A novel synthetic epothilone with potential antineoplastic activity. Epothilone ZK-219477 binds to microtubules, predominantly in tumor cells, thereby inducing microtubule bundling, formation of multipolar spindles, and mitotic arrest in a manner similar to taxanes. Epothilones are poor substrates for the multidrug resistance 1 (MDR1) P-glycoprotein drug efflux pump and, unlike the taxanes, appear to be able to evade some drug-resistance mechanisms.