due to the drug itself.

What we don't know yet

• Efficacy against placebo. We found no large, placebo-controlled, double-blind trials of Selank in international journals, and ClinicalTrials.gov lists no registered Selank trials ^[14].
• Independent replication. Most studies come from the developing institutes and their collaborators ^[2,5,10]. A US review describes the drug as poorly studied ^[4].
• Mechanism. The enkephalin, GABA and immune findings come from test tubes, rat gene-expression studies and small patient samples ^[2,6,9]; none has been confirmed as the main mechanism in people.
• Safety and dependence. Claims that Selank avoids benzodiazepine-type dependence come from Russian clinical work cited by its developers ^[2]; independent long-term safety data are lacking. The FDA has said it lacks important information about Selank's safety in humans ^[12].

Our guide to levels of evidence explains why a small comparison against another drug is weaker evidence than a placebo-controlled trial.

Regulatory status

• Russia: registered as an anxiolytic in 2009 and re-registered in 2025, as 0.15% nasal drops ^[11]. The current label lists anxiety states, panic attacks, neurasthenia, asthenia, sleep problems, adjustment disorders and the prevention and treatment of stress disorders in adults aged 18 and over, and it is sold without a prescription ^[11,13].
• United States: not FDA-approved. Selank acetate was placed in the FDA's "Category 2" of bulk substances that may pose significant safety risks in compounding, and was later removed after its nomination was withdrawn ^[12,15].
• European Union: no marketing authorisation that we found.

In the lab: handling and storage

Selank (product page) is typically supplied as a lyophilised powder. Long-term storage is at −20 °C, with 2–8 °C acceptable for short periods, protected from light and moisture. Its developers note that tuftsin-based peptides are vulnerable to enzymatic breakdown, which is why the stabilising tail was added ^[2]; even so, solutions are less stable than the dry powder. The licensed Russian nasal drops, for example, are labelled for storage at 2–8 °C, and for no more than 15 days at up to 25 °C once opened ^[13]. Our guide to storing research peptides covers reconstituted solutions in more detail.

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