A First-in-Human (FIH) Study of BG-C137, an Anti-Fibroblast Growth Factor Receptor 2b (FGFR2b) Antibody Drug Conjugate, in Participants With Advanced Solid Tumors

Inclusion Criteria:

1. Histologically or cytologically confirmed advanced or metastatic solid tumors.

2. Life expectancy of ≥ 3 months.

3. Prior standard systemic therapy in the advanced or metastatic setting. DoseEscalation: Participants for whom further standard treatment is not available, nottolerated or determined not appropriate based on the investigator's judgment. ComboDose Confirmation, Combo Safety Expansion, and Dose Expansion: Participants who havereceived at least 1 or 2 prior lines of systemic therapy, which included afluoropyrimidine and/or a platinum in the advanced or metastatic setting

4. Tumors with FGFR2b expression/ or FGFR2 gene amplification. Participants mustprovide agreement for collection of archival tissue or recently obtained fresh tumorbiopsy for central evaluation of FGFR2b expression levels and other biomarkerassessments.

5. ≥ 1 measurable lesion per RECIST v1.1.

6. Eastern Cooperative Oncology Group (ECOG) Performance Status of 0 or 1.

7. Adequate organ function as determined per protocol.

Exclusion Criteria:

1. Prior exposure to topoisomerase I inhibitor (TOP1i)-based antibody-drug conjugate (ADC) therapies or FGFR2b-targeted ADC therapies.

2. Active or chronic corneal disorder, history of corneal transplantation, cornealkeratitis, keratoconjunctivitis, keratopathy, corneal abrasion, inflammation orulceration, other active ocular conditions and any clinically significant cornealdisease that prevents adequate monitoring of drug-induced keratopathy.

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

4. Systemic antitumor therapy (including targeted therapy and immunotherapy ≤ 14 days, ≤ 28 days for immuno- oncological antibody, ≤ 14 days or 5 half-lives [whichever isshorter] for chemotherapy, ADCs, or investigational therapy) before first dose ofstudy drug(s).

5. Toxicities due to prior therapy that have not recovered.

6. Any malignancy ≤ 2 years before first dose of study drug(s) except for the specificcancer under investigation in this study and any locally recurring cancer that hasbeen treated curatively.

7. History of interstitial lung disease (ILD), noninfectious pneumonitis, oxygensaturation at rest < 92%, or requirement for supplemental oxygen at baseline.

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