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Background Manogepix is a new antifungal with a novel mechanism of action and potent in vitro activity against Candida (except C. krusei), Aspergillus, and rare mold isolates. The manogepix prodrug fosmanogepix is in Phase 2 development for the treatment of invasive mold infections caused by Aspergillus and rare molds (NCT04240886) and has completed Phase 2 studies for candidemia (NCT03604705) and C. auris (NCT04148287) infections. We evaluated the in vitro activity of manogepix and comparators against 2,810 geographically diverse fungal isolates collected in the SENTRY Surveillance Program during 2020-2021 and stratified them by infection type. Methods Antifungal susceptibility testing of manogepix and comparator agents was conducted according to CLSI M27 (2017) and M38 (2017) guidelines. Fungal surveillance isolates were collected from medical centers located in North America (30 sites; 37.9%), Europe (30 sites; 38.4%), Asia-Pacific (11 sites; 14.7%), and Latin America (6 sites; 9.0%). Infection sites included bloodstream infections (BSI; 48.3%), pneumonia in hospitalized patients (PIHP; 19.9%), skin and skin structure infections (SSSI; 7.8%), urinary tract infections (UTI; 3.1%), intra-abdominal infections (IAI; 1.6%), and other infection types (19.3%). Results Manogepix demonstrated potent in vitro activity against Candida spp. isolates (MIC50/90, 0.004-0.03/0.008-0.06 mg/L) regardless of infection type (Table). Similarly, manogepix was highly active against 534 Aspergillus spp. isolates (MEC50/90, 0.015/0.03 mg/L). Manogepix was active against 53 Cryptococcus neoformans var. grubii (MIC50/90, 0.25/1 mg/L), 19 Fusarium spp. (MEC50/90, 0.015/0.06 mg/L), 12 Lomentospora prolificans (MEC50/90, 0.03/0.06 mg/L), and 17 Scedosporium spp. isolates (MEC50/90, 0.06/0.12 mg/L). Conclusion Manogepix showed potent in vitro activity against Candida spp., Aspergillus spp., C. neoformans var. grubii, and rare molds, including Fusarium spp., L. prolificans, and Scedosporium spp. isolates. Notable activity was also demonstrated by manogepix against C. auris isolates. Further clinical development of fosmanogepix in difficult-to-treat, resistant fungal infections is warranted. Disclosures Michael D. Huband, BS, AbbVie: Grant/Research Support|Melinta: Grant/Research Support Cecilia G. Carvalhaes, MD, PhD, AbbVie: Grant/Research Support|Cidara: Grant/Research Support|Melinta: Grant/Research Support|Pfizer: Grant/Research Support Mariana Castanheira, PhD, AbbVie: Grant/Research Support|Cidara: Grant/Research Support|GSK: Grant/Research Support|Melinta: Grant/Research Support|Pfizer: Grant/Research Support|Shionogi: Grant/Research Support.

Background Existing antifungal agents are active against many common fungal pathogens; however, breakthrough fungal infections occur and often involve less frequently encountered yeast and mould isolates. These rarer isolates tend to exhibit diminished susceptibility to current agents. Manogepix (MGX, APX001A) is a novel inhibitor of the fungal Gwt1 enzyme. The prodrug (fosmanogepix), is being evaluated in Phase 2 clinical trials for invasive candidiasis/candidemia, Candida auris infections, and invasive aspergillosis. In this study, we evaluated the in vitro activity of MGX and comparators against 2,669 clinical fungal isolates collected worldwide (2018-2019) and stratified by infection type. Methods Fungal isolates were collected from medical centers located in North America (34 sites; 42.3%), Europe (30 sites; 37.9%), Asia-Pacific (11 sites; 12.3%), and Latin America (7 sites; 7.6%). Isolates were collected from bloodstream infections (BSI; 51.7%), pneumonia in hospitalized patients (PIHP; 21.1%), skin and skin structure infections (SSSI; 5.5%), urinary tract infections (UTI; 2.3%), intraabdominal infections (IAI; 1.9%), and other infection types (17.5%). Results MGX demonstrated potent in vitro activity against 1,887 Candida spp. isolates from BSI, PIHP, SSSI, and all infection types (MIC50/90, 0.008/0.03-0.06 mg/L) outperforming all comparator agents (Table). Similarly, MGX was equally active against 578 Aspergillus spp. isolates (MEC50/90, 0.015/0.03 mg/L), regardless of infection type. MGX was active against Cryptococcus neoformans var. grubii isolates from BSI and ALL infection types with MIC50/90 values of 0.5/2 mg/L. Scedosporium spp. isolates from PIHP and all infection types were inhibited by low concentrations of MGX (MEC50/90, 0.03/0.03 mg/L). Table 1 Conclusion MGX demonstrated potent antifungal activity against Candida spp., Aspergillus spp., C. neoformans var. grubii, and non-Aspergillus moulds, including Scedosporium spp. isolates. Notable activity was seen against C. auris, echinocandin-resistant Candida spp., azole-resistant Aspergillus, and Scedosporium spp. isolates. Further clinical development of fosmanogepix in difficult-to-treat resistant fungal infections is warranted. Disclosures Michael A. Pfaller, MD, Amplyx Pharmaceuticals (Research Grant or Support)Basilea Pharmaceutica International, Ltd (Research Grant or Support)Cidara Therapeutics (Research Grant or Support)Cidara Therapeutics (Research Grant or Support)Department of Health and Human Services (Research Grant or Support)Fox Chase Chemical Diversity Center (Research Grant or Support)Paratek Pharma, LLC (Research Grant or Support) Robert K. Flamm, PhD, A. Menarini Industrie Farmaceutiche Riunite S.R.L. (Research Grant or Support)Amplyx Pharmaceuticals (Research Grant or Support)Basilea Pharmaceutica International, Ltd (Research Grant or Support)Department of Health and Human Services (Research Grant or Support)Melinta Therapeutics, Inc. (Research Grant or Support) Shawn A. Messer, PhD, Amplyx Pharmaceuticals (Research Grant or Support)Fox Chase Chemical Diversity Center (Research Grant or Support) Beth A. Schaefer, n/a, Amplyx Pharmaceuticals (Research Grant or Support) Paul Bien, MS, Amplyx Pharmaceuticals (Employee) Mariana Castanheira, PhD, 1928 Diagnostics (Research Grant or Support)A. Menarini Industrie Farmaceutiche Riunite S.R.L. (Research Grant or Support)Allergan (Research Grant or Support)Allergan (Research Grant or Support)Amplyx Pharmaceuticals (Research Grant or Support)Cidara Therapeutics (Research Grant or Support)Cidara Therapeutics (Research Grant or Support)Cipla Ltd. (Research Grant or Support)Cipla Ltd. (Research Grant or Support)Fox Chase Chemical Diversity Center (Research Grant or Support)GlaxoSmithKline (Research Grant or Support)Melinta Therapeutics, Inc. (Research Grant or Support)Melinta Therapeutics, Inc. (Research Grant or Support)Melinta Therapeutics, Inc. (Research Grant or Support)Merck (Research Grant or Support)Merck (Research Grant or Support)Merck & Co, Inc. (Research Grant or Support)Merck & Co, Inc. (Research Grant or Support)Paratek Pharma, LLC (Research Grant or Support)Pfizer (Research Grant or Support)Qpex Biopharma (Research Grant or Support)

Current antifungal agents cover a majority of opportunistic fungal pathogens; however, breakthrough invasive fungal infections continue to occur and increasingly involve relatively uncommon yeasts and molds, which often exhibit decreased susceptibility. APX001A (manogepix) is a first-in-class small-molecule inhibitor of the conserved fungal Gwt1 protein. This enzyme is required for acylation of inositol during glycosylphosphatidylinositol anchor biosynthesis. APX001A is active against the major fungal pathogens, i.e., Candida (except Candida krusei), Aspergillus, and hard-to-treat molds, including Fusarium and Scedosporium. In this study, we tested APX001A and comparators against 1,706 contemporary clinical fungal isolates collected in 2017 from 68 medical centers in North America (37.3%), Europe (43.4%), the Asia-Pacific region (12.7%), or Latin America (6.6%). Among the isolates tested, 78.5% were Candida spp., 3.9% were non-Candida yeasts, including 30 (1.8%) Cryptococcus neoformans var. grubii isolates, 14.7% were Aspergillus spp., and 2.9% were other molds. All isolates were tested by CLSI reference broth microdilution. APX001A (MIC(50), 0.008 μg/ml; MIC(90), 0.06 μg/ml) was the most active agent tested against Candida sp. isolates; corresponding anidulafungin, micafungin, and fluconazole MIC(90) values were 16- to 64-fold higher. Similarly, APX001A (MIC(50), 0.25 μg/ml; MIC(90), 0.5 μg/ml) was ≥8-fold more active than anidulafungin, micafungin, and fluconazole against C. neoformans var. grubii. Against Aspergillus spp., AXP001A (50% minimal effective concentration [MEC(50)], 0.015 μg/ml; MEC(90), 0.03 μg/ml) was comparable in activity to anidulafungin and micafungin. Aspergillus isolates (>98%) exhibited a wild-type phenotype for the mold-active triazoles (itraconazole, posaconazole, and voriconazole). APX001A was highly active against uncommon species of Candida, non-Candida yeasts, and rare molds, including 11 isolates of Scedosporium spp. (MEC values, 0.015 to 0.06 μg/ml). APX001A demonstrated potent in vitro activity against recent fungal isolates, including echinocandin- and fluconazole-resistant strains. The extended spectrum of APX001A was also notable for its potency against many less common but antifungal-resistant strains. Further studies are in progress to evaluate the clinical utility of the methyl phosphate prodrug, APX001, in difficult-to-treat resistant fungal infections.

The in vitro activity and spectrum of tedizolid and comparators were analyzed against 6884 Gram-positive clinical isolates collected from multiple US and European sites as part of the Surveillance of Tedizolid Activity and Resistance Program in 2011 and 2012. Organisms included 4499 Staphylococcus aureus, 537 coagulase-negative staphylococci (CoNS), 873 enterococci, and 975 β-hemolytic streptococci. The MIC values that inhibited 90% of the isolates within each group (MIC90) were 0.25 μg/mL for Staphylococcus epidermidis and β-hemolytic streptococci and 0.5 μg/mL for S. aureus, other CoNS, and enterococci. Of 16 isolates with elevated tedizolid or linezolid MIC values (intermediate or resistant isolates), 10 had mutations in the genes encoding 23S rRNA (primarily G2576T), 5 had mutations in the genes encoding ribosomal proteins L3 or L4, and 5 carried the cfr multidrug resistance gene. Overall, tedizolid showed excellent activity against Gram-positive bacteria and was at least 4-fold more potent than linezolid against wild-type and linezolid-resistant isolates. Given the low overall frequency of isolates that would be resistant to tedizolid at the proposed break point of 0.5 μg/mL (0.19%) and potent activity against contemporary US and European isolates, tedizolid has the potential to serve as a valuable therapeutic option in the treatment of infections caused by Gram-positive pathogens.

Tedizolid (TR-700, formerly torezolid) is the active moiety of the prodrug tedizolid phosphate (TR-701), a next-generation oxazolidinone, with high potency against Gram-positive species, including methicillin-resistant Staphylococcus aureus (MRSA). A recently completed randomized, double-blind phase 2 trial evaluated 200, 300, or 400 mg of oral tedizolid phosphate once daily for 5 to 7 days in patients with complicated skin and skin structure infections. This report examines the in vitro activity of tedizolid and Zyvox (linezolid) against Gram-positive pathogens isolated at baseline and describes the microbiological and clinical efficacy of tedizolid. Of 196 isolates tested, 81.6% were S. aureus , and of these, 76% were MRSA. The MIC 50 and MIC 90 of tedizolid against both methicillin-susceptible S. aureus (MSSA) and MRSA were 0.25 μg/ml, compared with a MIC 50 of 1 μg/ml and MIC 90 of 2 μg/ml for linezolid. For coagulase-negative staphylococci ( n = 7), viridans group streptococci ( n = 15), and beta-hemolytic streptococci ( n = 3), the MICs ranged from 0.03 to 0.25 μg/ml for tedizolid and from 0.12 to 1 μg/ml for linezolid. The microbiological eradication rates at the test-of-cure visit (7 to 14 days posttreatment) in the microbiologically evaluable population ( n = 133) were similar in all treatment groups, with overall eradication rates of 97.7% for all pathogens, 97.9% for MRSA, and 95.7% for MSSA. The clinical cure rates for MRSA and MSSA infections were 96.9% and 95.7%, respectively, across all dose groups. This study confirms the potent in vitro activity of tedizolid against pathogenic Gram-positive cocci, including MRSA, and its 4-fold-greater potency in comparison with linezolid. All dosages of tedizolid phosphate showed excellent microbiological and clinical efficacy against MRSA and MSSA.

Torezolid (TR-700) is the active moiety of the prodrug torezolid phosphate ([TP] TR-701), a second-generation oxazolidinone with 4- to 16-fold greater potency than linezolid against Gram-positive species including methicillin-resistant Staphylococcus aureus (MRSA). A double-blind phase 2 study evaluated three levels (200, 300, or 400 mg) of oral, once-daily TP over 5 to 7 days for complicated skin and skin structure infections (cSSSI). Patients 18 to 75 years old with cSSSI caused by suspected or confirmed Gram-positive pathogens were randomized 1:1:1. Of 188 treated patients, 76.6% had abscesses, 17.6% had extensive cellulitis, and 5.9% had wound infections. S. aureus , the most common pathogen, was isolated in 90.3% of patients (139/154) with a baseline pathogen; 80.6% were MRSA. Cure rates in clinically evaluable patients were 98.2% at 200 mg, 94.4% at 300 mg, and 94.4% at 400 mg. Cure rates were consistent across diagnoses, regardless of lesion size or the presence of systemic signs of infection. Clinical cure rates in patients with S. aureus isolated at baseline were 96.6% overall and 96.8% for MRSA. TP was safe and well tolerated at all dose levels. No patients discontinued treatment due to an adverse event. Three-stage hierarchical population pharmacokinetic modeling yielded a geometric mean clearance of 8.28 liters/h (between-patient variability, 32.3%), a volume of the central compartment of 71.4 liters (24.0%), and a volume of the peripheral compartment of 27.9 liters (35.7%). Results of this study show a high degree of efficacy at all three dose levels without significant differences in the safety profile and support the continued evaluation of TP for the treatment of cSSSI in phase 3 trials.

Background Tedizolid is a novel oxazolidinone antibacterial with potent activity against a wide range of Gram-positive pathogens, including methicillin-resistant Staphylococcus aureus and vancomycin-resistant enterococci. Although tedizolid is approved by the US Food and Drug Administration (FDA) for treatment of patients with acute bacterial skin and skin structure infection, commercial susceptibility testing products for tedizolid are not currently available. This study evaluated the usefulness of applying linezolid susceptibility test results as a surrogate for predicting susceptibility to tedizolid in clinically significant Gram-positive pathogens. Methods Gram-positive isolates (N = 10,702) were obtained from annual surveillance programs conducted between 2009 and 2012, from 3 tedizolid clinical trials, and from a preclinical study of the antibacterial activity of tedizolid. Susceptibility testing of linezolid and tedizolid was performed using the reference broth microdilution method in accordance with Clinical and Laboratory Standards Institute methods. Results The minimum inhibitory concentration (MIC) distribution for tedizolid and linezolid against this set of isolates was consistent with that of previous reports. Scatter plot analysis of relevant subsets of organisms was performed and showed high categorical agreement between linezolid and tedizolid MIC results (>99% for staphylococci and streptococci; >98% for enterococci). Very major error rates (ie, tedizolid false-susceptible errors) were very low and within acceptable limits for a surrogate agent: S. aureus and other staphylococcal species, 0%; Enterococcus spp, 0.2%; and Streptococcus spp, 0%. Conclusions High categorical agreement between MIC values for tedizolid and linezolid and low very major error rates were shown for all organism groups tested, supporting the use of linezolid as a reliable surrogate for tedizolid susceptibility testing.