A Study to Investigate the Safety of Novel Dose Ramp-up Schedule(s) When Initiating Sonrotoclax in Participants Treated for Blood Cancers.

The purpose of this study is to establish the safety of novel dosing and ramp-up schedules for sonrotoclax in participants with hematological malignancies.

Inclusion Criteria: 1. Stable Eastern Cooperative Oncology Group (ECOG) Performance Status ≤ 2. 2. Adequate organ function and no very recent transfusion or blood growth factor 3. Participants of childbearing potential must be willing to use a highly effective method of birth control and refrain from egg donation for the duration of the study and for ≥ 7 days after the last dose of sonrotoclax or 1 month after the last dose of zanubrutinib, whichever is later. Only for participants with Chronic Lymphocytic Leukemia (CLL): 4. Confirmed diagnosis of CLL, based on Hallek et al 2018, and requiring treatment due to certain features of their disease 5. At least 1 measurable lesion based on computed tomography (CT)/magnetic resonance imaging (MRI) and no history of prolymphocytic leukemia or Richter's transformation. Only for participants with Mantle cell lymphoma (MCL): 6. Historically confirmed diagnosis of MCL based on the World Health Organization 2022 classification of Haematolymphoid Tumors (WHO-HEAM5) or based on International Consensus Classification (ICC). 7. Relapsed or refractory to the last line of therapy and have received at least 1 prior line of systemic therapy. Note: A line of therapy is considered ≥ 2 consecutive cycles of a systemic anticancer regimen. Patients with prior BTKi therapy should not have progressed during treatment or relapsed within 12 months after BTKi discontinuation. 8. Measurable disease defined as ≥ 1 nodal lesion that is \> 1.5 cm in longest diameter, or ≥ 1 extranodal lesion that is \> 1 cm in longest diameter. Exclusion Criteria: 1. Participants unable to comply with the requirements of the protocol 2. Serologic status reflecting active viral hepatitis B virus (HBV) or hepatitis C virus (HCV) infection 3. Positive HIV serology (HIVAb) status unless certain conditions are met. 4. Participants with any major surgical procedure ≤ 28 days before first dose of study treatment 5. Prior systemic treatment for the CLL 6. Uncontrolled autoimmune hemolytic anemia or immune thrombocytopenia requiring treatment 7. Prior exposure to a BCL-2 inhibitor NOTE: Other protocol defined Inclusion/Exclusion criteria may apply.