Study to Evaluate Adverse Events and Change in Disease Activity in Adult Participants With B-Cell Malignancies Receiving Oral ABBV-525 Tablets

Inclusion Criteria:

Dose Escalation (Part 1) Only: Participants with a documented diagnosis of one of the following third line or later of treatment (3L)+ mature B-cell malignancies, from the World Health Organization (WHO)-defined histologies as defined in the protocol.
Dose Optimization (Part 2) Only: Participants with documented diagnosis of chronic lymphocytic leukemia (CLL) who are 3L+, +/- cysteine-to-serine point mutation at residue 481 of BTK-domain active site (C481S with histology based on WHO criteria, with measurable disease requiring treatment as defined by the International Workshop on Chronic Lymphocytic Leukemia (iwCLL).
Dose Expansion (Part 3) Only: Participants with documented diagnosis of non-germinal center B cell (GCB) Diffuse large B-cell lymphoma (DLBCL) who are 3L+ chimeric antigen receptor T-cells (CAR-T)/Hematopoietic cell transplant (HCT) relapsed/refractory (R/R) and/or ineligible with histology based on WHO criteria, with measurable disease requiring treatment.
Participant has an Eastern Cooperative Oncology Group (ECOG) Performance Status (PS) of 0 or 1.
Participant has a life expectancy >= 12 weeks.
Adequate hematological and hepatic function as defined in the protocol.
Must have archival or freshly collected tumor tissue for correlative studies before study enrollment.
Participants with prior central nervous system (CNS) disease that has been effectively treated may be eligible.
Participants with resolved coronavirus disease 2019 (COVID-19) infection are eligible.

Exclusion Criteria:

Known active CNS disease, or primary CNS lymphoma.
Known bleeding disorders.
Known history of stroke or intracranial hemorrhage within 12 months prior to first dose of study treatment.
Uncontrolled active systemic infection, or active cytomegalovirus infection.
Active hepatitis B or C infection.
Known history of human immunodeficiency virus (HIV).
Known active COVID-19 infection. Participant must not have signs/symptoms associated with COVID-19 infection or known exposure to a confirmed case of COVID-19 infection during screening. If participant has signs/symptoms suggestive of COVID-19 infection, the participant must have a negative molecular (eg, polymerase chain reaction) test or 3 negative antigen test results at least 24 hours apart.