A Study of SI-B003, BL-B01D1+SI-B003 and BL-B01D1+PD-1 Monoclonal Antibody in Patients With Locally Advanced or Metastatic Esophageal Cancer, Gastric Cancer, Colorectal Cancer and Other Gastrointestinal Tumors

Inclusion Criteria: 1. Sign the informed consent form voluntarily and follow the protocol requirements; 2. Gender is not limited; 3. Age: ≥18 years old and ≤75 years old; 4. Expected survival time ≥3 months; 5. Patients with locally advanced or metastatic esophageal cancer, gastric cancer, colorectal cancer and other gastrointestinal tumors; 6. Agreed to provide primary tumors or metastases 2 years archive of tumor tissue samples or fresh tissue samples; 7. At least one measurable lesion meeting the RECIST v1.1 definition was required; 8. ECOG 0 or 1; 9. The toxicity of previous antineoplastic therapy has returned to ≤ grade 1 as defined by NCI-CTCAE v5.0; 10. No severe cardiac dysfunction, left ventricular ejection fraction ≥50%; 11. No blood transfusion, no use of cell growth factors and/or platelet-raising drugs within 14 days before screening, and organ function levels must meet the criteria; 12. Blood coagulation function: international standardization ratio of 1.5 or less, and the part activated clotting time live enzymes ULN 1.5 or less; 13. Urinary protein ≤2+ or ≤1000mg/24h; 14. For premenopausal women with childbearing potential, a pregnancy test must be performed within 7 days before starting treatment, serum or urine must be negative for pregnancy, and must be non-lactating; All enrolled patients (male or female) were advised to use adequate barrier contraception throughout the treatment cycle and for 6 months after the end of treatment. Exclusion Criteria: 1. Antitumor therapy such as chemotherapy or biological therapy was used within 4 weeks or 5 half-lives before the first dose in this study; Mitomycin and nitrosoureas were administered within 6 weeks before the first dose; Oral drugs such as fluorouracil; 2. Cohort using BL-B01D1, previously treated with an ADC drug with topoisomerase I inhibitor as toxin; Immunomodulatory drugs were administered within 2 weeks before the first dose in this study; 3. Systemic corticosteroids were required within 2 weeks before the first dose of the study; 4. Had received immunotherapy and developed grade ≥3 irAE or grade ≥2 immune-related myocarditis according to the CSCO guidelines; 5. History of severe heart disease; 6. QT prolongation, complete left bundle branch block, III degree atrioventricular block; 7. Active autoimmune and inflammatory diseases; 8. Other malignant tumors were diagnosed within 5 years before the first dose in this study; 9. Presence of: a) poorly controlled diabetes mellitus before starting study treatment; b) poorly controlled hypertension; c) history of hypertensive crisis or hypertensive encephalopathy; 10. Pulmonary disease defined as grade ≥3 according to CTCAE v5.0; The patient was diagnosed with grade ≥1 radiation pneumonitis according to the RTOG/EORTC definition. Patients with existing or a history of interstitial lung disease; 11. Unstable thrombotic events requiring therapeutic intervention within 6 months before screening; Infusion-related thrombosis was excluded; 12. Patients with unstable pericardial effusion, pleural effusion, ascites and other serous cavity effusion; 13. Patients with active central nervous system metastasis; 14. Patients with a history of allergy to recombinant humanized antibody or human-mouse chimeric antibody or to any ingredient of BL-B01D1 or SI-B003; 15. Prior organ transplantation or allogeneic hematopoietic stem cell transplantation (Allo-HSCT); 16. Human immunodeficiency virus antibody positive, active tuberculosis, active hepatitis B virus infection or hepatitis C virus infection; 17. Active infections requiring systemic therapy, such as severe pneumonia, bacteremia, sepsis, etc; 18. Enrolled in another clinical trial within 4 weeks before the first dose of this study; 19. Patients who received live vaccine within 4 weeks before the first dose; 20. Patients with a history of mental illness or drug abuse who are unable to cooperate with clinical trial requirements; 21. The investigator did not consider it appropriate to apply other criteria for participation in the trial.