Filanesib (ARRY 520) is a selective inhibitor of kinesin spindle protein (KSP, IC50 = 6 nM) with potent anti-proliferative activity.

KSP:6 nM

Exponentially growing cells (0.4×10^6/mL) are treated with ARRY-520 for up to 48 hours. For combination, HL-60 and HL-60Bcl-2 cells (0.4×10^6/mL) are incubated with ARRY-520, ABT-737, or both for up to 96 hours. DMSO is used as the control agent. Apoptosis is estimated by flow cytometry measurements of phosphatidylserine with the Annexin-V-FLUOS Staining Kit. Membrane integrity is simultaneously assessed by 7-amino-actinomycin D (7-AAD). To measure changes in the mitochondrial membrane potential (MMP), cells are loaded with CMXRos (300 nM) and MitoTracker Green (500 nM) for 1 hour at 37°C. The loss of MMP is then assessed by measuring CMXRos retention while simultaneously adjusting for mitochondrial mass [4].

Subcutaneous tumor xenografts are allowed to grow to a volume of 250-350 mm3. The mice are randomized into groups of 3-4 based on tumor size and are given a single dose of ARRY-520 i.p. At various time-points after administration of the drug, the mice are euthanized by CO2 inhalation and the tumors excised and placed in 10% neutral buffered formalin. The formalin-fixed tumors are processed and paraffin-embedded by standard procedures. Spindle morphology is analyzed by staining tumor sections for α-tubulin, and apoptosis is analyzed by TUNEL stain. Monopolar/abnormal spindles and TUNEL positive (apoptotic) cells are counted in three ×40 fields from each sample, analyzed using algorithms developed in software [1].

ARRY-520, ARRY 520

DMSO: 90 mg/mL (214.04 mM), Sonication is recommended.

10% DMSO+40% PEG300+5% Tween 80+45% Saline: 3.3 mg/mL (7.85 mM), Sonication is recommended.