Efficacy of Anti-CTLA-4 Antibody Combined With Sintilimab and Chemotherapy as Neoadjuvant Therapy for Resectable Stage II-III Non-Small Cell Lung Cancer

INCLUSION CRITERIA 1. The patient shall sign the informed consent. 2. Age ≥ 18 years. 3. Histologically or cytologically confirmed non-small-cell lung cancer (NSCLC). 4. No prior anticancer therapy, including (but not limited to) chemotherapy, immunotherapy or radiotherapy. Traditional Chinese medicine given for anticancer intent is permitted provided it was discontinued ≥ 2 weeks before first dose. 5. Investigator-assessed resectable Stage II-IIIB (N3 excluded) NSCLC per AJCC 9th. 6. Non-squamous NSCLC: no EGFR mutation, ALK rearrangement or any other driver mutation with an approved targeted agent. Squamous NSCLC: no known EGFR mutation, ALK rearrangement or other actionable driver mutation. 7. PD-L1 expression negative (22C3 or E1L3N). 8. ECOG performance status 0 or 1. 9. Adequate organ function within 7 days before first dose: * Haemoglobin ≥ 90 g/L (no transfusion within 28 days) * Absolute neutrophil count ≥ 1.5 × 10⁹/L * Platelet count ≥ 100 × 10⁹/L (no platelet transfusion or IL-11 within 14 days) * Creatinine clearance ≥ 60 mL/min (Cockcroft-Gault) * Total bilirubin ≤ 1.5 × ULN (≤ 2.5 × ULN in Gilbert's syndrome or hepatic metastases) * ALT and AST ≤ 3 × ULN * INR or aPTT ≤ 1.5 × ULN * FEV\> 2L, FEV1\> 1L, FEV1/FVC ≥ 70%, DLCO ≥ 70% predicted; or Investigator determination that pulmonary reserve is adequate for planned surgery. 10. Fertile female must have a negative serum pregnancy test within 7 days before first dose. 11. Fertile female and male patients with female partners of childbearing potential must use a highly effective contraceptive method (annual failure rate \< 1 %) from 7 days before first dose until 24 weeks after the last dose. EXCLUSION CRITERIA 1. Major thoracic or abdominal surgery within 28 days before first dose or incomplete recovery from previous surgery. 2. Participants who were systemically treated with corticosteroids (prednisone or other corticosteroids \>10 mg/day) or other immunosuppressive agents for ≥ 7 consecutive days within 14 days before first dose. Except for inhaled or topical corticosteroids, or corticosteroid therapy at physiological replacement doses for adrenal insufficiency; short- courses (\<7 days) corticosteroid use is permitted for the prevention or treatment of non-autoimmune conditions; 3. Participants who received live vaccines (including live attenuated vaccines) within 28 days before first dose. 4. Current or prior interstitial pneumonia or pulmonary diseases requiring systemic glucocorticoids. 5. Presence of any active autoimmune disease or history of autoimmune disease. Except in the following cases: Type 1 diabetes, stable hypothyroidism under hormone replacement therapy, psoriasis or vitiligo not requiring systemic treatment. 6. Other malignancy within 5 years before first dose, except for tumors assessed by the investigator as cured. 7. Uncontrolled comorbidities, including: * Active hepatitis B (HBsAg positive and HBV DNA \> 500 IU/mL or \> 2000 copies/mL) or hepatitis C (HCV antibody and HCV RNA positive). Subjects with HBV DNA ≤ 500 IU/mL who agree to antiviral prophylaxis are eligible. * Known HIV infection or history of AIDS. * Active tuberculosis. * Active infection requiring systemic antibiotics for \> 7 days within 28 days before first dose. * Clinically significant cardiovascular disease: cerebrovascular accident within 6 months, symptomatic heart failure (NYHA class II-IV), unstable angina or myocardial infarction within 6 months, risk of QTc prolongation or arrhythmia. * Urine protein qualitative≥ 2+, and 24-hour urine protein test \> 1g 8. History of allogeneic haematopoietic stem-cell or solid-organ transplantation. 9. Hypersensitivity to antibody therapies (≥ grade 3 NCI-CTCAE v6.0), history of anaphylaxis, uncontrolled asthma, or significant drug allergies. 10. Pregnancy or lactation. 11. Other conditions that may affect the safety or compliance of drug therapy in this study include, but are not limited to, psychiatric disorders, uncontrolled large serosal cavity effusions, or moderate to large serosal cavity effusions requiring repeated drainage (recurring within 2 weeks after intervention), such as pleural effusion, pericardial effusion, or ascites cachexia.