Mycobacterium tuberculosis codes for an essential NAD+-dependent DNA ligase (MtuLigA) which is a novel, validated, and attractive drug target. We created mutants of the enzyme by systematically deleting domains from the C-terminal end of the enzyme to probe for their functional roles in the DNA nick joining reaction. Deletion of just the BRCT domain from MtuLigA resulted in total loss of activity in in vitro assays. However, the mutant could form an AMP-ligase intermediate that suggests that the defects caused by deletion of the BRCT domain occur primarily at steps after enzyme adenylation. Furthermore, genetic complementation experiments using a LigA deficient E. coli strain demonstrates that the BRCT domain of MtuLigA is necessary for bacterial survival in contrast to E. coli and T. filiformis LigA, respectively. We also report the identification, through virtual screening, of a novel N-substituted tetracyclic indole that competes with NAD+ and inhibits the enzyme with IC50 in the low muM range. It exhibits approximately 15-fold better affinity for MtuLigA compared to human DNA ligase I. In vivo assays using LigA deficient S. typhimurium and E. coli strains suggest that the observed antibacterial activity of the inhibitor arises from specific inhibition of LigA over ATP ligases in the bacteria. In silico ligand-docking studies suggest that the exquisite specificity of the inhibitor arises on account of its mimicking the interactions of NAD+ with MtuLigA. An analysis of conserved water in the binding site of the enzyme suggests strategies for synthesis of improved inhibitors with better specificity and potency.

N-heterocycles, namely 1,2,4-oxadiazoles and 2,6 disubstituted pyrimidin-4-ones, have been synthesised in one pot via carboxamidation of amidines with aryl carboxylic acids and aryl propargylic acids under metal-free conditions.

Dithiolethiones are five-membered sulfur-containing cyclic scaffolds that exhibit antioxidative, anti-inflammatory, antithrombic and chemotherapeutic activities. Dithiolethiones display the chemopreventive and cytoprotective effects by activating the antioxidant response element and mounting the transcription of cytoprotective phase II enzymatic machinery. In addition, several classes of dithiolethiones efficiently modulate the activities of proteins that play crucial roles in normal and cancer cells, including glutathione S-transferase, cyclooxygenases and master regulator NF-κB. The present paper summarizes synthetic aspects, pharmacological potentials and biological attributes of dithiolethiones and its derivatives. Additionally, this review concludes with a discussion on how the current state-of-the-art technologies may help in defining a structure-activity relationship of dithiolethiones, thereby facilitating the design and synthesis of potent drug candidates.

The global effort to combat and contain the coronavirus disease 2019 (COVID-19) pandemic is now proceeding on a war footing. The world was slow to react to the developing crisis, but once the contours of the impending calamity became evident, the different state and non-state actors have raced to put their act together. The COVID-19 outbreak has blatantly exposed the shortcomings of our healthcare system and the limitations of medical science, despite considerable advances in recent years. To effectively tackle the current epidemic, almost unprecedented in the modern era, there is an urgent need for a concerted, sustained, and coordinated effort towards the development of new diagnostics, therapeutic and vaccines, and the ramping up of the healthcare infrastructure, especially in the poorer, underprivileged nations. Towards this end, researchers around the world are working tirelessly to develop new diagnostics, vaccines, and therapeutics. Efforts to develop a vaccine against COVID-19 are presently underway in several countries around the world, but a new vaccine is expected only by the end of the year-at the earliest. New drug development against COVID-19 and its approval may take even longer. Under such circumstances, drug repurposing has emerged as a realistic and effective strategy to counter the virus menace in the short run, and several antiviral and antimalarial medicines are currently in different stages of clinical trials. Researchers are also experimenting with nutrients, vitamins, monoclonal antibodies, and convalescent plasma as immunity boosters against the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). This report presents a critical analysis of the global clinical trial landscape for COVID-19 with an emphasis on the therapeutic agents and vaccines currently being tested at pandemic speed.

No abstract