Ispinesib is a potent, specific and reversible inhibitor of KSP (HsEg5) with Ki of 1.7 nM.
in vitro: Ispinesib is a potent, allosteric, reversible, and specific inhibitor of KSP, which changes the binding property of KSP to microtubules and disturbs its movement by inhibiting ADP release without altering the release of the KSP-ADP complex from the microtubule. Ispinesib shows potent cytotoxic activity in a panel of tumor cell lines, including Colo205, Colo201, HT-29, M5076, Madison-109, and MX-1, with IC50 of 1.2 nM to 9.5 nM. In PC-3 prostate cancer cells, Ispinesib (15 nM and 30 nM) blocks cell proliferation and induces apoptosis by regulating the expression levels of genes that controls apoptosis, cell proliferation, cell cycle, and cell signaling, such as EGFR, p27, p15, and IL-11. In a panel of 53 breast cell lines, Ispinesib (7.4 nM–600 nM) demonstrates broad inhibitory activity. In BT-474 and MDA-MB-468 cells, Ispinesib (150 nM) induces apoptosis, as revealed by a higher proportion of apoptotic cells, lower antiapoptotic Bcl-XL level, and higher proapoptotic Bax and Bid levels.
in vivo: Ispinesib (4.5 mg/kg–15 mg/kg) exhibits inhibitory effects against Colo205, Colo201, HT-29, but not MX-1 cells, in mouse xenograft models. SB-715992 (6 mg/kg–10 mg/kg ) also inhibits murine solid tumors, including Madison 109 lung carcinoma, M5076 sarcoma, as well as L1210 and P388 leukemias. In mice xenograft models of breast cancer cells MCF-7, HCC1954, MDA-MB-468, and KPL4, Ispinesib (8 mg/kg–10 mg/kg) inhibits tumor growth.
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