Isogen 125 mg is a targeted therapy containing the active constituent palbociclib. It belongs to the group of anticancer medications known as cyclin-dependent kinase inhibitors. It is used in treating hormone receptor-positive, human epidermal growth factor 2 negative advanced or metastatic (has spread to other parts of the body) breast cancer. Cancer is a condition in which cells multiply in an uncontrolled and abnormal manner. It is given in combination with certain other anticancer medications.