Dihexa (N-hexanoic-Tyr-Ile-(6) aminohexanoic amide, also designated PNB-0408) is a small peptidomimetic developed at Washington State University from the angiotensin IV analogue norleucine(1)-angiotensin IV. It was designed by modifying the N-terminal tripeptide Nle-Tyr-Ile to improve metabolic stability and barrier permeability. The compound has been studied in rodent models of cognitive impairment and neurodegeneration, in a zebrafish hair cell model and in a rat peripheral nerve repair model. Researchers should note the status of the originating literature: the 2013 paper describing dihexa carries an expression of concern published in 2021, and two related papers from the same group, including the 2014 study that tied its activity to the hepatocyte growth factor (HGF)/c-Met system, were retracted in 2025.