A Dose-Escalation and Expansion Study of BGB-16673 in Participants With B-Cell Malignancies

Open to people ages 18 years and up

:

1. Confirmed diagnosis (per World Health Organization (WHO) guidelines, unless otherwise noted) of one of the following: Marginal Zone Lymphoma (MZL) (Part 1a 1b, and 1c only), Follicular Lymphoma (FL) (Part 1a and 1c only), R/R MCL (parts 1a, 1b, and 2 only), R/R CLL/SLL (Parts 1a, 1b, and 2), WM (Part 1a and 1c only), DLBCL (Part 1a and 1c only), or >2 treatments per the Richter's transformation to DLBCL (Part 1a and 1c only). 2. Participants who have previously received a covalently-binding BTK inhibitor in any line of therapy must have received treatment with the BTK inhibitor for ≥ 8 weeks (unless reason for discontinuation is intolerance). 3. For dose-finding and dose-expansion, participants who had previously received a covalently-binding BTK inhibitor as monotherapy or in combination with other anticancer agents are eligible for the study if they meet any of the following criteria: discontinued the previous BTK inhibitor due to disease progression, experienced disease progression after completing treatment with a BTK inhibitor or discontinued the BTK inhibitor due to toxicity or intolerance. 4. Measurable disease by radiographic assessment or serum IgM level (WM only) 5. Eastern Cooperative Oncology Group (ECOG) Performance Status of 0 to 2 6. participants enrolling in the dose finding phase of the study may be previously treated with a BTKi or may be naïve to BTKi therapy depending on the diagnosis and country of enrollment; participants with CLL/SLL or MCL enrolling in the expansion cohorts (Part 2) must have been treated with a BTKi in a prior line of therapy.

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. Requires ongoing systemic treatment for any other malignancy
3. Requires ongoing systemic (defined as ≥ 10 mg/day of prednisone or equivalent) corticosteroid treatment.
4. Current or history of central nervous system involvement including the brain, spinal cord, leptomeninges, and cerebrospinal fluid (as documented by imaging, cytology, or biopsy) by B-cell malignancy, regardless of whether participants had received treatment for central nervous system disease

5. Known active plasma cell neoplasm, prolymphocytic leukemia, T-cell lymphoma, Burkitt lymphoma, acquired immunodeficiency syndrome (AIDS)-related B-cell lymphoma, Castleman disease, post-transplant lymphoproliferative disorders, hairy cell leukemia, GCB DLBCL, EBV+ DLBCL NOS, primary DLBCL of the central nervous system (CNS), primary cutaneous DLBCL - leg type, DLBCL associated with chronic inflammation, primary mediastinal (thymic) large B-cell lymphoma, intravascular large B-cell lymphoma, ALK+ large B-cell lymphoma, primary effusion lymphoma, high-grade B-cell lymphoma with MYC and BCL2 and/or BCL6 rearrangements, high-grade B-cell lymphoma - NOS, B-cell lymphoma unclassifiable with features intermediate between DLBCL and classical Hodgkin lymphoma, or history of or currently suspected Richter's transformation of an indolent lymphoma to an aggressive histology (only participants with Richter Transformation to DLBCL are eligible for Part 1a and 1c).

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