Synthesis of novel high-affinity FimH antagonists with improved pharmacokinetic properties

Abstract

Urinary tract infections (UTIs) belong to the most common bacterial infections worldwide. Uropathogenic Escherichia coli (UPEC) are held accountable for majority of the cases. Millions of people suffer from UTI each year, with the highest incidence rate reported among women. Moreover, woman once affected will most likely experience a recurrent infection. High prevalence and recurrence of UTI lead to considerable medical costs. The current treatment generally involves antibiotics. However, choosing a proper antibiotic therapy becomes more difficult as resistant strains rapidly proliferate. Therefore, the need to develop alternative, non-antibiotic strategies is more pressing than ever. UPEC express filamentous organelles called type 1 pili (fimbriae), which protrude from the bacterial surface and mediate the adhesion to the bladder-epithelial cells. The mannose-specific adhesin FimH is located on the distal end of the pili. It contains the mannose-specific carbohydrate recognition domain (CRD), which binds to highly mannosylated uroplakin 1a (UP1a) expressed by urothelial cells leading to the infection. The compounds capable of blocking the interaction between FimH and surface-exposed glycans pave the way for a novel anti-adhesive strategy to treat and prevent UTI. The first part of the thesis addresses the problem of poor oral bioavailability arising from high polarity of the FimH antagonists. The strategy involves a prodrug approach, in which lipophilic esters are introduced to the parent compounds either on the aglycone’s carboxylic acid or the mannose moiety. The absorption potential as well as propensity to hydrolysis by esterases of liver or plasma was evaluated. The second part of the thesis emphasizes the optimization of the pharmacodynamic properties of FimH antagonists. In the first approach, the mannose moiety was modified in order to explore a cavity located at the entrance to binding pocket. The obtained antagonists were evaluated in competitive binding assay and by isothermal titration calorimetry (ITC) to reveal their thermodynamic binding profile. The second approach involved an elongation of the aglycone to allow additional interactions with the guanidinium side chain of Arg98. For the evaluation of these antagonists, competitive binding assays with the wild type FimH and the R98A mutant was established.