Clinical Trial Evaluating TQB6411 Injection in Subjects With Esophageal Cancer

Inclusion Criteria: * Subjects voluntarily participate in this study, sign the informed consent form, and demonstrate good compliance. * Age between 18 and 75 years old (inclusive) * Eastern Cooperative Oncology Group (ECOG) score of 0-1 * Expected survival \>12 weeks * At least one measurable lesion per RECIST v1.1 * Laboratory criteria(no hematopoietic growth factor correction within 7 days)： * Hemoglobin (HGB) ≥90 g/L; * Absolute neutrophil count (NEUT) ≥1.5×10⁹/L; * Platelets (PLT) ≥90×10⁹/L; * Total bilirubin (TBIL) ≤1.5×ULN; * Alanine Aminotransferase (ALT)/Aspartate Aminotransferase (AST) ≤2.5×ULN (≤5×ULN if liver metastases present); * Serum creatinine (CR) ≤1.3×ULNorcreatinine clearance rate (CCR) ≥50 mL/min; * Histologically/cytologically confirmed recurrent or metastatic Esophageal cancer * Failure/intolerance to prior PD-1/PD-L1 inhibitor plus platinum-based chemotherapy for recurrent/metastatic Esophageal Carcinoma (EC) * Willingness to provide archived or fresh tumor tissue for biomarker analysis. * Females of childbearing potential: Negative serum/urine pregnancy test within 7 days before enrollment and agreement to use effective contraception during and for 6 months post-study. Males: Agreement to use effective contraception during and for 6 months post-study. Exclusion Criteria: * Current or History of Other Malignancies * Subjects with any condition that may compromise venous access for drug administration or blood sampling are excluded. * Subjects with prior treatment-related adverse reactions that have not recovered to ≤ Grade 1 per CTCAE v5.0 criteria. * Major surgical procedure or significant traumatic injury within 4 weeks prior to first dose, Scheduled major surgery during the study intervention period, Non-healing wound, ulcer, or bone fracture at screening * Subjects with any bleeding/hemorrhagic event ≥ Grade 3 (per CTCAE v5.0) occurring within 4 weeks before the first dose are excluded * History of Thromboembolic Events within 6 Months * Poorly Controlled Active Viral Hepatitis * Subjects with active syphilis infection requiring antimicrobial therapy are excluded * Subjects with any of the following pulmonary conditions are excluded: active tuberculosis, idiopathic pulmonary fibrosis (IPF), organizing pneumonia, drug-induced/radiation pneumonitis requiring treatment, symptomatic active pneumonia, or history of interstitial lung disease (ILD) requiring therapy * History of Substance Abuse or Psychiatric Disorders * History of Allogeneic Transplantation (Bone Marrow or Solid Organ) * History of Hepatic Encephalopathy * Major Cardiovascular Diseases * Active or Uncontrolled Severe Infections * Renal Failure Requiring Dialysis (Hemodialysis/Peritoneal Dialysis) * History of Immunodeficiency * Poorly Controlled Autoimmune Disease * Poorly Controlled Autoimmune Disease \& Epilepsy Requiring Treatment * Poorly Controlled Diabetes * Tumor-Related Symptoms and Treatment Considerations： * Exclusion Criterion - Recent Anticancer Treatment (≤3 Weeks or Within 5 Half-Lives) * Recent Use of National Medical Products Administration (NMPA) -Approved Anticancer Traditional Chinese Medicine (≤1 Week Prior to Treatment) * Radiologically Confirmed Tumor Encasement of Major Vessels with High Bleeding Risk * Uncontrolled Effusions Requiring Repeated Drainage * Known to have spinal cord compression, leptomeningeal metastasis/carcinomatous meningitis, or symptomatic brain metastases with less than 4 weeks of symptom/imaging control. * Known Hypersensitivity to Investigational Drug or Excipients * Prior Treatment with Topoisomerase I Inhibitor-Based ADCs and/or Irinotecan Chemotherapy * Prior Participation in Anticancer Clinical Trials Within 4 Weeks * Investigator-Assessed Safety or Compliance Concerns