Palbociclib, marketed under the brand name Palbocent 125 mg (Palbociclib) is an oral medication used in the treatment of hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2-) advanced or metastatic breast cancer. It is a cyclin-dependent kinase (CDK) 4/6 inhibitor that works by inhibiting the growth of cancer cells. Palbociclib is typically administered in combination with endocrine therapy such as letrozole or fulvestrant. The standard dosage is 125 mg once daily for 21 days followed by a 7-day break. Common side effects include neutropenia, fatigue, nausea, and infections. Palbociclib significantly improves progression-free survival in patients with HR+, HER2- breast cancer.