• Ability to understand and voluntarily sign a written informed consent form (ICF), which must be signed before the specified study procedures required for the study are performed； 2.18 to 75 years old (at the time of inform consent obtained)； 3.Have an Eastern Cooperative Oncology Group (ECOG) performance status of 0-1； 4.Have a life expectancy of at least 3 months； 5.Have histologically- or cytologically-confirmed diagnosis of Extensive Stage SCLC； 6.Had not received previous systemic therapy; Or ES-SCLC patients who had received definitive chemoradiotherapy for limited-stage small-cell lung cancer but had disease progression \> 6 months earlier; 7.Have measurable disease based on Response Evaluation Criteria in Solid Tumors (RECIST) 1.1 assessed by investigator； 8.Be able to provide formalin fixed, paraffin-embedded (FFPE) tumor tissue obtained from either a core or excisional tumor biopsy； 9.Have adequate organ function； 10.All female and male subjects of reproductive potential must agree to use an effective method of contraception, as determined by the Investigator, during and for 120 days after the last dose of study treatment；