We designed compounds that were expected to inhibit a binding of Cε3 domain of IgE to α2 (D2) domain of FcεRIα chain, and 41,169 compounds were selected from data base. The compounds were eventually narrowed down to 124 compounds through several steps including judgment of druglikeness and these selected compounds were evaluated as follows:
We established rat basophile leukemia cell line (RBL-2H3) that constitutively expresses human FceRI α chain and evaluated effect of test compounds on human IgE-induced degranulation of the cells. As a marker of degranulation, enzymatic activity of β-hexosaminidase in culture supernatant and cell lysate was measured with p-nitrophenyl-N-acetyl-β-D-glucopyranoside (PNAG), a substrate for β-hexosaminidase. Active compounds showed concentration-dependent inhibition of human IgE-induced degranulation of RBL-2H3 cells. A part of active compounds were confirmed to bind to IgE by SPR and/or NMR. Furthermore, hydrogen-deuterium exchange MS revealed that an active compound binds to the enzymatically digested IgE fragment including the proposed binding site.
Small molecule IgE inhibitor is expected to contribute to treatment for not only severe asthma but also mild and moderate asthma, allergic dermatitis including atopic dermatitis, allergic conjunctivitis, and allergic rhinitis including pollinosis.