OTS964

TOPK (TClymphokine-activated killer cellCoriginated protein kinase) is highly and frequently transactivated in various cancer tissues, including lung and triple-negative breast cancers, and plays an indispensable role in the mitosis of cancer cells. OTS964 is a potent TOPK inhibitor, which inhibits TOPK kinase activity with high affinity and selectivity. Similar to the knockdown effect of TOPK small interfering RNAs (siRNAs), this inhibitor causes a cytokinesis defect and the subsequent apoptosis of cancer cells in vitro as well as in xenograft models of human lung cancer. Although administration of the free compound induced hematopoietic adverse reactions (leukocytopenia associated with thrombocytosis), the drug delivered in a liposomal formulation effectively caused complete regression of transplanted tumors without showing any adverse reactions in mice. The esults suggest that the inhibition of TOPK activity may be a viable therapeutic option for the treatment of various human cancers.