A Phase II Study of QL1706 With Anti-angiogenesis Therapy and Chemotherapy in Extensive-stage Small Cell Lung Cancer.

Inclusion Criteria:

Participants must meet all of the following criteria to be eligible for the study:

1. Signed written informed consent and willingness to comply with study procedures.
2. Age ≥18 years.
3. Estimated life expectancy ≥3 months.
4. ECOG performance status of 0 or 1.
5. Histologically or cytologically confirmed, treatment-naïve extensive-stage small cell lung cancer (ES-SCLC).
6. Willing to provide archived or fresh tumor tissue samples. If unavailable, enrollment may proceed per investigator assessment.
7. At least one measurable lesion per RECIST v1.1.
8. Fully understands and voluntarily participates in the study.
9. Adequate organ function as defined below:

   * Absolute neutrophil count ≥1.5 × 10⁹/L
   * Platelets ≥100 × 10⁹/L
   * Hemoglobin ≥90 g/L (without transfusion in prior 14 days)
   * Serum creatinine ≤1× ULN or creatinine clearance \>50 mL/min (Cockcroft-Gault)
   * AST and ALT ≤2.5× ULN (≤5× ULN with liver metastases)
   * Total bilirubin ≤1.5× ULN (except Gilbert's syndrome \<51.3 µmol/L)
   * TSH, FT3, FT4 within ±10% of normal limits

Exclusion Criteria:

1. Prior chemotherapy, immunotherapy, targeted therapy, or radiotherapy.
2. Histologic or cytologic evidence of non-small cell or mixed small cell/non-small cell carcinoma.
3. Symptomatic brain metastases or leptomeningeal disease.
4. Active or suspected autoimmune disease, except for stable vitiligo, type 1 diabetes, hypothyroidism requiring only hormone replacement, or conditions not expected to recur.
5. Evidence or history of active pulmonary tuberculosis (TB), including treated TB within the past year.
6. Concomitant condition requiring systemic corticosteroids or other immunosuppressive therapy.
7. Pregnant or breastfeeding females.
8. Symptomatic interstitial lung disease or suspected drug-related pneumonitis.
9. Positive for HIV antibodies, active HBV (HBsAg+ with HBV DNA \>10³ copies/mL), or active HCV infection (HCV-Ab+ with detectable RNA).
10. History of significant neurological or psychiatric disorders (e.g., dementia, depression, epilepsy, bipolar disorder).
11. Participation in another investigational drug study within 4 weeks prior to randomization.
12. Use of anti-tumor traditional Chinese medicine within 2 weeks prior to first study dose.
13. History of other malignancies within 2 years, except for cured non-melanoma skin cancers or certain in situ carcinomas.
14. Clinically significant cardiovascular or cerebrovascular disease (e.g., NYHA class ≥2 heart failure, recent myocardial infarction or stroke within 6 months).
15. History of thromboembolic events (e.g., DVT, PE, arterial thrombosis) within 6 months, except catheter-related thrombosis.
16. Live vaccination within 28 days before randomization or planned during the study.
17. Major surgery or significant trauma within 4 weeks prior to treatment initiation.
18. Conditions affecting drug absorption (e.g., severe vomiting, GI obstruction, active GI bleeding or perforation).
19. Active, uncontrolled bacterial, viral, or fungal infections despite appropriate treatment.
20. Known hypersensitivity to any study drug or excipients.
21. Any other condition deemed unsuitable by the investigator due to safety or compliance concerns.