This study is an open, single-arm, single-center phase II clinical study, which aims to evaluate the efficacy and safety of adebelizumab combined with irinotecan liposome in the second-line treatment of advanced small cell lung cancer, explore biomarkers to predict the efficacy, and further select the dominant population in immunotherapy.

In this study, 46 patients with extensive SCLC who had previously received immunotherapy combined with chemotherapy were enrolled. Subjects who met the enrollment conditions will be given adebelizumab combined with irinotecan liposome at the same time. After 4-6 cycles of treatment, if their condition has not progressed, they will be treated with adebelizumab until the disease progresses, toxicity can not be tolerated or other reasons specified in the scheme can be terminated. Subjects who finish the treatment will enter the follow-up period for safety follow-up and survival follow-up.

Inclusion Criteria:

• 1. Age: 18-75 years old; 2. Small cell lung cancer diagnosed by histology; Compound small cell lung cancer is not allowed; 3. Progress in receiving first-line chemotherapy combined with immunotherapy (including PD-1 inhibitor and PD-L1 inhibitor); 4. According to RECIST 1.1 standard, there is at least one measurable objective lesion; 5.ECOG score 0-1; 6. The functions of important organs meet the following requirements:Bone marrow function: neutrophils ≥1.5×109/L, platelets ≥100×109/L, hemoglobin concentration ≥ 90g/L;Liver function: bilirubin ≤ 1.5× ULN; Aspartate aminotransferase and glutamate aminotransferase ≤2.5×ULN, and AST and ALT ≤ 5× ULN in case of liver metastasis; Total bilirubin ≤1.5 times the upper limit of normal value;Renal function: serum creatinine ≤1.5×ULN, or creatinine clearance rate (CCR) ≥ 60 ml/min; 7. Expected survival > 12 weeks;Patients have good compliance with the planned treatment, can understand the research process of this study and sign a written informed consent.

Exclusion Criteria:

1. Irinotecan liposome or Irinotecan has been used before; 2. Severe heart and lung diseases, new york Heart Association (NYHA) scores that patients with heart diseases above Grade II (including Grade II); 3. Patients with severe systemic infection or other serious diseases; 4. Patients who are known to be allergic or intolerant to chemotherapy drugs or their accessories; 5. Other malignant tumors have appeared in the past 5 years, except cured cervical carcinoma in situ and non-melanoma skin cancer; 6. Patients of childbearing age during pregnancy or lactation, and those who refused to take appropriate contraceptive measures during this experiment; 7. Have participated in clinical studies of other drugs within 21 days before the first dose of the study drug is given; 8. Combined with active autoimmune diseases and inflammatory diseases; 9. Grade 3-4 immune-related adverse reactions occurred during previous immunotherapy; 10. Symptomatic brain metastasis and meningeal metastasis; 11. Before the first administration, you are receiving long-term systemic corticosteroid therapy with prednisone > 10mg/d or equivalent anti-inflammatory active drugs or any form of immunosuppressive therapy. Subjects who need bronchodilators, inhaled or topical steroids or local steroid injections can be included in this study; 12. Patients with a large amount of serous cavity effusion, or serous cavity effusion with symptoms, or poor control of serous cavity effusion (poor control is defined as: puncture and drainage are needed twice or more in one month);The researcher judges the patients who are not suitable to participate in this study.

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