Targeted development and selective delivery of small molecule antibiotics for the treatment of multidrug resistant Pseudomonas aeruginosa infections

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PROJECT SUMMARY The continued rise in the number multidrug resistant (MDR) bacterial infections, especially those caused by Gram-negative pathogens, coupled with the dearth of novel antibiotics being FDA approved in the past 3 decades has led to a dire situation that could result in millions of deaths per year worldwide if current trends continue. MDR Pseudomonas aeruginosa (PA), a Gram-negative bacterium, is one of leading causes of nosocomial infections and has been designated as a “Serious Threat” by the CDC due to lack of viable treatment options. Two barriers that must be overcome when treating MDRPA infections are wide-spread resistance to currently prescribed antibiotics with similar mechanisms of action and poor accumulation of the antibiotic in the cell due to its additional outer membrane (OM) and promiscuous efflux pumps. Therefore, antibiotics that target unexplored cellular targets in MDRPA and methods for improved antibiotic delivery to those targets must be developed. This work proposes to first probe ATP synthase, an essential protein for all life, as an underexplored target for antibiotic development by modifying the known anti-tubercular drug bedaquiline. By comparing residue differences in the BDQ binding site between Mycobacterium tuberculosis and PA, bedaquiline-like molecules capable of inhibiting PA ATP synthase selectively will be designed. This work will also give insight into the role of ATP synthase inhibition in antibiotic drug discovery. Next, a cleavable adjuvant-antibiotic hybrid strategy will be developed to overcome the OM penetration problem in PA. The OM is made up of an asymmetric bilayer of lipopolysaccharides, porins, and substrate channels, which severely limits small molecule entry into the cell by size and charge. It has been recently demonstrated that polycationic molecules, such as aminoglycosides and bisamidines, are able to cross the OM by self-promoted uptake and are able to act as adjuvants to promote the uptake of other antibiotics. A cleavable bisamidine-antibiotic drug delivery system will be synthesized that capitalizes on the synthetic bisamidine being able to promote diffusion of the tethered antibiotic across the OM and the antibiotic being released upon enzymatic linker cleavage in the periplasm. Using a covalent but cleavable linker system ensures cellular uptake of the antibiotic without reducing antibiotic activity once in the cell. The work proposed herein will not only produce new and highly efficacious small molecules to treat MDRPA infections, it will also develop a robust and modifiable method for delivering a wide variety of antibiotics that cannot cross the OM on their own to the interior of the cell. This will ultimately increase the number of antibiotics capable of treating these infections and help to combat the growing number of resistant bacteria clinically.