Pyrrolidinone and pyrrolidine derivatives: Evaluation as inhibitors of InhA and Mycobacterium tuberculosis.

A series of GEQ analogues bearing pyrrolidinone or pyrrolidine cores were synthesized and evaluated against InhA, essential target for Mycobacterium tuberculosis (M.tb) survival. The compounds were also evaluated against M.tb H37Rv growth. Interestingly, some of the compounds, not efficient as InhA inhibitors, are active against M.tb with MICs up to 1.4 µM. In particular, compound 4b was screened with different M.tb mutated strains in order to identify the cellular target, but without success, suggesting a new possible mode of action.

Thiophenecarboxamide Derivatives Activated by EthA Kill Mycobacterium tuberculosis by Inhibiting the CTP Synthetase PyrG.

To combat the emergence of drug-resistant strains of Mycobacterium tuberculosis, new antitubercular agents and novel drug targets are needed. Phenotypic screening of a library of 594 hit compounds uncovered two leads that were active against M. tuberculosis in its replicating, non-replicating, and intracellular states: compounds 7947882 (5-methyl-N-(4-nitrophenyl)thiophene-2-carboxamide) and 7904688 (3-phenyl-N-[(4-piperidin-1-ylphenyl)carbamothioyl]propanamide). Mutants resistant to both compounds harbored mutations in ethA (rv3854c), the gene encoding the monooxygenase EthA, and/or in pyrG (rv1699) coding for the CTP synthetase, PyrG. Biochemical investigations demonstrated that EthA is responsible for the activation of the compounds, and by mass spectrometry we identified the active metabolite of 7947882, which directly inhibits PyrG activity. Metabolomic studies revealed that pharmacological inhibition of PyrG strongly perturbs DNA and RNA biosynthesis, and other metabolic processes requiring nucleotides. Finally, the crystal structure of PyrG was solved, paving the way for rational drug design with this newly validated drug target.