Maintenance Lurbinectedin in Combination With Serplulimab for Patients With ES-SCLC

Inclusion Criteria for the Induction Phase: * Fully informed about the study and voluntarily signed a written informed consent form, and able to comply with the requirements and restrictions listed in the informed consent form; * Male or female with age ≥ 18 years; * Eastern Cooperative Oncology Group (ECOG) performance status (PS) of 0-1; * Histologically or cytologically confirmed diagnosis of extensive-stage small cell lung cancer (ES-SCLC) and has not received any systemic treatment for ES-SCLC; * At least one measurable lesion (according to RECIST 1.1 criteria); * Having adequate bone marrow, hepatic, renal and metabolic function, meaning the functional level of the organs meets the following requirements: * Platelet count (PLT) ≥ 100×10\^9/L; Hemoglobin (Hb) ≥ 90 g/L; Absolute neutrophil count (ANC) ≥ 2.0×10\^9/L; * Regardless of whether liver metastasis is present, alanine aminotransferase (ALT) and aspartate aminotransferase (AST) ≤ 3.0×upper limit of normal (ULN); * Alkaline phosphatase (ALP) ≤ 5×ULN; * Total bilirubin (TBIL) ≤ 1.5×ULN, and direct bilirubin ≤ 1.0×ULN; * Serum creatinine ≤ 1.5×ULN or creatinine clearance rate ≥ 30 mL/min (calculated using the Cockcroft-Gault formula); * Creatine phosphokinase (CPK) ≤ 2.5×ULN; * Albumin ≥ 3.0 g/dL. * Women of childbearing potential(WOCBP) must have a negative serum pregnancy test before enrollment. WOCBP must use effective contraceptive measure during the trial drug treatment and for 6 months after the last administration. Male patients (with partners of WOCBP) must use effective contraceptive measure during the trial drug treatment and for 4 months after the last administration; * Human immunodeficiency virus (HIV)-negative, with no active hepatitis B virus (HBV) or hepatitis C virus (HCV) infection. Exclusion Criteria for the Induction Phase: * Have a history of central nervous system (CNS) metastasis or related history; * Have a history of active autoimmune disease or immunodeficiency, or related history; * Have a history of malignancies other than SCLC within 5 years before enrollment; * Previous treatment with immune checkpoint inhibitors or lurbinectedin; * Have a history of idiopathic pulmonary fibrosis or pneumonia, or active pneumonia detected in CT screening; * Treatment with any other investigational product within 28 days before enrollment. Inclusion Criteria for the Maintenance Phase: * Have a continuous response or stable disease according to RECIST 1.1 criteria after 4 cycles of induction therapy; * Toxicity from the induction therapy phase has recovered to ≤ Grade 1; * Have sufficient bone marrow and organ function. Exclusion Criteria for the Maintenance Phase: * Have a history of central nervous system (CNS) metastasis or related history; * Has received chest consolidation radiotherapy; * Severe infection within 2 weeks before enrollment.