A Study Comparing BL-B01D1 in Combination With Osimertinib Versus Osimertinib Alone in Patients With Locally Advanced, Unresectable EGFR-mutated Non-small Cell Lung Cancer(Stage III) Whose Disease Has Not Progressed Following Definitive Platinum-based Chemoradiation Therapy(PANKU-Lung08)

Inclusion Criteria: 1. Voluntarily sign the informed consent form and comply with the protocol requirements; 2. Age ≥ 18 years and ≤ 75 years, regardless of gender; 3. Expected survival time ≥ 3 months; 4. Unresectable Stage III non-small cell lung cancer; 5. Detection of one of the EGFR-sensitive mutation types in tumor tissue; 6. Agree to provide archived primary tumor tissue specimens or fresh tissue samples within 1 year; 7. In platinum-based radical chemoradiotherapy, the platinum-containing chemotherapy regimen must include one of the specified drugs in addition to the platinum agent; 8. In platinum-based radical chemoradiotherapy, patients must have received a total radiation dose of 60 Gy ± 10% before randomization; 9. Toxicities from prior chemoradiotherapy must have resolved to ≤ Grade 1 as defined by NCI-CTCAE v6.0; 10. ECOG performance status score of 0 or 1; 11. No severe cardiac dysfunction, with left ventricular ejection fraction ≥ 50%; 12. Organ function levels must meet the requirements; 13. Urine protein ≤ 1+ or \< 1000 mg/24h; 14. For premenopausal women with childbearing potential, a serum pregnancy test must be performed within 7 days before starting treatment, and the test must rule out pregnancy; they must not be lactating; all enrolled trial participants must take adequate barrier contraceptive measures throughout the treatment period and for 7 months after treatment ends. Exclusion Criteria: 1. SCLC, mixed SCLC and NSCLC, or other non-NSCLC pathological types; 2. The trial participant has received other chemotherapy, radiotherapy, etc., for NSCLC apart from radical chemoradiotherapy; 3. Major surgery within 4 weeks prior to the first dose; 4. Prior treatment with ADC drugs using topoisomerase I inhibitors as toxins, or antibodies/ADCs targeting EGFR and/or HER3; 5. History of severe heart disease or cerebrovascular disease; 6. Prolonged QTc interval, complete left bundle branch block, second- or third-degree atrioventricular block, or frequent and uncontrolled arrhythmias; 7. Any thrombotic events such as deep vein thrombosis, arterial thrombosis, or pulmonary embolism within 6 months prior to screening; 8. Diagnosis of active malignancy within 5 years prior to study randomization; 9. Hypertension poorly controlled by two antihypertensive medications; 10. Trial participants with poorly controlled blood glucose levels; 11. Current radiation pneumonitis of Grade ≥2 as defined by CTCAE; 12. Concurrent lung disease resulting in clinically severe respiratory impairment; 13. Severe infection within 4 weeks prior to study randomization; 14. Large serous cavity effusions or symptomatic serous cavity effusions; 15. Imaging findings suggesting tumor invasion or encasement of major blood vessels in the abdomen, chest, neck, or pharynx; 16. Severe non-healing wounds, ulcers, or fractures within 4 weeks prior to signing informed consent; 17. Trial participants with clinically significant bleeding or a clear tendency for bleeding within 4 weeks prior to signing informed consent; 18. Trial participants with a history of inflammatory bowel disease, extensive bowel resection, or immune-mediated enteritis; 19. History of allergy to recombinant humanized antibodies or chimeric human-mouse antibodies, or allergy to any excipient components of the investigational drug; 20. History of autologous or allogeneic stem cell transplantation; 21. Positive for human immunodeficiency virus antibodies, active hepatitis B virus infection, or hepatitis C virus infection; 22. History of severe neurological or psychiatric disorders, or a history of substance abuse, alcoholism, or drug addiction; 23. Trial participants planning to receive or having received live vaccines within 28 days prior to study randomization; 24. Other conditions deemed by the investigator as unsuitable for participation in this clinical trial due to complications or other reasons.