Definition

An orally bioavailable inhibitor of NUAK family SNF1-like kinase 1 (AMPK-related protein kinase 5; ARK5), and the cyclin-dependent kinases 4 (CDK4) and 6 (CDK6), with potential antineoplastic activity. Upon oral administration,narazaciclib specifically binds to and inhibits ARK5, which interferes with the activation of ARK5-mediated signal transduction pathways and reduces cell proliferation in cancer cells that overexpress ARK5. In addition, ON 123300 inhibits CDK4 and 6 and prevents the phosphorylation of retinoblastoma (Rb) protein in early G1. Inhibition of Rb phosphorylation prevents CDK-mediated G1-S phase transition, which causes G1 phase cell cycle arrest, suppresses DNA synthesis and inhibits cancer cell growth. ARK5, a member of the AMP-activated protein kinase (AMPK) family, is associated with tumor growth and invasion. Overexpression of CDK4/6, which is seen in certain types of cancer, causes cell cycle deregulation.