Compounds for use in the treatment of mycobacterial infections: a patent evaluation (WO2014049107A1)

Repurposing Drugs to Combat Drug Resistance in Leprosy: A Review of Opportunities

Leprosy is caused by extremely slow-growing and uncultivated mycobacterial pathogens, namely Mycobacterium leprae and M. lepromatosis. Nearly 95% of the new cases of leprosy recorded globally are found in India, Brazil, and 20 other priority countries [WHO, 2019], of which nearly two-thirds of the cases are reported in India alone. Currently, leprosy is treated with dapsone, rifampicin, and clofazimine, also known as multi-drug therapy [MDT], as per the recommendations of WHO since 1981. Still, the number of new leprosy cases recorded globally has remained constant in the last one-decade ,and resistance to multiple drugs has been documented in various parts of the world, even though relapses are rare in patients treated with MDT. Antimicrobial resistance testing against M. leprae or the evaluation of the anti-leprosy activity of new drugs remains a challenge as leprosy bacilli do not grow in vitro. Besides, developing a new drug against leprosy through the conventional drug development process is not economically attractive or viable for pharma companies. Therefore, a promising alternative is the repurposing of existing drugs/approved medications or their derivatives for assessing their anti-leprosy potential. It is an efficient method to identify novel medicinal and therapeutic properties of approved drug molecules. Any combinatorial chemotherapy that combines these repurposed drugs with the existing first-line [MDT] and second-line drugs could improve the bactericidal and synergistic effects against these notorious bacteria and can help in achieving the much-cherished goal of "leprosy-free world". This review highlights novel opportunities for drug repurposing to combat resistance to current therapeutic approaches.

Functional details of the Mycobacterium tuberculosis VapBC26 toxin-antitoxin system based on a structural study: insights into unique binding and antibiotic peptides

Toxin-antitoxin (TA) systems are essential for bacterial persistence under stressful conditions. In particular, Mycobacterium tuberculosis express VapBC TA genes that encode the stable VapC toxin and the labile VapB antitoxin. Under normal conditions, these proteins interact to form a non-toxic TA complex, but the toxin is activated by release from the antitoxin in response to unfavorable conditions. Here, we present the crystal structure of the M. tuberculosis VapBC26 complex and show that the VapC26 toxin contains a pilus retraction protein (PilT) N-terminal (PIN) domain that is essential for ribonuclease activity and that, the VapB26 antitoxin folds into a ribbon-helix-helix DNA-binding motif at the N-terminus. The active site of VapC26 is sterically blocked by the flexible C-terminal region of VapB26. The C-terminal region of free VapB26 adopts an unfolded conformation but forms a helix upon binding to VapC26. The results of RNase activity assays show that Mg²⁺ and Mn²⁺ are essential for the ribonuclease activity of VapC26. As shown in the nuclear magnetic resonance spectra, several residues of VapB26 participate in the specific binding to the promoter region of the VapBC26 operon. In addition, toxin-mimicking peptides were designed that inhibit TA complex formation and thereby increase toxin activity, providing a novel approach to the development of new antibiotics.

Solution NMR Studies of Mycobacterium tuberculosis Proteins for Antibiotic Target Discovery

Tuberculosis is an infectious disease caused by Mycobacteriumtuberculosis, which triggers severe pulmonary diseases. Recently, multidrug/extensively drug-resistant tuberculosis strains have emerged and continue to threaten global health. Because of the development of drug-resistant tuberculosis, there is an urgent need for novel antibiotics to treat these drug-resistant bacteria. In light of the clinical importance of M. tuberculosis, 2067 structures of M. tuberculsosis proteins have been determined. Among them, 52 structures have been solved and studied using solution nuclear magnetic resonance (NMR). The functional details based on structural analysis of M. tuberculosis using NMR can provide essential biochemical data for the development of novel antibiotic drugs. In this review, we introduce diverse structural and biochemical studies on M. tuberculosis proteins determined using NMR spectroscopy.