1113. Oral Tebipenem as Step-Down Therapy Following Intravenous Ertapenem in a 7-day Hollow-Fiber In Vitro Infection Model

Abstract Background Intravenous (IV) to oral (PO) antibiotic step-down therapy has many benefits including reducing the length of hospital stay and lowering the risk of nosocomial infections and overall cost. While fluoroquinolones have been utilized as a step-down therapy for urinary tract infections (UTI) for some time, increases in fluoroquinolone-resistant Escherichia coli makes this an increasingly unsuitable option. Tebipenem (TBP) is an orally bioavailable carbapenem administered as a pro-drug (tebipenem pivoxil hydrobromide) with broad-spectrum activity that is currently in development for the treatment of patients with complicated UTI. Herein we describe a series of 7-day hollow-fiber in vitro infection model (HFIM) assays designed to evaluate the potential of PO TBP as step-down therapy from IV ertapenem (ETP). Methods A panel of ESBL+ clinical E. coli isolates, selected based upon ETP and TBP MIC values and known resistance profiles, were evaluated at an initial burden of 107 CFU/mL. HFIM, ETP and TBP free-drug concentration-time profiles were simulated in the HFIM to represent those following IV and PO dosing, respectively. Each isolate was challenged in duplicate by ETP administered every 24 hours (q24h) for 1, 3 or 7 days of therapy. TBP 600 mg every 8 hours was simulated as a step-down therapy following either 1 or 3 days of ETP treatment as well as a 7-day monotherapy regimen. All active regimens were compared to a no-treatment control as well as ETP 1g q24h for 1 or 3 days followed by a halting of therapy. Samples were collected for enumeration of bacterial populations and observation of simulated PK profiles throughout. Results Bacteria grew well in the no-treatment control group, reaching densities > 1010 CFU/mL. ETP 1g q24h monotherapy successfully reduced bacterial burdens to below levels of detection over the 7-day period but was followed by regrowth matching that in the no-treatment control when treatment was halted on Days 1 and 3. Similar to ETP, TBP successfully reduced bacterial burdens as a 7-day monotherapy and following 1 and 3 days of IV ETP by preventing growth throughout the remainder of the study. Conclusion These data demonstrate the potential utility of TBP as oral step-down from IV ETP therapy and the need for evaluation as a step-down from other IV therapeutics. Disclosures Brian D. VanScoy, B.S., 3-V Biosciences (Grant/Research Support)Achogen (Grant/Research Support)Amplyx Pharmaceuticals, Inc. (Grant/Research Support)Arixa Pharmaceuticals (Grant/Research Support)Arsanis Inc. (Grant/Research Support)B. Braun Medical Inc. 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(Grant/Research Support)Institute for Clinical Pharmacodynamics (Employee)Iterum (Grant/Research Support)KBP Biosciences USA (Grant/Research Support)Kyoto Biopharma, Inc. (Grant/Research Support)Matinas (Grant/Research Support)Meiji Seika Pharma Co., Ltd. (Grant/Research Support)Melinta Therapeutics (Grant/Research Support)Menarini Ricerche S.p.A. (Grant/Research Support)Merck & Co., Inc (Grant/Research Support)Mutabilis (Grant/Research Support)Nabriva Therapeutics AG (Grant/Research Support)Naeja-RGM Pharmaceuticals (Grant/Research Support)Nosopharm SAS (Grant/Research Support)Novartis Pharmaceuticals Corp. (Grant/Research Support)NuCana Biomed (Grant/Research Support)Paratek Pharmaceuticals, Inc. (Grant/Research Support)Polyphor, Ltd. (Grant/Research Support)Prothena Corporation (Grant/Research Support)PTC Therapeutics (Grant/Research Support)Rempex Pharmaceuticals (Grant/Research Support)Roche TCRC (Grant/Research Support)Sagimet (Grant/Research Support)scPharmaceuticals Inc. 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