XmAbCD40 exhibits antiproliferative and CDC activity. Proliferation assays were performed on Raji (A) and Ramos (B) cells using a human FcγRIIIa-GST fusion receptor to provide antibody cross-linking. Cross-linked antibodies were incubated with 6 × 103 cells for 72 hours, and cell titers were analyzed using a luminescent cell viability assay. XmAbCD40, the IgG1 analog, and rituximab all show similar antiproliferative activity; cell growth is inhibited 60% to 95% relative to vehicle controls, and the inhibition is more pronounced in Ramos cells. (C) CDC assay was performed on Ramos cells using human serum complement. Antibodies were incubated with cells and complement for 2 hours at 37°C, Alamar Blue was added, cells were cultured overnight, and fluorescence was measured. XmAbCD40 and the IgG1 analog showed similar CDC that was reduced relative to rituximab by 30%. Data for all experiments were obtained in triplicate and represent the mean ± SD.
