A Phase 1a/1b Study Investigating the Safety, Tolerability, Pharmacokinetics, Pharmacodynamics, and Preliminary Antitumor Activity of BGB-A3055, Alone and in Combination With Tislelizumab in Patients With Selected Advanced or Metastatic Solid Tumors

Inclusion Criteria: 1. Age≥18 years on the day of signing the informed consent form (ICF) (or the legal age of consent in the jurisdiction in which the study is taking place, whichever is older). 2. All participants are also required to demonstrate an ECOG Performance Status score of ≤1 within 3 days before the first dose of study drug(s) and have adequate organ function. 3. Participants with histologically confirmed advanced or metastatic solid tumors associated with high CCR8 and who have previously received adequate available standard systemic therapy or for whom treatment is not available or not tolerated and who have not received any prior therapy targeting CCR8. 4. \>=1 Measurable disease per Response Evaluation Criteria in Solid Tumors (RECIST) v1.1 5. Participants should be able to provide archival tumor tissue samples (as block or unstained slides) or fresh biopsy if there is no archival tissue at baseline. For selected cohorts, participants should be willing to provide post-treatment fresh biopsy at specified timepoints. 6. Females of childbearing potential and nonsterile males must be willing to use a highly effective method of birth control for the duration of the study, and for ≥ 120 days after the last dose of BGB-A3055 or tislelizumab (whichever is later), or up to 9 months after the last dose of chemotherapy, whichever is later. Females of childbearing potential must also have a negative urine or serum pregnancy test result ≤ 7 days before the first dose of study drug(s).

Exclusion Criteria: 1. Active leptomeningeal disease or uncontrolled, untreated brain metastasis. 2. Active autoimmune diseases or history of autoimmune diseases that may relapse 3. Any malignancy ≤ 3 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 (eg, resected basal or squamous cell skin cancer, superficial bladder cancer, or carcinoma in situ of the cervix or breast). 4. Participants with hepatitis B infection with HBV DNA ≥ 500 IU/mL (or ≥ 2500 copies/mL). Participants with active hepatitis C, and participants with HIV infection. Note: Participants with chronic hepatitis B infection or resolved hepatitis B infection (HBV DNA \< 500 IU/mL or \< 2500 copies/mL) and considered stable are eligible. Participants with a negative HCV antibody test result at screening or a positive HCV antibody test result followed by a negative HCV RNA test result at screening are eligible to participate. Participants with treated HIV infection may be included if certain criteria are met. 5. History of interstitial lung disease, noninfectious pneumonitis, or uncontrolled lung diseases including pulmonary fibrosis, or acute lung diseases. 6. Grade 3 immune-mediated adverse events on prior immune-oncology agent. 7. Cardiovascular risk factors, including but not limited to pulmonary embolism ≤ 28 days or history of acute myocardial infarction or heart failure ≤ 6 months before the first dose of study drug(s). 8. Uncontrolled diabetes. NOTE: Other protocol defined Inclusion/Exclusion criteria may apply.