PATIENTS AND METHODS
The primary objectives of this Phase I study (PBTC-042, NCT02255461) were to determine the maximum tolerated dose (MTD)/recommended Phase II dose (RP2D), describe toxicities, and characterize palbociclib pharmacokinetics. Secondary objectives were to record preliminary evidence of palbociclib antitumor effect, evaluate CDK4/6, cyclin D1-3, Ink4a-ARF copy-number variations, explore potential relationships between palbociclib pharmacokinetics and pharmacodynamics, and relate pharmacogenetic polymorphisms to palbociclib pharmacokinetics.