Dose Determining Study of EXS73565 in Participants With Relapsed or Refractory B-Cell Malignancies

Key Inclusion Criteria: * Age ≥18 years at the time of signing the informed consent. * Eastern Cooperative Oncology Group (ECOG) performance status of 0-1. * Histologically confirmed diagnosis of one of the following B-cell malignancies: chronic lymphocytic leukemia (CLL), including Richter's transformation from CLL, mantle-cell lymphoma, diffuse large B-cell lymphoma, follicular lymphoma, marginal zone lymphoma, or waldenström macroglobulinaemia. * Participants that have relapsed after standard of care or have progressed during standard of care or are not suitable for standard of care therapy Key Exclusion Criteria: * Any medical or psychiatric condition that, in the view of the Principal Investigator, could jeopardize or would compromise the participant's safety or ability to participate in the study. * Known central nervous system (CNS) malignancy or primary CNS lymphoma. * Concurrent active or previous malignancy (other than the primary lymphoma/CLL for which the participant will be treated on this protocol within 5 years prior to randomization; participants with prior cancers may be enrolled with documented Sponsor approval. * Received anticancer therapy, including chemotherapy, immunotherapy, radiation therapy (with the exception of palliative radiotherapy), biologic therapy, cancer-related hormonal therapy, or any investigational therapy within 14 days or 5 half-lives (whichever is shorter) before the first dose of the study treatment.