4-oxo Docosahexaenoic acid (4-oxo DHA) is a bioactive DHA metabolite that acts as a covalent PPARγ agonist, activating transcription with an EC50 of ~8-16 μM. It exhibits antiproliferative activity against multiple triple-negative breast cancer cell lines in vitro at 50-100 μM, while paradoxically stimulating MCF-7 cell growth, making it a compound of interest for cancer and metabolic research.