This Phase I trial is trying to understand how safe and tolerable a targeted therapy (BGB-15025) alone and in combination with another targeted therapy (tislelizumab) in people with advanced solid cancersA Phase 1 Study Investigating the Safety, Tolerability, Pharmacokinetics, and Preliminary Antitumor Activity of HPK1 Inhibitor BGB-15025 Alone and in Combination With Anti-PD-1 Monoclonal Antibody Tislelizumab in Patients With Advanced Solid Tumors

Inclusion

1. Phase 1a (dose escalation): Participants with histologically or cytologically confirmed advanced, metastatic, and unresectable solid tumors who have previously received standard systemic therapy or for whom treatment is not available, not tolerated or refused, and who have not received prior therapy targeting HPK1
2. Phase 1b (dose expansion): Participant with histologically or cytologically confirmed advanced, metastatic, and unresectable solid tumors, including non-small cell lung cancer, esophageal cancer or gastric/Gastroesophageal junction cancer (other solid tumors may be included) who have progressed following systemic anticancer therapies or have no prior systemic treatment for advanced disease
3. At least 1 measurable lesion as defined per RECIST 1.1.
4. Eastern Cooperative Oncology Group (ECOG) Performance Status ≤ 1
5. Adequate organ function as indicated by the following laboratory values up to first dose of study treatment: Hemoglobin≥ 90 g/L, Absolute neutrophil count ≥ 1.5 x 109/L , Serum total bilirubin ≤ 1.5 x ULN (< 3 x ULN for participants with Gilbert syndrome ), AST and ALT≤ 2.5 x ULN