A Study Assessing Adverse Event and How Oral ABBV-453 Moves Through the Body in Adult Participants With Relapsed or Refractory (R/R) Chronic Lymphocytic Leukemia (CLL)/Small Lymphocytic Lymphoma (SLL)

Chronic lymphocytic leukemia (CLL) is the most common leukemia in Western countries. The purpose of this study is to assess how well ABBV-453 works adult participants with relapsed/refractory (R/R) untreated CLL/small lymphocytic lymphoma (SLL). Adverse events, pharmacokinetics, and change in disease activity will be assessed. ABBV-453 is an investigational drug for the treatment of CLL and SLL. Participants will be enrolled with a specific target dose and receive obinutuzumab during the debulking period followed escalating doses of ABBV-453, until the appropriate target dose is achieved. Approximately 60 adult participants with previously R/R CLL/SLL will be enrolled in the study in approximately 40 sites across the world. Participants will receive intravenous (IV) obinutuzumab as part of the debulking period, followed by escalating doses of oral ABBV-453 until the appropriate target dose is achieved. The estimated study duration is 3 years. 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. The effect of the treatment will be checked by medical assessments, blood tests, and checking for side effects.