A Study to Investigate the Antitumor Activity, Safety, Tolerability, and Pharmacokinetics of BGB-A445 in Combination With Tislelizumab in Participants With Select Advanced Solid Tumors.

Key Inclusion Criteria:

• Participants who were histologically or cytologically confirmed advanced and/or metastatic cancer. UC participants (Cohort A and B), RCC patients (Cohort C and D) or melanoma participants (Cohort E and F) who have received at least 1 but no more than 3 lines of prior systemic therapy. Cisplatin ineligible UC participants (Cohort G) who have received no prior systemic therapy and have PD-L1 CPS ≥ 10. Melanoma patients (Cohort H) with non-mucosal melanoma who have no previous systemic treatment. Melanoma participants (Cohort I) with non-mucosal melanoma who were CPI pretreated and have 1 or 2 lines of prior systemic therapy. Participants must not have received prior therapy targeting OX40 or any other T-cell agonists.
• Has at least 1 measurable lesion as defined per RECIST v1.1.
• Participants must be able to provide an archived formalin-fixed paraffin embedded (FFPE) tumor tissue sample
• ECOG PS ≤ 1 (Participants with UC could have an ECOG PS ≤ 2) and a life expectancy of≥ 3 months
• Adequate organ function as indicated by the laboratory values up to the first dose of study drug(s)

Key Exclusion Criteria:

• Active leptomeningeal disease or uncontrolled brain metastasis
• Active autoimmune diseases or history of autoimmune diseases that may relapse or history of life-threatening toxicity related to prior immune therapy
• Any active 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 with curative intent
• Any condition that required systemic treatment with either corticosteroids (> 10 mg daily of prednisone or equivalent) or other immunosuppressive medication ≤ 14 days before the first dose of study drug(s), with the following exceptions:

• Adrenal replacement steroid (dose ≤ 10 mg daily of prednisone or equivalent)
• Topical, ocular, intra-articular, intranasal, or inhalational corticosteroid with minimal systemic absorption
• Short course (≤ 7 days) of corticosteroid prescribed prophylactically (eg, for contrast dye allergy) or for the treatment of a nonautoimmune condition (eg, delayed-type hypersensitivity reaction caused by contact allergen)
• With uncontrolled diabetes, or > Grade 1 laboratory test abnormalities in potassium, sodium, or corrected calcium despite standard medical management, or ≥ Grade 3 hypoalbuminemia occurring ≤ 14 days before the first dose of study drug(s)

Note: Other protocol defined Inclusion/Exclusion criteria may apply