Small-molecule kinase inhibitors are gaining increasing importance in the field of drug research, development and use. There are many such inhibitors, some of which are more specific while some are less, and quite a few of them have already been approved for cancer therapy or are at least in clinical studies of different phases. CDK inhibitors are no exception, and there are many inhibitors used for research purposes and for therapeutic applications. Many CDK inhibitors have been enrolled in various phases of clinical trials both for cancers and other diseases. Several CDK4/6 are approved by U.S. Food and Drug Administration (FDA) for the treatment of various cancers. One of our major activities is design, development, production and testing of novel CDK inhibitors, which will lead to the FDA approval and use of these inhibitors as drugs against cancer and probably other diseases, which depend on CDKs.