RGB-286638 is a multi-targeted protein kinase inhibitor currently in Phase 1 clinical testing. In vitro cell-free kinase assays indicated that RGB-286638 inhibits CDK1, 2, 3, 4, 5, and 9 and is less active against CDK6 and 7. The RGB-286638 compound has been shown to inhibit the processes controlling cell division in cancer cells by targeting multiple cyclin-dependent kinase proteins involved in regulating the cell cycle. RGB-286638 has also been shown to induce apoptosis (programmed cell death) and to inhibit other important protein kinases involved in the proliferation of cancer cells. RGB-286638 treatment results in tumor regression and increased survival in a number of pre-clinical models of solid and hematological tumors.