1053. The β-Lactamase Inhibitor QPX7728 Restores the Activity of β-Lactam Agents against Contemporary Extended-Spectrum β-lactamase (ESBL)-Producing and Carbapenem-Resistant Enterobacterales (CRE) Isolates, Including Isolates Producing Metallo-β-lactamases

Abstract Background The β-lactam (BL)/ β-lactamase inhibitor (BLI) combinations approved in the last 10 years are active against most ESBL-producing Enterobacterales (ENT) and CRE isolates, but have limited activity against metallo-β-lactamase (MBL)-producing ENT. We evaluated the activity of QPX7728 (QPX), a novel BLI with intravenous (IV) and oral availability, in combination with BL agents. We tested ENT isolates carrying the most common BL genes such as blaCTX-M, transferable AmpCs, oxacillinases, MBLs, and serine carbapenemases. Methods A total of 1,027 ENT isolates were susceptibility (S) tested by reference broth microdilution against aztreonam (ATM), cefepime (FEP), cefdinir (CDR), ceftibuten (CTB), ceftolozane (CT) and piperacillin (PT) with fixed 4 mg/L of tazobactam, biapenem (BPM), meropenem (MER), and tebipenem (TEB) combined with QPX at fixed 4 and 8 mg/L. All isolates were genetically characterized using whole genome sequencing and included 520 ESBL-producers and 507 CRE with 168 producing MBLs. Results BL agents tested alone had limited activity against this challenge set of isolates (MIC90, ≥32 mg/L); however, MIC90 values decreased ≥32-fold with the addition of QPX at the highest concentration tested (Table). Oral agents, CTB,CDR and TEB were tested with QPX at a fixed 4 mg/L and showed a 32- to 128-fold increase in potency (MIC90, 0.5-4 mg/L). ATM and FEP were tested with QPX at a fixed 4 and 8 mg/L and displayed MIC90 values ranging from 0.12-0.5 mg/L. ATM and FEP, tested with 8 mg/L of QPX, inhibited 99.8% of isolates at the breakpoint for the BL agent alone. BLI inhibitor combinations PT and CT displayed MIC90 values of 2 and 4 mg/L with the addition of 8 mg/L QPX. MER with QPX at a fixed 4 mg/L and 8 mg/L inhibited 99.8% and 100% of isolates, respectively. Conclusion The activity of all BLs evaluated was restored when combined with QPX tested against this challenging collection of 1,027 ENT isolates displaying various resistance mechanisms, including difficult to treat CRE isolates and MBL producers. Further development of QPX with various orally- and IV-available BL agents appears warranted. Disclosures Jill Lindley, Bravos Biosciences (Research Grant or Support)ContraFect Corporation (Research Grant or Support)Pfizer, Inc. (Research Grant or Support)Qpex Biopharma (Research Grant or Support) Yahse Edah, AS, Qpex (Research Grant or Support) Olga Lomovskaya, PhD, Qpex Biopharma (Employee) Mariana Castanheira, PhD, AbbVie (formerly Allergan) (Research Grant or Support)Bravos Biosciences (Research Grant or Support)Cidara Therapeutics, Inc. (Research Grant or Support)Cipla Therapeutics (Research Grant or Support)Cipla USA Inc. (Research Grant or Support)GlaxoSmithKline (Research Grant or Support)Melinta Therapeutics, Inc. (Research Grant or Support)Melinta Therapeutics, LLC (Research Grant or Support)Pfizer, Inc. (Research Grant or Support)Qpex Biopharma (Research Grant or Support)Shionogi (Research Grant or Support)Spero Therapeutics (Research Grant or Support) Mariana Castanheira, PhD, Affinity Biosensors (Individual(s) Involved: Self): Research Grant or Support; Allergan (Individual(s) Involved: Self): Research Grant or Support; Amicrobe, Inc (Individual(s) Involved: Self): Research Grant or Support; Amplyx Pharma (Individual(s) Involved: Self): Research Grant or Support; Artugen Therapeutics USA, Inc. (Individual(s) Involved: Self): Research Grant or Support; Astellas (Individual(s) Involved: Self): Research Grant or Support; Basilea (Individual(s) Involved: Self): Research Grant or Support; Beth Israel Deaconess Medical Center (Individual(s) Involved: Self): Research Grant or Support; BIDMC (Individual(s) Involved: Self): Research Grant or Support; bioMerieux Inc. (Individual(s) Involved: Self): Research Grant or Support; BioVersys Ag (Individual(s) Involved: Self): Research Grant or Support; Bugworks (Individual(s) Involved: Self): Research Grant or Support; Cidara (Individual(s) Involved: Self): Research Grant or Support; Cipla (Individual(s) Involved: Self): Research Grant or Support; Contrafect (Individual(s) Involved: Self): Research Grant or Support; Cormedix (Individual(s) Involved: Self): Research Grant or Support; Crestone, Inc. (Individual(s) Involved: Self): Research Grant or Support; Curza (Individual(s) Involved: Self): Research Grant or Support; CXC7 (Individual(s) Involved: Self): Research Grant or Support; Entasis (Individual(s) Involved: Self): Research Grant or Support; Fedora Pharmaceutical (Individual(s) Involved: Self): Research Grant or Support; Fimbrion Therapeutics (Individual(s) Involved: Self): Research Grant or Support; Fox Chase (Individual(s) Involved: Self): Research Grant or Support; GlaxoSmithKline (Individual(s) Involved: Self): Research Grant or Support; Guardian Therapeutics (Individual(s) Involved: Self): Research Grant or Support; Hardy Diagnostics (Individual(s) Involved: Self): Research Grant or Support; IHMA (Individual(s) Involved: Self): Research Grant or Support; Janssen Research & Development (Individual(s) Involved: Self): Research Grant or Support; Johnson & Johnson (Individual(s) Involved: Self): Research Grant or Support; Kaleido Biosceinces (Individual(s) Involved: Self): Research Grant or Support; KBP Biosciences (Individual(s) Involved: Self): Research Grant or Support; Luminex (Individual(s) Involved: Self): Research Grant or Support; Matrivax (Individual(s) Involved: Self): Research Grant or Support; Mayo Clinic (Individual(s) Involved: Self): Research Grant or Support; Medpace (Individual(s) Involved: Self): Research Grant or Support; Meiji Seika Pharma Co., Ltd. (Individual(s) Involved: Self): Research Grant or Support; Melinta (Individual(s) Involved: Self): Research Grant or Support; Menarini (Individual(s) Involved: Self): Research Grant or Support; Merck (Individual(s) Involved: Self): Research Grant or Support; Meridian Bioscience Inc. (Individual(s) Involved: Self): Research Grant or Support; Micromyx (Individual(s) Involved: Self): Research Grant or Support; MicuRx (Individual(s) Involved: Self): Research Grant or Support; N8 Medical (Individual(s) Involved: Self): Research Grant or Support; Nabriva (Individual(s) Involved: Self): Research Grant or Support; National Institutes of Health (Individual(s) Involved: Self): Research Grant or Support; National University of Singapore (Individual(s) Involved: Self): Research Grant or Support; North Bristol NHS Trust (Individual(s) Involved: Self): Research Grant or Support; Novome Biotechnologies (Individual(s) Involved: Self): Research Grant or Support; Paratek (Individual(s) Involved: Self): Research Grant or Support; Pfizer (Individual(s) Involved: Self): Research Grant or Support; Prokaryotics Inc. (Individual(s) Involved: Self): Research Grant or Support; QPEX Biopharma (Individual(s) Involved: Self): Research Grant or Support; Rhode Island Hospital (Individual(s) Involved: Self): Research Grant or Support; RIHML (Individual(s) Involved: Self): Research Grant or Support; Roche (Individual(s) Involved: Self): Research Grant or Support; Roivant (Individual(s) Involved: Self): Research Grant or Support; Salvat (Individual(s) Involved: Self): Research Grant or Support; Scynexis (Individual(s) Involved: Self): Research Grant or Support; SeLux Diagnostics (Individual(s) Involved: Self): Research Grant or Support; Shionogi (Individual(s) Involved: Self): Research Grant or Support; Specific Diagnostics (Individual(s) Involved: Self): Research Grant or Support; Spero (Individual(s) Involved: Self): Research Grant or Support; SuperTrans Medical LT (Individual(s) Involved: Self): Research Grant or Support; T2 Biosystems (Individual(s) Involved: Self): Research Grant or Support; The University of Queensland (Individual(s) Involved: Self): Research Grant or Support; Thermo Fisher Scientific (Individual(s) Involved: Self): Research Grant or Support; Tufts Medical Center (Individual(s) Involved: Self): Research Grant or Support; Universite de Sherbrooke (Individual(s) Involved: Self): Research Grant or Support; University of Iowa (Individual(s) Involved: Self): Research Grant or Support; University of Iowa Hospitals and Clinics (Individual(s) Involved: Self): Research Grant or Support; University of Wisconsin (Individual(s) Involved: Self): Research Grant or Support; UNT System College of Pharmacy (Individual(s) Involved: Self): Research Grant or Support; URMC (Individual(s) Involved: Self): Research Grant or Support; UT Southwestern (Individual(s) Involved: Self): Research Grant or Support; VenatoRx (Individual(s) Involved: Self): Research Grant or Support; Viosera Therapeutics (Individual(s) Involved: Self): Research Grant or Support; Wayne State University (Individual(s) Involved: Self): Research Grant or Support


2
Walter Reed Army Institute of Research, Silver Spring, Maryland 204 and 205 study groups Session: P-60. New Vaccines Background. A safe and effective vaccine against dengue is needed to address an unmet medical need that affects a large portion of the world's population. Takeda's live attenuated tetravalent dengue vaccine candidate (TAK-003) has shown protection in an ongoing Phase 3 efficacy trial. TAK-003 contains an attenuated dengue type 2 virus (DENV-2), and 3 genetically modified viruses in which the structural proteins from each of the serotypes 1, 3 and 4 have been placed into the DENV-2 backbone. Exploratory immunological assessments have been a part of the TAK-003 clinical development plan to better understand the mechanisms of action of TAK-003, and to identify immune response signatures that may correlate with protection.
Methods. Cellular and humoral immune responses elicited by vaccination in dengue-naïve and dengue-exposed individuals were measured across several clinical trials. For the humoral response, several methods were used to measure the magnitude and characteristics of the antibodies following vaccination with TAK-003 including studies of neutralizing antibodies, antibodies that bind to the viral components of the vaccine, the affinity and complement fixing capabilities of antibodies specific to structural proteins, and additionally the level of antibodies specific to nonstructural protein 1 (NS1).
Results. A multifunctional cellular immune response was found following vaccination that primarily targeted nonstructural proteins in the DENV-2 backbone and was cross reactive to epitopes found in the other serotypes. The vaccine elicited neutralizing antibodies with high tetravalent seropositivity rates among participants. Further assessment of this response revealed that it consists of serotype-specific and cross-reactive neutralizing antibodies against all four serotypes. In addition, sera from vaccinated individuals neutralized genotypically diverse dengue strains. In addition to antibodies specific to structural components, antibodies to DENV-2 NS1 that were cross reactive to the NS1 proteins of the other serotypes were found.
Conclusion. The breadth of the cellular and humoral immune responses elicited by TAK-003 in vaccine recipients across a wide age range living in different endemicities aligns with the response profile expected of a multivalent live vaccine. Background. Clostridioides difficile infection (CDI) is recognised by the CDC as an "urgent threat" in the USA, responsible for nearly 13,000 deaths, and carries an economic burden ranging from $5.4 to $6.3 billion per year. In a phase II study, ridinilazole was shown to be effective at treating CDI and decreasing subsequent recurrence compared to vancomycin. However, the precise mechanism of action of ridinilazole has yet to be fully elucidated. We now present data that reveals ridinilazole clearly co-localises with DNA in C. difficile and binds with high affinity to the minor groove of DNA. These interactions are predicted to have consequences on cellular functions within C. difficile.
Methods. High resolution confocal microscopy was used to track the intracellular localisation of ridinilazole in C. difficile. Fluorescence intensity was used to characterise the DNA binding properties of ridinilazole; sequence specificity was demonstrated with AT-or GC-rich DNA polymers, and tight binding was shown using short double-stranded oligonucleotides. Hanging drop vapour diffusion enabled co-crystallisation and subsequent structural determination of DNA-bound ridinilazole.
Results. Confocal microscopy revealed clear co-localisation of ridinilazole to the DNA within C. difficile. Ridinilazole demonstrated a dose-dependent increase in fluorescence in response to increasing concentration of target DNA. Fluorescence binding studies revealed that ridinilazole shows a preference towards AT-rich DNA sequences. Tight binding characteristics were demonstrated by ridinilazole in complex with short double-stranded oligonucleotides, returning dissociation constants (K d ) of 20 -50 nM. Crystallisation enabled co-structures of ridinilazole bound to the minor groove of double-stranded DNA oligonucleotides to be solved.
Conclusion. Ridinilazole demonstrates tight binding with sequence specificity within the minor groove of DNA and co-localises with DNA in C. difficle. Further analysis is ongoing to fully understand this novel mechanism of action, the downstream consequences of these interactions and how they contribute to the bactericidal activity of ridinilazole.
Results. BL agents tested alone had limited activity against this challenge set of isolates (MIC 90 , ≥32 mg/L); however, MIC 90 values decreased ≥32-fold with the addition of QPX at the highest concentration tested (Table). Oral agents, CTB,CDR and TEB were tested with QPX at a fixed 4 mg/L and showed a 32-to 128-fold increase in potency (MIC 90 , 0.5-4 mg/L). ATM and FEP were tested with QPX at a fixed 4 and 8 mg/L and displayed MIC 90 values ranging from 0.12-0.5 mg/L. ATM and FEP, tested with 8 mg/L of QPX, inhibited 99.8% of isolates at the breakpoint for the BL agent alone. BLI inhibitor combinations PT and CT displayed MIC 90 values of 2 and 4 mg/L with the addition of 8 mg/L QPX. MER with QPX at a fixed 4 mg/L and 8 mg/L inhibited 99.8% and 100% of isolates, respectively.
Conclusion. The activity of all BLs evaluated was restored when combined with QPX tested against this challenging collection of 1,027 ENT isolates displaying various resistance mechanisms, including difficult to treat CRE isolates and MBL producers. Further development of QPX with various orally-and IV-available BL agents appears warranted.