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

Inclusion Criteria :

1. Confirmed diagnosis (per World Health Organization (WHO) guidelines, unlessotherwise noted) of one of the following: Marginal Zone Lymphoma (MZL), R/Rfollicular lymphoma (FL), mantle cell lymphoma (MCL), chronic lymphocytic leukemiaand small lymphocytic lymphoma (CLL/SLL), Waldenström macroglobulinemia (WM), R/Rdiffuse large B-cell lymphoma (DLBCL), or Richter's transformation to DLBCL.

2. Participants who have previously received a covalently-binding Bruton´s tyrosinekinase (BTK) inhibitor (BTKi) in any line of therapy must have received treatmentwith the BTK inhibitor for ≥ 8 weeks (unless reason for discontinuation isintolerance).

3. For dose-finding and dose-expansion, participants who had previously received acovalently-binding BTK inhibitor as monotherapy or in combination with otheranticancer agents are eligible for the study if they meet any of the followingcriteria: discontinued the previous BTK inhibitor due to disease progression,experienced disease progression after completing treatment with a BTK inhibitor ordiscontinued 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 previouslytreated with a BTKi or may be naïve to BTKi therapy depending on the diagnosis andcountry of enrollment; participants with MCL enrolling in the expansion cohorts (Phase 2) must have been treated with a BTKi in a prior line of therapy; CLL/SLLparticipants, in addition to being treated with a BTKi in a prior line of therapy,must also have received a Bcl-2 inhibitor in a prior line of therapy as well (Phase 2).

Exclusion Criteria:

1. Prior malignancy (other than the disease under study) within the past 2 years,except in situ malignancies that have been curatively resected, localized breastcancer treated with curative intent with no evidence of breast active disease formore than 3 years and receiving adjuvant hormonal therapy, localized Gleason score ≤ 6 prostate cancer undergoing observation or treatment with androgen depravation, orany other cancer treated with curative intent, not on adjuvant treatment, and in theopinion of the investigator is unlikely to recur.

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, spinalcord, leptomeninges, and cerebrospinal fluid (as documented by imaging, cytology, orbiopsy) by B-cell malignancy, regardless of whether participants had receivedtreatment for central nervous system disease

5. Known active plasma cell neoplasm, prolymphocytic leukemia, T-cell lymphoma, Burkittlymphoma, acquired immunodeficiency syndrome (AIDS)-related B-cell lymphoma,Castleman disease, post-transplant lymphoproliferative disorders, hairy cellleukemia, germinal center B-cell (GCB), DLBCL, EBV+ DLBCL NOS, primary DLBCL of thecentral nervous system (CNS), primary cutaneous DLBCL - leg type, DLBCL associatedwith chronic inflammation, primary mediastinal (thymic) large B-cell lymphoma,intravascular large B-cell lymphoma, ALK+ large B-cell lymphoma, primary effusionlymphoma, high-grade B-cell lymphoma with MYC and BCL2 and/or BCL6 rearrangements,high-grade B-cell lymphoma - NOS, B-cell lymphoma unclassifiable with featuresintermediate between DLBCL and classical Hodgkin lymphoma, or history of orcurrently suspected transformation of an indolent lymphoma to an aggressivehistology (except for participants with Richter Transformation to DLBCL are eligiblefor Part 1a, 1c, or Phase 2 and participants with history of follicular lymphomatransforming to non-GCB DLBCL who are eligible for Part 1a, 1c, or Phase 2).

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