Host Directed Orynotide for MDR Gram Negative Bacterial Infections

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PROJECT SUMMARY The goal of this grant proposal is to advance the preclinical development of a novel macrocyclic peptide, Orynotide™ MTD12813, for treatment of multidrug resistant (MDR) Gram negative bacterial infections, with the initial focus being on infections caused by carbapenem-resistant Enterobacteriaceae (CRE). The emergence of infections by multiple CRE pathogens has created an urgent public health threat, because carbapenems are drugs of last resort for infections caused by an increasing fraction of MDR bacterial pathogens. Just two species, Klebsiella pneumoniae and Escherichia coli, cause an estimated 140,000 nosocomial infections per year in the United States alone, and many are carbapenem resistant. There is global consensus that new preventive and therapeutic strategies are urgently needed to combat the growing problem of MDR bacterial infections. The applicants, leaders in the field of θ-defensin biology, are responding to this need by developing Orynotides, a new class of host-directed antimicrobial macrocyclic peptides bioinspired by the structural and biological properties of theta (θ)-defensins, macrocyclic peptides expressed exclusively in Old World monkeys (but not humans). Exploiting the pleiotropic host defense properties of θ-defensins, we produced a library of novel Orynotides that includes several compounds that are highly effective in MDR Gram negative septicemia models. Hit-to-lead studies identified MTD12813 as the lead Orynotide candidate for preclinical development as a first- in-class immunotherapeutic agent for MDR Gram negative infections. In the mouse peritoneal sepsis model, single dose administration of MTD12813 is highly effective (enhanced survival with concomitant bacterial clearance) against multiple strains of CRE-K. pneumoniae and CRE-E. coli, and additionally was shown to be effective in septicemia caused by MDR Acinetobacter baumannii. Consistent with the range of pathogens against which MTD12813 is active in vivo, we showed that the peptide’s mode of action is immunotherapeutic, promoting host-mediated bacterial clearance, stimulating phagocytosis and neutrophil recruitment, while modulating levels of otherwise dysregulated proinflammatory cytokines. These data indicate that MTD12813 is a novel immunotherapeutic agent effective in the treatment of Gram negative bacterial pathogens. The peptide is readily manufacturable ( ~1.5 g on hand), highly stable in human plasma and whole blood, resistant to bacterial proteases, and well tolerated when administered by numerous routes. In the proposed studies, we will advance the preclinical characterization of MTD12813. Aim 1 studies will include production of GLP MTD12813 and other critical reagents, pharmacokinetic (PK) and PK/pharmacodynamic analyses, and ADME studies. Aim 2 will focus on illuminating mechanism(s) of action at the cellular and molecular level. Aim 3 objectives will include preclinical non-GLP safety and toxicokinetic studies in rats and beagle dogs, evaluation of immunogenicity, development of an antidrug antibody assay, and culminate with formal GLP safety studies. The goal of these aims is to advance the preclinical development of MTD12813 to IND filing with the FDA.