Adverse events

Participants received bendamustine at a dose of 70 mg/m\^2 via IV infusion on Days 1 and 2 of each 28-day cycle for 6 cycles, in combination with rituximab at a dose of 375 mg/m\^2 via IV infusion on Day 1 of Cycle 1 and at a dose of 500 mg/m\^2 on Day 1 of Cycles 2-6.

Participants were initially placed on a venetoclax ramp-up period of 5 weeks, and received an initial dose of 20 mg via tablet orally QD for initial 1 to 7 days, then venetoclax dose was incremented weekly up to a maximum dose of 400 mg via tablet orally QD. Participants continued receiving venetoclax at a dose of 400 mg via tablet orally QD from Week 6 (Day 1 of Cycle 1 of combination therapy) onwards up to PD or 2 years, whichever occurred first, as directed by the investigator, in combination with rituximab at a dose of 375 mg/m\^2 via IV infusion on Day 1 of Cycle 1 and at a dose of 500 mg/m\^2 on Day 1 of Cycles 2-6.

Participants who entered the crossover substudy had a 5-week venetoclax dose ramp-up period to reach the target dose of 400 mg QD. Following the venetoclax ramp-up period, participants received 6 cycles of rituximab, 375 mg/m\^2, as IV infusion on the Day 1 of each 28-day cycle. Participants who did not progress following the completion of the 6 cycles continued to receive venetoclax monotherapy until disease progression or for a maximum of 2 years from Cycle 1 crossover Day 1 of the substudy.

Participants who entered the re-treatment substudy had a 5-week venetoclax dose ramp-up period to reach the target dose of 400 mg QD. Following the venetoclax ramp-up period, participants received 6 cycles of rituximab consisting of a single infusion on the first day of each 28-day cycle. Participants who did not progress following the completion of the 6 cycles continued to receive venetoclax monotherapy until disease progression or for a maximum of 2 year from Cycle 1 re-treatment Day 1 of the substudy.