Semax peptide is a synthetic polypeptide analog of the natural hormone fragment: adrenocorticotropic hormone fragment 4-10 (ACTH 4-10). ACTH fragment 4-10 is a peptide fragment from the adrenocorticotropic hormone secreted by the anterior pituitary gland. This fragment has been reported by researchers not to exhibit any action characteristic of ACTH itself but may have a proposed specific action on the brain.
Several naturally occurring peptides perform various biological functions and govern the main regulatory systems in an organism, including the nervous system. However, naturally occurring peptides may exhibit instability and may be easily degradable by the biological enzymes found in gastrointestinal and cerebrospinal fluids, amongst others. Consequently, researchers aim to synthesize analogs of such naturally occurring peptides, aiming to develop synthetics that demonstrate similar biological action and are highly stable in nature.