Assessing Minimal Residual Disease by Next- Generation Sequencing to Minimize Exposure in People With CLL or SLL Who Have Been Treated With Venetoclax

Screening Phase: Patients will be identified by clinical investigators at participating centers. Patients who sign the screening consent will undergo MRD assessment with the clonoSEQ® assay. If the assessment identifies the patient to be MRD negative, the patient will undergo a repeat MRD assessment ≥ 28 days later. If two consecutive MRD assessments indicate MRD-negativity, the patient will then sign the study intervention phase informed consent form and will undergo the rest of the screening process. Enrollment Once the patient fulfills all eligibility criteria, the patient will be enrolled into one of two cohorts based on the type of therapy they are receiving at the time of enrolled: Cohort A: Venetoclax monotherapy at time of enrollment. Cohort B: Venetoclax with anti CD20 monoclonal antibody at time of enrollment (The latter includes patients who initiated anti CD20 monoclonal antibody with venetoclax and have since completed the anti CD20 monoclonal antibody portion of the regimen.)