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:

1. 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.
2. Has at least 1 measurable lesion as defined per RECIST v1.1.
3. Participants must be able to provide an archived formalin-fixed paraffin embedded (FFPE) tumor tissue sample
4. ECOG PS ≤ 1 (Participants with UC could have an ECOG PS ≤ 2) and a life expectancy of≥ 3 months
5. Adequate organ function as indicated by the laboratory values up to the first dose of study drug(s)

Key Exclusion Criteria:

1. Active leptomeningeal disease or uncontrolled brain metastasis
2. Active autoimmune diseases or history of autoimmune diseases that may relapse or history of life-threatening toxicity related to prior immune therapy
3. 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
4. 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:

   1. Adrenal replacement steroid (dose ≤ 10 mg daily of prednisone or equivalent)
   2. Topical, ocular, intra-articular, intranasal, or inhalational corticosteroid with minimal systemic absorption
   3. 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)
5. 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