Combining “Bottom‐up” and “Top‐down” Approaches to Assess the Impact of Food and Gastric pH on Pictilisib (GDC‐0941) Pharmacokinetics

Pictilisib, a weakly basic compound, is an orally administered, potent, and selective pan‐inhibitor of phosphatidylinositol 3‐kinases for oncology indications. To investigate the significance of high‐fat food and gastric pH on pictilisib pharmacokinetics (PK) and enable label recommendations, a dedicated clinical study was conducted in healthy volunteers, whereby both top‐down (population PK, PopPK) and bottom‐up (physiologically based PK, PBPK) approaches were applied to enhance confidence of recommendation and facilitate the clinical development through scenario simulations. The PopPK model identified food (for absorption rate constant (K(a))) and proton pump inhibitors (PPI, for relative bioavailability (F(rel)) and K(a)) as significant covariates. Food and PPI also impacted the variability of F(rel). The PBPK model accounted for the supersaturation tendency of pictilisib, and gastric emptying physiology successfully predicted the food and PPI effect on pictilisib absorption. Our research highlights the importance of applying both quantitative approaches to address critical drug development questions.