A Phase II Single-arm Clinical Study in the Treatment of Locally Advanced Esophageal Cancer After Failed Neoadjuvant Chemoimmunotherapy

Inclusion Criteria: * Age 18 to 75 years, male or female; * Histologically confirmed locally advanced squamous cell carcinoma or adenocarcinoma of the esophagus or esophagogastric junction; * ECOG performance status 0-1; ④ Failure of or local progression after 2-4 cycles of first-line chemotherapy combined with immunotherapy, or deemed unresectable by surgical evaluation; ⑤ At least one measurable lesion according to RECIST v1.1 criteria; ⑥ Adequate major organ and bone marrow function: Hematology: Hemoglobin (Hb) ≥90 g/L (without transfusion within 14 days); Absolute neutrophil count (NEUT) ≥1.5×10⁹/L; Platelets (PLT) ≥100×10⁹/L; Biochemistry: Alanine aminotransferase (ALT) and aspartate aminotransferase (AST) ≤2.5×ULN (≤5×ULN in cases of liver metastases); Total bilirubin (TBIL) ≤2×ULN; Serum albumin (ALB) ≥28 g/L; Serum creatinine (Cr) ≤1.5×ULN and creatinine clearance \>50 μmol/L; Coagulation: International normalized ratio (INR) and activated partial thromboplastin time (APTT) ≤1.5×ULN (unless the subject is receiving anticoagulant therapy and INR and APTT are within the expected therapeutic range); ⑦ Effective contraception during the study period; * Voluntary participation in this study with signed informed consent and good compliance. Exclusion Criteria: * Active bleeding or high risk of bleeding (as assessed by the investigator); * Patients requiring systemic anti-infective therapy; * Concurrent primary malignant tumors other than esophageal cancer (excluding cured basal cell carcinoma of the skin and carcinoma in situ of the cervix); * Presence of brainstem, leptomeningeal metastasis, spinal cord metastasis, or compression; * Complicated with severe cardiovascular diseases, such as uncontrolled heart failure, coronary heart disease, cardiomyopathy, uncontrolled arrhythmia, uncontrolled hypertension, or history of myocardial infarction within the past 5 years; and complicated with other uncontrolled acute or chronic diseases; * Positive for human immunodeficiency virus antibody (HIVAb), active tuberculosis, active hepatitis B virus infection (HBsAg positive and HBV-DNA \> 500 IU/ml or the upper limit of normal, whichever is higher), or active hepatitis C virus infection (HCV antibody positive and HCV-RNA \> lower limit of detection); * Known allergy to any component of any study drug; known history of severe hypersensitivity reactions to other monoclonal antibodies; ⑧ Adverse reactions from prior immunotherapy not fully recovered; * Receiving systemic glucocorticoid therapy (excluding nasal spray, inhalation, or other topical glucocorticoids) or any other form of immunosuppressive therapy within 7 days prior to the first study drug administration; ⑩ Active autoimmune disease requiring systemic treatment (e.g., disease-modifying drugs, glucocorticoids, or immunosuppressants) within 2 years prior to study administration. Replacement therapies (e.g., thyroxine, insulin, or physiologic glucocorticoids for adrenal or pituitary insufficiency, etc.) are not considered systemic treatments; ⑪ Known history of mental illness, substance abuse, alcoholism, or drug addiction; ⑫ Pregnant or breastfeeding women; ⑬ Other conditions deemed unsuitable for participation in this study by the investigator, including but not limited to poor patient compliance, intolerance, etc.