The Dual Mechanism of Action of CO-005 Overcomes CD20 Resistance in Diffuse Large B-Cell Lymphoma

Despite the clinical success of anti-CD20 monoclonal antibodies (mAbs) such as rituximab in the treatment of B-cell lymphoma, therapeutic resistance and relapse remain significant challenges, particularly in tumors with low or heterogeneous CD20 expression resulting from antigen loss or phenotypic shifts. To address this limitation, new therapeutic strategies are needed that act independently of CD20 while maintaining robust immune effector engagement. CO-005 is a humanized anti-CD47 fusion protein designed to simultaneously disrupt the CD47-SIRPα checkpoint and induce direct programmed cancer cell death (PCCD) distinct from other anti-CD47 agents.

The capacity of therapeutic mAbs to induce PCCD was assessed in lymphoma cell lines by flow cytometric detection of cell death and apoptotic markers. Antibody binding, phagocytic activity, and mechanistic analyses assessed intracellular signaling events associated with PCCD were measured by flow cytometry following treatment. The antitumor activity of CO-005 was evaluated in NOD-scid IL2Rγnull (NSG) mice bearing subcutaneous lymphoma xenografts, with efficacy and survival outcomes assessed for CO-005 as monotherapy and in combination with rituximab.

CO-005 demonstrated potent and durable antitumor activity across multiple lymphoma xenograft models, including rituximab-resistant tumors model. CO-005 shares key mechanistic features with therapeutic anti-CD20 antibodies independent of CD20 signaling, including the induction of type III programmed cell death via receptor capping, calcium flux, reactive oxygen species generation, and actin cytoskeleton dependence, accompanied by surface calreticulin exposure. In vivo, CO-005 triggered robust intratumoral PCCD and remodelled the tumor microenvironment, characterized by increased macrophage and neutrophil infiltration, thereby enhancing innate immune activation and supporting a dual-mechanism mode of action that couples direct cancer cell killing with myeloid engagement.

These findings position CO-005 as a mechanistically distinct and immunologically active therapeutic with the potential to overcome limitations of both CD20- and CD47-directed therapies and expand treatment options for B-cell lymphoma.