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

This study is testing several drug combinations — including SI-B003 (an anti-PD-L1 antibody), BL-B01D1 (an antibody-drug conjugate), and a PD-1 antibody — in patients with advanced or metastatic cancers of the esophagus, stomach, colon/rectum, or other gastrointestinal tumors. **You may be eligible if:** - You are between 18 and 75 years old - You have locally advanced or metastatic esophageal, gastric, colorectal, or other gastrointestinal cancer - You have at least one measurable tumor on imaging - You are in good health (ECOG 0–1) - Your organ function (heart, blood, kidneys, liver) meets the required levels **You may NOT be eligible if:** - You received cancer treatment within the past 4 weeks (or 6 weeks for certain drugs) - You require ongoing steroids or immune-suppressing medications - You are pregnant or nursing - You previously received an antibody-drug conjugate with topoisomerase I inhibitor as the toxin (for certain cohorts) Talk to your doctor to see if this trial is right for you.