A Study of SI-B036 in Patients With Locally Advanced or Metastatic Breast Cancer and Other Solid Tumors

This study is an open-label, multicenter, dose-escalation and expansion, non-randomized Phase I clinical study evaluating the safety, tolerability, pharmacokinetic characteristics and preliminary efficacy of SI-B036 bispecific antibody injection in patients with locally advanced or metastatic breast cancer and other solid tumors.

Inclusion Criteria: 1. Voluntarily sign the informed consent form and comply with the protocol requirements; 2. No gender restriction; 3. Age: ≥18 years and ≤75 years; 4. Expected survival time ≥3 months; 5. Locally advanced or metastatic breast cancer and other solid tumors; 6. Agree to provide archived tumor tissue specimens from the primary or metastatic site within 2 years, or fresh tissue samples; 7. Must have at least one measurable lesion as defined by RECIST v1.1; 8. Eastern Cooperative Oncology Group (ECOG) performance status score of 0 or 1; 9. Toxicity from prior antitumor therapy must have recovered to ≤ Grade 1 as defined by NCI-CTCAE v6.0; 10. No severe cardiac dysfunction, with left ventricular ejection fraction ≥50%; 11. Organ function levels must meet the required criteria; 12. Coagulation function: international normalized ratio ≤1.5, and activated partial thromboplastin time ≤1.5 × upper limit of normal; 13. Urine protein ≤1+ or ≤1000 mg/24 h; 14. For premenopausal women of childbearing potential, a pregnancy test must be performed within 7 days before starting treatment, with a negative serum pregnancy result, and they must be non-lactating; all enrolled patients (both males and females) must adopt adequate barrier contraceptive measures throughout the entire treatment period and for 6 months after treatment completion; 15. The trial participant must be able and willing to comply with the protocol-specified visits, treatment plan, laboratory tests, and other study-related procedures. Exclusion Criteria: 1. Use of chemotherapy, biotherapy, immunotherapy, or similar treatments within 4 weeks or 5 half-lives prior to the first dose; 2. Receipt of immunosuppressive drug therapy within 2 weeks prior to the first dose; 3. History of severe cardiac or cerebrovascular disease; 4. Prolonged QTc interval, complete left bundle branch block, third-degree atrioventricular block, or frequent and uncontrolled arrhythmias; 5. Active autoimmune diseases and inflammatory diseases; 6. Prior experience of ≥ Grade 3 toxicity related to anti-angiogenic therapy during previous anti-angiogenic treatment; 7. Diagnosis of another solid tumor within 5 years prior to the first dose; 8. Unstable thrombotic events requiring therapeutic intervention within 6 months prior to the first dose; 9. Poorly controlled hypertension; 10. Diabetes mellitus with poor glycemic control; 11. History of interstitial lung disease (ILD) requiring steroid therapy, or current ILD, or ≥ Grade 2 radiation pneumonitis; 12. Concurrent pulmonary disease resulting in severe impairment of respiratory function; 13. Active central nervous system metastases; 14. History of allergy to recombinant humanized antibodies or human-mouse chimeric antibodies, or allergy to any excipient component of SI-B036; 15. Prior organ transplantation or allogeneic hematopoietic stem cell transplantation; 16. Positive for human immunodeficiency virus antibodies, active tuberculosis, active hepatitis B virus infection, or active hepatitis C virus infection; 17. Active infection requiring systemic therapy within 4 weeks prior to the first dose of the study drug; 18. Presence of pleural, abdominal, or pelvic effusion, or pericardial effusion requiring drainage and/or accompanied by symptoms within 4 weeks prior to the first dose of the study drug; 19. Imaging findings suggesting tumor invasion or encasement of major thoracic blood vessels, pericardium, or heart; 20. Trial participants with clinically significant bleeding or obvious bleeding tendency within 4 weeks prior to screening; 21. History of fistula, gastrointestinal perforation, or intra-abdominal abscess within 6 months prior to the first dose; 22. Use of another investigational drug within 4 weeks or 5 half-lives prior to the first dose; 23. Pregnant or breastfeeding women; 24. Other conditions deemed by the investigator to make the participant unsuitable for participation in this clinical trial.