The Centers for Disease Control and Prevention estimates that at least two million illnesses and 23,000 deaths annually are caused by antimicrobial-resistant bacteria in the United States. The Gram-negative (G-) pathogens are of particular concern, as they account for roughly 99,000 deaths and $20B in health care costs a year. Treatment options for G- infections have become increasingly limited due to rapid emergence of multi-drug resistance (MDR) to existing and newly approved antimicrobial agents, highlighting the need for alternative strategies to prevent MDR G- infections. Further, although it?s rare, MDR can potentially be a serious problem in G- Select Agents, given the highly transmissible nature of the MDR determinants in G- bacteria and the fact that select agents are persisting in the environment. Thus, a broad spectrum agent that leverages immunological mechanisms to prevent as well as to treat high-threat G- bacterial infections in high risk populations would possess a unique advantage in addressing this need. The innovative Cloudbreak? Antibody Drug Conjugates (ADCs) platform, developed at Cidara Therapeutics, is a broad-spectrum G- active drug candidate that uses a fundamentally new immune-based approach to prevent and treat G- infections. Similar to successful cancer bispecific agents, ADCs bind conserved targets on pathogens via a Targeting Moiety (TM) while simultaneously engaging multiple arms of the immune system via an Effector Moiety (EM). The TM is comprised of a dimeric peptide that binds tightly to lipopolysaccharide (LPS) and confers broad spectrum G- coverage with potent intrinsic antimicrobial activity. The EM is a human IgG1 Fc, which collectively activates complement dependent cytotoxicity (CDC), antibody (Ab)-dependent cell-mediated cytotoxicity (ADCC), and Ab-dependent cell phagocytosis (ADCP) to clear high-threat G- pathogens from the host, via recognition by Fc? receptors on host cells. This innovative approach involving efficient cell targeting with inherent cell killing catalyzes a robust immune response by more effectively presenting the pathogen to immune components for clearance. CTC-026 is our lead ADC candidate and has demonstrated highly promising properties as an immunoprophylactic and therapeutic agent: broad spectrum antibacterial activity that is both intrinsic and immune-driven, acute safety in rodents, in vivo efficacy in mouse models of Escherichia coli sepsis and Acinetobacter baumannii pneumonia, and a 67 hour plasma half-life in mice. Further optimization of potency and spectrum and in-depth evaluation of pharmacological and toxicological properties of this lead are proposed in this application. The overarching goal of this proposal is to identify a qualified lead development candidate in Year 3 and an Investigational new drug (IND) candidate by the end of Year 5, that meets these criteria: 1) acceptable stability and solubility for IV formulation, 2) MIC90s ?1 M against clinical isolates (including MDR) of Klebsiella, Acinetobacter, Pseudomonas, E. coli and select agents Francisella tularensis, Yersinia pestis and Brucella species, 3) MIC90s ?1 M against MCR-1, MCR-2 and other colistin-resistant G- clinical isolates, 4) robust in vivo prophylactic efficacy against MDR G- infections in a time window 48-72h prior to infection, and potent therapeutic efficacy better than standard of care with a ?3-fold therapeutic window after the infection, 5) PK/PD parameters to support once weekly or better dosing in humans, 6) a NOAEL in GLP toxicology studies in rats and Cynomolgus monkeys at least fivefold higher than the targeted clinical dose, and 7) a scalable synthesis to GMP product.
High-threat Gram-negative bacterial pathogens, including select agents (Yersinia pestis, Francisella tularensis, and Brucella spp.), and multidrug resistant Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Acinetobacter baumannii and Enterobacter species are associated with life-threatening systemic infections which pose an enormous burden to the public health system. Their ability to rapidly develop drug resistance and propagate as multi-drug resistant, and now pan-resistant pathogens, begs the need for new agents that leverage immunological mechanisms to both prevent and treat infection in high risk populations. In an effort to meet this challenge, we propose to develop a novel immunoprophylactic agent as a highly effective countermeasure against this increasingly serious public health threat.