• Part A (Dose-Escalation Cohorts): Consecutive cohorts of patients will receive escalating doses of oral palbociclib in combination with intravenous nab-P in 28-day cycles, in order to estimate the MTD(s) of the combination. The starting doses will be 75 mg palbociclib, and 100 mg/m2 nab-P. The observation period for dose-limiting toxicities (DLTs) will be from Day 1 to Day 28. Pharmacokinetic (PK) and pharmacodynamic (PD) properties of palbociclib and nab-P will also be assessed. Up to approximately 30 patients will be enrolled. The criteria for dose escalation will be based on a modified toxicity probability interval (mTPI) method.