This is a multicenter, open-label, single-arm phase I study in patients with advanced solid tumors which consists of a dose escalation part (Part A) and a dose extension part (Part B).

Part A aims to evaluate the safety and tolerability of BA1202, and determine the MTD. Part B will also evaluate the preliminary efficacy of BA1202.

Inclusion Criteria:

• Patients who voluntarily sign an IRB-approved informed consent form, and are willing to abide by the restrictions of the study.
• Part A: Patients with histologically and/or cytologically confirmed advanced and/or metastatic solid tumors who have progressed on Standard-Of-Care (SOC), are intolerant to SOC, or have no SOC.
• Part B: Patients with histologically and/or cytologically confirmed colorectal cancer, non-small cell lung cancer, pancreatic cancer, gastric cancer, who have progressed on Standard-Of-Care (SOC), are intolerant to SOC, or have no SOC.（Specific cohort will be determined after data of dose escalation phase is obtained）
• Part B: High expression of CEACAM5 (defined as ≥ 20% of tumor cells with IHC 2+ and/or 3+).
• Life expectancy of at least 3 months.
• At least one evaluable lesion in Part A and at least one measurable lesion in Part B according to RECIST v1.1.
• ECOG score of < 2.
• Absolute neutrophil count ≥ 1.5 x 10^9/L, platelet count ≥ 100 x 10^9/L, hemoglobin ≥ 90 g/L.
• Total bilirubin ≤ 1.5×ULN, ALT and AST ≤ 2.5×ULN (or ≤ 5.0×ULN for patients with liver metastases).
• Serum creatinine ≤ 1.5×ULN, or creatinine clearance ≥50 mL/min.
• International normalized ratio (INR) prothrombin time (PT) ≤1.5×ULN, activated partial thromboplastin time (APTT) ≤1.5×ULN.
• Blood pregnancy test results were negative for female patients with fertility potential. Patients with fertility potential must agree to use a reliable method of contraception with their sexual partners during the study period and at least 6 months after the last administration.

Exclusion Criteria:

• Other malignancies within 5 years prior to screening (other than cured stage Ib or lower cervical cancer, non-invasive basal cell or squamous cell skin cancer).
• Has a persistent or active infection that requires intravenous treatment.
• History of severe cardiovascular and cerebrovascular disease.
• Patients with autoimmune diseases requiring drug control or at risk of recurrence of autoimmune diseases.
• Received any radiotherapy (other than palliative radiotherapy for bone metastases), chemotherapy, targeted therapy, immunotherapy, cell therapy, or other investigational anticancer agents within 4 weeks prior to first dose of BA1202, unless chemotherapy or targeted therapy is less than 4 weeks after first dose but has eluted ≥5 half-lives.
• Have received any previous CEA targeting therapy, including but not limited to monoclonal antibodies, bisspecific antibodies, antibody-coupled drugs (ADCs), chimeric antigen receptor T cells (CAR-T), etc.
• A history of allergy to BA1202 or any component of Obinutuzumab, or to other monoclonal antibodies.
• Women are planning to become pregnant or are pregnant or breastfeeding.
• Other conditions considered unsuitable for enrollment by the investigator.