CDK2/CDK4/CDK6

Class

orally bioavailable small-molecule inhibitor selective for CDK2, CDK4 and CDK6

Pathway

inhibits CDK2/4/6-mediated Rb phosphorylation, blocking G1-to-S cell-cycle progression; the added CDK2 inhibition (beyond CDK4/6-only agents) targets a principal mediator of acquired CDK4/6-inhibitor resistance

CDK2, CDK4, and CDK6 are cyclin-dependent kinases, enzymes that drive cells through the cell cycle, the ordered process of growth and division. CDK4 and CDK6 pair with D-type cyclins to phosphorylate the retinoblastoma protein (Rb), a molecular brake on proliferation; phosphorylation inactivates Rb and releases E2F transcription factors that commit the cell to DNA replication, the transition from G1 phase to S phase. CDK2, paired with cyclin E, reinforces this transition and can substitute for CDK4/6 activity when tumors adapt. Many cancers rely on excessive CDK4/6 activity for uncontrolled division, making these kinases a rational target. Selective CDK4/6 inhibitors are widely used, but tumors often develop resistance by upregulating cyclin E-CDK2 signaling to bypass the blockade. Inhibiting CDK2 alongside CDK4 and CDK6 is intended to close this escape route, aiming for a more durable interruption of G1-to-S progression than CDK4/6-selective blockade alone. This combined profile is relevant across cancers driven by Rb-pathway dysregulation, particularly hormone receptor-positive and other proliferative tumors, and represents an evolution of cell-cycle-targeted therapy designed to address resistance mechanisms observed with earlier-generation agents.