Population pharmacokinetics and pharmacodynamics of sitafloxacin in patients with community-acquired respiratory tract infections

Pharmacokinetic/pharmacodynamic (PK/PD) simulation for dosage optimization of colistin and sitafloxacin, alone and in combination, against carbapenem-, multidrug-, and colistin-resistant Acinetobacter baumannii

To the best of our knowledge, to date, no study has investigated the optimal dosage regimens of either colistin or sitafloxacin against drug-resistant Acinetobacter baumannii (A. baumannii) infections by using specific parameters. In the current study, we aimed to explore the optimal dosage regimens of colistin and sitafloxacin, either in monotherapy or in combination therapy, for the treatment of carbapenem-, multidrug-, and colistin-resistant A. baumannii infections. A Monte Carlo simulation was applied to determine the dosage regimen that could achieve the optimal probability of target attainment (PTA) and cumulative fraction of response (CFR) (≥90%) based on the specific parameters of each agent and the minimal inhibitory concentration (MIC) of the clinical isolates. This study explored the dosage regimen of 90, 50, 30, and 10 mL/min for patients with creatinine clearance (CrCL). We also explored the dosage regimen for each patient with CrCL using combination therapy because there is a higher possibility of reaching the desired PTA or CFR. Focusing on the MIC90 of each agent in combination therapy, the dosage regimen for colistin was a loading dose of 300 mg followed by a maintenance dose ranging from 50 mg every 48 h to 225 mg every 12 h and the dosage regimen for sitafloxacin was 325 mg every 48 h to 750 mg every 12 h. We concluded that a lower-than-usual dose of colistin based on specific pharmacokinetic data in combination with a higher-than-usual dose of sitafloxacin could be an option for the treatment of carbapenem-, multidrug-, and colistin-resistant. A. baumannii. The lower dose of colistin might show a low probability of adverse reaction, while the high dose of sitafloxacin should be considered. In the current study, we attempted to find if there is a strong possibility of drug selection against crucial drug-resistant pathogen infections in a situation where there is a lack of new antibiotics. However, further study is needed to confirm the results of this simulation study.

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.

Colistin Monotherapy versus Colistin plus Sitafloxacin for Therapy of Carbapenem-Resistant Acinetobacter baumannii Infections: A Preliminary Study

The in vitro study of sitafloxacin against carbapenem-resistant (CR) Acinetobacter baumannii demonstrated activity against most strains of CR A. baumannii, and the combination of colistin and sitafloxacin showed an in vitro synergistic effect against CR A. baumannii. This study aimed to compare efficacy and safety between colistin plus sitafloxacin with colistin alone for therapy for CR A. baumannii infection. This randomized controlled trial enrolled 56 patients with CR A. baumannii infection (28/group) during 2018-2021, and the treatment duration was 7-14 days. The study outcomes were 28-day mortality, clinical and microbiological responses, and adverse events. There was no significant difference in 28-day mortality between groups (32.1% combination vs. 32.1% monotherapy, p = 1.000). Favorable clinical response at the end of treatment was comparable between groups (81.5% combination vs. 77.8% monotherapy, p = 0.788). Microbiological response at the end of treatment was also comparable between groups (73.1% combination vs. 74.1% monotherapy, p = 0.934). Acute kidney injury was found in 53.8% of the combination group, and in 45.8% of the monotherapy group (p = 0.571). In conclusion, there was no significant difference in 28-day mortality between the colistin monotherapy and the colistin plus sitafloxacin groups. There was also no significant difference in adverse events between groups.

Antimicrobial activities of sitafloxacin and comparators against the clinical isolates of less common nonfermenting Gram-negative bacteria

The in vitro antimicrobial activities of sitafloxacin and comparators against 320 clinical isolates of less common nonfermenting Gram-negative bacteria (NFGNB) were assessed by determining the minimum inhibitory concentrations (MICs) using broth microdilution method. In terms of MIC_50/90 values, sitafloxacin was highly active against Stenotrophomonas maltophilia (0.25/1 mg/L), Burkholderia cepacia complex (0.25/2 mg/L), Achromobacter xylosoxidans (0.25/1 mg/L), and Chryseobacterium gleum (1/2 mg/L), but less active for Elizabethkingia (1/8 mg/L) and Chryseobacterium indologenes (16/32 mg/L). Sitafloxacin was more active than other fluoroquinolones against these NFGNB except Chryseobacterium. The results are helpful for clinicians to be aware of the role of sitafloxacin in managing the infections caused by these NFGNB.

Methodological features of clinical pharmacokinetic-pharmacodynamic studies of antibacterials and antifungals: a systematic review

BACKGROUND

Pharmacokinetic (PK)-pharmacodynamic (PD) indices relate measures of drug exposure to antibacterial effect. Clinical PK-PD studies aim to correlate PK-PD indices with outcomes in patients. Optimization of dosing based on pre-clinical studies means that PK-PD relationships are difficult to establish; therefore studies need to be designed and reported carefully to validate pre-clinical findings.

OBJECTIVES

To describe the methodological features of clinical antibacterial and antifungal PK-PD studies that reported the relationship between PK-PD indices and clinical or microbiological responses.

METHODS

Studies published between 1980 and 2015 were identified through systematic searches. Methodological features of eligible studies were extracted.

RESULTS

We identified 85 publications containing 97 PK-PD analyses. Most studies were small, with fewer than 100 patients. Around a quarter were performed on patients with infections due to a single specific pathogen. In approximately one-third of studies, patients received concurrent antibiotics/antifungals and in some other studies patients received other treatments that may confound the PK-PD-outcome relationship. Most studies measured antimicrobial concentrations in blood/serum and only four measured free concentrations. Most performed some form of regression, time-to-event analysis or used the Hill/Emax equation to examine the association between PK-PD index and outcome. Target values of PK-PD indices that predict outcomes were investigated in 52% of studies. Target identification was most commonly done using recursive partitioning or logistic regression.

CONCLUSIONS

Given the variability in conduct and reporting, we suggest that an agreed set of standards for the conduct and reporting of studies should be developed.

Comparative activities of sitafloxacin against recent clinical isolates in hospitals across China

Sitafloxacin is one of the newer generation fluoroquinolones. Considering the ever-changing antimicrobial resistance, it is necessary to monitor the activities of sitafloxacin against recent pathogenic isolates. Therefore, we determined the minimum inhibitory concentrations (MICs) of sitafloxacin and comparators by broth microdilution or agar dilution method against 1101 clinical isolates collected from 2017 to 2019 in 31 hospitals across China. Sitafloxacin was highly active against gram-positive isolates evidenced by the MICs required to inhibit the growth of 50%/90% isolates (MIC_50/90): ≤ 0.03/0.25, ≤ 0.03/0.125, ≤ 0.03/2, 0.125/0.25, 0.25/2, and 0.125/0.125 mg/L for methicillin-susceptible Staphylococcus aureus (MSSA), methicillin-susceptible coagulase-negative Staphylococcus (MSCNS), methicillin-resistant S. aureus (MRSA), methicillin-resistant CNS, Enterococcus faecalis, and Streptococcus pneumoniae, respectively. Sitafloxacin inhibited 82.8% of the MRSA strains and 97.5% of MRCNS strains. Sitafloxacin was also potent against ciprofloxacin-susceptible Escherichia coli (MIC_50/90: ≤ 0.03/0.06 mg/L) and Klebsiella pneumoniae (MIC_50/90: ≤ 0.03/0.125 mg/L), non-ESBL-producing E. coli (MIC_50/90: ≤ 0.03/1 mg/L) and K. pneumoniae (MIC_50/90: ≤ 0.03/0.5 mg/L), Haemophilus influenzae (MIC_50/90: ≤0.015/0.06 mg/L), Haemophilus parainfluenzae (MIC_50/90: 0.125/0.5 mg/L), Moraxella catarrhalis (MIC_50/90: ≤ 0.015/≤ 0.015 mg/L), Bacteroides fragilis (MIC_50/90: 0.06/2 mg/L), Peptostreptococcus (MIC_50/90: 0.125/4 mg/L), and Mycoplasma pneumoniae (≤ 0.03/≤ 0.03 mg/L). However, sitafloxacin was less active for Enterococcus faecium, ciprofloxacin-resistant and/or ESBL-producing E. coli, and K. pneumoniae strains. Sitafloxacin was superior or comparable to most of the comparators in activities against the abovementioned isolates, so sitafloxacin is still highly active against most of the clinical isolates in hospitals across China, proving its utility in treatment of the abovementioned susceptible strains.

Effects of ABCB1, UGT1A1, and UGT1A9 Genetic Polymorphisms on the Pharmacokinetics of Sitafloxacin Granules in Healthy Subjects

Sitafloxacin, a new fluoroquinolone, has strong antibacterial activity. We evaluated the effects of sitafloxacin granules in single‐dose and multidose cohorts and the effects of ABCB1, UGT1A1, and UGT1A9 genetic polymorphisms on the pharmacokinetics (PK) of sitafloxacin in healthy subjects. The single‐dose study included 3 fasted cohorts receiving 50, 100, and 200 mg of sitafloxacin granules and 1 cohort receiving 50 mg of sitafloxacin granules with a high‐fat meal. The multidose study included 1 cohort receiving 100 mg of sitafloxacin granules once daily for 5 days. PK parameters were calculated using noncompartmental parameters based on concentration‐time data. The genotypes for ABCB1, UGT1A1, and UGT1A9 single‐nucleotide polymorphisms were determined using Sanger sequencing. Subsequently, the association between sitafloxacin PK parameters and target single‐nucleotide polymorphisms was analyzed. Sitafloxacin granules were well tolerated up to 200 and 100 mg in the single‐dose and multidose studies, respectively. Sitafloxacin AUC and C_max increased linearly within the detection range, and a steady state was reached within 3 days after the administration of multiple oral doses. Our findings showed that C_max was lower in the ABCB1 (rs1045642) mutation group, whereas t_1/2 was longer in the UGT1A1 (rs2741049) and UGT1A9 (rs3832043) mutation groups. In conclusion, sitafloxacin granules were safe at single doses and multiple doses up to 200 and 100 mg/day, respectively, with a linear plasma PK profile. However, ABCB1 (rs1045642), UGT1A1 (rs2741049), and UGT1A9 (rs3832043) genetic polymorphisms are likely to influence the C_max or t_1/2 and thereby merit further clinical evaluation.

Quinolone derivatives and their activities against methicillin-resistant Staphylococcus aureus (MRSA)

Methicillin-resistant Staphylococcus aureus (MRSA) is the most common pathogen both in hospital and community settings, and is capable of causing serious and even fatal infections. Several antibiotics have been approved for the treatment of infections caused by MRSA, but MRSA has already developed resistance to them. More than ever, it's imperative to develop novel, high effective and fast acting anti-MRSA agents. Quinolones are one of the most common antibiotics in clinical practice used to treat various bacterial infections, and some of them displayed excellent in vitro and in vivo anti-MRSA activities, so quinolone derivatives are one of the most promising candidates. This review summarizes the recent developments of quinolone derivatives with potential activity against MRSA, and the structure-activity relationship is also discussed.

A simple LC-MS/MS method for determination of sitafloxacin in human urine

Sitafloxacin is a new fluoroquinolone antimicrobial agent with high activity. In this article, we reported a simple, rapid and specific LC-MS/MS method for accurate determination of sitafloxacin concentrations in human urine from healthy volunteers in detail. A two-step dilution method for the analysis of sitafloxacin in human urine using LC coupled to positive MS/MS has been developed and validated according to US FDA guidelines and Chinese State Food and Drug Administration (CFDA) guidelines for the validation of bioanalytical methods. The method uses 50 μL of urine and covers a working range from 0.025 to 20 μg/mL with a LLOQ of 0.025 μg/mL. This new LC-MS/MS assay is sensitive and specific.