A Study of BG-C477 in Participants With Advanced Solid Tumors

Inclusion Criteria: * Participants must sign the informed consent form (ICF) and be capable of giving written informed consent * Participants must consent to provide an archival tumor tissue sample or a fresh baseline biopsy * Phase 1a (Dose Escalation): Histologically confirmed advanced, metastatic, or unresectable solid tumors, that were previously treated with at least 2 lines of standard systemic therapy or for whom no standard treatment is available in the medical judgment of the investigator * Phase 1b (Dose Expansion) Part A: Histologically confirmed advanced or metastatic select solid tumors that were previously treated with and progressed from at least 1 line of standard systemic therapy * Phase 1b (Dose Expansion) Part B: Histologically confirmed advanced or metastatic select solid tumors who have previously received 0 or 1 line of systemic therapy for advanced disease * ≥ 1 measurable lesion as assessed by RECIST v1.1 * Stable Eastern Cooperative Oncology Group (ECOG) Performance Status of ≤ 1 * Adequate organ function * Female participants of childbearing potential must be willing to use a highly effective method of birth control and refrain from egg donation for the duration of the study and for ≥ 8 months after the last dose of BG-C477, for ≥ 6 months after the last dose of chemotherapy, and for ≥ 4 months after the last dose of tislelizumab,whichever comes later * Nonsterile male participants must be willing to use a highly effective method of birth control and refrain from sperm donation for the duration of the study and for ≥ 5 months after the last dose of BG-C477, for ≥ 3 months after chemotherapy, and for ≥ 4 months after the last dose of tislelizumab, whichever comes later. Exclusion Criteria: * Prior treatment with any carcinoembryonic antigen (CEA)-targeted ADCs or ADCs containing topoisomerase 1 (TOP1) inhibitor as payload * History of severe allergic reactions, severe reaction to infusion, or hypersensitivity to the active ingredient and excipients of the study drug(s) or protein-based therapeutics * Active leptomeningeal disease or uncontrolled, untreated brain metastasis * Any malignancy ≤ 2 years before the first dose of study drug(s) except for the specific cancer under investigation in this study and any locally recurring cancer that has been treated curatively (eg, resected basal or squamous cell skin cancer, superficial bladder cancer, carcinoma in situ of the cervix or breast) Note: Other protocol-defined Inclusion/Exclusion criteria may apply.