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

The study consists of two phases: a dose-escalation phase (Phase Ia) and an expansion phase (Phase Ib).

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 solid tumors;
6. Agree to provide archived tumor tissue specimens from primary or metastatic lesions within 2 years or fresh tissue samples;
7. Must have at least one measurable lesion as defined by RECIST v1.1;
8. ECOG performance status score of 0 or 1;
9. Toxicity from prior anti-tumor therapy has recovered to ≤ Grade 1 as defined by NCI-CTCAE v6.0;
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 ≤1000 mg/24h;
14. For premenopausal women of childbearing potential, a pregnancy test must be performed within 7 days before starting treatment, serum pregnancy must be negative, and they must be non-lactating; all enrolled patients (regardless of male or female) must adopt adequate barrier contraceptive measures throughout the entire treatment period and for 6 months after treatment completion;
15. The trial participant is capable and willing to adhere to the visit schedule, treatment plan, laboratory tests, and other study-related procedures specified in the protocol.

Exclusion Criteria:

1. Use of chemotherapy, biological therapy, immunotherapy, etc. within 4 weeks or 5 half-lives prior to the first dose;
2. Receipt of immunosuppressive therapy within 2 weeks prior to the first dose;
3. History of severe cardiac or cerebrovascular disease;
4. QT interval prolongation, complete left bundle branch block, etc.;
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 event requiring therapeutic intervention within 6 months prior to the first dose;
9. Poorly controlled hypertension;
10. Diabetic patients with poorly controlled blood glucose;
11. History of ILD requiring steroid therapy, or current ILD, or ≥ grade 2 radiation pneumonitis;
12. Concomitant pulmonary disease causing severe respiratory impairment;
13. Active central nervous system metastases;
14. History of allergy to recombinant humanized or human-mouse chimeric antibodies, or hypersensitivity to any excipient component of SI-B036;
15. Prior organ transplantation or allogeneic hematopoietic stem cell transplantation;
16. Positive for human immunodeficiency virus antibody, 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 study drug;
18. Presence of pleural, abdominal, or pericardial effusion requiring drainage and/or accompanied by symptoms within 4 weeks prior to the first dose of study drug;
19. Imaging findings indicating tumor invasion or encasement of major thoracic blood vessels, pericardium, or heart;
20. Study participants with clinically significant bleeding or a clear 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 enrollment in this clinical trial.