T-900607 is a pentafluorophenylsulphonamide derivative patented by Tularik Inc. as antiproliferative agent. Antitumor mechanism of T900607 is similar to the vinca alkaloids in terms of disruption of microtubule polymerization but uniquely causes a specific covalent modification of β-tubulin. In preclinical studies, T900607 was shown to bind irreversibly and specifically to the β1, β2, and β4 isotypes of β-tubulin is not a substrate for p-glycoprotein drug pump and has activity in the preclinical setting in MDR models. T900607 was evaluated in human tumor xenografts and showed activity in MX-1, MCF-7, and MCF-7/ADR mammary, C13 ovarian, HT 29 colon, and Caki-1 renal carcinoma as well as lymphoblastic leukemia, with equal or more efficacious effects compared to vinblastine, doxorubicin and paclitaxel. In a clinical trial, T-900607 shows significant toxicity, consisting of thrombocytopenia, nausea/vomiting, fatigue, and apparent cardiac toxicity.