For dose escalation (Part 1) only: Participants with documented diagnosis of B-cell malignancies including (but not limited to) the following, with histology based on criteria established by the World Health Organization (WHO) (Swerdlow et al 2016), and measurable disease requiring treatment:  CLL/small lymphocytic lymphoma  Mantle cell lymphoma  Marginal zone lymphoma  Waldenstrom macroglobulinemia (WM)  DLBCL o Germinal center B-cell type o Activated B-cell type o Primary cutaneous DLBCL, leg type o Epstein-Barr virus–positive (EBV+) DLBCL, not otherwise specified o DLBCL associated with chronic inflammation o Human herpesvirus 8-positive (HHV8+) DLBCL, not otherwise specified o B-cell lymphoma, unclassifiable, with features intermediate between DLBCL and classical Hodgkin lymphoma o High-grade B-cell lymphoma, not otherwise specified o High-grade B-cell lymphoma, with MYC and BCL2 and/or BCL6 rearrangements o DLBCL arising from FL (transformed FL)  FL Grades 1 to 3B  Participants must be considered relapsed or refractory to, or intolerant of, at least 2 previous therapies known to provide a clinical benefit for their condition, and for whom there is no locally available therapy known to provide clinical benefit (eg, standard chemotherapy or autologous stem cell transplantation [ASCT]). Complion Document ID: 6768000 CONFIDENTIAL Protocol M22-716, Version 3.0 39 of 131  CLL and indolent NHL patients must meet relevant disease specific requirements for treatment (eg, International Workshop on Chronic Lymphocytic Leukemia [iwCLL], National Comprehensive Cancer Network [NCCN], Groupe d’Etude des Lymphomes Folliculaires [GELF]).  Participants in additional enrollment cohorts (including at lower doses) must provide archival or fresh tumor biopsies. If archived tissue is not available, a fresh tumor biopsy is required, unless collecting a biopsy at screening would place participant at risk of harm, would require a technically complicated procedure based on tumor location, or could hinder participant's ability to participate in the study. For participants previously treated with a CD19-targeting therapy (eg, CD19 monoclonal antibody) a core or excision tumor biopsy subsequent to the most recent CD19-targeting therapy must be collected. Screening archival or fresh biopsy is not required for CLL subtype. Tumor biopsy requirements may be modified by Sponsor during the study.