A Study of Lutetium [177Lu] BL-ARC001 in Patients With Locally Advanced or Metastatic Gastrointestinal Tumors and Other Solid Tumors

Inclusion Criteria: 1. Voluntarily sign the informed consent form and comply with the protocol requirements; 2. Gender: no restriction; 3. Age: ≥18 years and ≤75 years (Phase Ia); ≥18 years (Phase Ib); 4. Expected survival time ≥3 months; 5. Locally advanced or metastatic solid tumors; 6. Agree to provide archived tumor tissue specimens or fresh tissue samples from primary or metastatic lesions within the past 3 years; 7. Must have at least one measurable lesion meeting the RECIST v1.1 criteria; 8. ECOG performance status score of 0 or 1; 9. Toxicities from prior antitumor therapy have recovered to ≤ Grade 1 as defined by NCI-CTCAE v5.0; 10. No severe cardiac dysfunction, left ventricular ejection fraction ≥50%; 11. Organ function levels must meet the requirements; 12. Coagulation function: international normalized ratio ≤1.5, and activated partial thromboplastin time ≤1.5 × ULN; 13. Urine 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 pregnancy must be negative, and must not be breastfeeding; all enrolled patients (regardless of gender) should use adequate barrier contraception throughout the treatment cycle and for 6 months after treatment ends. Exclusion Criteria: 1. Use of chemotherapy, biotherapy, or immunotherapy within 4 weeks or 5 half-lives (whichever is shorter) prior to the first dose; 2. History of severe heart disease; 3. QT interval prolongation, complete left bundle branch block, or third-degree atrioventricular block; 4. Active autoimmune or inflammatory diseases; 5. Diagnosis of other malignancies within 5 years prior to the first dose; 6. Hypertension poorly controlled by two antihypertensive medications; 7. History of interstitial lung disease (ILD) requiring steroid treatment, current ILD, or ≥ Grade 2 radiation pneumonitis; 8. Symptoms of active central nervous system metastases; 9. History of allergy to recombinant humanized or chimeric antibodies, or allergy to any excipient of Lutetium \[177Lu\] BL-ARC001; 10. Previous organ transplantation or allogeneic hematopoietic stem cell transplantation; 11. Cumulative dose of anthracyclines \> 360 mg/m² in previous (neo)adjuvant anthracycline therapy; 12. Positive human immunodeficiency virus antibody, active tuberculosis, active hepatitis B virus infection, or active hepatitis C virus infection; 13. Active infection requiring systemic treatment; 14. Participation in another clinical trial within 4 weeks prior to the first dose; 15. Pregnant or lactating women; 16. Any other condition deemed by the investigator as unsuitable for participation in this clinical trial.