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Updated: Sep 16, 2025
System for Efficacy and Cytotoxicity Screening of Inhibitors Targeting Intracellular Mycobacterium tuberculosis
Published on: April 5, 2017
Thienopyrimidine amide analogs target MmpL3 in Mycobacterium tuberculosis
Vanessa Pietrowski Baldin1, Christopher L Harding1, Diana Quach2
1Center for Global Infectious Disease Research, Seattle Children's Research Institute, Seattle, United States.
Objectives:
The identification of novel agents with mechanisms of action distinct from those currently utilized in tuberculosis treatment remains a significant challenge. The mycobacterial protein MmpL3 has emerged as a promising drug target due to its essential role in the synthesis of the cell wall of Mycobacterium tuberculosis. We previously identified novel thienopyrimidine amides with good anti-tubercular activity.
Methods:
We profiled a subset of thienopyrimidine amides determining activity against intracellular bacteria and bactericidal activity against replicating bacteria. We ran assays to determine mode of action by measuring cell wall stress, ATP production, and bacterial cytological profiling. We determined activity against a strain of M. tuberculosis with mutations in MmpL3. We isolated and sequenced resistant mutants.
Results:
We tested five analogs against a strain of M. tuberculosis with mutations in MmpL3 and determined that they lost potency. Analogs induced PiniBAC, a reporter for cell wall stress, and led to an ATP boost characteristic of cell wall inhibitors. Bacterial cytological profiling of a representative compound revealed a morphological profile consistent with other MmpL3 inhibitors.
Conclusions:
Together, our data support MmpL3 as the most probable drug target for the TPA analogs and add to the growing list of scaffolds that can inhibit this vulnerable transporter.
Insights
Novel thienopyrimidine amides show promise as tuberculosis treatments by targeting the essential MmpL3 protein. These compounds induce cell wall stress, supporting their potential as new anti-tubercular agents.
Area of Science:
- Microbiology
- Drug Discovery
- Medicinal Chemistry
Background:
- Tuberculosis (TB) treatment requires novel agents with distinct mechanisms of action.
- The mycobacterial protein MmpL3 is crucial for Mycobacterium tuberculosis cell wall synthesis and is a promising drug target.
- Previous research identified thienopyrimidine amides (TPAs) with anti-tubercular activity.
Purpose of the Study:
- To investigate the anti-tubercular activity and mechanism of action of novel thienopyrimidine amides.
- To confirm MmpL3 as the drug target for these compounds.
- To assess activity against intracellular and replicating M. tuberculosis.
Main Methods:
- Profiling of TPAs for activity against intracellular and replicating bacteria.
- Assays to determine mode of action, including cell wall stress (PiniBAC induction), ATP production, and bacterial cytological profiling.
- Testing TPA analogs against M. tuberculosis strains with MmpL3 mutations and sequencing resistant mutants.
Main Results:
- Five TPA analogs showed reduced potency against M. tuberculosis strains with MmpL3 mutations.
- TPAs induced PiniBAC, indicating cell wall stress, and increased ATP production, consistent with cell wall inhibitors.
- Bacterial cytological profiling supported MmpL3 as the target.
Conclusions:
- MmpL3 is the likely drug target for the TPA analogs.
- These findings contribute to the development of novel scaffolds targeting MmpL3 for tuberculosis treatment.
