Ixabepilone (BMS247550) is a semisynthetic derivative of the natural product that optimizes the properties observed with epothilone B. This compound has some similarities with taxanes in targeting and stabilizing microtubules, but it also has major differences. Interestingly, ixabepilone was evaluated in patients with well-characterized resistance to taxanes and was able to overcome the overexpression of multidrug resistance and was unaffected by mutations in the beta-tubulin genes. The interest in ixabepilone was clinically confirmed in Phase II and III clinical studies, which have demonstrated a strong activity in patients with metastatic breast cancer resistant to taxanes and in patients suffering from other types of chemoresistant tumors.