Tetrapeptides

Carfilzomib, sold under the brand name Kyprolis, is an anti-cancer medication acting as a selective proteasome inhibitor. Chemically, it is a tetrapeptide epoxyketone and an analog of epoxomicin. It was developed by Onyx Pharmaceuticals.

Tuftsin is a tetrapeptide (Thr-Lys-Pro-Arg, TKPR) located in the Fc-domain of the heavy chain of immunoglobulin G (residues 289-292). It has an immunostimulatory effect. It is named for Tufts University where it was first discovered in 1983.

thumb|300px|A tetrapeptide (example Valine|Val-Gly-Ser-Ala) with green marked amino end (L-Valine) and blue marked carboxyl end (L-Alanine). A tetrapeptide is a peptide, classified as an oligopeptide, since it only consists of four amino acids joined by peptide bonds. Many tetrapeptides are pharmacologically active, often showing affinity and specificity for a variety of receptors in protein-protein signaling. Present in nature are both linear and cyclic tetrapeptides (CTPs), the latter of which mimics protein reverse turns which are often present on the surface of proteins and druggable targe

Tentoxin is a natural cyclic tetrapeptide produced by phytopathogenic fungus Alternaria alternata. It selectively induces chlorosis in several germinating seedling plants. Therefore, tentoxin may be used as a potential natural herbicide, and is a lactam.

Morphiceptin is a tetrapeptide (Tyr-Pro-Phe-Pro-NH2) that is a selective μ-opioid receptor agonist. It is derived from β-casomorphin and has over 1,000 times selectivity for μ- over δ-opioid receptors. When injected intracerebroventricularly (into the ventricular system of the brain), morphiceptin had an analgesic ED50 of 1.7 nmol per animal. The analgesic effects of morphiceptin were reversed by naloxone, meaning that the analgesic effect is mediated by the μ-opioid receptor.

Rapastinel () (former developmental code name GLYX-13) is a novel antidepressant that was under development by Allergan (previously Naurex) as an adjunctive therapy for the treatment of treatment-resistant depression. It is a centrally active, intravenously administered (non-orally active) amidated tetrapeptide that acts as a novel and selective modulator of the NMDA receptor. The drug is a rapid-acting and long-lasting antidepressant as well as robust cognitive enhancer by virtue of its ability to enhance NMDA receptor-mediated signal transduction and synaptic plasticity.

Cholecystokinin tetrapeptide (CCK-4, tetragastrin, Trp-Met-Asp-Phe-NH2) is a peptide fragment derived from the larger peptide hormone cholecystokinin. Unlike cholecystokin which has a variety of roles in the gastrointestinal system as well as central nervous system effects, CCK-4 acts primarily in the brain as an anxiogenic, although it does retain some GI effects, but not as much as CCK-8 or the full length polypeptide CCK-58.

Hemorphin-4 is an endogenous opioid peptide of the hemorphin family which possesses antinociceptive properties and is derived from the β-chain of hemoglobin in the bloodstream. It contains a tetrapeptide core with the amino acid sequence Tyr-Pro-Trp-Thr. Hemorphin-4 serves as a opioid receptor ligand that has affinities for the μ-, δ-, and κ-opioid receptors in the same range as the structurally related β-casomorphins, although affinity to the κ-opioid receptor is markedly higher in comparison. It acts as an agonist at these sites. It presents high affinity for other receptors such as angioten