Dirk Brohm

Discovery of substituted N-phenylbenzenesulphonamides as a novel class of non-nucleoside hepatitis C virus polymerase inhibitors

The RNA-dependent RNA polymerase NS5B of the hepatitis C virus (HCV) has emerged as one of the key targets for antiviral drug discovery. Here we describe a novel non-nucleoside inhibitor (NNI) chemotype identified by screening: The substituted N-phenylbenzenesulphonamides (SPBS) which showed reversible inhibition of NS5B from HCV genotype 1b with IC(50) values up to 40 nM. Based on the decreased inhibitory activity against a recombinant NS5B protein carrying the mutation L419M or M423T we assumed that the SPBS inhibitors bind to the thumb site II which has already been described as the allosteric binding site for the NNI carboxy thiophene. The postulated binding site was consequently confirmed by solving two co-crystal structures of NS5B in complex with SPBS analogues at 2.3 and 2.2Å resolutions. The inhibitors are hydrogen-bonded to the main chain Ser476 and Tyr477 and to the side chain of Arg501. In addition, the inhibitors displayed van der Waals interactions with several residues of the hydrophobic binding pocket Leu419, Ile482, Leu497, Met423 and Trp528. Notably, the two SPBS analogues reported here revealed significant differences in addressing the NH-group of the main chain Tyr477 by hydrogen-bonds, water-mediated or directly, which provoked a shift of the carboxyphenyl group of the inhibitors towards the His475 position for the water-mediated binding mode. Interestingly, the differences observed in the binding mode led to a different cross resistance profile at positions M423 and I482. Using a panel of 38 individual NS5B proteins derived from different HCV genotypes, we could demonstrate inhibitory activity of the SPBS against polymerases from HCV genotypes 1a and 1b whereas the inhibitor class failed to inhibit any of the non-genotype 1 polymerases efficiently. Furthermore we demonstrated initial antiviral activity for SPBS against the subgenomic replicons of HCV genotypes 1a and 1b, respectively, and no considerable cytotoxic potential against a panel of ten different cell types.

Abstract 1739: Preclinical profile of BAY 1163877 - a selective pan-FGFR inhibitor in phase 1 clinical trial

Fibroblast growth factors (FGFs) orchestrate a variety of cellular functions by binding to their transmembrane tyrosine-kinase receptors (FGFR1-4) and activating downstream signaling pathways. FGF signaling has been demonstrated to be altered in a high proportion of cancers, with activating mutations and/or overexpression of FGFRs frequently observed in lung, gastric, breast and urothelial tumors. Therefore, targeting FGFRs using selective FGFR inhibitors is an attractive therapeutic approach to treat cancer patients. BAY 1163877 is as an orally available, selective and potent inhibitor of FGFR-1, -2 and -3 kinase activity. BAY 1163877 has been advanced through preclinical development and we disclose here the first details of its preclinical profile. BAY 1163877 inhibited FGFR-1, -2, -3 kinase activity in the nanomolar range and demonstrated a kinase selectivity profile for FGFR-1, -2 and -3 over 222 kinases tested. BAY 1163877 inhibited proliferation of various cancer cell lines in vitro and phosphorylation of downstream signaling molecules. BAY 1163877 was also tested in vivo in monotherapy and combination therapy on various human xenografts and syngeneic tumors and inhibited growth of tumors presenting at least one FGFR alteration.Overall, the in vitro and in vivo studies confirm that the FGFR inhibitor BAY 1163877 is a potent and selective inhibitor of altered FGFRs pathways in cancer models. A Phase 1 clinical trial (NCT01976741) has been initiated. Citation Format: Melanie Heroult, Peter Ellinghaus, Christian Sieg, Dirk Brohm, Sylvia Gruenewald, Marie-Pierre Collin, Ulf Boemer, Mario Lobell, Walter Huebsch, Matthias Ocker, Stuart Ince, Andrea Haegebarth, Rolf Jautelat, Holger Hess-Stumpp, Michael Brands, Karl Ziegelbauer. Preclinical profile of BAY 1163877 - a selective pan-FGFR inhibitor in phase 1 clinical trial. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1739. doi:10.1158/1538-7445.AM2014-1739