Palbociclib is a medication used primarily to treat certain types of breast cancer, particularly hormone receptor-positive and human epidermal growth factor receptor 2-negative (HR+ HER2-) breast cancer. It works by inhibiting specific proteins called cyclin-dependent kinases (CDK4 and CDK6), which are involved in cell division. By blocking these proteins, Palbociclib helps slow down the growth of cancer cells. This drug is often prescribed in combination with other treatments, such as letrozole or anastrozole, to enhance its effectiveness. It is typically taken orally in pill form and is part of a broader treatment plan that may include surgery, radiation, or other therapies. Regular monitoring by healthcare professionals is essential to manage any potential side effects.