The development of immune checkpoint inhibitors has made a significant breakthrough in the treatment of non-small-cell lung cancer (NSCLC). However, there remains a huge unmet clinical need for patients with acquired resistance after initial treatment response.This study evaluated the combination of IBI310 (an anti-cytotoxic T lymphocyte-associated antigen-4 [CTLA-4] antibody) and sintilimab (an anti-programmed death 1 [PD-1]) antibody) in NSCLC patients who have previously been treated with anti-PD-1/ligand (L)1 and acquired resistance. The patients were randomly assigned to receive either a lower dose of IBI310 (1 mg/kg Q3W, cohort A) or a higher dose of IBI310 (3 mg/kg Q3W, cohort B) in combination with sintilimab (200 mg Q3W). The primary endpoints of the study were objective response rate (ORR) assessed by RECISTv1.1 and safety, while secondary endpoints included disease control rate (DCR), progression-free survival (PFS), and overall survival (OS).As of November 2, 2023, the study had enrolled 30 patients, with 15 patients in each cohort. The ORR was 13.3% (2/15, 95% confidence interval [CI], 1.7-40.5) in cohort B. DCR were 46.7% (95% CI, 21.3-73.4) and 66.7% (95% CI, 38.4-88.2) in cohorts A and B, respectively. In cohorts A and B of this trial, the median follow-up times were 4.2 and 5.6 months, respectively. Median PFS was 1.45 (95% CI, 1.35-2.73) versus 2.73 (95% CI, 1.41-4.90) months for cohort A versus B; the median OS was 7.03 (95% CI, 3.09-not calculable [NC]) months in cohort A and 8.90 (95% CI, 5.13-NC) months in cohort B. Of the 30 patients, 86.7% in both cohorts experienced treatment-related adverse events (TRAEs) with Grade ≥3 TRAEs occurring in 40% and 53.3% of patients in cohorts A and B, respectively.IBI310 3 mg/kg Q3W plus sintilimab was effective in a small number of previously treated anti-PD-1/L1-resistant NSCLC patients.© 2024 The Authors. Cancer Medicine published by John Wiley & Sons Ltd.