A Study Investigating BGB-26808 Alone or in Combination With Tislelizumab in Participants With Advanced Solid Tumors

Able to provide a signed and dated written informed consent prior to any study-specific procedures, sampling, or data collection.

Eastern Cooperative Oncology Group (ECOG) Performance Status ≤ 1.

Phase 1a: Participants with histologically or cytologically confirmed advanced, metastatic, and unresectable solid tumors that are immune-sensitive who have previously received standard systemic therapy, or for whom treatment is not available or not tolerated, or for whom treatment is determined not appropriate based on investigator's judgment and who have not received prior therapy targeting hematopoietic progenitor kinase 1 (HPK1).

Phase 1b: Participants with histologically confirmed locally advanced unresectable or metastatic tumor types and who have not had prior systemic treatment. Participants who received prior systemic therapy in a neo-adjuvant or adjuvant setting with curative intent for nonmetastatic disease must have experienced a disease-free interval of ≥ 6 months from the last dose of systemic therapy prior to the first dose of study treatments.