FimH Antagonists: Structure–Activity and Structure–Property Relationships for Biphenyl α‐D‐Mannopyranosides

Abstract

Urinary tract infections (UTIs) are caused primarily by uropathogenic Escherichia coli (UPEC), which encode filamentous surface-adhesive organelles called type 1 pili. FimH is located at the tips of these pili. The initial attachment of UPEC to host cells is mediated by the interaction of the carbohydrate recognition domain (CRD) of FimH with oligomannosides on urothelial cells. Blocking these lectins with carbohydrates or analogues thereof prevents bacterial adhesion to host cells and therefore offers a potential therapeutic approach for prevention and/or treatment of UTIs. Although numerous FimH antagonists have been developed so far, few of them meet the requirement for clinical application due to poor pharmacokinetics. Additionally, the binding mode of an antagonist to the CRD of FimH can switch from an in-docking mode to an out-docking mode, depending on the structure of the antagonist. In this communication, biphenyl α-D-mannosides were modified to improve their binding affinity, to explore their binding mode, and to optimize their pharmacokinetic properties. The inhibitory potential of the FimH antagonists was measured in a cell-free competitive binding assay, a cell-based flow cytometry assay, and by isothermal titration calorimetry. Furthermore, pharmacokinetic properties such as log D, solubility, and membrane permeation were analyzed. As a result, a structure-activity and structure-property relationships were established for a series of biphenyl α-D-mannosides.

The Tyrosine Gate of the Bacterial Lectin FimH: A Conformational Analysis by NMR Spectroscopy and X‐ray Crystallography

“…Later on, the aryl moieties were derivatized to optimize this interaction, as reported by our group and others. [15] An impressive example of this is represented by biphenyl mannoside 4,w ith an ortho-chloro substituent on the inner aromatic ring and ac yano group in the para position of the outer ring as ab ioorthogonal replacement fort he carboxylate group present in antagonist 3. [21] Both ring substituents of 4 reduce the electron density in the aglycone and therebye nhancet he p-p interaction, thus leadingt oam ore than tenfolda ffinity improvement relative to the unsubstituted antagonist 2 (Table 2, below).…”

“…Chemically easily accessible aromatic derivatives such as 4-nitrophenyl and 4-methylumbelliferyl mannosides were soon discovered. [11a, 13] These were followed by derivatives of squaric acid, [14] biphenyls and other diaryls, [15] triazoles, [16] and indolines, [17] among others. We routinelyt est new candidates for in vitro binding to FimH-CRD [15b, [16][17][18] and to UPEC, [19] as well as for efficacy in aU TI mousem odel.…”

“…[24] CSP effects hence identify residues in direct proximity to ab ound ligand and, in addition, indicatec onformational changes in allosteric sites. We used 1 H, 15 NHSQC experimentsw ith 15 N-enriched FimH-CRD in the presence of various antagonists to monitort he CSP effects on the backbone amide groups. Previous NMR studies of binding of methyl a-d-mannoside [6] and n-heptyl a-d-mannoside [25] to FimH-CRD only noted ag eneral match of the CSP maps and the ligand binding interface identified from X-ray co-crystal structures.…”

New Approaches to Control Infections: Anti-biofilm Strategies against Gram-negative Bacteria

“…Based on the initial discovery of heptyl mannosides opening the tyrosine gate, biphenyl mannosides [41] were identified as potent inhibitors. Subsequent optimization by the Ernst [42,43] and Hultgren [44,45] labs resulted in the nanomolar FimH inhibitors 18 and 19, which are monovalent (and not multivalent) ligands but represent still very potent lectin antagonists. In both groups, the compounds were tested in a urinary tract infection model in mice and showed efficacy against infection with UPEC.…”

“…Pharmacokinetic optimization with mouse liver microsomes in vitro and in vivo studies in mice indicate 18 (K d = 3.7 nM, free acid) as a prodrug with high metabolic stability but low oral availability. [42,43] By introducing phosphates at the hydroxy groups of the mannose moiety, the low oral bioavailability could be overcome by an increased solubility of the resulting prodrug. [46] Furthermore, squaric acid derivatives of mannose [47,48] and indolylphenyl derivatives [49] were reported and selectivity studies [42,50] for FimH anfound to inhibit biofilm formation and disrupt mature biofilms in vitro (IC 50 = 4 and 92 µM, respectively) and influence both las and rhl quorum sensing systems.…”