A Study of BL-B01D1+PD-1 Monoclonal Antibody in Patients With Extensive-stage Small Cell Lung Cancer

Inclusion Criteria: 1. Subject volunteered to participate in the study and signed an informed consent; 2. Male or female aged ≥18 years and ≤75 years; 3. Expected survival time ≥3 months; 4. ECOG score 0-1; 5. Newly diagnosed patients with extensive-stage small cell lung cancer confirmed by histopathology and / or cytology; 6. A archived tumor tissue sample or fresh tissue sample of the primary or metastatic lesion must be provided within 3 years; 7. At least one measurable lesion meeting the RECIST v1.1 definition was required; 8. No blood transfusion and no use of cell growth factors and/or platelet-raising drugs within 14 days before screening, and the organ function level must meet the requirements; 9. The toxicity of previous antineoplastic therapy has returned to ≤ grade 1 as defined by NCI-CTCAE v5.0; 10. For premenopausal women of childbearing potential, a pregnancy test must be performed within 7 days before the initiation of treatment, a serum or urine pregnancy test must be negative, and the patient must not be lactating; All enrolled patients should take adequate barrier contraception during the entire treatment cycle and for 6 months after the end of treatment. Exclusion Criteria: 1. Prior use of ADC drug therapy with small molecule toxins as topoisomerase I inhibitors; 2. Prior treatment with any systemic anti-tumor regimen for extensive-stage small cell lung cancer; 3. Pathology suggested small cell carcinoma containing non-small cell carcinoma components; 4. Subjects had used immunomodulatory drugs within 14 days before the first use of the study drug ; 5. Screening the history of severe cardiovascular and cerebrovascular diseases in the first half of the year ; 6. QT interval prolongation, complete left bundle branch block, III degree atrioventricular block, frequent and uncontrollable arrhythmia ; 7. Active autoimmune diseases and inflammatory diseases ; 8. Receiving long-term systemic corticosteroid therapy or equivalent anti-inflammatory active drugs or any form of immunosuppressive therapy prior to the first dose; 9. Other malignancies that have progressed or require treatment within 5 years prior to the first dose; 10. Have ILD requiring steroid therapy, or currently have ILD, or suspected ILD at screening; 11. Prior to initiation of study treatment, there were: a) poorly controlled diabetes mellitus; b) with severe complications of diabetes; c) glycosylated hemoglobin levels of 8% or more; d) hypertension that is poorly controlled by two antihypertensive drugs; e) history of hypertensive crisis or hypertensive encephalopathy; 12. Unstable thrombotic events requiring therapeutic intervention within 6 months prior to screening; Except for infusion set-related thrombosis; 13. Concurrent pulmonary disease leading to severe clinical impairment of respiratory function; 14. Patients with active central nervous system metastases; 15. Patients with large serosal effusions, or symptomatic serosal effusions, or poorly controlled serosal effusions; 16. History of allergy to recombinant humanized antibody or human-mouse chimeric antibody or to any excipient component of the experimental drug; 17. Prior organ transplantation or allogeneic hematopoietic stem cell transplantation; 18. Positive human immunodeficiency virus antibody, active tuberculosis, active hepatitis B virus infection, or active hepatitis C virus infection; 19. Severe infection within 4 weeks prior to first dose of study drug; Lung infection or active lung inflammation within 4 weeks; 20. Have participated in another clinical trial within 4 weeks prior to the first dose; 21. Have a history of psychotropic substance abuse and cannot be abstained from or have a history of severe neurological or psychiatric disorders; 22. Imaging examination showed that the tumor had invaded or encapsulated the large blood vessels in the chest; 23. Severe and non-healing wounds, ulcers, or fractures within 4 weeks prior to signing the informed policy; 24. Clinically significant bleeding or obvious bleeding tendency within 4 weeks prior to signing the informed policy; 25. Subjects who are scheduled to receive or receive a live vaccine within 28 days prior to the first dose; 26. Other conditions that the investigator considers unsuitable to participate in this clinical trial.