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

We 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 IgE(DNP) (K-d = 0.33 mu M) and in inhibition of allergen binding to IgE(DNP) (IC50 = 0.45 mu M) than the monovalent hapten (K-d(mono) = 41 mu m; IC50mono = 55.4 mu M, respectively). In cellular assays, HBL2 effectively inhibits mast cell degranulation (IC50 = 15 mu M), 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.