The study is being conducted to evaluation of the Efficacy and Safety of QL1706 Combined with Chemotherapy Induction in Sequential Immunotherapy Consolidation After Concurrent Chemoradiotherapy for Limited-Stage Small Cell Lung Cancer(LS-SCLC), and Exploration of the Correlation Between Biomarkers (PD-L1, TMB, ctDNA, etc.) Related to QL1706 Treatment and Treatment Efficacy and Prognosis.

QL1706 (Iparomlimab and Tuvonralimab) is a single bifunctional MabPair product against PD-1 and CTLA-4. QL1604 is a monoclonal antibody against PD-1.

Inclusion Criteria:

1. The patient must be aged between 18 and 75 years (inclusive of boundary values), and both males and females are eligible.
2. Pathologically confirmed LS-SCLC
3. Investigator confirmation of at least one measurable lesion, as defined by RECIST v1.1
4. ECOG performance status of 0 or 1
5. Forced expiratory volume in one second (FEV₁) > 1.0 L
6. No clinically significant interstitial lung disease on baseline CT or PET/CT.
7. Adequate organ and bone-marrow function (all tests performed within 7 days prior to first dose; no transfusions, growth factors, albumin, or other corrective therapies within 14 days):Hemoglobin ≥ 90 g/L, ANC ≥ 1.5 × 10⁹/L, PLT ≥ 90 × 10⁹/L,Serum creatinine ≤ 1.5 × ULN, TBIL ≤ 1.5 × ULN, ALT and AST ≤ 3 × ULN, Albumin (ALB) ≥ 25 g/L,INR ≤ 1.5 × ULN, PT and APTT ≤ 1.5 × ULN (subjects on prophylactic anticoagulation must have values within a safe therapeutic range, per investigator)
8. Women of childbearing potential must have a negative serum or urine pregnancy test within 7 days prior to enrollment and agree to use reliable contraception from screening until 3 months after the last dose; male subjects must agree to use effective contraception or have undergone surgical sterilization for the same period.
9. No prior systemic anti-tumor therapy before enrollment.
10. Estimated life expectancy ≥ 12 weeks.

Exclusion Criteria:

1. Known hypersensitivity to QL1706 or any of its excipients
2. Histologically confirmed non-small cell lung cancer (NSCLC) or mixed tumor containing an NSCLC component.
3. History of another primary malignancy or previous allogeneic organ transplantation.
4. Surgery (other than diagnostic biopsy) within 4 weeks before first dose of study drug.
5. Active substance abuse (e.g., illicit drug use), chronic alcoholism, AIDS, or known HIV infection.
6. Active autoimmune disease, or history of autoimmune disease likely to recur. Systemic corticosteroid therapy equivalent to >10 mg/day prednisone (or other immunosuppressive therapies) within 14 days before first dose.
7. Prior therapy with any antibody or agent targeting T-cell co-regulatory proteins (e.g., PD-1, PD-L1, CTLA-4, TIM-3, LAG-3).
8. Interstitial lung disease (ILD), or history of ILD requiring steroid therapy. History of idiopathic pulmonary fibrosis, drug-induced pneumonitis, organizing pneumonia (e.g., bronchiolitis obliterans), or evidence of active pneumonia on screening chest CT.
9. Live vaccine administration within 28 days prior to first study drug dose. Any condition or comorbidity contraindicating chemo- or radiotherapy (e.g., active infection, myocardial infarction within 6 months, symptomatic heart disease including unstable angina, congestive heart failure, uncontrolled arrhythmia, ongoing immunosuppressive therapy).
10. Pregnant or breastfeeding women; women of childbearing potential or men unwilling to use adequate contraception.
11. Known hereditary bleeding diathesis or coagulation disorder.
12. Prior malignancy, except adequately treated non-melanoma skin cancer, or in situ carcinoma (e.g., breast, oral, cervical) with expected survival >3 years.
13. Any other medical, psychiatric, or laboratory abnormality that, in the investigator's judgment, could interfere with trial participation or interpretation of results.