Atezolizumab, Obinutuzumab, and Venetoclax in Treating Patients With Chronic Lymphocytic Leukemia, Small Lymphocytic Lymphoma, or Relapsed or Refractory Richter Syndrome

PRIMARY OBJECTIVES: I. To determine the efficacy of atezolizumab in combination with obinutuzumab and venetoclax in patients with chronic lymphocytic leukemia (CLL)/small lymphocytic lymphoma (SLL)/Richter transformation (RT). SECONDARY OBJECTIVES: I. To determine the safety of atezolizumab combined with obinutuzumab and venetoclax in patients with CLL/SLL/RT. II. To determine overall response rate (ORR), complete response rate (CR), duration of response (DOR), and minimal residual disease (MRD) negative remission rate. III. To determine the progression-free survival (PFS). IV. To determine the overall survival (OS). EXPLORATORY OBJECTIVES: I. To determine immunological and molecular features, at baseline and/or that change with treatment, that correlate with outcomes in patients treated with atezolizumab combined with obinutuzumab and venetoclax. OUTLINE: Patients are assigned to 1 of 2 cohorts. COHORT I: Patients receive obinutuzumab intravenously (IV) over 4-6 hours on days 1, 2, 8, and 15 of cycle 1 and on day 1 of cycles 2-9 and atezolizumab IV over 30-60 minutes on days 3-4 of cycle 1 and on days 1-2 of cycles 2-9. Treatment repeats every 28 days for 9 cycles in the absence of disease progression or unacceptable toxicity. Beginning cycle 3, patients also receive venetoclax orally (PO) on days 1-28. Treatment repeats every 28 days for 14 cycles in the absence of disease progression or unacceptable toxicity. COHORT II: Patients receive obinutuzumab intravenously IV over 4-6 hours on days 1, 2, 8, and 15 of cycle 1 and on day 1 of cycles 2-9 and atezolizumab IV over 30-60 minutes on days 3-4 of cycle 1 and on days 1-2 of cycles 2-9. Treatment repeats every 28 days for 9 cycles in the absence of disease progression or unacceptable toxicity. Beginning cycle 2, patients receive venetoclax PO on days 1-28. Treatment repeats every 28 days for 25 cycles in the absence of disease progression or unacceptable toxicity. After completion of study treatment, patients are followed up for 1 year.