Comparing probability of target attainment against Staphylococcus aureus for ceftaroline fosamil, vancomycin, daptomycin, linezolid, and ceftriaxone in complicated skin and soft tissue infection using pharmacokinetic/pharmacodynamic models

Real-World Use and Treatment Outcomes of Ceftaroline Fosamil in Patients with Complicated Skin and Soft Tissue Infection: A Multinational Retrospective Study

Background

Ceftaroline fosamil is approved for the treatment of complicated skin and soft tissue infections (cSSTI) and community-acquired pneumonia (CAP); however, data on its real-world use and effectiveness in Europe and Latin America are currently limited. This retrospective observational study assessed ceftaroline fosamil use and treatment outcomes in adults hospitalized with cSSTI or CAP treated with ceftaroline fosamil in a usual care setting in Europe and Latin America. Results for patients with cSSTI are reported.

Methods

Data from patients with cSSTI who received ≥4 consecutive intravenous ceftaroline fosamil doses up to May 31, 2019, were collected from sites in Brazil, Colombia, France, Greece, Italy, and Spain. Patient characteristics, clinical management, hospitalization information, microbiological diagnosis, and clinical responses were summarized descriptively. Healthcare resource use variables were evaluated by clinical response to ceftaroline fosamil.

Results

Data for 132 patients were included (58.3% male; mean age 58.5 years). Most common lesions were cellulitis/fasciitis (62.1%), abscess (34.1%), and post-surgical wounds (19.7%). Pathogens most frequently identified were methicillin-resistant (18.2%) and methicillin-susceptible Staphylococcus aureus (17.4%). Median (range) ceftaroline fosamil treatment duration was 8 (2-60) days (daily doses of 1200 [400-2400] mg); 78 patients (59.1%) received monotherapy. In total, 75 (56.8%) patients had additional antibiotics after ceftaroline fosamil. Clinical response occurred in 118 (89.4%) patients. All-cause 30-day readmission occurred in 13 (9.8%) patients, and all-cause 30-day mortality in 7 (5.3%). Clinical response to ceftaroline was associated with >25% shorter length of hospital and intensive care stay, and with ~40% lower hospital costs, versus non-responders.

Conclusion

Ceftaroline fosamil was effective in treating adults with cSSTI and clinical response to ceftaroline fosamil was associated with reductions in healthcare resource use compared with non-responders, in Europe and Latin America.

Clinicaltrialsgov Identifier

NCT04198571.

Integrative model-based comparison of target site-specific antimicrobial effects: A case study with ceftaroline and lefamulin

OBJECTIVE

Predictions of antimicrobial effects typically rely on plasma-based pharmacokinetic-pharmacodynamic (PK-PD) targets, ignoring target-site concentrations and potential differences in tissue penetration between antibiotics. In this study, we applied PK-PD modelling to compare target site-specific effects of antibiotics by integrating clinical microdialysis data, in vitro time-kill curves, and antimicrobial susceptibility distributions. As a case study, we compared the effect of lefamulin and ceftaroline against methicillin-resistant Staphylococcus aureus (MRSA) at soft-tissue concentrations.

METHODS

A population PK model describing lefamulin concentrations in plasma, subcutaneous adipose and muscle tissue was developed. For ceftaroline, a similar previously reported PK model was adopted. In vitro time-kill experiments were performed with six MRSA isolates and a PD model was developed to describe bacterial growth and antimicrobial effects. The clinical PK and in vitro PD models were linked to compare antimicrobial effects of ceftaroline and lefamulin at the different target sites.

RESULTS

Considering minimum inhibitory concentration (MIC) distributions and standard dosages, ceftaroline showed superior anti-MRSA effects compared to lefamulin both at plasma and soft-tissue concentrations. Looking at the individual antibiotics, lefamulin effects were highest at soft-tissue concentrations, while ceftaroline effects were highest at plasma concentrations, emphasising the importance of considering target-site PK-PD in antibiotic treatment optimisation.

CONCLUSION

Given standard dosing regimens, ceftaroline appeared more effective than lefamulin against MRSA at soft-tissue concentrations. The PK-PD model-based approach applied in this study could be used to compare or explore the potential of antibiotics for specific indications or in populations with unique target-site PK.

Target attainment of intravenous lefamulin for treatment of acute bacterial skin and skin structure infections

OBJECTIVES

Lefamulin is a pleuromutilin antibiotic approved for the treatment of community-acquired bacterial pneumonia (CABP). Its spectrum of activity, good penetration into soft tissues and low rates of cross-resistance also make lefamulin a potentially valuable option for treatment of acute bacterial skin and skin structure infections (ABSSSIs). A Phase 2 trial of lefamulin for ABSSSI indicated similar efficacy of 100 and 150 mg q12h IV dosing regimens. In the present study, the potential of lefamulin for this indication was further evaluated from a translational pharmacokinetic/pharmacodynamic perspective.

METHODS

PTA was determined for various dosages using Monte Carlo simulations of a population pharmacokinetic model of lefamulin in ABSSSI patients and preclinical exposure targets associated with bacteriostasis and a 1-log reduction in bacterial count. Overall target attainment against MSSA and MRSA was calculated using lefamulin MIC distributions.

RESULTS

Overall attainment of the bacteriostasis target was 94% against MSSA and 84% against MRSA for the IV dosage approved for CABP (150 mg q12h). Using the same target, for the 100 mg q12h regimen, overall target attainment dropped to 68% against MSSA and 50% against MRSA. Using the 1-log reduction target, overall target attainment for both regimens was <40%.

CONCLUSIONS

Lefamulin at the currently approved IV dosage covers most Staphylococcus aureus isolates when targeting drug exposure associated with bacteriostasis, suggesting potential of lefamulin for the treatment of ABSSSIs. Lefamulin may not be appropriate in ABSSSI when rapid bactericidal activity is warranted.

Optimal drug therapy for Staphylococcus aureus bacteraemia in adults

PURPOSE OF REVIEW

Staphylococcus aureus is a significant human pathogen, causing a variety of infections, from skin and soft tissue infections to endocarditis, bone and joint infections and deep tissue abscesses. Mortality from S. aureus bacteraemia remains high, without major therapeutic advances in recent decades.

RECENT FINDINGS

In recent years, optimized dosing of antibiotics is increasingly being recognized as a cornerstone of management for severe infections including S. aureus bacteraemia. This comprehensive review details the pharmacokinetics/pharmacodynamics (PK/PD) targets for commonly used antistaphylococcal antibiotics and the doses predicted to achieve them in clinical practice. Recent advances in dosing of teicoplanin and use of cefazolin in CNS infections and findings from combination therapy studies are discussed. Drug exposure relationships related to toxicity are also detailed.

SUMMARY

This review details the different PK/PD targets for drugs used to treat S. aureus bacteraemia and how to apply them in various scenarios. The drug doses that achieve them, and the risks of toxicity are also provided.

A physiologically based pharmacokinetic model to optimize the dosage regimen and withdrawal time of cefquinome in pigs

Cefquinome is widely used to treat respiratory tract diseases of swine. While extra-label dosages of cefquinome could improve clinical efficacy, they might lead to excessively high residues in animal-derived food. In this study, a physiologically based pharmacokinetic (PBPK) model was calibrated based on the published data and a microdialysis experiment to assess the dosage efficiency and food safety. For the microdialysis experiment, in vitro/in vivo relative recovery and concentration-time curves of cefquinome in the lung interstitium were investigated. This PBPK model is available to predict the drug concentrations in the muscle, kidney, liver, plasma, and lung interstitial fluid. Concentration-time curves of 1000 virtual animals in different tissues were simulated by applying sensitivity and Monte Carlo analyses. By integrating pharmacokinetic/pharmacodynamic target parameters, cefquinome delivered at 3-5 mg/kg twice daily is advised for the effective control of respiratory tract infections of nursery pig, which the bodyweight is around 25 kg. Based on the predicted cefquinome concentrations in edible tissues, the withdrawal interval is 2 and 3 days for label and the extra-label doses, respectively. This study provides a useful tool to optimize the dosage regimen of cefquinome against respiratory tract infections and predicts the concentration of cefquinome residues in edible tissues. This information would be helpful to improve the food safety and guide rational drug usage.

Clinical evidence supporting ceftaroline fosamil and ceftobiprole for complicated skin and soft tissue infections

PURPOSE OF REVIEW

Ceftaroline and ceftobiprole are advanced generation cephalosporins with activity against methicillin-resistant Staphylococcus aureus (MRSA). This review summarizes their clinical efficacy for complicated skin and soft tissue infections (cSSTIs).

RECENT FINDINGS

Both these agents retain excellent in vitro activity against both MRSA and Gram-negative isolates from patients with CSSTIs. Both these agents are registered for the management of cSSTIs based on the results of large scale phase III noninferiority trials. Ceftaroline and ceftobiprole are noninferior to the combination of vancomycin and aztreonam as this was assessed by their clinical cure rate at the test-of-cure visits. Furthermore, ceftobiprole is noninferior to comparators for the achievement of early clinical success at 72 h. Ceftaroline achieves 81% clinical cure against diabetic foot infections.

SUMMARY

Ceftaroline and ceftobiprole can be used as monotherapy for the treatment of cSSTIs.

Concept and application of the probability of pharmacological success (PoPS) as a decision tool in drug development: a position paper

BACKGROUND

In drug development, few molecules from a large pool of early candidates become successful medicines after demonstrating a favourable benefit-risk ratio. Many decisions are made along the way to continue or stop the development of a molecule. The probability of pharmacological success, or PoPS, is a tool for informing early-stage decisions based on benefit and risk data available at the time.

RESULTS

The PoPS is the probability that most patients can achieve adequate pharmacology for the intended indication while minimising the number of subjects exposed to safety risk. This probability is usually a function of dose; hence its computation typically requires exposure-response models for pharmacology and safety. The levels of adequate pharmacology and acceptable risk must be specified. The uncertainties in these levels, in the exposure-response relationships, and in relevant translation all need to be identified. Several examples of different indications are used to illustrate how this approach can facilitate molecule progression decisions for preclinical and early clinical development. The examples show that PoPS assessment is an effective mechanism for integrating multi-source data, identifying knowledge gaps, and forcing transparency of assumptions. With its application, translational modelling becomes more meaningful and dose prediction more rigorous. Its successful implementation calls for early planning, sound understanding of the disease-drug system, and cross-discipline collaboration. Furthermore, the PoPS evolves as relevant knowledge grows.

CONCLUSION

The PoPS is a powerful evidence-based framework to formally capture multiple uncertainties into a single probability term for assessing benefit-risk ratio. In GSK, it is now expected for governance review at all early-phase decision gates.

Population Pharmacokinetic-Pharmacodynamic Modeling and Probability of Target Attainment Analysis of Rocuronium and Sugammadex in Children Undergoing Surgery

BACKGROUND AND OBJECTIVES

Probability of target attainment (PTA) curves are commonly used to support dose recommendations of antibiotics for different patient groups. In this study we propose PTA analysis to optimize sugammadex dosing in children.

METHODS

This study involved data from an observational cohort study of 30 American Society of Anesthesiologists (ASA) Physical Status I and II children undergoing surgery requiring muscle relaxation. All patients received 0.6 mg/kg rocuronium, with sugammadex administered at the end of surgery in three different doses (0.5, 1.0, and 2.0 mg/kg) to reverse the neuromuscular blockade.

RESULTS

The data were analyzed using a population Bayesian-based approach. The developed model was used to simulate pharmacokinetic-pharmacodynamic profiles for different patient groups and dosing regimens before the PTA analysis was performed to translate these simulations into a clinically useful measure. The target was defined as neuromuscular blockade reversal measured by Train-of-Four (TOF ratio > 90%) at 1.5, 3, and 5 min post sugammadex dose. The sugammadex doses leading to 90% PTA were determined for different patients' body weights, rocuronium doses, and time gaps between rocuronium and sugammadex administration assuming the model, priors, and gathered data. For comparison, PTA curves for a range of clinical scenarios are provided to illustrate the usefulness of PTA analysis in selecting the appropriate dose for a given patient.

CONCLUSIONS

The proposed PTA analysis is useful to support the sugammadex dose selection in different clinical scenarios.

TRIAL REGISTRATION

The study was registered by ClinicalTrials.gov under number NCT04851574 on 21 April 2021.

Retrospective Comparison of the Effectiveness and Safety of Ceftriaxone 1 g Twice Daily versus 2 g Once Daily for Treatment of Aspiration Pneumonia

Although a 2 g once daily administration of ceftriaxone remains the standard dosing regimen for the treatment of aspiration pneumonia, there are no studies to investigate the optimal dosing method. Hence, we retrospectively evaluated the effectiveness and safety of 1 g twice daily versus 2 g once daily administration of ceftriaxone in adult patients with aspiration pneumonia. Patients who received ceftriaxone for the treatment of aspiration pneumonia between 2015 and 2021 were included in this study. Clinical responses, inflammatory markers, and incidence of adverse events after completion of ceftriaxone therapy were investigated. In total, 33 patients received 1 g twice daily (group 1) and 28 received 2 g once daily (group 2) ceftriaxone for the treatment of mild-to-moderate aspiration pneumonia. Compared with that of group 1, group 2 demonstrated significantly improved clinical responses (group 1 vs. group 2, 84.8% vs. 100%, p = 0.0316). Although the safety profile was not significantly different between the two groups, the incidence of choleliths during ceftriaxone therapy in group 1 was higher than that in group 2 (31.3% vs. 9.1%, p = 0.174). Therefore, a 2 g once daily administration of ceftriaxone appeared to be a simple regimen adequate for the treatment of inpatients with mild-to-moderate aspiration pneumonia, which might not be heavily involved by anaerobes.

Ceftaroline Fosamil for Treatment of Pediatric Complicated Skin and Soft Tissue Infections and Community-Acquired Pneumonia

Community-acquired pneumonia (CAP)/community-acquired bacterial pneumonia (CABP) and complicated skin and soft tissue infection (cSSTI)/acute bacterial skin and skin structure infection (ABSSSI) represent major causes of morbidity and mortality in children. β-Lactams are the cornerstone of antibiotic treatment for many serious bacterial infections in children; however, most of these agents have no activity against methicillin-resistant Staphylococcus aureus (MRSA). Ceftaroline fosamil, a β-lactam with broad-spectrum in vitro activity against Gram-positive pathogens (including MRSA and multidrug-resistant Streptococcus pneumoniae) and common Gram-negative organisms, is approved in the European Union and the United States for children with CAP/CABP or cSSTI/ABSSSI. Ceftaroline fosamil has completed a pediatric investigation plan including safety, efficacy, and pharmacokinetic evaluations in patients with ages ranging from birth to 17 years. It has demonstrated similar clinical and microbiological efficacy to best available existing treatments in phase III-IV trials in patients aged ≥ 2 months to < 18 years with CABP or ABSSSI, with a safety profile consistent with the cephalosporin class. It is also approved in the European Union for neonates with CAP or cSSTI, and in the US for neonates with ABSSSI. Ceftaroline fosamil dosing for children (including renal function adjustments) is supported by pharmacokinetic/pharmacodynamic modeling and simulations in appropriate age groups, and includes the option of 5- to 60-min intravenous infusions for standard doses, and a high dose for cSSTI patients with MRSA isolates, with a ceftaroline minimum inhibitory concentration of 2-4 mg/L. Considered together, these data suggest ceftaroline fosamil may be beneficial in the management of CAP/CABP and cSSTI/ABSSSI in children.

Antibiotics in Necrotizing Soft Tissue Infections

Necrotizing soft tissue infections (NSTIs) are rare life-threatening bacterial infections characterized by an extensive necrosis of skin and subcutaneous tissues. Initial urgent management of NSTIs relies on broad-spectrum antibiotic therapy, rapid surgical debridement of all infected tissues and, when present, treatment of associated organ failures in the intensive care unit. Antibiotic therapy for NSTI patients faces several challenges and should (1) carry broad-spectrum activity against gram-positive and gram-negative pathogens because of frequent polymicrobial infections, considering extended coverage for multidrug resistance in selected cases. In practice, a broad-spectrum beta-lactam antibiotic (e.g., piperacillin-tazobactam) is the mainstay of empirical therapy; (2) decrease toxin production, typically using a clindamycin combination, mainly in proven or suspected group A streptococcus infections; and (3) achieve the best possible tissue diffusion with regards to impaired regional perfusion, tissue necrosis, and pharmacokinetic and pharmacodynamic alterations. The best duration of antibiotic treatment has not been well established and is generally comprised between 7 and 15 days. This article reviews the currently available knowledge regarding antibiotic use in NSTIs.

PK/PD modeling of daptomycin against MRSA and MRSE and Monte Carlo simulation for bacteremia treatment

OBJECTIVES

The aim of this study was to investigate the effect of daptomycin against methicillin-resistant staphylococci (MRSA and MRSE) bacteremia using computer modeling.

METHODS

A pharmacokinetic/pharmacodynamic (PK/PD) modeling strategy to explain the data from an in vitro dynamic model employing time-kill curves for MRSA and MRSE was proposed. Bacterial killing was followed over time by determining viable counts and the resulting time-kill data was analyzed. Monte Carlo simulations were performed using pharmacokinetic parameters and pharmacodynamic data to determine the probabilities of target attainment and cumulative fractions of response in terms of area under the concentration curve/minimum inhibition concentration (MIC) targets of daptomycin. Simulations were conducted to assess the reduction in the number of colony-forming units (CFU)/mL for 18 days of treatment with daptomycin at doses of 6, 8, and 10 mg/kg/24 h or 48 h with variations in creatinine clearance (CL_CR): 15-29 mL/min/1.73 m², 30-49 mL/min/1.73 m², 50-100 mL/min/1.73 m², as well as for defining the probability of reaching the target fAUC/MIC = 80 in the same dose and clearance range. A PK/PD model with saturation in the number of bacteria in vitro, growth delay, and bacterial death, as well as Hill's factor, was used to describe the data for both MRSA and MRSE.

RESULTS

Monte Carlo simulations showed that for MRSA there was a reduction > 2 log CFU/mL with doses ≥ 6 mg/kg/day in 75th percentile of the simulated population after 18 days of treatment with daptomycin, whereas for MRSE this reduction was observed in 95th percentile of the population.

CONCLUSIONS

The presented in vitro PK/PD model and associated modeling approach were able to characterize the time-kill kinetics of MRSA and MRSE. Our study based on PTAs suggests that doses ≥ 6 mg/kg/day of daptomycin should be used to treat bacteremia caused by MRSA and MRSE in patients with CL_CR of 15-29 mL/min/1.73 m². For patients with CL_CR ≥ 50 mL/min/1.73 m², it would be necessary to employ a dose of 10 mg/kg/day to treat complicated bacteremias.

Population pharmacokinetics and dose optimization of vancomycin in neonates

The pharmacokinetics of vancomycin vary among neonates, and we aimed to conduct population pharmacokinetic analysis to determine the optimal dosage of vancomycin in Korean neonates. From a retrospective chart review, neonates treated with vancomycin from 2008 to 2017 in a neonatal intensive care unit (NICU) were included. Vancomycin concentrations were collected based on therapeutic drug monitoring, and other patient characteristics were gathered through electronic medical records. We applied nonlinear mixed-effect modeling to build the population pharmacokinetic model. One- and two-compartment models with first-order elimination were evaluated as potential structural pharmacokinetic models. Allometric and isometric scaling was applied to standardize pharmacokinetic parameters for clearance and volume of distribution, respectively, using fixed powers (0.75 and 1, respectively, for clearance and volume). The predictive performance of the final model was developed, and dosing strategies were explored using Monte Carlo simulations with AUC_0–24 targets 400–600. The patient cohort included 207 neonates, and 900 vancomycin concentrations were analyzed. Only 37.4% of the analyzed concentrations were within trough concentrations 5–15 µg/mL. A one-compartment model with first-order elimination best described the vancomycin pharmacokinetics in neonates. Postmenstrual age (PMA) and creatinine clearance (CLcr) affected the clearance of vancomycin, and model evaluation confirmed the robustness of the final model. Population pharmacokinetic modeling and dose optimization of vancomycin in Korean neonates showed that vancomycin clearance was related to PMA and CLcr, as well as body weight. A higher dosage regimen than the typical recommendation is suggested.