Targeting of palpable B16-F10 melanoma tumors with polyclonal antibodies on white blood cells

Background: Antibodies and other recognition molecules direct cancer cell death by multiple types of immune cells. Therapy directed at only one target typically results in tumor regrowth because of tumor heterogeneity. Our goal is to direct therapy to multiple targets simultaneously. Our previous studies showed that multiple antibodies targeting mutated tumor proteins inhibited tumor growth when injected subcutaneously near the time of cancer cell implantation.Methods: A cocktail of rabbit antibodies against B16-F10 cell surface related mutated proteins were generated. Implanted B16-F10 cells were allowed to grow to palpable size before treatment. Antibodies were administered using different routes of exposure. Free antibody was compared to antibody armed on mouse splenic white blood cells (WBCs). Binding of the antibody cocktail was determined for mouse and human WBCs.Results: The antibody cocktail inhibited tumor growth and prolonged survival when administered as free anti-body or armed on WBCs. The antibody cocktail armed on WBCs achieved similar tumor inhibition as free antibody but at a dose 1000-fold less. Armed WBCs achieved tumor inhibition by intravenous and subcutaneous administration. The antibody cocktail bound well to human WBCs and saturation dose was defined. Binding was stable under simulated in vivo condition in human plasma at 37 degrees C.Conclusions: Antibodies targeting multiple tumor mutated proteins inhibited tumor growth and prolonged sur-vival. Effective antibody dose was reduced 1000-fold by arming WBCs. Rabbit antibodies saturated human WBCs using <1 mg per billion cells. A phase I trial in cancer patients using this strategy has been approved by the FDA.