Fig. 3: Disruption of FcεRI:IgE complexes by ligelizumab or omalizumab.

a and b Removal of FcεRI pre-complexed human recombinant Sus11-IgE by ligelizumab (a) or omalizumab (b) IgG by SPR. Each color refers to an individual measurement cycle. Black line refers to baseline buffer control. Black arrows indicate time of injection. c Isolated primary human basophils (n = 3 donors) were incubated for 3 or 6 days with indicated concentrations of ligelizumab and omalizumab IgG. Levels of cell surface IgE were quantified by flow cytometry (shown as mean ± SEM). d–f Interaction of ligelizumab or omalizumab IgG with FcεRI-bound IgE-Fc_3-4. d and e Binding of ligelizumab (d) and omalizumab (e) IgG to FcεRI pre-complexed human recombinant wt C328 IgE-Fc_3-4 by SPR. f The monoclonal anti-IgE antibody Le27 was included as positive control. Each color refers to an individual measurement. Black line refers to baseline buffer control. Black arrows indicate the time of injection. g, h Comparisons of ligelizumab- and FcεRIα-IgE complex structures. Complexes were superimposed using the primary VH-interacting Cε3 domain (corresponding to FcεRIα site 2), predominantly exposed in the IgE-Fc_3-4 receptor-bound complex because of the absent Cε2 domains. A single ligelizumab (g) and FcεRIα (h) are shown in surface representations (light orange and light blue). Two conformations of the IgE-Fc are shown. g Binding of ligelizumab restricts secondary Cε3 domain conformation, preferring displacement (downward arrows). h FcεRIα binding to ligelizumab-stabilized Fc conformation is sterically blocked, requiring displacement of the Cε3 domain (upward arrows). Surface IgE levels (i) and percentage of activated cells (j) of JW8-IgE sensitized primary human basophils incubated for 30 min with ligelizumab or omalizumab IgG. Surface IgE levels (k) and percentage of activated cells (l) of IgE-Fc_3-4 sensitized primary human basophils incubated for 30 min with ligelizumab or omalizumab IgG. i–l Biological triplicates are displayed as mean ± SEM. Different conditions were compared to each other using two-way ANOVA with Sidak’s multiple comparison. *P < 0.05, ***P < 0.001, ns = not significant. Source data are provided as Source Data file.