Jason G. Lewis

N-Alkyl Urea Hydroxamic Acids as a New Class of Peptide Deformylase Inhibitors with Antibacterial Activity

ABSTRACT Peptide deformylase (PDF) is a prokaryotic metalloenzyme that is essential for bacterial growth and is a new target for the development of antibacterial agents. All previously reported PDF inhibitors with sufficient antibacterial activity share the structural feature of a 2-substituted alkanoyl at the P1′ site. Using a combination of iterative parallel synthesis and traditional medicinal chemistry, we have identified a new class of PDF inhibitors with N-alkyl urea at the P1′ site. Compounds with MICs of ≤4 μg/ml against gram-positive and gram-negative pathogens, including Staphylococcusaureus, Streptococcuspneumoniae, and Haemophilusinfluenzae, have been identified. The concentrations needed to inhibit 50% of enzyme activity (IC50s) for Escherichiacoli Ni-PDF were ≤0.1 μM, demonstrating the specificity of the inhibitors. In addition, these compounds were very selective for PDF, with IC50s of consistently >200 μM for matrilysin and other mammalian metalloproteases. Structure-activity relationship analysis identified preferred substitutions resulting in improved potency and decreased cytotoxity. One of the compounds (VRC4307) was cocrystallized with PDF, and the enzyme-inhibitor structure was determined at a resolution of 1.7 Å. This structural information indicated that the urea compounds adopt a binding position similar to that previously determined for succinate hydroxamates. Two compounds, VRC4232 and VRC4307, displayed in vivo efficacy in a mouse protection assay, with 50% protective doses of 30.8 and 17.9 mg/kg of body weight, respectively. These N-alkyl urea hydroxamic acids provide a starting point for identifying new PDF inhibitors that can serve as antimicrobial agents.

Gastrointestinal Inhibition of Sodium-Hydrogen Exchanger 3 Reduces Phosphorus Absorption and Protects against Vascular Calcification in CKD

In CKD, phosphate retention arising from diminished GFR is a key early step in a pathologic cascade leading to hyperthyroidism, metabolic bone disease, vascular calcification, and cardiovascular mortality. Tenapanor, a minimally systemically available inhibitor of the intestinal sodium-hydrogen exchanger 3, is being evaluated in clinical trials for its potential to (1) lower gastrointestinal sodium absorption, (2) improve fluid overload-related symptoms, such as hypertension and proteinuria, in patients with CKD, and (3) reduce interdialytic weight gain and intradialytic hypotension in ESRD. Here, we report the effects of tenapanor on dietary phosphorous absorption. Oral administration of tenapanor or other intestinal sodium-hydrogen exchanger 3 inhibitors increased fecal phosphorus, decreased urine phosphorus excretion, and reduced [(33)P]orthophosphate uptake in rats. In a rat model of CKD and vascular calcification, tenapanor reduced sodium and phosphorus absorption and significantly decreased ectopic calcification, serum creatinine and serum phosphorus levels, circulating phosphaturic hormone fibroblast growth factor-23 levels, and heart mass. These results indicate that tenapanor is an effective inhibitor of dietary phosphorus absorption and suggest a new approach to phosphate management in renal disease and associated mineral disorders.

Design of Gut-Restricted Thiazolidine Agonists of G Protein-Coupled Bile Acid Receptor 1 (GPBAR1, TGR5)

Bile acid signaling and metabolism in the gastrointestinal tract have wide-ranging influences on systemic disease. G protein-coupled bile acid receptor 1 (GPBAR1, TGR5) is one of the major effectors in bile acid sensing, with demonstrated influence on metabolic, inflammatory, and proliferative processes. The pharmacologic utility of TGR5 agonists has been limited by systemic target-related effects such as excessive gallbladder filling and blockade of gallbladder emptying. Gut-restricted TGR5 agonists, however, have the potential to avoid these side effects and consequently be developed into drugs with acceptable safety profiles. We describe the discovery and optimization of a series of gut-restricted TGR5 agonists that elicit a potent response in mice, with minimal gallbladder-related effects. The series includes 12 (TGR5 EC50: human, 143 nM; mouse, 1.2 nM), a compound with minimal systemic availability that may have therapeutic value to patients with type 2 diabetes mellitus, nonalcoholic steatohepatitis, or inflammatory bowel disease.