Fig. 2: Inhibition of IgE binding to FcεRIα and CD23 by ligelizumab or omalizumab.

a Inhibition of IgE binding to FcεRIα through ligelizumab or omalizumab IgG by ELISA. b Isolated primary human blood basophils are gated as SSC^low, FSC^low, CD123⁺, CD193⁺ double-positive cells. A histogram of basophil surface IgE levels before (black line) and after desensitization with 5 µM disruptive-anti-IgE DARPin^® bi53_79 (gray line) and after resensitization with recombinant human JW8-IgE (dashed gray line) is shown. c Inhibition of IgE binding to FcεRIα on isolated bi53_79-treated basophils by ligelizumab or omalizumab IgG. Binding curves were fitted using a non-linear regression model. d Inhibition of IgE:antigen complex binding to CD23 by ligelizumab or omalizumab IgG by ELISA. e Surface expression of CD23 on RPMI8866 cells by flow cytometry. f Inhibition of IgE binding to RPMI8866 cells by ligelizumab or omalizumab IgG. Binding curves (technical duplicates as mean ± SEM) were fitted using a non-linear regression model. g–i Ligelizumab sterically blocks FcεRI binding overlaps with receptor-binding residues in both IgE subunits. g Ligelizumab complex in surface representation with the view along the IgE twofold axis (PDB ID: 6UQR). VH and VL domains are (light orange and wheat) and IgE subunits (white and light gray) are shown. h The structure of IgE-Fc_2-4 with FcεRIα (PDB ID: 2Y7Q⁵³) in surface format, with the receptor (salmon) and IgE chains (white and light gray). One ligelizumab scFv sterically blocks receptor binding, while second scFv overlaps the position of the IgE Cε2 domains. i Overlap of IgE residues involved in both FcεRI and ligelizumab binding. IgE-Fc_3-4 in a surface representation is shown with common contacts shared by ligelizumab and FcεRIα (magenta), FcεRIα-specific contacts (red) and ligelizumab-specific (blue). j Structure of CD23:IgE-Fc_3-4 complex (PDB ID: 4EZM⁵⁷). IgE in surface representation with CD23 (light green). k IgE binding sites for CD23 have minimal overlap with ligelizumab epitope. IgE residues involved solely in ligelizumab binding (blue), those involved only in CD23 binding (green) and the overlapping contact residues (cyan) are shown. a, c, d, f Data shown for technical duplicates as mean ± SEM. Source data are provided as Source Data file.