Osimertinib Plus Durvalumab versus Osimertinib Monotherapy in EGFR T790M–Positive NSCLC following Previous EGFR TKI Therapy

Introduction: Osimertinib is a third-generation EGFR-tyrosine kinase inhibitor (TKI). Durvalumab is an anti–programmed death ligand 1 monoclonal antibody. The phase III open-label CAURAL trial (NCT02454933) investigated osimertinib plus durvalumab versus osimertinib monotherapy in patients with EGFR-TKI sensitizing and EGFR T790M mutation–positive advanced NSCLC and disease progression after EGFR-TKI therapy. Methods: Patients were randomly assigned 1:1 to receive orally administered osimertinib (80 mg once daily) with or without durvalumab (10 mg/kg administered intravenously every 2 weeks) until progression. Treatment could continue beyond progression, providing clinical benefit continued (judged by the investigator). The amended primary objective was to assess the safety and tolerability of osimertinib plus durvalumab; efficacy was an exploratory objective. Results: CAURAL recruitment was terminated early because of increased incidence of interstitial lung disease–like events in the osimertinib plus durvalumab arm from the separate phase Ib TATTON trial (NCT02143466). At termination of CAURAL recruitment, 15 patients had been randomly assigned to treatment with osimertinib and 14 to treatment with osimertinib plus durvalumab. The most common AEs were diarrhea (53% [grade ≥3 in 6% of patients]) in the osimertinib arm and rash (67% [grade ≥3 in 0 patients]) in the combination arm. One patient who had been randomized to the combination arm reported grade 2 interstitial lung disease while receiving osimertinib monotherapy (after discontinuing durvalumab therapy after one dose). The objective response rates were 80% in the osimertinib arm and 64% in the combination arm. Conclusion: Limited patient numbers preclude formal safety and efficacy comparisons between the two treatment arms. The combination of programmed cell death 1/programmed death ligand 1 inhibitors and EGFR-TKIs as therapy for NSCLC is not well understood, but it requires a careful approach if considered in the future.