Dihexa, also known as PNB-0408, N-hexanoic-Tyr-Ile-(6) aminohexanoic amide, is an oligopeptide drug derived from angiotensin IV that binds with high affinity to hepatocyte growth factor (HGF) and potentiates its activity at its receptor, c-Met. Dihexa has been found to potently improve cognitive function in animal models of Alzheimer's disease-like mental impairment. In an assay of neurotrophic activity, Dihexa was found to be seven orders of magnitude more potent than brain-derived neurotrophic factor.