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A novel indole antimitotic compound, GTx-230, was identified in cell-based screening assays that binds to the colchicine site in tubulin and destabilizes microtubules. In this study, the pharmacokinetics, antitumor efficacy, neurotoxicity, and vascular disrupting ability of GTx-230 were evaluated. GTx-230 inhibited the in vitro growth of a number of human cancer cell lines including DU-145, LNCaP, PC-3, and PPC-1 prostate cancer cells with low nanomolar IC50 values. Following a 10 mg/kg intravenous (i.v.) dose to mice, the plasma clearance (CL), volume of distribution at steady state (Vdss), and terminal half-life (T1/2) of GTx-230 were 19 ml/min/kg, 2.9 l/kg, and 1.7 h, respectively. Oral bioavailability of GTx-230 was 36% in mice. In vivo, GTx-230 (6.7 mg/kg, qd, p.o.) was effective with near 100% tumor growth inhibition in xenograft models using PC-3/TXR cells over-expressing P-glycoprotein. In contrast, docetaxel, a known antimitotic agent, was not effective in the PC-3/TXR xenograft model. In vivo studies of mouse performance on an accelerating rotarod and hotplate showed that GTx-230 did not induce any symptoms of peripheral neuropathy. In addition, we evaluated the effect of GTx-230 on in vitro vascular permeability using a transwell system with confluent HUVEC monolayers. GTx-230 resulted in increased permeability after 1 h incubation and showed potency similar to CA4. In summary, the potent in vitro and in vivo antitumor activities of GTx-230 suggest that it may represent a new antimitotic agent for management of solid malignancies, particularly for patients with drug resistant cancer. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2788. doi:1538-7445.AM2012-2788