LP002 is a highly selected recombinant humanized anti-PD-L1 monoclonal antibody. This is a single-arm, multicenter study to evaluate the efficacy and safety of LP002 in combination with chemotherapy in patients with extensive stage samll cell lung cancer.

Inclusion Criteria:

• Be willing and able to provide written informed consent for the trial;
• Age ≥ 18 and ≤ 79 years old, male or female;
• Histologically or cytologically diagnosed with ES-SCLC (according to the Veterans Administration Lung Study Group staging system).
• No prior systemic therapy for ES-SCLC.
• Patients who have received prior chemoradiotherapy for limited-stage SCLC must have been treated with curative intent and experienced a treatment-free interval of at least 6 months since last chemotherapy, radiotherapy, or chemoradiotherapy cycle from diagnosis of extensive-stage SCLC.
• Has Eastern Cooperative Oncology Group (ECOG) Performance Status of 0 or 1
• Has a life expectancy of ≥3 months.
• Has at least one measurable lesion based on Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1.
• Has adequate organ function.
• Female participants of childbearing potential should have a negative pregnancy within 72 hours before the first dose of trial treatment. Male and female participants should agree to use an adequate method of contraception during the experiment and 24 weeks after the last administration of the test drugs.

Exclusion Criteria:

• Histologically or cytologically confirmed mixed SCLC.
• Suffered from other malignant tumors in the past 5 years (except skin basal cell carcinoma, squamous cell carcinoma, and cervical carcinoma in situ that have been effectively controlled).
• Prior to the first administration of the study drug, there was a grade > 1 toxicity (excluding hair loss) caused by previous anti-tumor treatments.
• Has received prior therapy with an anti-PD-1, or anti-PD-L1, or anti-CTLA-4 agents.
• Has known active central nervous system (CNS) metastases and/or carcinomatous meningitis.
• Has uncontrolled pleural effusion, pericardial effusion, or ascites requiring repeated drainage.
• Uncontrolled or symptomatic hypercalcemia.
• Spinal cord compression not definitively treated with surgery and/or radiation or previously diagnosed and treated spinal cord compression without evidence that disease has been clinically stable for ≤ 1 week prior to the first dose of trial treatment.
• Has active autoimmune disease that has required systemic treatment in past 2 years.
• Has received a major surgery within 4 weeks prior to the first dose of trial treatment.
• Has received system treatment with corticosteroids (dose >10mg/day prednison or other therapeutic hormones) within 2 weeks prior to the first dose of trial treatment.
• Previous or present interstitial lung disease or non-communicable pneumonia, except for radiation pneumonia.
• Has uncontrolled systemic disease, such as diabetes or hypertension.
• Has a history of testing positive for human immunodeficiency virus (HIV), or known acquired immunodeficiency syndrome (AIDS), or stem cell transplantation or organ transplantation.
• Has untreated chronic hepatitis B or chronic hepatitis B virus (HBV) DNA exceeding 500 IU/ mL or active hepatitis C virus (HCV). Subjects with non-active HBsAg carriers, treated and stable hepatitis B (HBV DNA < 10^3 copies/ml or <500 IU/ mL) , and cured hepatitis C can be enrolled. Subjects with positive HCV antibodies are eligible only if the HCV RNA test results are negative.
• Has serious infections within 4 weeks or active infections requiring systemic treatment within 2 weeks prior to the first dose of trial treatment.
• Has a history of severe allergic reaction to any other monoclonal antibodies.
• Has participated in other anticancer drug clinical trials within 4 weeks.
• Is pregnant or breastfeeding.
• Has received a live vaccine within 30 days prior to the first dose of trial treatment.
• According to the judgement of the investigators, there are other factors that may lead to the termination of the study.