Bypassing the immunosuppressive effects of CA125/MUC16 via re-engineered rituximab (NAV-006) to improve its antitumor activity <i>in vivo</i>

The monoclonal antibody rituximab functions through complement-dependent cytotoxicity (CDC) and antibody-dependent cellular cytotoxicity (ADCC) and is used to treat non-Hodgkin's lymphoma. Elevated serum CA125/MUC16 levels, present in some follicular lymphoma patients, have been shown to correlate with reduced efficacy of rituximab. Previous studies revealed that CA125/MUC16 binds to rituximab, diminishing its CDC and ADCC. A rituximab variant, NAV-006, was engineered to counteract CA125/MUC16's immunosuppressive effects. NAV-006 demonstrated enhanced CDC and ADCC activities and was unaffected by CA125/MUC16. In the present study, NAV-006 showed improved <i>in vivo</i> antitumor activity compared to rituximab in a human lymphoma model with reconstituted CA125/MUC16. Additionally, CA125/MUC16 bound to newer antibody-based lymphoma treatment agents, including obinutuzumab and tafasitamab, suppressing their immune effector functions. Bispecific antibodies mosunetuzumab and glofitamab also exhibited reduced cytotoxicity in the presence of CA125/MUC16. These findings suggest that NAV-006 could improve therapeutic efficacy in B-cell lymphomas, particularly in patients with elevated CA125/MUC16 levels.