Antibiotic resistant bacteria are a major threat to human health. Each year in the United States, approximately 2 million people are infected with bacteria that are resistant to antibiotics resulting in at least 23,000 deaths. The development of novel antibiotics is needed. However, de novo antibiotic development is resource intensive. Given the poor return on investment, major pharmaceutical companies have significantly decreased antibiotic Research and Development efforts. Academic labs generally do not have access to compounds and sufficient data for rationale design. Veterans who undergo surgical procedures for trauma, including head trauma, are vulnerable to multiple surgical infection, sometimes with organisms that are unlikely to ever represent an attractive target for pharmaceutical companies. Antibiotic development that capitalizes on existing drug designwork conducted by industry, may avoid some of the expensive missteps due to poor pharmacologic properties that can inadvertently arise in the lead selection. Our approach uses structure-based computational modeling to repurpose drugs as antibiotics. Previous work in our lab demonstrated that inhibition of a Listeria kinase, belonging to a family of Penicillin binding And Serine/Threonine kinase Associated (PASTA) proteins, can sensitize the bacteria to beta-lactam antibiotics. Bacterial Serine/Threonine kinases are signal transducers and our work suggests they are a novel drug development target. While PASTA kinases are common in some gram-positive bacteria, we found there is drug selectivity, not only between human and bacterial kinases, but also between bacterial kinases. We are targeting the subset of PASTA kinase containing bacteria with a large back pocket. We have already obtained a crystal structure of our target bacterial kinase (PknB) with a lead compound demonstrating this pocket. This information enables us to specifically modify the lead to both increase potency and maximize selectivity using previously defined structure activity relationships with human kinases. Furthermore, our atomic resolution drug: target structure will guide us on regions of the drug that can be modified to explicitly test Lipinski's rules for drug development and determine if they should be modified for antibiotic drug development. In this proposal, we will build on our existing work with the following Specific Aims: Aim 1: Design, synthesize, and test both biochemically and microbiologically novel aminofurazan kinase inhibitors that exploit the uniquely shaped back pocket of some of the PknB family of kinases. Aim 2: Test the toxicity of these novel kinase inhibitors, as well as determine the effectiveness of combined beta lactam antibiotics with kinase inhibition in an animal model (Danio rerio). We will analyze the effect of our kinase inhibitors on both a panel of human kinases as well as on embryogenesis and fertility in zebrafish. When this work is complete, we will have generated data on how to design kinase inhibitors that act poorly against human and zebrafish kinases, but are potent against certain bacterial kinases. Pathogens that include kinases with this unique back pocket morphology include diverse skin and soil bacteria that complicate traumatic and surgical infections in the VA such as Clostridia, Nocardia, Propionibacterium acnes, and Mycobacterium. Furthermore, our work will set the stage for early stage trials on treating drug resistant mycobacterial and nocardial infections as well as atypical skin organisms that can complicate surgical infections common in veterans using a novel agent that synergizes with an existing antibiotic class with low toxicity.
NIH ExPorter
NIH ExPorter