Dihexa

Dihexa, also known as PNB-0408 and N-hexanoic-Tyr-Ile-(6) amino-hexanoic amide, is a hexapeptide-derived small molecule developed in the Harding laboratory at Washington State University as a procognitive analog of angiotensin IV. It was foundationally hypothesized to act through agonism of the hepatocyte growth factor (HGF) / c-Met receptor system, a mechanism that promised oral bioavailability, blood-brain barrier penetration at picomolar potency, and rapid synaptogenesis in cortical and hippocampal neurons. Between 2011 and 2014, four peer-reviewed publications established the compound's commercial pipeline and underwrote the formation of Athira Pharma, a publicly traded biotechnology firm that raised over 204 million dollars in a 2020 initial public offering. Each of these four publications was retracted by the Journal of Pharmacology and Experimental Therapeutics in April 2025 following findings of academic misconduct, specifically the splicing and duplication of Western blot bands across distinct experimental conditions. The Department of Justice settled a False Claims Act qui tam action against Athira Pharma in January 2025 for 4.07 million dollars. The clinical lead derived from this program, fosgonimeton (ATH-1017, NDX-1017), failed to meet primary endpoints in the LIFT-AD Phase 2/3 trial in mild-to-moderate Alzheimer disease and the SHAPE Phase 2 trial in dementia with Lewy bodies. This monograph reviews what is now established about Dihexa's chemistry, pharmacokinetics, behavioral effects, and clinical record, separating the verified record from the retracted, and provides sourcing, identity verification, reconstitution, and handling guidance for in vitro and in vivo investigative work.