ABSTRACT
Scaffold hopping from the thiazolopyridine ureas led to thiazolopyridone ureas with potent antitubercular activity acting through inhibition of DNA GyrB ATPase activity. Structural diversity was introduced, by extension of substituents from the thiazolopyridone N-4 position, to access hydrophobic interactions in the ribose pocket of the ATP binding region of GyrB. Further optimization of hydrogen bond interactions with arginines in site-2 of GyrB active site pocket led to potent inhibition of the enzyme (IC50 2 nM) along with potent cellular activity (MIC=0.1 µM) against Mycobacterium tuberculosis (Mtb). Efficacy was demonstrated in an acute mouse model of tuberculosis on oral administration.
Subject(s)
Mycobacterium tuberculosis/drug effects , Pyridones/chemical synthesis , Thiazoles/chemical synthesis , Topoisomerase II Inhibitors/chemical synthesis , Topoisomerase II Inhibitors/pharmacology , Urea/chemical synthesis , Urea/pharmacology , Administration, Oral , Animals , Antitubercular Agents/chemical synthesis , Antitubercular Agents/chemistry , Antitubercular Agents/pharmacology , Disease Models, Animal , Inhibitory Concentration 50 , Mice , Microbial Sensitivity Tests , Molecular Structure , Pyridones/chemistry , Pyridones/pharmacology , Thiazoles/chemistry , Thiazoles/pharmacology , Topoisomerase II Inhibitors/chemistry , Urea/chemistryABSTRACT
A pharmacophore-based search led to the identification of thiazolopyridine ureas as a novel scaffold with antitubercular activity acting through inhibition of DNA Gyrase B (GyrB) ATPase. Evaluation of the binding mode of thiazolopyridines in a Mycobacterium tuberculosis (Mtb) GyrB homology model prompted exploration of the side chains at the thiazolopyridine ring C-5 position to access the ribose/solvent pocket. Potent compounds with GyrB IC50 ≤ 1 nM and Mtb MIC ≤ 0.1 µM were obtained with certain combinations of side chains at the C-5 position and heterocycles at the C-6 position of the thiazolopyridine core. Substitutions at C-5 also enabled optimization of the physicochemical properties. Representative compounds were cocrystallized with Streptococcus pneumoniae (Spn) ParE; these confirmed the binding modes predicted by the homology model. The target link to GyrB was confirmed by genetic mapping of the mutations conferring resistance to thiazolopyridine ureas. The compounds are bactericidal in vitro and efficacious in vivo in an acute murine model of tuberculosis.
