The present invention relates to the area of improved anti-IgE antibodies and antigen binding agents, and compositions thereof, which target IgE, for instance: for use in treating disorders caused by IgE (such as allergic responses, or certain autoimmune responses); and, in particular, disorders caused by the interaction of IgE with the FcεRI receptor. In particular, this invention relates to improved anti-IgE antibodies and antigen binding agents related to novel mutants of omalizumab (Xolair®). The improved anti-IgE antibodies and antigen binding agents of the invention may have improved affinity for IgE and/or an improved interaction with the Cε2 domain of IgE and/or an improved modified epitope on IgE (for instance further involving the Cε2 domain of IgE) and/or the ability to disassociate IgE from the FcεRI receptor for instance at pharmaceutically-relevant concentrations. In one aspect, improved or novel treatments for IgE mediated disorders are disclosed in which IgE is targeted (for instance free IgE and/or IgE complexed with the FcεRI receptor).