A Phase 1a/1b Study to Investigate the Safety, Tolerability, Pharmacokinetics, Pharmacodynamics, and Preliminary Antitumor Activity of BGB-53038, a Pan-KRAS Inhibitor, as Monotherapy or in Combinations in Patients With Advanced or Metastatic Solid Tumors With KRAS Mutations or Amplifications

1. Must sign a written ICF; and understand and agree to comply with the requirements of the study and the schedule of activities.
2. Eastern Cooperative Oncology Group (ECOG) Performance Status ≤ 1.
3. Participants must have evidence of a KRAS mutation or wild-type amplification (copy number ≥ 8) based on testing of either tumor tissue or liquid biopsy (blood or plasma) as determined by local laboratory
4. Able to provide an archived tumor tissue sample or fresh biopsy sample.
5. ≥ 1 measurable lesion per RECIST v1.1.
6. Adequate organ function.
7. Females of childbearing potential must be willing to use a highly effective method of birth control for the duration of the study, for > 7 days after the last dose of BGB-53038, > 120 days after the last dose of tislelizumab, or > 2 months after the last dose of cetuximab, whichever is later
8. Nonsterile males must be willing to use a highly effective method of birth control for the duration of the study treatment period and for ≥ 4 months after the last dose of study drug(s).

1. Participants with tumors harboring KRAS G12R mutation.
2. Participants who have prior therapy with other anti-RAS treatment, including, but not limited to, therapy targeting specific KRAS allele mutation inhibitors, pan-KRAS inhibitors, and other pan-RAS inhibitors
3. Participants with active leptomeningeal disease or uncontrolled, untreated brain metastasis. Participants with a history of treated and, at the time of screening, stable CNS metastases are eligible, provided they meet select criteria.
4. Any malignancy ≤ 2 years before the first dose of study treatment(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).
5. Participants with untreated chronic hepatitis B or chronic HBV carriers with HBV DNA ≥ 500 IU/mL (or ≥ 2500 copies/mL) at screening. Participants with active hepatitis C.
6. Participants with clinically significant infections (including tuberculosis infection) requiring systemic (oral or intravenous) antibacterial, antifungal, or antiviral therapy ≤ 14 days before the first dose of study treatment.

Note: Other protocol defined Inclusion/Exclusion criteria may apply.