- Arm D: Refractory to ≥ 1 regimen containing any anti-CD20-based therapy, including salvage regimens and maintenance rituximab. Refractory subjects are defined as any subject with less than a PR to any prior anti-CD20-based therapies or progressed within 6 months after completing therapy with any anti-CD20-based regimens, including maintenance rituximab. These subjects must not be eligible for hematopoietic SCT or BM transplant