Study of BG-T187 Alone and in Combination With Other Therapeutic Agents in Participants With Advanced Solid Tumors

Inclusion Criteria:

1. Able to provide a signed and dated written informed consent prior to anystudy-specific procedures, sampling, or data collection.

2. Patients must be ≥ 18 years of age or the legal age of consent in the jurisdictionin which the study is taking place.

3. Eastern Cooperative Oncology Group (ECOG) Performance Status ≤ 1.

4. Participants with selected histologically or cytologically confirmed advanced,metastatic, and unresectable solid tumors who have been previously treated.

5. ≥ 1 measurable or nonmeasurable lesion as assessed by RECIST v1.1. for Phase 1a PartA; ≥ 1 measurable lesion per RECIST v1.1. for Phase 1a Part B and Phase 1b.

6. Adequate organ function.

Exclusion Criteria:

1. Prior severe allergic reactions or hypersensitivity to the active ingredient andexcipients of BG-T187 or other monoclonal antibodies.

2. Spinal cord compression, active leptomeningeal disease, or uncontrolled, untreatedbrain metastasis.

3. Any malignancy ≤ 3 years before the first dose of study drug(s) except for thespecific cancer under investigation in this study and any locally recurring cancerthat has been treated with curative intent (eg, resected basal or squamous cell skincancer, superficial bladder cancer, or carcinoma in situ of the cervix or breast).

4. History of ILD or noninfectious pneumonitis requiring steroids or other immunesuppressive agents ≤ 2 years before the first dose of the study drug, or withcurrent ILD/noninfectious pneumonitis, or where suspected ILD/noninfectiouspneumonitis cannot be ruled out by imaging during screening.

5. Uncontrollable pleural effusion, pericardial effusion, or ascites requiring frequentdrainage (recurrence ≤14 days after intervention).

6. Active hepatitis C.

7. Infection (including tuberculosis infection, or other) requiring systemic (oral orintravenous) antibacterial, antifungal, or antiviral therapy ≤ 14 days before thefirst dose of study drug(s).

Note: Other protocol defined Inclusion/Exclusion criteria may apply.