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

Open to people ages 18 years and up

• 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.

• 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.