A Study Evaluating the Efficacy and Safety of Pirtobrutinib in Participants With Relapsed or Refractory Chronic Lymphocytic Leukemia/Small Lymphocytic Lymphoma

Inclusion Criteria

• Have confirmed diagnosis of CLL/SLL as defined by iwCLL 2018 criteria.
• Part 1: Have received prior CLL/SLL treatment
• Have received at least 1, but not more than 3 lines of prior treatment for CLL/SLL
• Have received a covalent BTK inhibitor
• Part 2: Have received no prior treatment for CLL/SLL
• Part 1 - Known 17p deletion status (positive or negative)
• Part 2 - Must have 17p deletion (positive)
• Have a requirement for therapy consistent with iwCLL 2018 criteria for initiation of therapy
• Capable of swallowing oral study medication.
• Have an Eastern Cooperative Oncology Group Performance Status (ECOG) score of 0 to 2.

Exclusion Criteria

• Have received prior treatment with a BTK degrader or a noncovalent BTK inhibitor
• Have a history of greater than or equal to (>=) Grade 3 bleeding due to treatment with a BTK inhibitor
• Have known or suspected Richter's transformation
• Have known or suspected history of central nervous system involvement by CLL/SLL
• Previous or concurrent cancer distinct from CLL/SLL within 3 years before randomization. Exceptions may occur with documented sponsor approval. Examples include:
• nonmelanoma skin cancer or lentigo malignant melanoma
• cervical carcinoma in situ
• localized prostate cancer undergoing active surveillance, and
• localized (for example, lymph node negative) breast cancer with no evidence of active disease present for more than 3 years. Individual may be receiving adjuvant hormonal therapy