Harnessing Amide Linkers for Antitubercular Drug Development

PROJECT SUMMARY Tuberculosis (TB) is a global health crisis. As the second leading cause of death due to infectious disease, it claims roughly 1.5 million lives a year. Although TB can be treated, the curative regimen is complicated and takes several months. Drug-resistant Mycobacterium tuberculosis (Mtb), including totally drug-resistant strains, is steadily increasing in prevalence. Therefore, novel therapeutics with the potential to decrease treatment duration and increase barriers to resistance are essential for disease eradication. Most TB drug discovery programs have taken target-based approaches and largely ignored intrabacterial metabolism. However, several first- and second- line antituberculars penetrate Mtb as prodrugs and are intrabacterially metabolized into their active form. When faced with the markedly lipid-rich, hydrophobic environment of the Mtb cell envelope, prodrugs have the ability to enter the cell and subsequently release more polar, Mtb-active moieties within the bacterium. Most Mtb prodrugs are activated by non-essential enzymes, and, as a consequence, resistance develops quickly. For example, pyrazinamide (PZA), a key first-line antitubercular that enables a shortened TB drug regimen, is activated to pyrazinoic acid (POA) by the non-essential amidase PncA, and the vast majority of PZA resistance is caused by mutations in this activating gene. Notably, several other Mtb amidases have also been shown to metabolize amide antituberculars, thereby activating prodrugs and inactivating active drug compounds. We hypothesize that we can harness Mtb amidases to design and activate amide prodrugs within Mtb that are active in drug-resistant disease and that have increased barriers to resistance. Our proposal aims to 1) study the amide-amidase interactions to identify amide prodrugs that are activated by more than one amidase and 2) link POA to amine metabolites from parent compounds that demonstrate amide hydrolysis within Mtb to generate potential POA-releasing conjugates that are activated by non-PncA amidases. The majority of amidases are non-essential and likely have overlapping functions, enabling the discovery of amide-containing antituberculars that are activated by multiple amidases. Furthermore, the release of POA by amidases other than PncA would retain PZA-like activity in PZA-resistant strains, restoring the activity of a first-line antitubercular critical for shorter TB regimens. This approach will introduce a novel framework for TB prodrug discovery that can be applied to other classes of small molecules and their activating enzymes. In all, the proposed project and training plan will greatly further my development as a researcher and independent scientific thinker by introducing me to new scientific concepts and techniques and providing ample opportunity for me the integrate my research and clinical experiences. Together, Rutgers New Jersey Medical School, the Public Health Research Institute, and the Global TB Institute create a highly collaborative and highly translational environment that uniquely benefit my training as an infectious disease physician-scientist.