Evaluation of the Effect of Proton Pump Inhibitors on the Efficacy of Dacomitinib and Gefitinib in Patients with Advanced Non-Small Cell Lung Cancer and EGFR-Activating Mutations

Introduction: Dacomitinib and gefitinib are irreversible epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKI) indicated for the first-line treatment of patients with advanced non-small cell lung cancer (NSCLC) and EGFR-activating mutations. Pharmacokinetic (PK) studies in healthy volunteers suggested that acid-reducing drugs such as proton pump inhibitors (PPI) decreased dacomitinib and gefitinib exposure by limiting the pH-dependent absorption. This analysis retrospectively evaluates the effect of concomitant PPI use on dacomitinib exposure and on progression-free survival (PFS) and overall survival (OS) in patients treated with dacomitinib 45 mg QD or gefitinib 250 mg QD in a 1:1 randomized phase 3 study (ARCHER 1050). Methods: The analysis grouped all patients (n = 452) treated in each arm of the study as non-PPI users, PPI users, or extensive PPI users. PFS and OS data were presented by Kaplan-Meier plots and analyzed using Cox proportional hazards models. Dacomitinib exposure was compared using a linear mixed-effects model. Results: Results showed that dacomitinib PFS and OS did not differ significantly when comparing PPI users (N = 59) to non-PPI users (N = 152), while extensive PPI users (N = 24) had shorter PFS [hazard ratio (HR): 1.94, p = 0.011] and OS (HR: 1.77, p = 0.027) when compared to non-PPI users. For patients treated with gefitinib, PFS did not differ significantly when comparing PPI users (N = 51) and extensive PPI users (N = 19) to non-PPI users (N = 159); however, both PPI users (HR: 1.65, p = 0.007) and extensive PPI users (HR: 1.70, p = 0.050) had shorter OS when compared to non-PPI users. Further analysis by adjusting potential confounders indicated no statistically significant differences in PFS or OS between any PPI user vs. non-PPI user groups in the dacomitinib and gefitinib arms. PPI use did not appear to affect dacomitinib exposure. Conclusion: In conclusion, PPI use in patients with NSCLC likely has minimal impact on dacomitinib or gefitinib efficacy despite decreased absorption of these drugs observed in PK studies.