XmAbCD40 enhances macrophage phagocytosis. ADCP was determined by flow cytometry. Purified CD14⁺ monocytes were cultured with macrophage colony-stimulating factor for 5 days, and differentiated macrophages were identified by a combination of anti-CD11b–allophycocyanin (APC) and anti-CD14–APC. Target Ramos or IM-9 cells were fluorescently labeled with carboxyfluorescein succinimidyl ester, opsonized with antibodies, and incubated with the monocyte-derived macrophages for 4 hours at an E/T ratio of 4:1. Cells were double-stained with anti-CD11b–APC and anti-CD14–APC and evaluated by fluorescence-activated cell sorting; percentage ADCP was calculated as the number of double-positive cells divided by the total number of tumor cells. With Ramos cells (A), XmAbCD40 markedly enhances ADCP potency and efficacy relative to both the IgG1 analog and rituximab. With IM-9 cells (B), XmAbCD40 and the IgG1 analog are equally effective, and both demonstrate greater ADCP than rituximab. Data were obtained in triplicate and represent the mean ± SD.