Ortataxel (previously known as IDN 5109 or BAY59-8862), a second-generation taxane derivative that was developed as an antitumor agent. Ortataxel binds to and stabilizes tubulin molecules, thereby interfering with the dynamics of microtubule assembly/disassembly. This results in the inhibition of cell division and cellular proliferation. In addition, ortataxel modulates multi-drug resistance mechanisms and may be useful for treating multi-drug resistant tumors that express Pgp, MRP-1, and BCRP. This drug participated in phase II clinical trials in patients with advanced renal cell carcinoma and in patients with Non-Hodgkin's lymphoma. However, these studies were discontinued. Ortataxel was also involved in phase II clinical trials for patients with glioblastoma; however, in a limited number of patients, the drug produced a benefit that lasted for a long time. Besides, ortataxel successfully completed phase II trials in taxane-resistant metastatic breast cancer patients and in taxane-resistant non-small cell lung cancer patients.