Ceftolozane/tazobactam dose regimens in severely/morbidly obese patients with complicated intra-abdominal infection or complicated urinary tract infection.

Ceftolozane/tazobactam is approved for treatment of complicated intra-abdominal infection (cIAI) and complicated urinary tract infection (cUTI) with renal function-based dose adjustment. Given that creatinine clearance, body weight and sex are highly correlated in severely/morbidly obese patients, this study investigated whether approved dosing regimens for ceftolozane/tazobactam are appropriate in severely/morbidly obese patients based on simulated pharmacokinetic/pharmacodynamic target attainment, with confirmation from observed clinical outcomes data from the phase 3 clinical development programme. Using a previously published population pharmacokinetic model, 1000 patients were randomly sampled from an internal pooled database of 201 severely/morbidly obese patients (BMI ≥ 35 kg/m2) and were used for Monte Carlo simulation to test whether the labelled dose regimens can achieve ≥90% probability of a target of 32.2% (1-log kill) time above free ceftolozane concentration against pathogens at an MIC up to 8 mg/L. Clinical outcomes data for severely/morbidly obese patients with cIAI or cUTI from pivotal phase 3 studies were summarised to calculate clinical and composite cure rates as a complimentary support. With the approved renal function-based dosing regimens, >90% target attainment of bactericidal activity was achieved at MICs up to 8 mg/L in the simulated severely/morbidly obese patients with cIAI or cUTI, similar to target attainment in non-obese patients and further confirmed by phase 3 outcomes where cure rates in severely/morbidly obese patients and non-obese patients are similar. Approved dosing regimens of ceftolozane/tazobactam, adjusted according to renal function, can achieve adequate target attainment and high clinical cure rates in severely/morbidly obese patients with cIAI or cUTI.

PK/PD Target Attainment With Ceftolozane/Tazobactam Using Monte Carlo Simulation in Patients With Various Degrees of Renal Function, Including Augmented Renal Clearance and End-Stage Renal Disease.

INTRODUCTION: Ceftolozane/tazobactam is an antibacterial agent with potent in vitro activity against Gram-negative pathogens, including many extended-spectrum ß-lactamase-producing Enterobacteriaceae and drug-resistant Pseudomonas aeruginosa. Because ceftolozane/tazobactam is primarily excreted renally, appropriate dose adjustments are needed for patients with renal impairment. Monte Carlo simulations were used to determine the probability of pharmacokinetic/pharmacodynamic target attainment for patients with varying degrees of renal function, including augmented renal clearance (ARC) and end-stage renal disease (ESRD) with hemodialysis. METHODS: Monte Carlo simulations were conducted for 1000 patients with ARC and normal renal function, mild renal impairment, moderate renal impairment, or severe renal impairment, and for 5000 patients with ESRD. Simulated dosing regimens were based on approved doses for each renal function category. Attainment targets for ceftolozane were 24.8% (bacteriostasis), 32.2% (1-log kill; bactericidal), and 40% (2-log kill) fT > minimum inhibitory concentration (MIC). The target for tazobactam was to achieve a 20% fT > minimum effective concentration (MEC) at an MEC of 1 mg/L, which was derived from a neutropenic mouse thigh infection model and was confirmed by efficacy data from clinical studies for complicated intraabdominal infections and complicated urinary tract infections. RESULTS: In patients with ARC or normal renal function, ≥91% achieved bactericidal activity (32.2% fT > MIC) up to an MIC of 4 mg/L with a 1000-mg ceftolozane dose. In patients with renal impairment (mild, moderate, severe, ESRD), ≥93% achieved bactericidal activity up to an MIC of 8 mg/L. In patients of all renal function categories, the approved dosing regimens of tazobactam achieved ≥91% target attainment against a target of 20% fT > MEC. CONCLUSIONS: At the approved dosing regimens for ceftolozane/tazobactam, ≥91% of patients in all renal function categories, including ARC (up to 200 mL/min) and ESRD, reached target attainment for bactericidal activity at MICs that correspond to susceptibility breakpoints for Enterobacteriaceae and P. aeruginosa.

Ceftolozane/tazobactam pharmacokinetic/pharmacodynamic-derived dose justification for phase 3 studies in patients with nosocomial pneumonia.

Ceftolozane/tazobactam is an antipseudomonal antibacterial approved for the treatment of complicated urinary tract infections (cUTIs) and complicated intra-abdominal infections (cIAIs) and in phase 3 clinical development for treatment of nosocomial pneumonia. A population pharmacokinetic (PK) model with the plasma-to-epithelial lining fluid (ELF) kinetics of ceftolozane/tazobactam was used to justify dosing regimens for patients with nosocomial pneumonia in phase 3 studies. Monte Carlo simulations were performed to determine ceftolozane/tazobactam dosing regimens with a > 90% probability of target attainment (PTA) for a range of pharmacokinetic/pharmacodynamic targets at relevant minimum inhibitory concentrations (MICs) for key pathogens in nosocomial pneumonia. With a plasma-to-ELF penetration ratio of approximately 50%, as observed from an ELF PK study, a doubling of the current dose regimens for different renal functions that are approved for cUTIs and cIAIs is needed to achieve > 90% PTA for nosocomial pneumonia. For example, a 3-g dose of ceftolozane/tazobactam for nosocomial pneumonia patients with normal renal function is needed to achieve a > 90% PTA (actual 98%) for the 1-log kill target against pathogens with an MIC of ≤ 8 mg/L in ELF, compared with the 1.5-g dose approved for cIAIs and cUTIs.