Poseidon: a phase 3 study of first-line durvalumab ± tremelimumab + chemotherapy vs chemotherapy alone in metastatic NSCLC

Background: Immunotherapy is an important new treatment modality for NSCLC. Dual blockade of the non‐redundant PD‐1/PD‐L1 and CTLA‐ 4 pathways may provide additive or synergistic effects. Durvalumab is a selective, high‐affinity, engineered human IgG1 mAb that blocks PDL1 binding to PD‐1 and CD80. Tremelimumab is a selective human IgG2 mAb against CTLA‐4. A combination regimen of immunotherapy with chemotherapy may further enhance clinical benefit. In a Phase 1b study (NCT02537418), durvalumab ± tremelimumab combined with chemotherapy demonstrated manageable tolerability and preliminary signs of clinical activity in patients with solid tumors, including NSCLC. Method: POSEIDON (NCT03164616) is a Phase 3, randomized, multicenter, open‐label, global study to investigate durvalumab ± tremelimumab + platinum‐based chemotherapy vs platinum‐based chemotherapy alone as first‐line treatment in metastatic NSCLC. Patients must be immunotherapy‐ and chemotherapy‐naïve with EGFR/ ALK wild‐type metastatic NSCLC, and have confirmed tumor PD‐L1 expression status, and a WHO/ECOG performance status of 0/1. Approximately 801 patients will be randomized 1:1:1 to receive durvalumab + tremelimumab + chemotherapy (Arm 1); durvalumab + chemotherapy (Arm 2); or chemotherapy alone (Arm 3). After induction, patients in the immunotherapy arms will receive durvalumab monotherapy, and non‐squamous patients who initially received pemetrexed during induction will receive it as maintenance therapy if eligible. Treatment will continue until disease progression or another discontinuation criterion has been met. The primary endpoint is PFS according to blinded independent central review (RECIST v1.1). Secondary endpoints include OS; ORR; duration of response; best overall response; proportion of patients alive and progression‐free at 12 months; disease‐related symptoms and HRQoL; and safety and tolerability. Recruitment is ongoing. (Figure Presented).