Abstract 2472: SEA-CD40, a sugar engineered non-fucosylated anti-CD40 antibody with improved immune activating capabilities

SEA-CD40 is a non-fucosylated, humanized IgG1 monoclonal antibody directed against human CD40, a co-stimulatory receptor of the TNF receptor superfamily. SEA-CD40 is derived from dacetuzumab, a humanized IgG1 previously developed and studied for B-lineage malignancies. Glycosylation of the antibody Fc is essential for Fc receptor-mediated activity and non-fucosylated antibodies show improved efficacy, particularly via increased binding to low affinity FcγRIIIa. Enhanced functionality of SEA-CD40 was determined through FcγRIIIa binding affinity, antibody-dependent cellular cytotoxicity (ADCC) activity, activation of the immune response, and induction of antigen-specific T-cells. While SEA-CD40 and the parent antibody dacetuzumab bind to CD40 with similar affinity, the non-fucosylated SEA-CD40 binds equally well to the low (158F) and high (158V) affinity versions of FcγRIIIa with higher affinity than dacetuzumab. The consequence of enhanced SEA-CD40/FcγRIIIa binding is potent ADCC activity against a CD40+ lymphoma B cell line and improved agonistic signaling to antigen presenting cells (APCs). SEA-CD40 treatment of human PBMCs elicits a robust immune response as measured by increased cytokine production and up-regulation of maturation markers on APCs with maintained activity at antibody concentrations as low as 10 ng/ml. The immune stimulatory properties of SEA-CD40 were observed in vivo as increased activity in xenograft and syngenic tumor models as well as induction of cytokine production in cynomolgus monkeys. Both in-vitro and in-vivo activity of SEA-CD40 was significantly greater than with dacetuzumab. The increased functionality of SEA-CD40 occurs through the non-fucosylated Fc domain as a F(ab’)2 version loses the ability to induce ADCC, stimulate cytokines, or up-regulate APC activation markers. SEA-CD40 induction of antigen specific T-cells was assessed using human peripheral blood mononuclear cells (PBMCs) exposed to influenza antigen. In the presence of SEA-CD40 influenza specific T-cells mount a robust antigen-specific response characterized by tetramer staining and elevated production of IFNγ. SEA-CD40 activity on PBMCs from donors with melanoma, pancreatic, or breast cancer was assessed and tumor antigen specific T-cell proliferation and IFNγ production was observed. SEA-CD40 is a non-fucosylated agonistic anti-CD40 antibody that shows enhanced binding to FcγRIIIa resulting in amplified cytokine production, co-stimulatory molecule up regulation