To Evaluate Efficacy and Safety of Serplulimab + Chemotherapy (Carboplatin- Etoposide) in US Patients With ES-SCLC

Inclusion Criteria: Voluntary participation in clinical studies. Male or female aged ≥ 18 years at the time of signing the ICF. Histologically or cytologically diagnosed with ES-SCLC (according to the Veterans Administration Lung Study Group staging system). No prior systemic therapy for ES-SCLC. At least one measurable lesion as assessed according to RECIST 1.1 within 4 weeks prior to randomization. Major organs are functioning well. Every effort should be made to provide tumor tissues for the determination of PD-L1 expression. An ECOG PS score of 0 or 1. An expected survival ≥ 12 weeks. Subjects with prior denosumab use that can and agree to switch to bisphosphonate therapy for bone metastases starting prior to randomization and throughout treatment. Participant must keep contraception. Exclusion Criteria: Histologically or cytologically confirmed mixed SCLC. Known history of severe allergy to any monoclonal antibody. Known hypersensitivity to carboplatin or etoposide. Patients with myocardial infarction within half a year before the first dose of the study drug, poorly controlled arrhythmia. Pregnant or breastfeeding females. Patients with a known history of psychotropic drug abuse or drug addiction. Patients who have other factors that could lead to the early termination of this study based on the investigator's judgment.