1. Provision of signed and dated written informed consent prior to any study
2. Eastern Cooperative Oncology Group (ECOG) Performance Status of 0 to 2
3. Adequate organ function of coagulation function, liver function, renal function and pancreatic function and measure disease per disease-specific response criteria
4. Phase 1: Confirmed diagnosis of R/R Marginal Zone Lymphoma (MZL), Follicular Lymphoma (grade 1-3a), Waldenström Macroglobulinemia (WM), non-germinal center B-cell (non-GCB) diffuse large B-cell lymphoma (DLBCL), Richter's transformation to DLBCL, MCL, or CLL/SLL
5. Phase 2: Confirmed diagnosis of MCL, or CLL/SLL
6. Highly effective method of birth control during study treatment period, and for at least 90 days after the last dose of the study drug
You may not be if
1. Prior malignancy (other than the disease under study) within the past 2 years, except for curatively treated basal or squamous skin cancer, superficial bladder cancer, carcinoma in situ of the cervix or breast, or localized Gleason score ≤ 6 prostate cancer
2. Require ongoing systemic treatment for any other malignancy or systemic corticosteroid treatment
3. Receiving treatment with a strong CYP3A inhibitor or inducer ≤ 14 days before the first dose of BGB-16673, or proton-pump inhibitors ≤ 5 days before the first dose of BGB-16673.
4. Current or history of central nervous involvement
5. Prior autologous stem cell transplant unless ≥ 3 months after transplant, prior chimeric cell therapy unless ≥ 6 months after cell infusion, prior allogeneic stem cell transplant ≤ 6 months before the first dose of the study drug
