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

Inclusion Criteria:

• Histologically or cytologically confirmed advanced or metastatic, and unresectablesolid tumors who have previously received standard systemic therapy for advanced ormetastatic disease or for whom treatment is not available or not tolerated.

• Agreement for collection of formalin-fixed paraffin-embedded (FFPE) tumor tissue forcentral CLDN6 testing and other biomarker assessments.

• Tumor CLDN6 expression (CDLN6+) by central immunohistochemistry testing is requiredfor Phase 1a dose escalation Cohort 5 and higher.

• ≥ 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 orChinese [or other country] patent medicines, ≤ 14 days or 5 half-lives (whichever isshorter) before the first dose of study drug(s).

• Palliative radiation treatment or other locoregional therapies ≤ 14 days before thefirst dose of study drug(s).

• Live vaccine ≤ 28 days before the first dose of study drug(s). Vaccines for COVID-19are allowed except for any live vaccine that may become available. Seasonal vaccinesfor influenza are generally inactivated vaccines and are allowed. Intranasalvaccines 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 notrecovered to baseline or stabilized, except for adverse events not considered alikely safety risk (eg, alopecia, neuropathy, and specific laboratoryabnormalities).

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