The phase 3 NEPTUNE study (NCT02542293) evaluated first-line durvalumab plus tremelimumab (DT) versus chemotherapy for metastatic NSCLC. Prespecified exploratory analyses were conducted in an extended cohort enrolled in China.Patients were randomized (1:1) to DT or standard chemotherapy, stratified by PD-L1 tumor cell (TC) expression (≥25 % vs < 25 %), histology, and smoking history. The primary analysis for this cohort was overall survival (OS) in patients with PD-L1 TC < 1 %. Secondary analyses included OS and progression-free survival (PFS) in the ITT population and PD-L1 subgroups, and safety. No alpha was allocated to these cohort analyses (data cut-off, 21-September-2020).78 and 82 patients were randomized to DT and chemotherapy, respectively; 26 and 29 had PD-L1 TC < 1 % (median follow-up, 31.2 and 29.7 months [censored patients]). Among patients with PD-L1 TC < 1 %, OS favored DT versus chemotherapy (HR 0.60; 95 % CI, 0.32-1.11), with medians of 15.0 months (95 % CI, 10.5-27.4) and 11.7 months (95 % CI, 8.6-20.5), respectively; 24-month rates were 36.0 % (95 % CI, 18.2-54.2) and 17.9 % (95 % CI, 6.5-33.7). In the ITT population, OS was prolonged with DT versus chemotherapy (HR 0.70; 95 % CI, 0.48-1.02); medians were 20.0 and 14.1 months and 24-month rates were 44.2 % and 30.4 %. PFS was similar in the PD-L1 TC < 1 % (HR 1.13; 95 % CI, 0.59-2.14) and ITT (HR 0.95; 95 % CI, 0.66-1.36) populations; 12-month rates were 15.6 % versus 11.3 % and 23.9 % versus 16.6 %. Grade 3/4 treatment-related adverse events (TRAEs) occurred in 31.2 % with DT and 52.6 % with chemotherapy; 3.9 % versus 10.3 % discontinued due to TRAEs.In exploratory analyses, first-line DT showed a trend towards improved OS versus chemotherapy among Chinese patients in the PD-L1 TC < 1 % population and ITT population, with 24-month OS and 12-month PFS rates indicating benefit in survival curve tails. DT was well tolerated with no new safety signals.Copyright © 2023 The Authors. Published by Elsevier B.V. All rights reserved.