Various clinical trials within the framework of the PALOMA, MONALEESA, and MONARCH study families form the basis for the FDA approvals, showing improved progression-free survival (PFS) and OS for treatment with CDK4/6 inhibitors and endocrine therapy in breast cancer patients (Finn et al., 2016b; Cristofanilli et al., 2016; Tripathy et al., 2018a; Turner et al., 2018; Im et al., 2019; Johnston et al., 2020; Slamon et al., 2020; Sledge et al., 2020). The gene discussed is CDK4; the disease is breast cancer.