An International, Phase 3, Open-Label, Randomized Study of BGB-3111 Compared With Bendamustine Plus Rituximab in Patients With Previously Untreated Chronic Lymphocytic Leukemia or Small Lymphocytic Lymphoma (CLL/SLL)

Experimental: Cohort 1: Bendamustine + Rituximab

Participants will receive bendamustine plus rituximab for up to six 28-day cycles (Arm B)

Experimental: Cohort 1: Zanubrutinib

Participants will receive zanubrutinib until unacceptable toxicity or disease progression (Arm A)

Experimental: Cohort 1a (China only): Bendamustine + Rituximab

Participants will receive bendamustine plus rituximab for up to six 28-day cycles (Arm B, China only)

Experimental: Cohort 1a (China only): Zanubrutinib

Participants will receive zanubrutinib until unacceptable toxicity or disease progression (Arm A, China only)

Experimental: Cohort 2: Zanubrutinib

Participants will receive zanubrutinib until unacceptable toxicity or disease progression (Arm C)

Experimental: Cohort 3: Venetoclax + Zanubrutinib

Approximately 110 participants, 50 without del17p and 60 with del\[17p\] or TP53 mutation will receive zanubrutinib plus venetoclax; Participants will also receive zanubrutinib starting on Cycle 1 Day 1 then daily for a minimum of 27 cycles, or until unacceptable toxicity or disease progression, whichever occurs first. Participants will receive venetoclax starting Cycle 4 Day 1 according to a 5-week dose-up schedule then daily until unacceptable toxicity, disease progression, or for a maximum of 24 cycles. Each cycle is 28 days. (Arm D)