Selank was developed at the Institute of Molecular Genetics of the Russian Academy of Sciences alongside Semax. It is based on the tetrapeptide tuftsin (Thr-Lys-Pro-Arg), a fragment of the Fc region of IgG that regulates immune function, with a Pro-Gly-Pro extension. The resulting heptapeptide retains tuftsin's immunomodulatory properties while gaining anxiolytic and nootropic effects.

Selank's anxiolytic mechanism is distinct from benzodiazepines — it acts as a positive allosteric modulator of GABA-A receptors at different binding sites, producing anxiolysis without sedation, tolerance, or withdrawal. It also upregulates BDNF expression, modulates the enkephalin and serotonergic systems, and has demonstrated immunomodulatory effects including NK cell activation and IL-6 regulation.