Ribociclib (KISQALI®), a cyclin-dependent kinase 4/6 inhibitor approved for the first-line treatment of HR+/HER2– advanced breast cancer with an aromatase inhibitor, is administered with no restrictions on concomitant gastric pH-elevating agents or food intake. The influence of proton pump inhibitors (PPIs) on ribociclib bioavailability was assessed using (1) biorelevant media solubility, (2) physiologically based pharmacokinetic (PBPK) modeling, (3) non-compartmental analysis (NCA) of clinical trial data, and (4) population PK (PopPK) analysis. This multi-pronged approach indicated no effect of gastric pH changes on ribociclib PK and served as a platform for supporting ribociclib labeling language, stating no impact of gastric pH altering agents on the absorption of ribociclib, without a dedicated drug-drug interaction trial. The bioequivalence of ribociclib exposure with or without a high-fat meal was demonstrated in a clinical trial. Lack of restrictions on ribociclib dosing may facilitate better patient compliance and therefore clinical benefit.