AG-024322 is a potent and selective multi-targeted CDK inhibitor with broad spectrum anti-proliferative activity

4415 Uncontrolled cell proliferation is the hallmark of cancer, and is typically manifested by a de-regulation of the cell-division cycle. Cyclin-dependent-kinases (CDKs) play critical roles in regulating the cell cycle by phosphorylating several cellular proteins. The CDKs are de-regulated and activated in most (if not all) human cancers in a variety of ways, including down-regulation or inactivation of the endogenous CDK inhibitory proteins, overexpression of the essential cyclin subunits of the CDKs, and activating mutations in CDK substrates such as the Retinoblastoma (Rb) protein. The activation of CDKs in tumors highlights these enzymes as important cancer targets for novel therapeutic intervention. An integrated strategy of structure-based drug design and combinatorial chemistry efforts was used to optimize compounds with potent and selective inhibition of the major cell cycle kinases CDK1, CDK2 and CDK4. AG-024322 displays potent inhibition of these CDKs, with Ki’s in the 1-3 nM range and selectivity over a number of other kinases. This potent enzymatic inhibition translates to cellular activity, in that AG-024322 also inhibits Rb phosphorylation in cells. Potent antiproliferative activity was demonstrated in multiple human tumor cell lines, with IC50 values ranging from 30 to 200 nM. As expected for a multi-targeted (pan)-CDK inhibitor, AG-024322 causes arrest at multiple stages of the cell cycle. In addition, AG-024322 is cytotoxic and induces cell death by apoptosis in a time- and dose-dependent manner. These results identify AG-024322 as a potent, multi-targeted CDK inhibitor with broad spectrum anti-proliferative activity.