Cyclin-dependent kinases (CDKs) are serine-threonine protein kinases that are involved in regulating the cell cycle, transcription, mRNA processing, and nerve differentiation. CDK’s action is dependent upon its binding to the regulatory protein, cyclin. Animal cells contain at least four cell cyclins (named CDK1,2,3,4). CDK inhibition is a potential target for cancer drug development and mediation of inflammation for diseases such as arthritis and cystic fibrosis. While several CDK inhibitors are undergoing clinical trials as potential cancer treatment, there is some concern that inhibition of CDK may cause serious side-effects because of its involvement with other cell processes.