Pharmacokinetics and Pharmacodynamics of Nemonoxacin in a Neutropenic Murine Lung Infection Model Against Streptococcus Pneumoniae

Pharmacokinetics and Pharmacodynamics of a Novel Vancomycin Derivative LYSC98 in a Murine Thigh Infection Model Against Staphylococcus aureus

Introduction

LYSC98 is a novel vancomycin derivative used for gram-positive bacterial infections. Here we compared the antibacterial activity of LYSC98 with vancomycin and linezolid in vitro and in vivo. Besides, we also reported the pharmacokinetic/pharmacodynamic (PK/PD) index and efficacy-target values of LYSC98.

Methods

The MIC values of LYSC98 were identified through broth microdilution method. A mice sepsis model was established to investigate the protective effect of LYSC98 in vivo. Single-dose pharmacokinetics of LYSC98 was studied in thigh-infected mice and liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was used to determine LYSC98 concentration in plasma. Dose fractionation studies were performed to evaluate different PK/PD indices. Two methicillin-resistant Staphylococcus aureus (MRSA) clinical strains were used in the dose ranging studies to determine the efficacy-target values.

Results

LYSC98 showed a universal antibacterial effect in Staphylococcus aureus with a MIC range of 2-4 µg/mL. In vivo, LYSC98 demonstrated distinctive mortality protection in mice sepsis model with an ED₅₀ value of 0.41-1.86 mg/kg. The pharmacokinetics results displayed maximum plasma concentration (C_max) 11,466.67-48,866.67 ng/mL, area under the concentration-time curve from 0 to 24 h (AUC_0-24) 14,788.42-91,885.93 ng/mL·h, and elimination half-life (T_1/2) 1.70-2.64 h, respectively. C_max/MIC (R ² 0.8941) was proved to be the most suitable PK/PD index for LYSC98 to predict its antibacterial efficacy. The magnitude of LYSC98 C_max/MIC associated with net stasis, 1, 2, 3 and 4 - log ₁₀ kill were 5.78, 8.17, 11.14, 15.85 and 30.58, respectively.

Conclusion

Our study demonstrates that LYSC98 is more effective than vancomycin either in killing vancomycin-resistant Staphylococcus aureus (VRSA) in vitro or treating S. aureus infections in vivo, making it a novel and promising antibiotic. The PK/PD analysis will also contribute to the LYSC98 Phase I dose design.

Integrative population pharmacokinetic/pharmacodynamic analysis of nemonoxacin capsule in Chinese patients with community-acquired pneumonia

Introduction: Nemonoxacin is an innovative quinolone antibiotic for treatment of community-acquired pneumonia (CAP). As more data are available from clinical studies, it is necessary to perform an integrative pharmacokinetic/pharmacodynamic (PK/PD) analysis to support and justify the optimal dosing regimen of nemonoxacin in clinical practice. Methods and Results: We developed a population PK model using non-linear mixed effect model based on the data of 195 Chinese subjects receiving nemonoxacin in phase I to III clinical trials. The base model was a standard two-compartment PK model defined by clearance (12 L/h) and central volume of distribution (86 L). Covariates included creatinine clearance (CL_cr), body weight (BW), sex, disease status and food. Compared to the subject with BW 60 kg, C_max and A U C 0 - 24 ,   ss reduced by 24% and 19% in the subject with BW 80 kg, respectively. Compared to the subject with CL_cr 150 ml/min, A U C 0 - 24 ,   ss and T_1/2 increased by 28% and 24%, respectively in the subject with CL_cr 30 ml/min. Compared to the fasted status, T_max of nemonoxacin increased by 1.2 h in the subject with fed status. Effects of sex and disease status on PK parameters were small (change of PK parameters ≤19%). AUC_0-24/MIC and %T > MIC were identified as the optimal PK/PD indices for predicting clinical efficacy. The AUC_0-24/MIC target was 63.3, 97.8, and 115.7 against Streptococcus pneumoniae, Staphylococcus aureus, and Haemophilus influenzae, respectively. The %T > MIC target was 7.96% against Klebsiella pneumoniae. Monte Carlo simulation showed that treatment with nemonoxacin 500 mg q24 h could attain a PK/PD cutoff value higher than the MIC₉₀ against S. pneumoniae and S. aureus. The corresponding cumulative fraction of response (CFR) was greater than 93%, while nemonoxacin 750 mg q24 h would provide higher PK/PD cutoff value against Haemophilus parainfluenzae, and higher CFR (83%) than 500 mg q24 h. Conclusion: Integrative PK/PD analysis justifies the reliable clinical and microbiological efficacy of nemonoxacin 500 mg q24 h in treating CAP caused by S. pneumoniae, S. aureus, and K. pneumoniae, irrespective of patient sex, mild renal impairment, empty stomach or not. However, nemonoxacin 750 mg q24 h would provide better efficacy than 500 mg q24 h for the CAP caused by H. parainfluenzae in terms of CFR.

Pharmacodynamic Parameters of Pharmacokinetic/Pharmacodynamic (PK/PD) Integration Models

Pharmacokinetic/pharmacodynamic (PK/PD) integration models are used to investigate the antimicrobial activity characteristics of drugs targeting pathogenic bacteria through comprehensive analysis of the interactions between PK and PD parameters. PK/PD models have been widely applied in the development of new drugs, optimization of the dosage regimen, and prevention and treatment of drug-resistant bacteria. In PK/PD analysis, minimal inhibitory concentration (MIC) is the most commonly applied PD parameter. However, accurately determining MIC is challenging and this can influence the therapeutic effect. Therefore, it is necessary to optimize PD indices to generate more rational results. Researchers have attempted to optimize PD parameters using mutant prevention concentration (MPC)-based PK/PD models, multiple PD parameter-based PK/PD models, kill rate-based PK/PD models, and others. In this review, we discuss progress on PD parameters for PK/PD models to provide a valuable reference for drug development, determining the dosage regimen, and preventing drug-resistant mutations.