Peptide-Conjugated Phosphorodiamidate Morpholino Oligomers Retain Activity against Multidrug-Resistant Pseudomonas aeruginosa In Vitro and In Vivo

Most antimicrobials currently in the clinical pipeline are modifications of existing classes of antibiotics and are considered short-term solutions due to the emergence of resistance. Pseudomonas aeruginosa represents a major challenge for new antimicrobial drug discovery due to its versatile lifestyle, ability to develop resistance to most antibiotic classes, and capacity to form robust biofilms on surfaces and in certain hosts such as those living with cystic fibrosis (CF). A precision antibiotic approach to treating Pseudomonas could be achieved with an antisense method, specifically by using peptide-conjugated phosphorodiamidate morpholino oligomers (PPMOs). Here, we demonstrate that PPMOs targeting acpP (acyl carrier protein), lpxC (UDP-(3-O-acyl)-N-acetylglucosamine deacetylase), and rpsJ (30S ribosomal protein S10) inhibited the in vitro growth of several multidrug-resistant clinical P. aeruginosa isolates at levels equivalent to those that were effective against sensitive strains. Lead PPMOs reduced established pseudomonal biofilms alone or in combination with tobramycin or piperacillin-tazobactam. Lead PPMO dosing alone or combined with tobramycin in an acute pneumonia model reduced lung bacterial burden in treated mice at 24 h and reduced morbidity up to 5 days postinfection. PPMOs reduced bacterial burden of extensively drug-resistant P. aeruginosa in the same model and resulted in superior survival compared to conventional antibiotics. These data suggest that lead PPMOs alone or in combination with clinically relevant antibiotics represent a promising therapeutic approach for combating P. aeruginosa infections. IMPORTANCE Numerous Gram-negative bacteria are becoming increasingly resistant to multiple, if not all, classes of existing antibiotics. Multidrug-resistant Pseudomonas aeruginosa bacteria are a major cause of health care-associated infections in a variety of clinical settings, endangering patients who are immunocompromised or those who suffer from chronic infections, such as people with cystic fibrosis (CF). Herein, we utilize antisense molecules that target mRNA of genes essential to bacterial growth, preventing the formation of the target proteins, including acpP, rpsJ, and lpxC. We demonstrate here that antisense molecules targeted to essential genes, alone or in combination with clinically relevant antibiotics, were effective in reducing biofilms and protected mice in a lethal model of acute pneumonia.