CDK4 and neoplasm: The NCT01037790 phase II clinical trial is studying activity, safety and tolerability of single agent palbociclib in preatreated refractory solid tumors, including metastatic colorectal cancer that harbors the Kras or BRAF mutation, metastatic breast cancer, advanced or metastatic esophageal and/or gastric cancer, cisplatin-refractory, unresectable germ cell tumors and any tumor type if tissue tests positive for CCND1 amplification, CDK4/6 mutation, CCND2 amplification or any other functional alteration at the G1/S checkpoint.