Palbociclib is a medication used primarily to treat certain types of breast cancer, specifically 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 4 and 6 (CDK4/6), 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 aromatase inhibitors or hormonal therapies, to enhance its effectiveness. It is typically taken orally in pill form and is part of a broader treatment plan tailored to individual patients' needs. Regular monitoring by healthcare professionals is essential to manage any potential side effects.