Epothilones are polyketide natural products that inhibit cancer cells by a mechanism similar to paclitaxel, and also are effective against paclitaxel-resistant tumours. Epothilone B is what is known as a microtubule stabilizer. When a cell divides, the chromosomes that will end up in each cell are separated by thin filaments called microtubules. Normally these microtubules then break down as the cell division progresses. This class of cytotoxic chemo drugs prevents that break down and thus prevents cells from completing division.