Development and validation of a high performance liquid chromatography assay for the determination of temocillin in serum of haemodialysis patients

Evaluation of temocillin efficacy against KPC-2-producing Klebsiella pneumoniae isolates in a hollow-fibre infection model

BACKGROUND

Temocillin is an old antimicrobial that is resistant to hydrolysis by ESBLs but has variable activity against carbapenemase-producing Enterobacteriaceae. The current EUCAST susceptibility breakpoints for Enterobacterales are set at ≤16 mg/L (susceptible with increased exposure) based on a dose of 2 g q8h, but there is limited information on the efficacy of this dose against temocillin-susceptible carbapenemase-producing Klebsiella pneumoniae isolates.

OBJECTIVES

To evaluate the efficacy of this dose using a hollow-fibre infection model (HFIM) against six KPC-2-producing clinical isolates of K. pneumoniae.

METHODS

The isolates were characterized by WGS and temocillin susceptibility was determined using standard and high inoculum temocillin. Mutant frequencies were estimated and temocillin activity was tested in time-kill assays and in the HFIM. At standard conditions, three of the isolates were classified as susceptible (MIC ≤ 16 mg/L) and three as resistant (MIC > 16 mg/L). The HFIM was performed over 3 days to mimic human-like pharmacokinetics of 2 g q8h. Bacterial counts were performed by plating on Mueller-Hinton agar (MHA) and MHA containing 64 mg/L temocillin to detect resistant subpopulations.

RESULTS

All isolates showed a reduction in bacterial population of at least 3 log cfu/mL within the first 8 h of simulated treatment in the hollow-fibre assay. Regrowth was observed for the three resistant isolates and one of the susceptible ones. The MIC value for these isolates was higher by at least two dilutions compared with their initial values.

CONCLUSIONS

These data suggest that an optimized pharmacokinetic regimen may be of clinical interest for the treatment of KPC-2-producing K. pneumoniae susceptible to temocillin. These data showed activity of temocillin against KPC-2-producing K. pneumoniae susceptible to temocillin; however, a dose of 2g q8h administered over 30 min may be inadequate to prevent the emergence of resistant variants.

Stability of temocillin in outpatient parenteral antimicrobial therapy: is it a real option?

BACKGROUND

Temocillin is an interesting alternative to carbapenems for susceptible Enterobacteriaceae. Although its use in outpatient parenteral antimicrobial therapy (OPAT) programmes has generated interest, this has been hampered by the lack of stability data.

OBJECTIVES

The purpose of the present study was to evaluate the physical and chemical stability of temocillin at the recommended dose for its use in OPAT programmes, contained in polypropylene infusion bags or polyisoprene elastomeric devices at different temperatures, and to describe a novel LC-MS/MS developed for the quantification of temocillin.

METHODS

Temocillin daily dose (6 g) was diluted in 500 mL of 0.9% sodium chloride to obtain a final concentration of 12 g/L. This solution was stored at 4°C, 25°C, 32°C and 37°C for 72 h, both in polypropylene infusion bags and in polyisoprene elastomeric pumps. Physical and chemical stability were evaluated during 72 h after manufacturing. Solutions were considered stable if colour, clearness and pH remained unchanged and if the percentage of intact drug was ≥90%.

RESULTS

Temocillin attained the chemical stability criterion of ≥90% of the original concentration for the whole experiment in both devices at 4°C, 25°C and 32°C. At 37°C, temocillin was stable for 24 h but its concentration dropped below 90% from that timepoint. No precipitation occurred and minor colour changes were observed.

CONCLUSIONS

Temocillin is stable under OPAT conditions and it would be an appropriate candidate for the treatment of patients who can be discharged to complete therapy in an OPAT programme. For this study, an LC-MS/MS method was developed.

Temocillin versus meropenem for the targeted treatment of bacteraemia due to third-generation cephalosporin-resistant Enterobacterales (ASTARTÉ): protocol for a randomised, pragmatic trial

INTRODUCTION

Alternatives to carbapenems are needed in the treatment of third-generation cephalosporin-resistant Enterobacterales (3GCR-E). Temocillin is a suitable candidate, but comparative randomised studies are lacking. The objective is to investigate if temocillin is non-inferior to carbapenems in the targeted treatment of bacteraemia due to 3GCR-E.

METHODS AND ANALYSIS

Multicentre, open-label, randomised, controlled, pragmatic phase 3 trial. Patients with bacteraemia due to 3GCR-E will be randomised to receive intravenously temocillin (2 g three times a day) or carbapenem (meropenem 1 g three times a day or ertapenem 1 g once daily). The primary endpoint will be clinical success 7-10 days after end of treatment with no recurrence or death at day 28. Adverse events will be collected; serum levels of temocillin will be investigated in a subset of patients. For a 10% non-inferiority margin, 334 patients will be included (167 in each study arm). For the primary analysis, the absolute difference with one-sided 95% CI in the proportion of patients reaching the primary endpoint will be compared in the modified intention-to-treat population.

ETHICS AND DISSEMINATION

The study started after approval of the Spanish Regulatory Agency and the reference institutional review board. Data will be published in peer-reviewed journals.

TRIAL REGISTRATION NUMBER

NCT04478721.

A rapid, automatic and accurate assay for quantifying temocillin in human serum and CSF using turbulent flow liquid chromatography coupled to high-resolution mass spectrometry. Clinical application

Temocillin is a β-lactamase-resistant penicillin used for the treatment of multiple drug-resistant Gram-negative bacteria. To maximize efficacy and avoid adverse effects, the dose regimen has to be quickly adjusted to the clinical situations. This necessitates the development of a rapid, reliable and accurate analytical method. Temocillin and the stable isotopically labeled internal standard ([¹³ C₆ ]-amoxicillin) were extracted from either serum or cerebrospinal fluid by a turbulent flow liquid chromatographic method and eluted onto an octadecyl-silica phase with polar endcapping. Mass spectrometry was conducted using an exact mass determination method by electrospray positive ionization high-resolution mass spectrometry. The LLOQ and ULOQ of the present method were determined to be 0.4 and 200 μg/ml for serum and cerebrospinal fluid samples, respectively. The total analysis time was <7 min. The recovery ranged from 87.7 to 120.8%. Intra- and inter-day precision and trueness were tested at four concentration levels: 0.4, 8, 40 and 160 μg/ml. Values were 6.33 ± 1.53, 8.8 ± 1.3, 8.8 ± 0.36 and 2.1 ± 0.76%, and 5.0 ± 0.54, 9.9 ± 1.0, 5.8 ± 1.6 and 0.1 ± 1.1%, for inter- and intra-day analysis, respectively. Temocillin was found to be stable under all relevant laboratory conditions. The method was cross-validated with a microbiological assay. This method is suitable for accurate measurement of temocillin concentration in small volumes of serum or cerebrospinal fluid. Thanks to the online extraction procedure, the overall analytical time is compatible with high-throughput analysis for clinical application.

Temocillin dosing in haemodialysis patients based on population pharmacokinetics of total and unbound concentrations and Monte Carlo simulations

Objectives

To develop a population model describing temocillin pharmacokinetics (PK) in patients undergoing haemodialysis and investigate how pharmacokinetic/pharmacodynamic (PD) targets can be met with different dosage regimens.

Patients and methods

Sixteen patients received the currently licenced dosing of 1, 2 or 3 g of temocillin (total of 61 doses) corresponding to an inter-dialytic period of 20, 44 or 68 h, respectively, and a dialysis period of 4 h. A non-linear mixed-effects model was developed jointly for total and unbound temocillin serum concentrations. The performance of clinically feasible dosing regimens was evaluated using a 5000-subject Monte Carlo (MC) simulation for determining the highest MIC for which the PK/PD target of 40%ƒT>MIC would be reached in 90% of patients [probability of target attainment (PTA)]. This PK study was registered at ClinicalTrials.gov (NCT02285075).

Results

Temocillin unbound and total serum concentrations (429 samples) were used to fit an open two-compartment model with non-linear albumin binding and first-order elimination. In addition to total body clearance, dialysis clearance was modelled using the Michaels function. The currently licenced dosing achieved a 90% PTA for an MIC up to 8 mg/L. A new temocillin dosage regimen was designed that would achieve a 90% PTA for an MIC of 16 mg/L (MIC90 of target organisms) adjusted to patient weight and inter-dialytic period.

Conclusions

Currently licensed dosage regimen is suboptimal for MICs >8 mg/L (frequently found in clinical isolates). Model-based simulations allowed suggestion of a new dosage regimen with improved probability of microbiological success, applicability in routine clinical practice and more appropriate for empirical therapy.

Pharmacokinetics and Pharmacodynamics of Temocillin

Temocillin, a 6-α-methoxy derivative of ticarcillin, is a forgotten antibiotic that has recently been rediscovered, and issues about clinical breakpoints and optimal therapeutic regimens are still ongoing. Temocillin spectrum is almost restricted to Enterobacteriaceae. The addition of the α-methoxy moiety on ticarcillin confers resistance to hydrolysis by Ambler classes A and C β-lactamases (extended spectrum β-lactamases, Klebsiella pneumoniae carbapenemase and AmpC hyperproduced enzymes). Temocillin is bactericidal, and the effect of inoculum size on its activity is relatively mild. The proportion of spontaneous resistant mutants in vitro to temocillin is low, as found in vivo. After intravenous infusion, temocillin showed a prolonged elimination half-life of approximately 5 h. The percentage of protein binding of temocillin is high (approximately 80%), and is concentration-dependent. Temocillin clearance is mainly renal, and urinary recovery is high, ranging from 72 to 82% after 24 h. Furthermore, the penetration of temocillin into bile and peritoneal fluid is high, but poor into cerebrospinal fluid. The cumulative percentage of a 24-h period during which the free drug concentration exceeds the minimum inhibitory concentration (fT > MIC) at steady-state pharmacokinetic conditions seems to be the best pharmacokinetic/pharmacodynamic (PK/PD) index correlating with temocillin efficacy. An fT > MIC of 40-50% is associated with antibacterial effect and survival in vivo. Monte Carlo simulations performed in critically ill patients showed that the 2 g every 12 h and 2 g every 8 h regimens provide a 95% probability of target attainment of 40% fT > MIC up to an MIC of 8 mg/L. In less severely ill patients or in specific foci of infection, such as urinary tract infection, a 4 g daily regimen should be adequate for strains with temocillin MIC up to 16 mg/L. Data regarding actual wild-type MIC distribution, clinical efficacy, PK profiling in volunteers or patients, and PD targets are scarce, and further studies are required to support appropriate dosing recommendations and determination of clinical breakpoints.

Delivering precision antimicrobial therapy through closed-loop control systems

Sub-optimal exposure to antimicrobial therapy is associated with poor patient outcomes and the development of antimicrobial resistance. Mechanisms for optimizing the concentration of a drug within the individual patient are under development. However, several barriers remain in realizing true individualization of therapy. These include problems with plasma drug sampling, availability of appropriate assays, and current mechanisms for dose adjustment. Biosensor technology offers a means of providing real-time monitoring of antimicrobials in a minimally invasive fashion. We report the potential for using microneedle biosensor technology as part of closed-loop control systems for the optimization of antimicrobial therapy in individual patients.

Thrice-weekly temocillin administered after each dialysis session is appropriate for the treatment of serious Gram-negative infections in haemodialysis patients

In patients with end-stage renal disease (ESRD) treated with intermittent haemodialysis, a limited number of antibiotics have been studied for their suitability for parenteral administration after dialysis sessions only in a thrice-weekly regimen. Temocillin is a β-lactam antibiotic with a long half-live and enhanced activity against most Gram-negative bacteria, including extended-spectrum β-lactamase-producers, thus making it an ideal candidate for use in this setting. This study aimed to evaluate the reliability of thrice-weekly parenteral temocillin in haemodialysis patients by characterising the pharmacokinetics of total and free temocillin. Free and total temocillin concentrations were determined with a validated HPLC method in 448 samples derived from 48 administration cycles in 16 patients with ESRD treated with intermittent haemodialysis and temocillin. Pharmacokinetics were non-linear partly due to saturation in protein binding. Median clearance and half-life for the free drug during intradialysis and interdialysis periods were 113 mL/min vs. 26 mL/min and 3.6 h vs. 24 h, respectively, with dialysis extracting approximately one-half of the residual concentration. The free temocillin concentration remained >16 mg/L (MIC90 threshold for most Enterobacteriaceae) during 48%, 67% and 71% of the dosing interval for patients receiving 1 g q24h, 2 g q48h and 3 g q72h, respectively, suggesting appropriate exposure for the two latter therapeutic schemes. Temocillin administered on dialysis days only in a dosing schedule of 2 g q48h and 3 g q72h is appropriate for the treatment of serious and/or resistant Gram-negative infections in patients with ESRD undergoing intermittent haemodialysis. These doses are higher than those previously recommended.