Cell experiment:

K562 and KCL22 cells are seeded in six-well plates at a number of 5 × 105 in 2 mL RPMI-1640 medium supplemented with 10% FBS in a 5% CO2 atmosphere at 37℃, and are treated with control (2% DMSO), 50 nM imatinib, 2 nM SB-743921 and 50 nM imatinib + 2 nM SB-743921, respectively. Cell number and viability are determined every 24 h. Results are plotted for live cells against time to generate a growth curve[2].

Animal experiment:

The animal experiments are performed with female NMRI nu/nu mice. Tumor fragments are obtained from xenografts in serial passage in nude mice. Mice are randomized to the various groups, and dosing is started when the required number of mice carries a tumor of 50-250 mm3 volume, preferably 80-200 mm3. Vehicle for 1: 10% ethanol, 10% cremophor, 80% D5W (dextrose 5%); vehicle for all other compounds (including SB-743921): 8% DMSO, 2% Tween 80, distilled water (pH 5). All treatments are given intraperitoneally. Vehicle control mice (group 1) are treated with 10 mL/kg vehicle on days 0, 3, 6, 8, 10, 13, 20, 22, 24, 29, 31, 34, 36, 38, 48, 51, 55, 58, 62, 65, and 69[3].

SB743921 is an inhibitor of kinesin spindle protein (KSP) with Ki value of 0.1nM [1].

As an inhibitor of mitotic kinesin KSP, SB743921 causes cell cycle arrest in mitosis, results in cell death. SB743921 is developed to treat for cancers. SB743921 is a potent and selective inhibitor. In the affinity assays, SB743921 shows Ki values of 0.1nM and 0.12nM for human KSP and mouse KSP, respectively. It has no affinity with other kinesins. In the cellular assay, SB743921 exerts anti-proliferation efficacy in SKOV3, Colo205, MV522 and MX1 with IC50 values of 0.02nM, 0.07nM, 1.7nM and 0.06nM. Moreover, SB743921 is shown to have activity against human tumor xenografts Colo205, MCF-7, SK-MES, H69, OVCAR-3, HT-29, MDA-MB-231 and A2780. SB743921 is also effective against P388 lymphocytic leukemia xenografts in mice [1].

References:
[1] Jackson J R, Gilmartin A, Dhanak D, et al. A second generation KSP inhibitor, SB-743921, is a highly potent and active therapeutic in preclinical models of cancer. Proceedings of the American Association for Cancer Research, 2006, 2006(2): B11.