ESR1 and ovarian cancer: Besides the above four, multiple CDK4/6 inhibitors have also stepped into clinical trials, such as FCN-437c and XZP-3287, both under phase I clinical trials for advanced solid tumors [40,41]; lerociclib, targeting CDK4/6 and CDK9, under phase I/II clinical trials for ER+/HER2− metastatic breast cancer and EGFR+ metastatic NSCLC [42]; PF-06873600, targeting CDK4/6 and CDK2, under phase I/IIa trials for ER+/HER2− metastatic breast cancer, TNBC and ovarian cancer [43], etc. For more information, readers can refer to some recent references [44,45,46].