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

B-cell malignancies are a group of cancers of B lymphocytes, a type of white blood cell responsible for fighting infections. The purpose of this study is to assess safety, tolerability, pharmacokinetics and preliminary efficacy of ABBV-525 as a monotherapy. ABBV-525 is an investigational drug being developed for the treatment of B-Cell Malignancies. Study doctors put the participants in groups called treatment arms. Participants will receive ABBV-525 at different doses. Approximately 150 adult participants will be enrolled in the study across sites worldwide. In part 1 (dose escalation), participants will receive escalating oral doses of ABBV-525. In part 2 (dose optimization), participants will receive one of two oral doses of ABBV-525, until the recommended phase 2 dose (RP2D) is determined. In part 3 (dose expansion), participants will receive the RP2D oral dose of ABBV-525. The estimated duration of the study is up to 64 months. There may be higher treatment burden for participants in this trial compared to their standard of care. Participants will attend regular visits during the study at a hospital or clinic and may require frequent medical assessments, blood tests, and scans.