Ispinesib

Biological Activity

Ispinesib (SB-715992), a potent and selective small molecule inhibitor of KSP, functions by inhibiting KSP ATPase and is 40000 times more selective for KSP compared to other kinesins. In preclinical studies, ispinesib inhibited growth in a wide range of human and murine cell lines with IC50 values of 1.2-9.5nm. Treatment of SKOV3 ovarian tumour cells in vitro with 20nm of ispinesib, or a Colo 205 colon cancer murine xenograft model with 30mgkg^-1 of intraperitoneal ispinesib, caused mitotic arrest with cells demonstrating unseparated centrosomes and monopolar mitotic spindles. Tumour growth delay was observed in xenograft models of colon (HT29, Colo201, Colo205), non-small cell lung (Calu-3) and pancreatic (Panc-01) cancers.

Protocol

Cell Experiment
Cell lines	BT-474 and MDA-MB-468 cells line
Preparation method	Cell lines were obtained from the American Type Culture Collection and from collections developed by Drs. Steve Ethier and Adi Gazdar. KPL4 was kindly provided by Dr J. Kurebayashi (Kawasaki Medical School, Kurashiki, Okayama, Japan). Cell culture reagents were from Cellgro-Mediatech. Cells were plated in log phase of growth in 96-well plates and treated for 72 h with ispinesib at concentrations of 3.3 × 10−5 to 8.5 × 10−11 mol/L. Cell growth was measured using CellTiter-Glo (Promega), and luminescence was recorded using BioTek FLx800. Data were analyzed according to the method described previously by the National Cancer Institute/NIH Developmental Therapeutics Program Human Tumor Cell Line Screen Process. The GI50 value is the drug concentration that results in 50% growth inhibition after 72 h of drug exposure relative to control.
Concentrations	0~1000 n M
Incubation time	72 h

Animal Experiment
Animal models	MCF-7, BT-474 and MDA-MB-468 xenograft model in nude mice or SCID mice
Formulation	formulated in 10% ethanol, 10% cremophor, and 80% D5W (dextrose 5%)
Dosages	q4d×3 schedule at 10 mg/kg in nu/nu mice or 8 mg/kg in SCID mice
Administration	i.p.

Conversion of different model animals based on BSA (Value based on data from FDA Draft Guidelines)

Species	Mouse	Rat	Rabbit	Guinea pig	Hamster	Dog
Weight (kg)	0.02	0.15	1.8	0.4	0.08	10
Body Surface Area (m2)	0.007	0.025	0.15	0.05	0.02	0.5
Km factor	3	6	12	8	5	20

Animal A (mg/kg) = Animal B (mg/kg) multiplied by	Animal B Km
	Animal A Km

For example, to modify the dose of resveratrol used for a mouse (22.4 mg/kg) to a dose based on the BSA for a rat, multiply 22.4 mg/kg by the K_m factor for a mouse and then divide by the K_m factor for a rat. This calculation results in a rat equivalent dose for resveratrol of 11.2 mg/kg.

Chemical Information

References

Activity of the kinesin spindle protein inhibitor ispinesib (SB-715992) in models of breast cancer.
Purcell et al. Clin Cancer Res. 2010 Jan 15;16(2):566-76. PMID: 20068098.

Thermodynamics of nucleotide and inhibitor binding to wild-type and ispinesib-resistant forms of human kinesin spindle protein.
Sheth et al. Biochemistry. 2009 Nov 24;48(46):11045-55. PMID: 19824700.