Anti–cytotoxic T-lymphocyte–associated antigen-4 monoclonal antibody quavonlimab in combination with pembrolizumab: Safety and efficacy from a phase I study in previously treated extensive-stage small cell lung cancer

•Anti-CTLA-4 antibody quavonlimab + pembrolizumab was assessed in extensive-stage SCLC.•Encouraging antitumor activity was observed in patients with extensive-stage SCLC.•The combination was tolerable with manageable toxicities. This first-in-human phase I study (NCT03179436) investigated anti–cytotoxic T-lymphocyte-associated protein 4 monoclonal antibody quavonlimab and anti–programmed death 1 monoclonal antibody pembrolizumab in patients with advanced solid tumors. The study was conducted in two parts: dose-escalation (part 1) and dose-confirmation (part 2). First-line treatment with quavonlimab + pembrolizumab conferred encouraging antitumor activity (objective response rate [ORR], 28%-40%) and was generally well tolerated (grade ≥ 3 treatment-related adverse events [TRAEs] were lowest with quavonlimab 25 mg every 6 weeks [Q6W] at 30% and highest with quavonlimab 75 mg Q3W at 57%) in non–small cell lung cancer. We present data from patients with extensive-stage small cell lung cancer (SCLC) receiving second-line or later therapy. Patients with stage III/IV SCLC received quavonlimab 75 mg Q6W plus pembrolizumab 200 mg Q3W for ≤ 2 years. Primary endpoints were safety and tolerability; ORRs as assessed by blinded independent central review per Response Evaluation Criteria In Solid Tumorsv1.1 was a secondary endpoint. Progression-free survival (PFS), overall survival (OS), and the correlation of response with PD-L1 expression were exploratory endpoints. Forty patients with extensive-stage SCLC received treatment; median follow-up was 13 months. Dose-limiting toxicity occurred in 4 patients (10%). TRAEs occurred in 80% of patients; grade 3 events occurred in 33% of patients and no grade 4/5 events were reported. Confirmed ORRs (95% CI) were 18% (7–33) among all patients, 7% (