Cefiderocol pharmacokinetics during acute pulmonary exacerbations in hospitalized adult persons with cystic fibrosis

Persons with CF (pwCF) present altered pharmacokinetics (PK) and are often infected with multidrug-resistant (MDR) bacteria. Herein, we describe the PK of cefiderocol, a siderophore cephalosporin with potent activity against MDR Gram-negative rods, in hospitalized adult pwCF with acute pulmonary exacerbation (APE). PwCF received ≥3 doses of 2 g cefiderocol (3 h infusion) with frequency determined according to their estimated glomerular filtration rate (eGFR). Blood sampling collected at steady state. Concentrations were fitted using the non-parametric adaptive grid algorithm in Pmetrics for R. Ten pwCF were enrolled; nine completed the study with six receiving 2 g q8 h and three 2 g q6 h. A two-compartment model best fitted the data. Mean (SD) PK parameters were clearance, 5.66 (1.28) L/h; volume of central compartment, 5.81 (3.52) L, and intercompartment transfer constants, k12, 4.29 (3.46) and k21, 2.25 (2.76) h^-1. Protein binding was 48% (35-57). The 2 g q8 h regimen achieved a mean free time above the MIC (<i>f</i>T >MIC) of 99% (94-99), 90% (69-100), and 64% (41-81) at MICs of 4 (susceptible), 8 (intermediate), and 16 (resistant) mg/L, respectively, with AUC_24h of 1,191 (781-1,496) mg/L*h. In pwCF with eGFR >120 mL/min, 2 g q6 h attained 100% <i>f</i>T >MIC up to 8 mg/L and 87% (83-92) at 16 mg/L, with AUC_24h of 1,279 (1,054-1,590) mg/L*h. Among these nine pwCF with APE with normal or augmented renal clearance, cefiderocol using label prescribed dosing regimens according to eGFR was well tolerated and achieved optimal <i>f</i>T >MIC exposure for pathogens up to MICs of 8 mg/L and AUC_24h estimates similar to previously reported estimates in non-CF patients.