1258. Activity of a Series of Investigational Compounds Tested Against Invasive Fungal Isolates

Abstract Background Fox Chase Chemical Diversity Center (FCC) is developing non-peptide analogs of host defense proteins for the treatment of invasive fungal infections mainly caused by Candida (CAN) and Aspergillus (ASP). We evaluated the activity of 6 novel compounds and 2 comparators against 150 isolates from 15 fungal groups. Methods Susceptibility testing was performed per CLSI broth microdilution methods for investigational compounds and comparators against 70 CAN and 40 ASP isolates in addition to 10 Cryptococcus spp. (CRYP), 10 Fusarium spp. (FUS), 10 Mucorales, and 10 Scedosporium spp. (SCED) isolates from recent (2017-2019) clinical infections. MIC results were determined as ≥ 50% reduction at 24 and 72 hours for CAN and CRYP respectively, and 100% reduction at 24, 72, and 48 hours for Mucorales, SCED, and other moulds, respectively. CLSI clinical breakpoint (CBP) and epidemiological cutoff value (ECV) interpretive criteria were applied for comparators. Results Compounds FC10790, FC11083, FC11212, and FC11275 had MIC50 results at ≤ 0.015 mg/L and MIC90 results at ≤ 0.015 to 0.12 mg/L against CRYP, ASP, and FUS isolates. Compounds FC5096 and FC11022 were 2- to 4-fold less active while demonstrating MIC50 and MIC90 results of 0.03 to 0.5 mg/L against CAN, CRYP, ASP, and FUS isolates. The Mucorales isolate set showed the widest range of MIC results for FC compounds. FC10790 exhibited the greatest potency with a MIC50/90 at 0.5/2 mg/L. FC compounds showed potent activity against SCED with MIC90 results of 0.03 to 0.25 mg/L. Fluconazole showed a wide range of MIC results, from 0.06 to >64 mg/L, but the highest results observed were for Candida auris (MIC50/90, 64/ > 64 mg/L) and Candida krusei (MIC50/90; 16/32 mg/L). Itraconazole was active against all ASP (MIC50/90, 1/1 mg/L), but showed poor activity against FUS (MIC50/90, > 8/ > 8 mg/L). Amphotericin B showed a narrow range of MIC results (0.5 to 2 mg/L) for all isolates except 1 ASP and most SCED. Conclusion Novel FCC compounds showed equal or greater activity than comparators against most CAN, ASP, SCED, and FUS. FC10790, FC11212, and FC11275 showed the greatest activity against all tested fungal isolates. development of this series of compounds for clinical studies. Table 1 Disclosures Paul R. Rhomberg, n/a, Cidara Therapeutics (Research Grant or Support)Fox Chase Chemical Diversity Center (Research Grant or Support)Merck (Research Grant or Support) Shawn A. Messer, PhD, Amplyx Pharmaceuticals (Research Grant or Support)Fox Chase Chemical Diversity Center (Research Grant or Support) Richard W. Scott, PhD, Fox Chase Chemical Diversity Center (Employee) Simon DP Baugh, PhD, Fox Chase Chemical Diversity Center (Employee) 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) 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) Cecilia G. Carvalhaes, MD, PhD, A. Menarini Industrie Farmaceutiche Riunite S.R.L. (Research Grant or Support)Allergan (Research Grant or Support)Cidara Therapeutics (Research Grant or Support)Cipla Ltd. (Research Grant or Support)Fox Chase Chemical Diversity Center (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)Pfizer (Research Grant or Support)