Superior ADCC and B cell–depleting activities of GA101 compared with rituximab. GA101 exhibits a more potent ADCC-inducing ability than rituximab, both in the presence and absence of nonspecific human IgG. Representative ADCC assay with Raji cells as target cells and NK cells from human PBMCs (F/V 158) as effector cells (calcein release, E/T ratio = 20:1) in the absence (A) and presence (B) of physiologic concentrations of nonspecific human IgG (20 mg/mL RedImune; n = 3). In the absence of nonspecific IgG, GA101 (black) was approximately 35-fold more potent in terms of EC₅₀ values than rituximab (gray) at inducing ADCC. In the presence of nonspecific IgG, GA101 (black) still exhibited significant ADCC-inducing activity, whereas that of rituximab (gray) was completely abolished. (C). Enhanced B cell–depletion activity of GA101, as demonstrated in a whole blood B cell–depletion assay with whole blood from a healthy donor (CD16 genotype F158/F158). Representative results for the depletion of CD19-positive B cells are depicted here. GA101 (black) was approximately 25-fold more potent in terms of EC₅₀ values and 1.9-fold more effective (in terms of absolute B-cell depletion) compared with rituximab (gray). Evaluation of relative B-cell depletion was performed using the B-/T-cell ratio set to 0% for untreated control samples (n = 4). (D) Representative whole blood B cell–depletion assay with whole blood from a B-CLL patient. GA101 (black) was more effective at depleting B cells compared with rituximab (gray) and the CD52 antibody alemtuzumab (dotted line). Because alemtuzumab also depletes T cells, the evaluation of relative B-cell depletion was performed based on the absolute B-cell counts. The B-cell numbers were then set to 100% for maximal depletion, and results were compared between the antibodies (n = 4).