A Phase 1/1b Open-Label Dose-Escalation Study of Bcl-2 Inhibitor BGB-21447 in Patients with Mature B-Cell Malignancies

Inclusion Criteria 1. Confirmed diagnosis (per World Health Organization \[WHO\] guidelines, unless otherwise noted) of one of the following: Cohort A1 and Cohort A2: 1. R/R DLBCL (for Cohort A1 and Cohort A2.1)
*  High-grade B-cell lymphomas with translocations of MYC and Bcl-2 and/or Bcl-6 are not allowed in Cohort A1 but may be allowed in Cohort A2.1 2. R/R FL (for Cohort A1 and Cohort A2.2) 3. R/R MZL (for Cohort A1 and Cohort A2.2) 4. Transformed B-cell NHL (for Cohort A1 only) 5. Richter's transformation to DLBCL (for Cohort A1 only) 2. Measurable disease by computed tomography/magnetic resonance imaging.

Exclusion Criteria: 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 or lentigo maligna melanoma that has been curatively resected 2. Known central nervous system involvement by lymphoma/leukemia 3. Prior autologous stem cell transplant \< 3 months before the first dose of study drug. Or prior chimeric antigen receptor T-cell (CAR-T) therapy \< 3 months before the first dose of study drug 4. Prior allogeneic stem cell transplant. 5. Major surgery \< 4 weeks before the first dose of study treatment NOTE: Other protocol-defined Inclusion/Exclusion criteria may apply.