Pembrolizumab With Rituximab or Obinutuzumab in Treating Patients With Relapsed or Refractory Follicular Lymphoma or Diffuse Large B Cell Lymphoma

OUTLINE: Patients are assigned to 1 of 3 arms. ARM I: INDUCTION: Patients diagnosed with R/R FL receive pembrolizumab intravenously (IV) over 30 minutes on day 1. Treatment repeats every 3 weeks for 4 cycles in the absence of disease progression or unacceptable toxicity. Patients also receive rituximab IV on days 1, 8, and 15 of cycle 1, and on day 1 of cycle 2. EXTENDED THERAPY: Patients with at least a partial response receive pembrolizumab IV over 30 minutes on day 1. Cycles repeat every 3 weeks for up to 2 years (35 cycles) in the absence of disease progression or unacceptable toxicity. ARM II: INDUCTION: Patients diagnosed with R/R DLBCL receive pembrolizumab intravenously (IV) over 30 minutes on day 1. Treatment repeats every 3 weeks for 4 cycles in the absence of disease progression or unacceptable toxicity. Patients also receive rituximab IV on days 1, 8, and 15 of cycle 1, and on day 1 of cycle 2. EXTENDED THERAPY: Patients with at least a partial response receive pembrolizumab IV over 30 minutes on day 1. Cycles repeat every 3 weeks for up to 2 years (35 cycles) in the absence of disease progression or unacceptable toxicity. Arm III: INDUCTION: Patients diagnosed with R/R FL receive pembrolizumab IV over 30 minutes on day 1. Treatment repeats every 3 weeks for 4 cycles in the absence of disease progression or unacceptable toxicity. Patients also receive obinutuzumab IV on days 1, 8, and 15 of cycle 1, and on day 1 of cycle 2. EXTENDED THERAPY: Patients with at least a partial response receive pembrolizumab IV over 30 minutes on day 1. Cycles repeat every 3 weeks for up to 2 years (35 cycles) in the absence of disease progression or unacceptable toxicity. Patients with stable disease or better, who are experiencing clinical benefit in the judgment of the investigator, may receive obinutuzumab IV on day 1 of cycles 5, 9, 13, 17, 21, and 25. After completion of study treatment, patients are followed up for 90 days.