Bispecific CD20xCD40 Antibodies Achieve Multi-Lineage Modulation of Humoral and Cellular Immunity

Monoclonal antibodies targeting CD20 and CD40 modulate humoral and cellular immunity and have shown therapeutic benefit in B cell malignancies and autoimmune diseases. Here, we describe the generation and preclinical evaluation of two novel bispecific antibodies (DFI201 and DFI205) that combine CD20-mediated B cell depletion inhibition of CD40-mediated influencing populations of B cells, myeloid cells, and T cells. Both bispecifics retained potent B cell cytotoxicity and uniquely extended depletion to non-classical monocytes. A study in cynomolgus macaques showed that administration of bispecific at 5 and 50 mg/kg, or combination therapy with ofatumumab and the anti-CD40 mAb DFI105, achieved rapid and sustained depletion of CD19 ⁺ CD20 ⁺ B cells in blood and lymphoid tissues, with superior memory B cell clearance compared to monospecific controls Both bispecifics transiently reduced non-classical monocytes and potently depleted dendritic cell subsets (DC1 and DC2). The bispecifics expand regulatory T cells and induce T cell exhaustion without activating T Cells. No cytokine release syndrome or adverse safety signals were observed. Functional immunization with keyhole limpet hemocyanin demonstrated that CD40 engagement was essential to suppress KLH-specific IgG formation. These results establish CD20 × CD40 bispecific antibodies as a safe and effective approach to achieve deep, multi-lineage immunomodulation with potential for autoimmune indications.