Safety and Efficacy Study of First-line Treatment With QL1706 Plus Chemotherapy in Extensive-Stage Small Cell Lung Cancer

Inclusion Criteria: 1. Subjects participate voluntarily and sign informed consent. 2. Histologically or cytologically confirmed ES-SCLC (per the Veterans Administration Lung Study Group \[VALG\] staging system) 3. No prior systemic treatment for ES-SCLC 4. Eastern Cooperative Oncology Group performance status of 0 or 1 5. Measurable disease, as defined by RECIST v1.1 6. Adequate hematologic and end organ function Exclusion Criteria: 1. Active or untreated central nervous system (CNS) metastases as determined by computed tomography (CT) or magnetic resonance imaging (MRI) evaluation 2. Active, known or suspected autoimmune disease 3. History of idiopathic pulmonary fibrosis, organizing pneumonia, drug-induced pneumonitis, idiopathic pneumonitis, radiation pneumonia requiring steroid treatment or evidence of active pneumonitis on screening chest CT scan. History of radiation pneumonitis in the radiation field (fibrosis) is permitted. 4. Positive test result for human immunodeficiency virus (HIV) 5. Active hepatitis B or hepatitis C 6. Significant cardiovascular disease