A protein kinase inhibitor specific for the cyclin-dependent kinase 4 (CDK4) with potential antineoplastic activity. CDK4 inhibitor P1446A-05 specifically inhibits CDK4-mediated G1-S phase transition, arresting cell cycling and inhibiting cancer cell growth. The serine/threonine kinase CDK4 is found in a complex with D-type G1 cyclins and is the first kinase to become activated upon mitogenic stimulation, releasing cells from a quiescent stage into the G1/S growth cycling stage; CDK-cyclin complexes have been shown to phosphorylate the retinoblastoma (Rb) transcription factor in early G1, displacing histone deacetylase (HDAC) and blocking transcriptional repression. Check for active clinical trials using this agent. (NCI Thesaurus)