• Confirmed diagnosis of CLL/SLL requiring therapy per iwCLL 2018 criteria

• Part 1 - Known 17p deletion status (wildtype or deleted). Part 2 - Must have deletion of 17p as determined by FISH testing

• Eastern Cooperative Oncology Group (ECOG) Performance Status 0-2

• Adequate organ function

‣ Platelets greater than or equal to ≥ 50 x 10⁹/liter (L) or ≥30 x 10⁹/L in participants with documented bone marrow involvement considered to impair hematopoiesis,

⁃ Hemoglobin ≥8 grams/deciliter (g/dL) or ≥6 g/dL in participants with documented bone marrow involvement considered to impair hematopoiesis

⁃ Absolute neutrophil count ≥0.75 x 10⁹/L or ≥0.50 × 10⁹/L in participants with documented bone marrow involvement considered to impair hematopoiesis

⁃ Kidney function: Estimated creatinine clearance ≥30 milliliters per minute (mL/min)