Population pharmacokinetics and probability of target attainment of meropenem in critically ill patients

Purpose: Patients admitted to intensive care unit (ICU) with Klebsiella pneumoniae infections are characterized by high mortality. The aims of the present study were to investigate the population pharmacokinetics parameters and to assess the probability of target attainment of meropenem in critically ill patients to provide information for more effective regimens. Methods: Twenty-seven consecutive patients were included in the study. Meropenem was administered as 3-h intravenous (i.v.) infusions at doses of 1\u20132 g every 8 or 12 h. Meropenem plasma concentrations were measured by a high-performance liquid chromatography (HPLC) method, and a population pharmacokinetics analysis was performed using NONMEM software. Meropenem plasma disposition was simulated for extended (3 h; 5 h) or continuous i.v. infusions, and the following parameters were calculated: time during which free drug concentrations were above minimum inhibitory concentration (MIC) (fT > MIC), free minimum plasma concentrations above 4 7 MIC (fCmin > 4 7 MIC), probability of target attainment (PTA), and cumulative fraction of response (CFR). Results: Gender and severity of sepsis affected meropenem clearance, whose typical population values ranged from 6.22 up to 12.04 L/h (mean \ub1 standard deviation (SD) value, 9.38 \ub1 4.47 L/h). Mean Cmin value was 7.90 \ub1 7.91 mg/L, suggesting a high interindividual variability. The simulation confirmed that 88 and 97.5 % of patients achieved effective Cmin > 4 7 MIC values after 3- and 5-h i.v. infusions of meropenem 2 g  7 3/day, respectively. On the contrary, the same total daily doses reached the target Cmin > 4 7 MIC values in 100 % of patients when administered as continuous i.v. infusions. Conclusions: Several factors may influence meropenem pharmacokinetics in ICU patients. Continuous i.v. infusions of meropenem seem to be more effective than standard regimens to achieve optimal therapeutic targets

Studi di farmacologia clinica di nuovi antimicrobici per il trattamento di gravi infezioni batteriche.

Il progetto di ricerca presentato in questa tesi si è prefisso come obiettivo principale quello di valutare criticamente, tramite un approccio PK/PD, le caratteristiche farmacocinetiche e la simulazione delle concentrazioni plasmatiche e tissutali di farmaci antibatterici mediante l’applicazione di protocolli di monitoraggio terapeutico eseguiti presso la Divisione di Farmacologia dell’Azienda Ospedaliero Universitaria Pisana. In seconda valutazione, l’adozione e l’applicazione di questi protocolli e della farmacocinetica di popolazione per identificare tutte quelle variabili che possono influenzare la cinetica di farmaci antibatterici mediante l’elaborazione di modelli matematici di farmacocinetica di popolazione. Nella prima parte della tesi (Capitolo 1, “ Introduzione”), sono descritti gli aspetti più importanti della farmacocinetica clinica. L’importanza di questa disciplina è determinante per la valutazione globale dei farmaci in studio, la comprensione dei meccanismi molecolari e la complessità dei fattori che entrano in gioco nel corso di una terapia farmacologica. Un’altra parte introduttiva ha invece il compito di spiegare l’impiego di nuove molecole antibiotiche soprattutto in popolazioni speciali di pazienti e in trattamento per gravi malattie infettive. D’altro canto, per ottimizzare il trattamento, sono descritti i parametri pk/pd predittivi di efficacia per queste molecole, sono identificati i fattori di variabilità che influenzano la cinetica del farmaco determinando diverse risposte al trattamento e infine sono raccolti i dati di efficacia terapeutica e i possibili rischi di resistenza e tossicità. Nel secondo capitolo sono descritte le caratteristiche farmacologiche di daptomicina e l’elaborazione e la validazione di una metodica di cromatografia liquida ad elevate prestazioni da utilizzare nella pratica clinica in protocolli di monitoraggio terapeutico delle concentrazioni sia plasmatiche che tissutali e in altri fluidi biologici di daptomicina e linezolid. Nel terzo capitolo sono sommariamente ripercorsi i principali risultati di uno studio sulle cararatteristiche farmacocinetiche di linezolid in pazienti affetti da infezioni sostenute da batteri MRSA. L’obiettivo dello studio è stato quello di valutare la capacità di linezolid di distribuirsi nel liquor a livello dei ventricoli del Sistema Nervoso Centrale e di monitorare le concentrazioni sia plasmatiche che liquorali per l’ottimizzazione del trattamento e per comprendere i meccanismi che possono consentire di ridurre la notevola variabilità interindividuale riportata in letteratura. Sono poi riportati nel capitolo 4 i risultati di alcuni studi condotti presso la U.O. di Farmacologia sulle capacità diffusive di daptomicina. In particolare, sono analizzati i risultati di due lavori, il primo del 2011 che ha valutato il caso di un paziente trattato con successo per una colecistite batterica prodotta da MRSA ed Enterococcus faecium Vancomicino-resisteste e il secondo del 2013 che ha valutato le concentrazioni di daptomicina nella valvola mitralica e nella vegetazione su un paziente affetto da endocardite batterica. La strategia intrapresa e descritta nei primi capitoli della tesi, è necessaria nell’ultima parte (Capitolo 5) che rappresenta il punto di partenza per lo sviluppo di modelli di farmacocinetica di popolazione. In questo ultimo capitolo mediante una analisi di farmacocinetica con modelli non lineari utilizzando il software NONMEM, sono stati simulati i profili farmacocinetici di daptomicin

Pharmacogenetics of BCR/ABL Inhibitors in Chronic Myeloid Leukemia

Chronic myeloid leukemia was the first haematological neoplasia that benefited from a targeted therapy with imatinib nearly 15 years ago. Since then, several studies have investigated the role of genes, their variants (i.e., polymorphisms) and their encoded proteins in the pharmacokinetics and pharmacodynamics of BCR-ABL1 tyrosine kinase activity inhibitors (TKIs). Transmembrane transporters seem to influence in a significant manner the disposition of TKIs, especially that of imatinib at both cellular and systemic levels. In particular, members of the ATP-binding cassette (ABC) family (namely ABCB1 and ABCG2) together with solute carrier (SLC) transporters (i.e., SLC22A1) are responsible for the differences in drug pharmacokinetics. In the case of the newer TKIs, such as nilotinib and dasatinib, the substrate affinity of these drugs for transporters is variable but lower than that measured for imatinib. In this scenario, the investigation of genetic variants as possible predictive markers has led to some discordant results. With the partial exception of imatinib, these discrepancies seem to limit the application of discovered biomarkers in the clinical settings. In order to overcome these issues, larger prospective confirmative trials are needed

Methods: For studying pharmacogenetic profiles of combination chemotherapeutic drugs

Molecular and genetic analysis of tumors and individuals has led to patient-centered therapies, through the discovery and identification of genetic markers predictive of drug efficacy and tolerability. Present therapies often include a combination of synergic drugs, each of them directed against different targets. Therefore, the pharmacogenetic profiling of tumor masses and patients is becoming a challenge, and several questions may arise when planning a translational study. AREAS COVERED: The review presents the different techniques used to stratify oncology patients and to tailor antineoplastic treatments according to individual pharmacogenetic profiling. The advantages of these methodologies are discussed as well as current limits. EXPERT OPINION: Facing the rapid technological evolution for genetic analyses, the most pressing issues are the choice of appropriate strategies (i.e., from gene candidate up to next-generation sequencing) and the possibility to replicate study results for their final validation. It is likely that the latter will be the major obstacle in the future. However, the present landscape is opening up new possibilities, overcoming those hurdles that have limited result translation into clinical settings for years

Case Report of a Successful Treatment of Methicillin-Resistant Staphylococcus aureus (MRSA) Bacteremia and MRSA/Vancomycin-Resistant Enterococcus faecium Cholecystitis by Daptomycin▿

A 72-year-old man, receiving 8 mg daptomycin/kg body weight/day for methicillin-resistant Staphylococcus aureus (MRSA) bacteremia, was diagnosed with MRSA/vancomycin-resistant Enterococcus faecium (VRE) cholecystitis (daptomycin MIC values, 1 and 2 mg/liter, respectively). After the fifth drug dose, the bile concentration of daptomycin was 66 mg/liter 5 min after drug administration, with the biliary concentration/MIC values higher than 30 for both bacterial strains. Therefore, daptomycin achieved therapeutic levels in bile, hence suggesting a role for the drug in the treatment of MRSA/VRE cholecystitis

Polycomb genes are associated with response to imatinib in chronic myeloid leukemia.

Aim: Imatinib is a tyrosine kinase inhibitor that has revolutionized the treatment of chronic myeloid leukemia (CML). Despite its efficacy, about a third of patients discontinue the treatment due to therapy failure or intolerance. The rational identification of patients less likely to respond to imatinib would be of paramount clinical relevance. We have shown that transmembrane transporter hOCT1 genotyping predicts imatinib activity. In parallel, Polycomb group genes (PcGs) are epigenetic repressors implicated in CML progression and in therapy resistance. Patients & methods: We measured the expression of eight PcGs in paired pre- and post-imatinib bone marrow samples from 30 CML patients. Results: BMI1, PHC3, CBX6 and CBX7 expression was significantly increased during imatinib treatment. Post-treatment levels of CBX6 and CBX7 predicted 3-month response rate. Measurement of post-treatment BMI1 levels improved the predictive power of hOCT1 genotyping. Conclusion: These results suggest that the expression levels of PcGs might be useful for a more accurate risk stratification of CML patients

Reduced circulating B-lymphocytes and altered B-cell compartments in patients suffering from chronic myeloid leukaemia undergoing therapy with Imatinib

imatinib modify the B circulating immunophenotype patter

Transmembrane Transporters hOCT1 and SLCO1B3 Polymorphisms Could Have a Role in Patients Affected By Chronic Myeloid Leukemia Treated with Nilotinib

Background. Nilotinib represents an effective drug for the treatment of chronic myeloid leukemia after imatinib failure or, as more recently advocated, as first-line therapy. Its efficacy and tolerability allow the chronic administration of the drug, and some studies suggested that the greater benefit could be experienced when minimum plasma concentrations are above the limit of 1 mg/L. However, nilotinib is characterized by a non-negligible interpatient variability in its pharmacokinetics. The variable activity of transmembrane transporters should be not ruled out despite nilotinib has a lower substrate affinity for these proteins. In fact, recent in vitro studies demonstrated that SLCO1B3 and OCT3 are associated with nilotinib IC50 (Zimmermann, Clin Cancer Res 2013; Minematsu, Mol Cancer Ther 2011). Purpose. Therefore, the aim of this study was to investigate any possible influence of genetic polymorphisms in transmembrane transporters ABCB1, ABCG2, hOCT1 and SLCO1B3 on nilotinib pharmacokinetics, according to the procedures of the TIKlet protocol (ClinicalTrials.gov identifier: NCT 01860456). Methods. To accomplish with this objective, a population pharmacokinetic analysis was applied to investigate drug disposition in 21 men and 15 women (median age=62 years, range 38-84; Sokal high risk 15%, Hasford high risk 2%, EUTOS high risk 12%) who received nilotinib as second line therapy. Nilotinib plasma concentrations were measured by a validated UV-HPLC method, while patients’ genotype was obtained by real-time PCR on an ABI Prism 7900 HT instrumentation. The results were analysed through population pharmacokinetic modeling using NONMEM vers. 7.3. Results. With a median follow-up from nilotinib start of 42 months (range 3-86 months), 63% of patients were event-free, 25% of patients discontinuated treatment (2 deaths for MOF, other one for toxicity). After 3 months, all cases achieved the CHR, 82% presented a BCR-ABL1/ABL1 ratio MR4. When nilotinib plasma levels were measured, 80% of our patients had values higher than 1 mg/L. Results showed that elimination constant k10 was influenced by patient’s body mass index and the c.2677G>T/A polymorphism in exon 21 of the mdr1 gene. More interestingly, the polymorphism c.334T>G of the SLCO1B3 transporter was significantly associated with nilotinib bioavailability (F%). In particular, the wild-type genotype (TT) was associated with a 11% increase of F%, whereas the presence of at least one polymorphic allele (genotypes GT and GG) caused a reduction of F% of approximately 6%. Even if nilotinib plasma levels did not significantly influence its efficacy or toxicity, patients carrying the hOCT1 c.480C>G SNP (with lower influx pump activity) showed a shorter 3-year EFS (87% versus 54%, p=0.001) and cases with SLCO1B3 c.521 C allele showed a longer time to the CCyR (4.5 months vs 2.8, p=0.03) and to MR3 (14 months versus 9 months, p=n.s.). Conclusions. In conclusion, although the number of enrolled patients is limited, the present study suggests a role of transmembrane transporters hOCT1 and SLCO1B3 in the disposition of nilotinib

Combined FAMD and ANOVA investigation leads to significant association between the hOCT1/ABCB1 diplotype and both efficacy and tolerability in patients affected by chronic myeloid leukemia

Background. In spite of the dramatically positive changes in the outcome of Chronic Myeloid Leukemia (CML) patients due to the introduction of imatinib, several aspects of both the pharmacokinetics and pharmacodynamics of this TKI remain unclear. In particular, the possible relations between patients' specific characteristics and the efficacy and toxicity of treatment are still matter of debate. Aim of the study. The purpose of this study was twofold: 1) set up an innovative and unsupervised mathematical model that helps in explaining the variability of imatinib plasma levels through the analysis of the main pharmacokinetic parameters in terms of patient-specific features as BMI, renal and hepatic function, alpha1-acid glycoprotein, age, sex and polymorphisms of transporters; 2) set up a specifically tailored analysis of variance technique which allows to detect in limited databases also possible correlations between efficacy, toxicity and genetic covariates either as single SNP or in the form of more complex combinations of different polymorphisms. Patients and Methods. The study has been carried out on 53 CML adult patients (30 males and 23 females) receiving imatinib as first-line therapy at the Section of Hematology of the Department of Clinical and Experimental Medicine of the University of Pisa and from the Department of Internal Medicine of Orbassano, Turin. Patients gave their informed consent to the participation to the study before enrollment. The pharmacokinetic model has been constructed following the indication of the Factor Analysis of Mixed Data (FAMD), a procedure that permitted us to select the possible important covariates and eventually which of them aggregate in a single factor using an unsupervised approach. For what concerns imatinib pharmacodynamics, we studied first the possible relation between treatment efficacy and genetic covariates (either as single SNPs or diplotypes) and then whether the pharmacogenetic variables obtained are also relevant for the tolerability of the drug. The genetic variables considered were represented by the following polymorphisms: rs72552763 [MI420I], rs12208357 [c.181C>T] and rs683369 [c.480C>G] (hOCT1), rs1128503 [c.1236C>T], rs2032582 [c.2677G>T/A] and rs1045642 [c.3435C>T] (ABCB1), rs4149117 [c.334G>T] (SLCO1B3). Results. The FAMD procedure allowed us to identify three main factors (single or aggregated covariates) which properly included in the pharmacokinetic model reduced significantly the uncertainties on all pharmacokinetic parameters. The selected factors are: hOCT1 polymorphism c.480C>G, a combination of BMI and gender and the glomerular filtration rate. Such a procedure led to ka = 0.786 ± 5.9 %, c1 = 0.0282 ± 24.5 %, where ka and c1 are the absorption and elimination rate, respectively. Through our investigation of the pharmacodynamics, we found that both the complete cytogenetic response (CCyR) and the maximum toxicity are related to a particular combination of hOCT1 rs683369 [c.480C>G] and ABCB1 rs1045642 [c.3435C>T] polymorphisms. Furthermore, since the toxic effects of the drug have a strong incidence on the discontinuation of the therapy, we have studied whether the manifestation and the onset time of the most frequent specific toxic effects of Imatinib can be associated to the genetic characteristics of the patients and/or to a combination of them. Edema toxicity has resulted to be correlated with combinations between c.3435C>T and gender or ABCB1 rs1128503 [c.1236C>T]. Cramp toxicity has resulted to be correlated to gender alone or in combination with SCLO1B3 rs4149117 [c.334G>T]. Discussion. Results of this study obtained provide relevant insights on the role of covariates in imatinib treatment and suggest that FAMD analyses in combination with ANOVA tests may allow the unsupervised identification of covariates that significantly affect drug disposition and pharmacodynamics