A Study of BGB-B455 in Adults With Advanced or Metastatic Solid Tumors

Inclusion Criteria: * Histologically or cytologically confirmed advanced or metastatic, and unresectable solid tumors who have previously received standard systemic therapy for advanced or metastatic disease or for whom treatment is not available or not tolerated. Only participants with CLDN6+ high-grade OC (ie, ovarian cancer, fallopian tube cancer, or primary peritoneal cancer) will be enrolled in dose escalation cohorts, starting from Protocol Amendment 3.0. * Agreement for collection of formalin-fixed paraffin-embedded (FFPE) tumor tissue for central CLDN6 testing and other biomarker assessments. * Tumor CLDN6 expression (CDLN6+) by central immunohistochemistry testing is required for certain cohorts. * ≥ 1 measurable lesion as assessed by RECIST v1.1. * Stable Eastern Cooperative Oncology Group (ECOG) Performance Status of 0 or 1. * Adequate organ function. Exclusion Criteria: * Prior systemic anticancer therapy, including chemotherapy, immunotherapy (eg, interleukin, interferon, thymosin), targeted therapy, and antibody drug conjugates (ADCs) that are standard or investigational agents (including herbal medicine or Chinese \[or other country\] patent medicines, ≤ 14 days or 5 half-lives (whichever is shorter) before the first dose of study drug(s). * Palliative radiation treatment or other locoregional therapies ≤ 14 days before the first dose of study drug(s). * Live vaccine ≤ 28 days before the first dose of study drug(s). Vaccines for COVID-19 are allowed except for any live vaccine that may become available. Seasonal vaccines for influenza are generally inactivated vaccines and are allowed. Intranasal vaccines are live vaccines and are not allowed. * Any major surgical procedure ≤ 28 days before the first dose of study drug(s). * History of prior ≥ Grade 3 cytokine release syndrome (CRS). * Participants with toxicities (because of prior anticancer therapy) that have not recovered to baseline or stabilized, except for adverse events not considered a likely safety risk (eg, alopecia, neuropathy, and specific laboratory abnormalities). Note: Other protocol defined Inclusion/Exclusion criteria may apply.