Design of a Heterobivalent Ligand to Inhibit IgE Clustering on Mast Cells

SummaryWe describe the design, synthesis, and characterization of a heterobivalent ligand (HBL) system that competitively inhibits allergen binding to mast cell bound IgE antibody, thereby inhibiting mast cell degranulation. HBLs are composed of a hapten conjugated to a nucleotide analog allowing simultaneous targeting of the antigen-binding site as well the “unconventional nucleotide binding site” on IgE Fab domains. Simultaneous bivalent binding to both sites provides HBLs with over 100-fold enhancement both in avidity for IgEDNP (Kd = 0.33 μM) and in inhibition of allergen binding to IgEDNP (IC50 = 0.45 μM) than the monovalent hapten (Kdmono = 41 μM; IC50mono = 55.4 μM, respectively). In cellular assays, HBL2 effectively inhibits mast cell degranulation (IC50 = 15 μM), whereas no inhibition is detected by the monovalent hapten. In conclusion, this study establishes the use of multivalency in a novel HBL design to inhibit mast cell degranulation