New pyrazole-based derivatives targeting MmpL3 transporter in Mycobacterium tuberculosis: design, synthesis, biological evaluation and molecular docking studies.

This study addresses the urgent need for new drugs to combat multi-drug-resistant tuberculosis (MDR-TB). Focusing on MmpL3, a protein essential for mycobacterial cell wall synthesis, we designed and synthesised 50 new pyrazole-based amide derivatives. These compounds were then tested for their ability to inhibit the growth of various Mycobacterium tuberculosis (Mtb) strains, including both drug-susceptible and drug-resistant strains (resistant to isoniazid, rifampicin, or both). Two compounds, 15 and 35, emerged as potent inhibitors. They showed strong activity against both drug-susceptible and drug-resistant Mtb strains, with low minimum inhibitory concentration (MIC) values of 2 µg/mL and 2-4 µg/mL, respectively. Importantly, these compounds also demonstrated a high selectivity index, meaning they were significantly more toxic to Mtb cells than to human liver cells (HepG2). Compound 15 further proved to be bactericidal, effectively killing Mtb within six days. Interestingly, compounds 15 and 35 were inactive against lab-generated Mtb strains resistant to SQ109, a known MmpL3 inhibitor. This finding, supported by molecular docking, molecular dynamics simulations, and genetic analysis of the mmpl3 gene in the SQ109-resistant strains, strongly suggests that these novel compounds also target MmpL3. This research highlights the potential of pyrazole-based amides as a promising new class of anti-TB drugs. By targeting MmpL3, these compounds offer a novel mechanism of action to combat drug-resistant TB, potentially leading to improved treatment outcomes.