LEE011 succinate is primarily used in the treatment of certain types of cancer, particularly breast cancer. It functions as a cyclin-dependent kinase (CDK) inhibitor, specifically targeting CDK4 and CDK6, which play a crucial role in cell cycle regulation. By inhibiting these kinases, it helps to halt the proliferation of cancer cells, especially in hormone receptor-positive (HR+) and human epidermal growth factor receptor 2-negative (HER2-) breast cancer. It is often administered in combination with hormone therapy to enhance its efficacy. Additionally, ongoing research is exploring its potential in treating other cancers, such as lymphoma and solid tumors, due to its mechanism of action in disrupting cell cycle progression.