An inhibitor of the NF-κB subunit c-Rel; inhibits NF-κB DNA binding (IC50 = 0.1 μM); reduces TNF-α-induced NF-κB activity (IC50 = 4 μM); decreases proliferation of ABC and GCB DLBCLL cells at 3 μM; increases HO-1 expression and ROS production in mitochondria of DLBCL cells but not normal leukocytes; increases survival in a mouse model of GVHD at 24 mg/kg every other day beginning eight days after HSCT; reduces tumor growth in mouse xenograft models of EBV-induced B cell lymphoma, CLL, and Richter syndrome