Anti-IgE monoclonal antibodies that bind to IgE bound by CD23 but not to IgE bound by IgE Fc receptors on basophils

[[abstract]]IgE is a central mediator responsible for immediate-type hypersensitivity reactions. The anti-IgE monoclonal antibody (mAb), omalizumab, has been shown in numerous clinical trials to be efficacious in the treatment of severe allergic asthma and other allergic diseases. Omalizumab was designed to bind to free IgE in blood and membrane-bound IgE (mIgE) on B cells, but not to IgE bound by the high-affinity IgE Fc receptors (FcϵRI) on basophils and mast cells and by the low-affinity IgE Fc receptors (CD23) on B cells and many other cell types. Additionally, omalizumab can bind to IgE and prevent it from binding to both FcϵRI and CD23. Studies by other groups have also shown that CD23 is involved in the synthesis of IgE and that interfering CD23 function, such as by cross-linking CD23 on B cell surface, can cause the down-regulation of IgE production. We have developed anti-IgE mAbs that mimic omalizumab in various aspects except their ability to bind to IgE on CD23. These newly developed mAbs bind to linear epitopes on IgE. They do not induce the degranulation of IgE-pulsed rat basophilic leukemic cells (RBL SX-38), which had been transfected with the genes of human FcϵRI. The ability of the mAbs to cross-link IgE-occupied CD23 on the cell surface of B cell lines is being tested. The results suggest that these anti-IgE mAbs may render a set of pharmacological mechanisms, which are somewhat different from that of omalizumab, for controlling IgE in patients with allergic diseases