Cyclin-Dependent Kinase Inhibitors (CDK inhibitors) are a group of proteins that play a crucial role in regulating the cell cycle. They work by inhibiting the activity of cyclin-dependent kinases (CDKs), which are enzymes that help control the progression of cells through different phases of the cell cycle. By doing so, CDK inhibitors can prevent uncontrolled cell division, which is a hallmark of cancer. These inhibitors are important in cancer research and treatment, as they can help slow down or stop the growth of tumors. Some CDK inhibitors are being developed as targeted therapies for various types of cancer, aiming to improve patient outcomes by specifically blocking the pathways that allow cancer cells to proliferate.