The epothilones are a new class of cytotoxic molecules identified as potential chemotherapeutic drugs. As of September 2008[update], epothilones A to F have been identified and characterised. Early studies in cancer cell lines and in human cancer patients indicate superior efficacy to the taxanes. Their mechanism of action is similar, but their chemical structure is simpler. Due to their better water solubility, cremophors (solubilizing agents used for paclitaxel which can affect cardiac function and cause severe hypersensitivity) are not needed. Endotoxin-like properties known from paclitaxel, like activation of macrophages synthesizing inflammatory cytokines and nitric oxide, are not observed for epothilone B.
Epothilones A (R = H) and B (R = CH3)
Epothilones C (R = H) and D (R = CH3)
Epothilones were originally identified as metabolites produced by the myxobacterium Sorangium cellulosum.
The structure of epothilone A was determined in 1996 using x-ray crystallography.