KU-55933

Biological Activity

KU-55933 is a cell-permeable, potent, selective and ATP-competitive inhibitor of ATM (Ataxia telangiectasia mutated), a serine/threonine protein kinase, that exhibits an IC50 of 13 nmol/L and a Ki of 2.2 nmol/L. KU-55933 shows specificity with respect to inhibition of other phosphatidylinositol 3'-kinase-like kinases. Cellular inhibition of ATM by KU-55933 was demonstrated by the ablation of ionizing radiation-dependent phosphorylation of a range of ATM targets, including p53, gammaH2AX, NBS1, and SMC1. KU-55933 did not show inhibition of UV light DNA damage induced cellular phosphorylation events. Exposure of cells to KU-55933 resulted in a significant sensitization to the cytotoxic effects of ionizing radiation and to the DNA double-strand break-inducing chemotherapeutic agents, etoposide, doxorubicin, and camptothecin. Inhibition of ATM by KU-55933 also caused a loss of ionizing radiation-induced cell cycle arrest. By contrast, KU-55933 did not potentiate the cytotoxic effects of ionizing radiation on ataxia-telangiectasia cells, nor did it affect their cell cycle profile after DNA damage. We conclude that KU-55933 is a novel, specific, and potent inhibitor of the ATM kinase.

Customer Product Validations & Biological Datas

	Source	J Neurooncol (2012). Figure 2. KU-55933
	Method	clonogenic assay
	Cell Lines	U251 and U87 malignant glioma cell lines
	Concentrations	10 microM
	Incubation Time	24 hours or 72 hours
	Results	U87 cells also were sensitized by KU-55933 treatment, although the extent of sensitization was less profound

Protocol

Cell Experiment
Cell lines	LU1205 and WM35 cells
Preparation method	Apoptosis studies. Cells were exposed to soluble TRAIL (50 ng/mL) alone or in combination with cycloheximide (2 μg/mL). Different variants of combined treatment were used, including γ-irradiation (5 Gy), in the presence or absence of specific inhibitors of signaling pathways followed by TRAIL treatment. Apoptosis was then assessed by quantifying the percentage of hypodiploid nuclei using fluorescence-activated cell sorting analysis.
Concentrations	10 μM
Incubation time	48 h

Animal Experiment
Animal models	LU1205 cells Human melanoma transplant in nude mice.
Formulation	DMSO
Dosages	10 μM
Administration

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 Compound A used for a mouse (20 mg/kg) to a dose based on the BSA for a rat, multiply 20 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 Compound A of 10 mg/kg.

Chemical Information

References

[1] Ivanov VN, et al. Cancer Res. Inhibition of ataxia telangiectasia mutated kinase activity enhances TRAIL-mediated apoptosis in human melanoma cells.