Inclusion Criteria:
* 1\. Patients with pathologically confirmed extensive stage small cell lung cancer (VALG stage).
* 2\. No prior systemic therapy for extensive-stage small cell lung cancer;
* 3\. Patients who have received prior radiotherapy for limited-stage SCLC must have received radical therapy with a treatment-free interval of at least 6 months between the end of chemotherapy, radiotherapy, or radiochemotherapy and the diagnosis of extensive-stage SCLC (counting the time of completion of the last cycle of chemotherapy/time of completion of the last dose of radiotherapy);
* 4\. The presence of a Measurable lesions as defined by the RECIST 1.1 criteria, where a previously irradiated lesion shows definite progression after radiotherapy and where this previously irradiated lesion is not the only lesion;
* 5\. 18-75 years of age or older; ECOG score: 0-1; expected survival ≥ 3 months.
* 6\. Adequate hematology and organ function, i.e., the following criteria are met:
a) Hematology (no transfusion of blood or blood products within 14 days, not corrected with G-CSF and other hematopoietic stimulating factors): i. Absolute neutrophil count (ANC) ≥ 1.5 × 109/L (1,500/mm3); ii. Platelet count (PLT) ≥ 100 × 109/L (100,000 /mm3); iii. Hemoglobin (HB) ≥ 80 g/L.
b) Renal: i. Creatinine clearance\* (CrCl) calculated ≥ 50 mL/min; ii. Urine Protein \< 2+ or 24 hour (h) urine protein quantification \< 1.0 g.
c) Liver: i. Serum total bilirubin (TBil) ≤ 1.5 × ULN; ii. AST and ALT ≤ 2.5 × ULN; iii. serum albumin (ALB) ≥ 28 g/L.
d) Coagulation: i. International Normalized Ratio (INR) and Activated Partial Thromboplastin Time (APTT) ≤ 1.5 × ULN.
e) Cardiac Function: i. Left Ventricular Ejection Fraction (LVEF) ≥ 50%.
* 7, Subjects voluntarily enrolled in this study and signed an informed consent form, complied well and cooperated with the follow-up.
Exclusion Criteria:
* 1, Patients with symptomatic brain metastases. Brain metastatic lesions that have been treated and kept in a clinically stable state of symptoms for at least 1 month, and do not use steroids and anticonvulsant drugs for at least 1 month prior to entering the study can be enrolled;
* 2\. Previous use of anti-angiogenic drugs such as anlotinib, apatinib, bevacizumab, or related immunotherapeutic drugs targeting PD-1, PD-L1, etc.;
* 3\. Those who have a wide range of factors affecting oral administration of the medication (e.g., the inability to swallow, After gastrointestinal resection, chronic diarrhea and intestinal obstruction, etc.);
* 4\. Uncontrollable pleural effusion, pericardial effusion, or ascites that requires repeated drainage;
* 5\. Patients with imaging evidence of tumor invasion of important perivascular vessels, or patients who, in the judgment of the investigator, are at high risk of fatal hemorrhage due to tumor invasion of an important blood vessel during the follow-up period of the study;
* 6\. Patients with a history of severe hemorrhagic tendency or coagulation dysfunction including, but not limited to, clinical symptoms within 3 months prior to entry into the study. Clinically significant hemoptysis (greater than one tablespoon of hemoptysis per day) within 3 months prior to enrollment; or clinically significant bleeding symptoms or bleeding tendency within 4 weeks prior to enrollment, such as peptic hemorrhage, hemorrhagic gastric ulcers (including gastrointestinal perforation and/or fistulae, except that gastrointestinal perforation or fistulae that have been surgically resected may be permitted to be enrolled), non-healing wounds, ulcers, or bone fracture;
* 7\. Patients who have received major Surgical treatment, incisional biopsy, or significant traumatic injury within 28 days prior to enrollment;
* 8\. Arterial/venous thrombotic events, such as cerebrovascular accidents (including transient ischemic attacks), deep vein thrombosis, and pulmonary embolism, within 6 months prior to enrollment;
* 9\. Active autoimmune disease requiring systemic therapy (e.g., palliative medications, corticosteroids, or immunosuppressants) within 2 years of the first dose;
* 10\. Increased risk associated with participation in the study or study drug; and Other conditions that increase the risk associated with participation in the study or the study drug and, in the investigator's judgment, make the patient unsuitable for enrollment in the study;
