A Study to Investigate Progression-Free Survival With Sonrotoclax Plus Obinutuzumab Or Sonrotoclax Plus Rituximab Compared With Venetoclax Plus Rituximab Treatment In Patients With Relapsed and/or Refractory Chronic Lymphocytic Leukemia/Small Lymphocytic Lymphoma (CELESTIAL-RRCLL)

Inclusion Criteria: * Confirmed diagnosis of CLL/SLL that meets the International Workshop on Chronic Lymphocytic Leukemia (iwCLL) criteria * Received one or more prior therapies for CLL/SLL. For each line of therapy, participants must have received at least 2 cycles of the therapy * Participants with prior BCL2i exposure are eligible if remission duration was ≥3 years with ≥2 years from last BCL2i intake * Eastern Cooperative Oncology Group (ECOG) Performance Status score of 0, 1, or 2 * Adequate organ function Exclusion Criteria: * Known active prolymphocytic leukemia or currently suspected Richter's transformation * Prior autologous stem cell transplantation or chimeric antigen receptor T-cell therapy within 3 months before first dose of study drug * Prior allogeneic stem cell transplant with active graft-versus-host disease (GVHD), requiring immunosuppressive drugs for treatment of GVHD, or have taken calcineurin inhibitors within 4 weeks prior to consent * Known central nervous system involvement by CLL/SLL * Severe or debilitating pulmonary disease * Clinically significant cardiovascular disease NOTE: Other protocol defined Inclusion/Exclusion criteria may apply.