165. Cefiderocol Treatment for Serious Infections Caused by Carbapenem-resistant Bacteria: Post-hoc Analysis of Outcomes by Pathogen in the CREDIBLE-CR Study

Background The efficacy and safety of cefiderocol (CFDC), a novel siderophore cephalosporin, for the treatment of serious infections due to carbapenem-resistant (CR) Gram-negative pathogens was assessed in the CREDIBLE-CR study. The current analysis evaluated clinical and microbiological outcomes by baseline CR pathogen. Methods An open-label, prospective, randomised 2:1, Phase 3 study (CREDIBLE-CR; NCT02714595) was conducted in adult patients with hospital-acquired, ventilator-associated, and healthcare-associated pneumonia, bloodstream infections or sepsis, and complicated urinary tract infections caused by CR Gram-negative pathogens. Patients received either intravenous (IV) CFDC 2g, q8h, 3-h infusion, or IV best available therapy (BAT: up to 3 drugs in combination), for 7–14 days (extendable to 21 days). Clinical and microbiological outcomes were assessed in the CR microbiological intent-to-treat (CR-MITT) population by CR pathogen, baseline MIC and by mechanism of carbapenem resistance at test of cure (TOC). Only summary statistics were collected. Results In the CR-MITT population (CFDC N=80; BAT N=38), Acinetobacter baumannii (46.3% and 44.7%), Klebsiella pneumoniae (33.8% and 31.5%), and Pseudomonas aeruginosa (15% and 26%) were the most frequent pathogens in CFDC and BAT arms, respectively. For all CR pathogens, clinical cure rates were achieved in 52.5% in the CFDC arm and 50.0% in the BAT arm at TOC; rates were similar between treatment arms by baseline CR pathogen (Table 1). Numerically higher clinical cure and microbiological outcomes were observed with CFDC for Enterobacterales (Table 1), especially against NDM-producing bacteria or those with porin-channel mutations (Table 1). CFDC MIC values ranged between ≤0.03 and 4 μg/mL, except for one pathogen (Table 2). Microbiological outcomes for CR A. baumannii, CR K. pneumoniae, and CR P. aeruginosa at TOC by baseline MICs of ≤4 μg/mL ranged between 0–40%, 0–100%, and 0–100%, respectively; at MIC ≤4 μg/mL, clinical and microbiological outcomes were equal (Table 2). Conclusion CFDC, via a novel mechanism of entry and its stability against β-lactamases, was effective against serious infections caused by CR pathogens with various resistance mechanisms or baseline MIC values. Disclosures Yuko Matsunaga, MD, Shionogi Inc. (Employee) Mari Ariyasu, BPharm, Shionogi & Co., Ltd. (Employee) Miki Takemura, MSc, Shionogi & Co., Ltd. (Employee) Yoshinori Yamano, PhD, Shionogi & Co., Ltd. (Employee) Kiichiro Toyoizumi, PhD, Shionogi & Co., Ltd. (Employee) Masahiro Kinoshita, MPharm, Shionogi & Co., Ltd. (Employee) Roger Echols, MD, Shionogi Inc. (Consultant) Tsutae Den Nagata, MD, Shionogi & Co., Ltd. (Employee)