A Study to Evaluate the Effect of Venetoclax on Participants Receiving a Covalent Bruton's Tyrosine Kinase Inhibitor (cBTKi) for First-line Chronic Lymphocytic Leukemia (1L CLL) to Achieve Deep Durable Remissions to Allow Off-treatment Period

CR/CRi Rate at EOCT as Determined by the Investigator According to International Workshop on Chronic Lymphocytic Leukemia (iwCLL) Guidelines

Complete response (CR)/complete response with incomplete recovery of the bone marrow (CRi) rate is defined as the percentage of participants with a CR or CRi at EOCT, as determined by the investigator according to the iwCLL.

Time frame: Up to approximately 12 months

PR Rate at EOCT as Determined by the Investigator According to iwCLL Guidelines

PR rate is defined as the percentage of participants with a PR at EOCT, as determined by the investigator according to the iwCLL.

Time frame: Up to approximately 12 months

Overall Response Rate (ORR) at EOCT as Determined by the Investigator According to iwCLL Guidelines

ORR is defined as the percentage of participants with a CR/CRi or PR at EOCT, as determined by the investigator according to the iwCLL.

Time frame: Up to approximately 12 months

Number of Participants With Adverse Events (AEs) and Serious Adverse Events (SAEs)

AE and SAEs will be collected as part of this study at baseline and every clinical visit, until 30 days after the final dose of study treatment.

Time frame: Up to approximately 13 months

Number of Participants Who Withdrew Prematurely from the Study

Participants who discontinued treatment before Cycle 12 Day 28 (cycle length= 28 days).

Time frame: Up to approximately 12 months

Overall Survival (OS)

OS is defined as the time from the first study treatment to death from any cause.

Time frame: Up to approximately 48 months

Progression-free Survival (PFS) as Determined by the Investigator According to iwCLL Guidelines

PFS is defined as the time from the first study treatment to the first occurrence of disease progression (PD) or death from any cause during study, whichever occurs first, as determined by the investigator according to the iwCLL.

Time frame: Up to approximately 48 months

Event-free Survival (EFS) as Determined by the Investigator According to iwCLL Guidelines

EFS is defined as the time from the first study treatment to the first occurrence of PD, anti-leukemic treatment subsequent to the study treatment, or death from any cause during study, whichever occurs first, as determined by the investigator according to the iwCLL.

Time frame: Up to approximately 48 months

Duration of Response (DOR) in Participants With CR/CRi or PR as Determined by the Investigator According to iwCLL Guidelines

DOR is defined as the time from the first occurrence of a documented objective response (i.e., CR/CRi or PR) to PD or death from any cause, whichever occurs first, as determined by the investigator according to the iwCLL.

Time frame: Up to approximately 12 months

DOR in Participants With CR or CRi as Determined by the Investigator According to iwCLL Guidelines

DOR is defined as the time from the first occurrence of a documented objective response (i.e., CR or CRi ) to PD or death from any cause, whichever occurs first, as determined by the investigator according to the iwCLL.

Time frame: Up to approximately 12 months

Time to Next CLL Treatment (TTNT)

TTNT is defined as the time from the first study treatment to the start of anti-leukemic treatment subsequent to the study treatment or death, whichever occurs first.

Time frame: Up to approximately 12 months