Confronting Tuberculosis: A Synthetic Quinoline-Isonicotinic Acid Hydrazide Hybrid Compound as a Potent Lead Molecule Against Mycobacterium tuberculosis

The current tuberculosis (TB) treatment is challenged by a complex first-line treatment for drug-sensitive (DS) TB. Additionally, the prevalence of multidrug (MDR)- and extensively drug (XDR)-resistant TB necessitates the search for new drug prototypes. We synthesized and screened 30 hybrid compounds containing aminopyridine and 2-chloro-3-formyl quinoline to arrive at a compound with potent antimycobacterial activity, UH-NIP-16. Subsequently, antimycobacterial activity against DS and MDR Mycobacterium tuberculosis (M.tb) strains were performed. It demonstrated an MIC50 value of 1.86 +/- 0.21 mu M for laboratory pathogenic M.tb strain H37Rv and 3.045 +/- 0.813 mu M for a clinical M.tb strain CDC1551. UH-NIP-16 also decreased the MIC50 values of streptomycin, isoniazid, ethambutol, and bedaquiline to about 45, 55, 68, and 76%, respectively, when used in combination, potentiating their activities. The molecule was active against a clinical MDR M.tb strain. Cytotoxicity on PBMCs from healthy donors and on human cell lines was found to be negligible. Further, blind docking of UH-NIP-16 using Auto Dock Vina and MGL tools onto diverse M.tb proteins showed high binding affinities with multiple M.tb proteins, the top five targets being metabolically critical proteins CelA1, DevS, MmaA4, lysine acetyltransferase, and immunity factor for tuberculosis necrotizing toxin. These bindings were confirmed by fluorescence spectroscopy using a representative protein, MmaA4. Envisaging that a pathogen will have a lower probability of developing resistance to a hybrid molecule with multiple targets, we propose that UH-NIP-16 can be further developed as a lead molecule with the bacteriostatic potential against M.tb, both alone and in combination with first-line drugs.