Selank: tuftsin, rebuilt to last

Selank is a synthetic heptapeptide built on tuftsin, a natural immune-signalling tetrapeptide (Thr-Lys-Pro-Arg) released by enzymatic cleavage of an immunoglobulin heavy chain. Selank keeps that tuftsin core intact and adds a Pro-Gly-Pro tail at the C-terminus, the same stability strategy used in its better-known sibling Semax. The extension slows enzymatic degradation, letting the tuftsin-like activity persist long enough to be examined in living systems rather than vanishing on contact with tissue. The molecule is a linear chain of seven standard L-amino acids, so it can be represented directly as a residue sequence, and it sits at the intersection of two research traditions: the immune biology of tuftsin and the neuropeptide work that produced Semax. That dual heritage is unusual and is part of why the compound is studied across both neuroscience and immunology rather than in a single silo.

Like Semax, Selank was developed in Russia, at the Institute of Molecular Genetics of the Russian Academy of Sciences in collaboration with the Zakusov Institute of Pharmacology. It was designed as a stabilised analogue of tuftsin with a broader behavioural profile, and it has been studied for decades in the Russian literature as an anxiolytic and immunomodulatory research peptide. As with Semax, most of that work sits in domestic journals and has seen only limited replication abroad. The two peptides are often discussed together because they share both a national research lineage and the same Pro-Gly-Pro stabilising motif, but they descend from different parent molecules and their reported activity profiles are not interchangeable. Reading across the literature, it is easy to conflate them; the chemistry says otherwise.

The reported mechanisms are several and overlapping, which is characteristic of this class. Selank is studied for interaction with GABAergic signalling, the classic axis for anxiety-related behaviour in rodents, and for effects on monoamine systems including serotonin. It has also been reported to modulate the expression of BDNF and to inhibit enkephalin-degrading enzymes, an action it shares with Semax that would extend the presence of the nervous system's own opioid and regulatory peptides. Separately, its tuftsin heritage surfaces in immunomodulatory studies, where the peptide is examined for effects on cytokine balance and immune-cell activity. As with its sibling, the absence of a single well-defined receptor means the mechanistic account is a composite drawn from many partial observations rather than one clean pathway.

Behavioural pharmacology dominates the animal literature. Elevated-plus-maze and related paradigms are used as readouts for anxiety-like behaviour, alongside tests of learning and adaptive response under stress. Transcriptomic studies have profiled gene-expression shifts in the hippocampus and spleen, a pairing that reflects the dual neuro and immune framing of the molecule and distinguishes it from purely central-nervous-system peptides. A smaller set of exploratory human studies, mostly from the originating groups, examined generalised-anxiety and adaptive-response endpoints; these are early, limited in scale, and have not been reproduced by independent teams. The overall shape of the evidence is a broad but shallow map: many endpoints touched, few of them deeply and independently confirmed. That pattern should temper how much weight any single result can carry.

Chemically, Selank is a linear chain of seven standard L-amino acids and can be written directly as its residue sequence, with the verified molecular formula and mass listed below. A doubly capped variant, N-acetyl Selank amidate, acetylates the N-terminus and amidates the C-terminus to blunt exopeptidase activity even more aggressively, and it is sometimes studied as a longer-lived alternative to the parent. The unmodified heptapeptide, however, is the reference form in most reports and the one most analytical benchmarks describe. Because every residue is a standard amino acid, the molecule can be confirmed against well-defined identity criteria, which matters whenever a research supply needs to verify that the material actually matches the label on the vial.

The same cautions that apply to Semax apply here, more or less unchanged. The evidence is overwhelmingly preclinical and geographically concentrated, the human work is preliminary and small, and the mechanistic account spans several systems without a single receptor to anchor it. Effect sizes in behavioural models are frequently modest, and publication is skewed toward the groups that developed the compound in the first place. None of that rules out genuine biological activity, and the tuftsin lineage gives the molecule a coherent rationale that is more than hand-waving. It simply means the peptide belongs in the research-tool category, where claims stay provisional and independent confirmation is still owed, rather than in any settled or established role.

For laboratory research use only. Not for human or veterinary use.

Verified molecule

• Sequence: TKPRPGP (tuftsin core Thr-Lys-Pro-Arg, extended with Pro-Gly-Pro)
• Molecular formula: C33H57N11O9
• Molecular weight: 751.9 g/mol
• CAS number: 129954-34-3

Common questions

How is Selank related to tuftsin?

Tuftsin is a natural four-residue immune peptide produced when an antibody heavy chain is cleaved. Selank keeps that exact sequence and adds a Pro-Gly-Pro tail, which makes the molecule far more resistant to enzymatic breakdown while retaining the tuftsin-like character that research examines. In effect Selank is tuftsin re-engineered to survive long enough to study.

Is Selank the same as Semax?

No, but they are close cousins. Both are Russian-developed heptapeptides that use the same Pro-Gly-Pro stability cap, and both are reported to inhibit enkephalin-degrading enzymes. Their cores differ, though: Semax comes from ACTH and is framed as a neurotrophic peptide, while Selank comes from tuftsin and carries a stronger immune-signalling emphasis. Their research profiles diverge accordingly.

What does the research actually show?

Mostly rodent behavioural and gene-expression findings centred on anxiety-like behaviour and immune signalling, with a little early human work from the originating labs. Independent replication is limited, so the compound is handled as a research reference material and its reported effects are best read as preliminary rather than established.

References

1. Kost NV, et al. Semax and selank inhibit the enkephalin-degrading enzymes from human serum. Russian Journal of Bioorganic Chemistry, 2001.
2. Kolomin T, Shadrina M, Slominsky P, Limborska S, Myasoedov N. A new generation of drugs: synthetic peptides based on natural regulatory peptides. Neuroscience and Medicine, 2013.