bluuebunny/crossref_metadata_2025_split huggingface dataset:
1233. Identification of Novel Inhibitors of Clostridioides difficile Enoyl-Reductase II (FabK) by High-Throughput Virtual and Experimental Screening
Authors: Wahrmund Rebecca D , Avad Kristiana A , Reeve Stephanie M , Jones Jesse A , La Thao , Lee Richard E , Hevener Kirk E 
Published: January 2021

Abstract

Background
Clostridioides difficile is one of only three bacteria categorized as an ‘urgent’ drug-resistant threat by the CDC. This pathogen is responsible for nearly 500,000 hospital-acquired infections and 29,000 deaths per year at a cost of nearly $4.8 billion. There is a critical need for the identification of novel, anti-difficile agents with narrow-spectrum activity that can spare the human microbiome. We previously reported the essentiality of the FAS-II enzyme, enoyl-ACP reductase (FabK) in C. difficile, and the narrow-spectrum activity of a series of phenylimidazole inhibitors. We present here experimental and virtual compound screening studies that identified novel FabK inhibitors with sub-micromolar activity and follow-up SAR and structural studies.

Methods
Using a novel luminescence assay, 20K diverse compounds from the St. Jude drug-like and lead-like libraries were screened. In parallel, a ligand-based virtual screen was performed against 2.4 million lead- and drug-like compounds from commercial libraries. Hit compounds were confirmed using an orthogonal fluorescence-intensity assay and SAR studies were performed by testing commercially available hit analogs. The most potent inhibitor was advanced into co-crystallography structural studies.

Results
The compound screening campaigns resulted in the identification of several confirmed hit compounds with low to sub-micromolar activity and novel scaffolds relative to the known phenylimidazole inhibitors. Importantly, the first confirmed nanomolar inhibitor of C. difficile FabK was identified and validated with an IC50 of 0.35 μM. SAR studies of the hits along with a high-resolution co-crystal structure have allowed new insights into the key binding determinants and structural requirements for activity as well as the structural requirements for species specificity.

Conclusion
The C. difficile FabK enzyme offers a promising narrow-spectrum drug target that can potentially spare the human microbiome. The known activity of the phenylimidazole inhibitor series supports the druggability of this target. The newly discovered inhibitor class presented here further demonstrates the potential of FabK inhibition and will facilitate the development of clinically relevant, narrow-spectrum anti-difficile agents.

Disclosures
All Authors: No reported disclosures
1234. Increasing private sector investment in neglected tropical disease (NTD) research and development: a mixed methods study
Authors: Barofsky Jeremy , Xu Jacqueline , Schneider Jake , Manne-Goehler Jennifer 
Published: January 2021

Abstract

Background
This study explores the drug development environment for Human African Trypanosomiasis and Chagas disease and investigates ways to stimulate greater investment in the small molecule drug pipeline for NTDs.

Methods
We conducted qualitative case studies of successful public-private partnerships (PPPs) that have supported the research pipeline for treatment of HAT (Fexinidazole & Acoziborole) & Chagas disease (Benznidazole). We conducted semi-structured interviews with 21 key informants. We then performed an economic modeling analysis to evaluate the development costs compared to estimates of potential revenue in order to identify expected private investment returns, inclusive of the contribution of the Priority Review Voucher (PRV) program. We also investigate under what circumstances one can expect positive returns if R&D for NTDs was executed by a private biopharmaceutical firm. We calculate the net present value of R&D costs both for an average NTD drug and use the specific features of these three candidates to estimate the private ROI that would have prevailed for each drug had they been developed by a for-profit entity.

Results
The major themes that emerged from the case studies were: (1) the importance of pre-existing philanthropic efforts for a given disease, (2) the desire to align the social goals of the company with its actions, (3) the vital role of PPPs in coordinating development and reducing private-sector risk & (4) the limited role that the PRV played in motivating these activities. Overall, the current NTD R&D landscape is driven by PPPs. The modeling analysis shows why: although the PRV is an important incentive for drug development, it is not sufficient to generate a positive private return for novel drug development when adjusting for capitalized costs and failure risk. However, for a pre-existing, unapproved drug such as Benzinadozole, returns are positive in the current environment (Table 1). We find that both a restricted PRV supply & better estimates of approval probabilities would generate positive returns (Fig 1 + 2).
Table 1: Return on investment by small molecule drug

Figure 1. Return on Investment Sensitivity Analysis for Fexinidazole (Source: Authors’ calculations)

Figure 2. Return on Investment Sensitivity Analysis for Acoziborole (Source: Authors’ calculations)

Conclusion
We find support for NTD drug development within the private sector, but no novel R&D without nonprofit stewardship. Our findings intend to foster PPPs that stimulate this pipeline from very low current levels.

Disclosures
All Authors: No reported disclosures
1237. Robust Adjuvant Activity and Dose-sparing Potential of the Novel Semisynthetic Saponin Adjuvant TQL1055 for Seasonal and Pandemic Influenza
Authors: Buzz Chloe , Farris Eric , Bennett Sean R , Frenchick Pat , Martin Tyler 
Published: January 2021

Abstract

Background
Vaccination against both seasonal and pandemic influenza requires effective adjuvants to maximize the utility of limited antigen and to enhance immunogenicity in hyporesponsive at-risk populations. First-generation natural saponins are potent immuno-enhancers but are reactogenic and have supply constraints. As part of a NIH-funded project, the novel semisynthetic saponin TQL1055 was evaluated for its potential to augment the immunogenicity of influenza antigens.
Figure 1: TQL1055 Enhances the Antibody Response to a Recombinant Antigen Influenza Vaccine (Flublok®) and Exhibits Antigen Dose-Sparing Effects

Figure 2: TQL1055 Exhibits Improved Systemic Tolerability Over QS-21.

Methods
Groups of 10 C57BL/6J mice were immunized subcutaneously (SC) with Flublok® (H3N2 antigen) alone at either a 4.5 mcg or 1.1 mcg dose, or at a 1.1 mcg dose in combination with 10, 30 or 100 mcg TQL1055 on Days 0 and 21. Sera were analyzed at days 0, 21 and 42 by ELISA for H3N2-specific IgG. Body weights were measured serially.

Results
A 2-dose series of 1.1 mcg Flublok with TQL1055 elicited anti-H3N2 antibodies in all mice. This effect was TQL1055 dose-dependent, with GMTs of 2178 in the 10 mcg group, 13674 in the 30 mcg group and 48959 in the 100 mcg group. The GMT in all TQL1055 groups was higher than the GMT of 176 in the group receiving 4.5 mcg of Flublok alone. Mice receiving TQL1055 gained weight steadily after immunization, compared with a maximum weight loss of &gt;10% in mice receiving 20 mcg of QS-21.

Conclusion
TQL1055 exhibits robust adjuvant activity for influenza antigens, demonstrating a dose-sparing effect and improved systemic tolerability compared with QS-21. Taken together, these finding support further evaluation of its potential as an adjuvant for influenza vaccines.

Disclosures
Chloe Buzz, BS, Adjuvance Technologies (Employee) Eric Farris, PhD, Adjuvance Technologies (Employee) Sean R. Bennett, MD PhD, Adjuvance Technologies (Employee) Pat Frenchick, PhD, Adjuvance Technologies (Consultant) Tyler Martin, MD, Adjuvance Technologies (Employee, Shareholder)
1240. Persistence of Circulating Antibody Through 12 Months Following Vaccination With a 20-Valent Pneumococcal Conjugate Vaccine in Adults 60–64 Years of Age
Authors: Hurley Donald , Griffin Carl , Young Jr. Mariano , Scott Daniel , Pride Michael W , Scully Ingrid L , Ginis John , Peng Yahong , Jansen Kathrin U , Gruber William C , Watson Wendy 
Published: January 2021

Abstract

Background
While widespread use of pneumococcal conjugate vaccines (PCVs) has reduced disease burden, expanding serotype coverage remains an unmet need in disease prevention. The 20-valent PCV (PCV20) contains capsular polysaccharide conjugates from serotypes included in the 13-valent PCV (PCV13; Prevnar 13®) as well as 7 additional serotypes. In a phase 2 study of PCV20 in adults 60–64 years of age, robust immune responses were observed at 1 month after vaccination; antibody persistence up to 12 months after vaccination from that study is described herein.

Methods
In this randomized, active-controlled, double-blind study (ClinicalTrials.gov NCT03313037), adults aged 60–64 years received a single PCV20 dose followed 1 month later by saline placebo or PCV13 followed 1 month later by 23-valent pneumococcal polysaccharide vaccine (PPSV23), which provided benchmarks for all PCV20 serotypes. Immunogenicity was assessed at baseline and at 1 and 12 months after vaccination as serotype-specific opsonophagocytic activity (OPA) geometric mean titers (GMTs) and immunoglobulin G (IgG) geometric mean concentrations (GMCs). OPA and IgG geometric mean fold rises (GMFRs) from baseline to 12 months after vaccination were assessed.

Results
In the PCV20 group, OPA GMTs (n=185–200 at Month 12) for all PCV20 serotypes increased substantially from baseline to 1 month after vaccination and then declined by Month 12 but remained elevated above baseline. OPA GMFRs from baseline to Month 12 after PCV20 vaccination were 1.9–15.0 for the serotypes in common with PCV13 and 5.6–15.6 for the 7 additional serotypes. Similar results were observed for IgG concentrations, with GMFRs of 2.4–9.4 for the PCV13 serotypes and 3.0–15.5 for the 7 additional serotypes. At Month 12, 11 months after PPSV23 vaccination (n=162–195), OPA GMFRs were 5.3–11.5 for the 7 additional serotypes; IgG GMFRs were 5.0–10.4. Benchmarking to PCV13 serotypes in the control group was not appropriate as these subjects received both PCV13 and PPSV23, which overlap in polysaccharide composition for 12 serotypes.

Conclusion
Immune responses induced by PCV20 persisted at 12 months after vaccination in adults 60–64 years of age, further supporting the potential of PCV20 to expand serotype protection against adult pneumococcal disease.

Disclosures
Mariano Young Jr., MD, Pfizer Inc (Employee, Shareholder) Daniel Scott, MD, Pfizer (Employee, Shareholder) Michael W. Pride, PhD, Pfizer (Employee, Shareholder) Ingrid L. Scully, PhD, Pfizer Inc (Employee, Shareholder) John Ginis, BS, Pfizer Inc (Employee, Shareholder) Yahong Peng, PhD, Pfizer (Employee, Shareholder) Kathrin U. Jansen, PhD, Pfizer (Employee, Shareholder) William C. Gruber, MD, Pfizer (Employee, Shareholder) Wendy Watson, MD, Pfizer (Employee, Shareholder)
1249. Genetic Evidence That Gepotidacin Shows Well-balanced Dual Targeting against DNA Gyrase And Topoisomerase IV in Neisseria gonorrhoeae
Authors: Chan Pan , Ingraham Karen , Min Sharon , Scangarella-Oman Nicole , Rittenhouse Steve , Huang Jianzhong 
Published: January 2021

Abstract

Background
Gepotidacin (GEP) is a novel triazaacenaphthylene bacterial type II topoisomerase inhibitor targeting both bacterial DNA gyrase and topoisomerase IV by a different mechanism from fluoroquinolone antibiotics. Although in vitro frequency of resistance to GEP in Neisseria gonorrhoeae (NG) is low, during a phase 2 trial, clinical resistance to gepotidacin in NG emerged in a subset of fluoroquinolone-resistant NG isolates that contained a pre-existing ParC D86N mutation by introduction of a new GyrA A92T mutation. The objective of this study was to evaluate the role of GyrA A92T & Parc D86N mutations in resistance to GEP.

Methods
We utilized the high frequency of natural transformation to introduce GyrA A92T and ParC D86N mutations, individually and in combination, into NG isolates either with GyrA S91F D95G mutations or with wild type (WT) GyrA by selection on ciprofloxacin (CIP) or GEP to generate isogenic strains for susceptibility evaluation.

Results
Results are summarized in enclosed table. Overall, GyrA A92T and ParC D86N mutations alone did not confer a significant (&gt;4-fold) increase in GEP MIC; whereas together they gave &gt;16-fold increases in GEP MIC. Importantly, quinolone target mutations (GyrA S91F D95G and ParC D86N) together showed no significant effect on the GEP MIC; while they gave &gt;1000-fold increase in CIP MIC. As expected, GyrA A92T and ParC D86N mutations alone or together in WT GyrA background had no significant effect on CIP susceptibility.
Susceptibility of isogenic NG strains to gepotidacin and ciprofloxacin

Conclusion
Our results indicated that unlike fluoroquinolones that primarily target DNA gyrase in NG, there is no obvious primary target for GEP, supporting well-balanced dual targeting of DNA gyrase and topoisomerase IV by GEP in NG. Though, the pre-existing ParC D86N mutation is a potential risk marker for clinical resistance development, as this mutation compromises dual targeting of GEP, our studies provide mechanistic insight for appropriate clinical dose selection to potentially suppress further resistance development in this subset of clinical isolates.

Disclosures
Pan Chan, PhD, GlaxoSmithKline (Employee, Shareholder) Karen Ingraham, MS, GlaxoSmithKline (Employee, Shareholder) Sharon Min, MS, GlaxoSmithKline (Employee, Shareholder) Nicole Scangarella-Oman, MS, GlaxoSmithKline plc. (Employee, Shareholder) Steve Rittenhouse, PhD, GlaxoSmithKline (Employee, Shareholder) Jianzhong Huang, PhD, GlaxoSmithKline (Employee, Shareholder)
1252. In Vitro Activity of Cefiderocol Against Metallo-β-Lactamase-Producing Gram-Negative Bacteria Collected in North America and Europe Between 2014 and 2017: SIDERO-WT-2014–2016 Studies
Authors: Takemura Miki , Kazmierczak Krystyna , Hackel Meredith , Sahm Daniel F , Echols Roger , Yamano Yoshinori 
Published: January 2021

Abstract

Background
Metallo-β-lactamases (MBLs; eg, NDM, VIM, and IMP) can inactivate most commonly-used β-lactam antibiotics, including carbapenems. Infections caused by MBL producers are difficult to treat due to their resistance to many antibiotics. Cefiderocol (CFDC) is a siderophore cephalosporin antibiotic approved in the USA in 2019, with potent activity against carbapenem-resistant Gram-negative bacteria (GNB), including both serine- and metallo-carbapenemase positive strains. We evaluated the in vitro activity of CFDC and comparator agents against MBL-producing strains of GNB from North America and Europe in 3 years’ of consecutive surveillance studies (SIDERO-WT-2014–2016).

Methods
Susceptibility testing for CFDC, ceftazidime-avibactam (CZA), ceftolozane-tazobactam (C/T), meropenem (MEM), cefepime (FEP), ciprofloxacin (CIP), and colistin (CST) was performed by broth microdilution according to CLSI guidance. CFDC was tested in iron-depleted medium. A total of 275 MBL-producing strains, consisting of 120 Enterobacterales (45 NDM; 75 VIM), 5 NDM-producing Acinetobacter baumannii, and 150 Pseudomonas aeruginosa (134 VIM; 16 IMP), identified among 4985 (654 Enterobacterales and 4331 non-fermenters) MEM non-susceptible (based on CLSI breakpoints) strains were used for the current analysis.

Results
The minimum inhibitory concentration (MIC) range and MIC90 for CFDC and comparators for each MBL-producing organism group are shown in the Table. Against NDM-producing Enterobacterales, of which 42% and 33% were isolated in Turkey and Russia, respectively, CFDC inhibited the growth of 84% of isolates tested at ≤4 µg/mL. CFDC MIC90 was 4 μg/mL for VIM-producing Enterobacterales (41% and 31% isolated in Greece and Italy, respectively), 1 μg/mL for VIM-producing P. aeruginosa (50% isolated in Russia), and 4 μg/mL for IMP-producing P. aeruginosa (88% isolated in Czech Republic). Other comparators (except for CST) were not active against these MBL producers.
Table. MIC range and MIC90 (μg/mL) for CFDC and comparators of MBL-producing organisms

Conclusion
CFDC inhibited the growth of 100% of MBL-positive GNB at ≤8 mg/mL and showed MIC90 of 4 μg/mL against all 275 MBL producers, indicating that CFDC has high potential for treating infections caused by these difficult-to-treat strains.

Disclosures
Miki Takemura, MSc, Shionogi & Co., Ltd. (Employee) Krystyna Kazmierczak, PhD, Shionogi & Co., Ltd. (Independent Contractor) Daniel F. Sahm, PhD, IHMA (Employee)Pfizer, Inc. (Consultant)Shionogi & Co., Ltd. (Independent Contractor) Roger Echols, MD, Shionogi Inc. (Consultant) Yoshinori Yamano, PhD, Shionogi & Co., Ltd. (Employee)
1254. In vitro activity of sulbactam-durlobactam against recent global clinical Acinetobacter baumannii-calcoaceticus complex isolates
Authors: McLeod Sarah , Moussa Samir , Hackel Meredith , Miller Alita 
Published: January 2021

Abstract

Background
Acinetobacter baumannii-calcoaceticus complex (ABC) causes severe infections that are difficult to treat due to increasing resistance to antibacterial therapy. Sulbactam (SUL) has intrinsic antibacterial activity against ABC, but its clinical utility has been compromised by the prevalence of serine β-lactamases. Durlobactam (DUR, previously ETX2514) is a diazabicyclooctenone β-lactamase inhibitor with potent activity against Ambler classes A, C and D serine β-lactamases that effectively restores SUL activity against ABC isolates. SUL-DUR is an antibiotic designed to treat serious infections caused by Acinetobacter, including multidrug-resistant strains, which is currently in Phase 3 clinical testing. The potency of SUL-DUR against geographically diverse ABC isolates collected in 2018 was measured.

Methods
929 ABC isolates, including 698 A. baumannii, 13 A. calcoaceticus, 54 A. nosocomialis, and 164 A. pittii, were collected in 2018 from geographically diverse medical centers in the United States, Europe, Latin America, Israel and the Asia-Pacific region. Susceptibility testing was performed according to CLSI guidelines. Data analysis was performed using CLSI and EUCAST breakpoint criteria where available. Select isolates were subjected to whole genome sequencing with an Illumina MiSeq V2 instrument and analysis using CLCBio Genomics Workbench v6.5.

Results
In surveillance of 929 global isolates from 2018, the SUL-DUR MIC90 was 2 mg/L compared with 64 mg/L for SUL alone. This level of potency was consistent across species, regions, source of infection and subsets of resistance phenotypes. Fifty percent of the isolates were non-susceptible to carbapenems. Only 7 isolates (0.75%) had SUL-DUR MIC values &gt;4 mg/L. Whole genome sequencing of these 7 isolates revealed that they either encoded the metallo-β-lactamase NDM-1, which DUR does not inhibit, or single amino acid substitutions near the active site of PBP3, the primary target of SUL.

Conclusion
SUL-DUR demonstrated potent antibacterial activity against recent, geographically diverse clinical isolates of ABC, including MDR isolates. These data support the potential utility of SUL-DUR for the treatment of antibiotic-resistant infections caused by ABC.

Disclosures
Sarah McLeod, PhD, Entasis Therapeutics (Employee) Samir Moussa, PhD, Entasis Therapeutics (Employee) Alita Miller, PhD, Entasis Therapeutics (Employee)
1256. In Vivo Activity and Structural Characterization of a New Generation γ-Lactam Siderophore Antibiotic Against Multidrug-Resistant Gram-Negative Bacteria and Acinetobacter spp
Authors: Goldberg Joel , Bethel Christopher , Hujer Andrea M , Marshall Steven , Taracila Magdalena A , Papp-Wallce Krisztina M , Kumar Vijay , van den Akker Focco , Plummer Mark , Bonomo Robert A 
Published: January 2021

Abstract

Background
Multidrug-resistant (MDR) A. baumannii presents a critical need for innovative antibacterial development. We have identified a new series of γ-lactam (oxopyrazole) antibiotics that target penicillin binding proteins (PBPs) and incorporate a siderophore moiety to facilitate periplasmic uptake. YU253911, an advanced iteration of this class shows potent in vitro activity against clinically relevant Gram-negative organisms including Acinetobacter spp.

Methods
Minimum inhibitory concentrations (MICs) for YU253911 were determined using broth microdilution against a 198-member panel of clinical isolates of Acinetobacter spp. Resistant strains were further evaluated for susceptibility to YU253911 in combination with sulbactam. The antibiotic’s target protein was evaluated by binding studies with Bocillin™, a fluorescent penicillin analogue, and modeled in the PBP active site. YU253911 was evaluated in vivo in a mouse soft tissue infection model.

Results
MIC testing for YU253911 revealed an MIC50 of 0.5 μg/mL and an MIC90 of 16 μg/mL, which compared favorably to all tested β-lactam antibiotics including penicillins, cephalosporins, monobactams and carbapenems (MIC50 = 2 to &gt; 16 μg/mL). Combination with sulbactam augmented the activity of the agent. There was no apparent correlation between YU253911-resistance and the presence of specific β-lactamase genes, and incubation with representative β-lactamase proteins (KPC-2, OXA-23, OXA-24, PER-2, PDC-3, NDM-1, VIM-2, and IMP-1) showed negligible hydrolysis of the agent. YU253911 showed promising preclinical pharmacokinetics in mice with a 15 h half-life from intravenous administration and demonstrated a dose-dependent reduction in colony forming units from 50 and 100 mg/kg q6h dosing in a mouse thigh infection model using P. aeruginosa.

Conclusion
YU253911, a new generation γ-lactam antibiotic effective against MDR A. baumannii demonstrated promising in in vitro potency and favorable pharmacokinetics which correlated with in vivo efficacy.

Disclosures
Krisztina M. Papp-Wallce, PhD, Entasis (Grant/Research Support)Merck (Grant/Research Support)Venatorx (Grant/Research Support) Robert A. Bonomo, MD, Entasis, Merck, Venatorx (Research Grant or Support)