BACKGROUND Bispecific antibodies targeting programmed death 1 (PD-1) and vascular endothelial growth factor (PD1-VEGF) have shown promising efficacy in non-small-cell lung cancer (NSCLC). In our previous report of the HARMONi-6 study, we aimed to evaluate the efficacy and safety of ivonescimab plus chemotherapy versus tislelizumab plus chemotherapy as a first-line therapy for patients with advanced squamous NSCLC. Ivonescimab combined with chemotherapy significantly prolonged progression-free survival compared with tislelizumab plus chemotherapy. Here we report the prespecified interim overall survival analysis. METHODS HARMONi-6 is a double-blind, randomised, phase 3 trial, which was conducted at 50 hospitals across China. Patients aged 18-75 years with previously untreated, pathologically confirmed, unresectable stage IIIB, IIIC, or stage IV squamous NSCLC and an Eastern Cooperative Oncology Group performance status score of 0 or 1 were eligible for inclusion. Eligible patients were randomly assigned in a 1:1 ratio to receive ivonescimab or tislelizumab, in combination with paclitaxel and carboplatin for four cycles, followed by maintenance ivonescimab or tislelizumab monotherapy. The primary endpoint was progression-free survival assessed by the independent radiographic review committee as per Response Evaluation Criteria in Solid Tumours guidelines (version 1.1) in all randomly assigned patients. Overall survival was a key secondary endpoint; an interim analysis was planned when approximately 225 overall survival events were observed, but it was triggered after 204 overall survival events to meet regulatory deadlines. Safety, defined as adverse events and serious adverse events related to treatment, as well as adverse events related to immunity or VEGF blockade, were analysed in all randomly assigned patients who received at least one dose of the assigned study treatment. This study is registered at ClinicalTrials.gov (NCT05840016), has completed enrolment, and is ongoing for treatment and follow-up. FINDINGS From Aug 17, 2023, to Jan 21, 2025, 761 patients were assessed for eligibility, and after 229 exclusions a total of 532 patients were randomly allocated (266 per group). 494 (93%) of patients were male and 38 (7%) of patients were female. The median age was 64 years (IQR 59-69). At data cutoff (Feb 27, 2026), 204 deaths had occurred: 84 (32%) patients in the ivonescimab plus chemotherapy group and 120 (45%) in the tislelizumab plus chemotherapy group. With a median follow-up of 21·4 months (95% CI 20·27-21·91), the median overall survival was 27·9 months (95% CI 27·89-not evaluable NE) with ivonescimab versus 23·7 months (20·11-NE) with tislelizumab (hazard ratio for death 0·66 95% CI 0·50-0·87; pone-sided=0·0017), meeting the prespecified boundary (p<0·0049). The overall survival benefit with ivonescimab plus chemotherapy was consistent across key subgroups. Treatment-related adverse events of grade 3 or higher occurred in 184 (69%) of 266 patients in the ivonescimab group and 156 (59%) of 265 patients in the tislelizumab group. The incidence of grade 3 or higher haemorrhage was seven (3%) of 266 and two (1%) of 265, respectively. INTERPRETATION Ivonescimab plus chemotherapy demonstrated a statistically significant and clinically meaningful improvement in overall survival compared with tislelizumab plus chemotherapy in previously untreated patients with advanced squamous NSCLC. This regimen could provide a novel treatment option as first-line treatment in this patient group. FUNDING Akeso Biopharma.
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