Therapeutic Drug Monitoring Of Everolimus Research Articles

Volumetric Absorptive Microsampling for the Therapeutic Drug Monitoring of Everolimus in Patients Who Have Undergone Liver Transplant.

Therapeutic drug monitoring (TDM) of everolimus is required to prevent organ rejection in patients who have undergone transplant. Volumetric absorptive microsampling (VAMS) is a minimally invasive method for accurately collecting a small amount of blood from a patient's fingers. This study aimed to assess the applicability of VAMS for TDM of everolimus. VAMS and venous blood samples were collected from 45 liver transplant recipients who had been receiving stable everolimus doses for at least 7 days. Whole blood everolimus concentrations were measured using ultrahigh performance liquid chromatography with tandem mass spectrometry. Deming regression and Bland-Altman analysis were performed to compare everolimus concentrations measured using VAMS (C VAMS ) and venous blood samples (C IV ). The regression coefficient (r 2 ) between C VAMS and C IV was calculated using a linear regression. The effects of the hematocrit and blood sampling time on the difference between C VAMS and C IV were investigated. Thirty-two participants were included in the final analysis. The Deming regression line was C IV = 1.04 × C VAMS + 0.55 [95% confidence interval (CI) of slope, 0.91-1.18; 95% CI of intercept, -0.05 to 1.16]. C VAMS and C IV were strongly correlated (r 2 = 0.92), with no proportional or constant bias. The mean difference between C VAMS and C IV was -0.79 ng/mL, with the 95% limit of agreement ranging from -2.55 to 0.97 ng/mL in a Bland-Altman plot. No effect of the hematocrit or blood sampling time was observed. VAMS and venous blood sampling showed good agreement for the measurement of whole blood everolimus concentrations. Less invasive VAMS can substitute for more invasive venous blood sampling in the TDM of everolimus in liver transplant patients.

Analytical Performance of the New Siemens Affinity Chrome-Mediated Immunoassay Everolimus Assay and Its Interchangeability With the Thermo Quantitative Microsphere System for Routine Therapeutic Drug Monitoring of Patients After Solid Organ Transplantation.

A new homogeneous affinity chrome-mediated immunoassay (ACMIA) "EVRO" from Siemens Healthcare was evaluated for therapeutic drug monitoring of everolimus (EVL) with automated sample pretreatment and compared with quantitative microsphere system (QMS) "EVER" from Thermo Fisher Scientific. Imprecision, inaccuracy, and limit of quantitation (LoQ) of ACMIA/EVRO were verified using both hemolysate quality control (QC) samples and pooled whole blood specimens. The interchangeability of methods and the agreement of results were analyzed using 72 specimens (from 38, 30, and 4 kidney, liver, and lung transplant recipients, respectively). Within-run imprecision ranged within %CV = 2.81-2.53 with pooled whole blood specimens and within %CV = 2.88-2.53 with QCs; total imprecision with QCs was within %CV = 2.14-1.51. Inaccuracy with value assigned QC was %△ = 5.36 at the 5.6 ng/mL level and %△ = 5.56 at the 11.7 ng/mL level. LoQ was 0.93 ng/mL (%CV = 10). Passing-Bablok regression showed a constant bias of 0.679 ng/mL (95% CI: 0.216-1.026) and a proportional bias of 1.326 (95% CI: 1.240-1.425). Bland-Altman analysis showed 5/72 (6.9%) paired differences exceeding the limits of agreement and 1/72 (1.4%) paired differences exceeding 1.96 SD to a combined bias of 39.9% after detrending. ACMIA/EVRO shows satisfactory analytical performances that comply with recommendations, but it does not fulfill requirements for interchangeability with QMS/EVER. Particularly, this new assay using sirolimus-specific antibody shows a sizable proportional bias versus the more specific comparator, which may be because of EVL metabolites. This is supported by the lack of agreement for individual differences in most samples collected at the peak concentration (C2). Therefore, further evidence is needed to support the transition of EVL level monitoring from QMS/EVER to ACMIA/EVRO without making extensive changes to both reference interval and patient's baseline.

Evaluation of the interchangeability between the new fully-automated affinity chrome-mediated immunoassay (ACMIA) and the Quantitative Microsphere System (QMS) with a CE-IVD-certified LC-MS/MS assay for therapeutic drug monitoring of everolimus after solid organ transplantation.

This study aims to evaluate the interchangeability between the Siemens Healthineers' "EVRO" new affinity chrome-mediated immunoassay (ACMIA/EVRO) and Thermo Fisher Scientific's "EVER" Quantitative Microsphere System (QMS/EVER) with Chromsystems' CE-IVD-certified "MassTox" liquid-chromatography/tandem-mass spectrometry (LC-MS/MS) assay for the therapeutic drug monitoring of everolimus. A single lot of reagent, calibrators and controls were used for each assay. A total of 67 whole blood samples (n=67) from patients receiving solid organ transplant were analyzed (n=31 with kidney transplant and n=36 with liver transplant); Passing-Bablok regression and Bland-Altman difference plot were used to evaluate bias and individual agreement; LC-MS/MS analysis was used to measure the actual concentrations of calibrators and controls compared to the assigned value. ACMIA/EVRO did not show any systematic bias compared to LC-MS/MS (intercept=0.244ng/mL, 95% CI:-0.254 to 0.651ng/mL). Nevertheless, significant proportional bias (slope=1.511, 95% CI: 1.420 to 1.619) associated to a combined bias of 44.8% (95% CI: 41.2-48.3%) was observed. Conversely, QMS/EVER did not show any bias at both systematic (intercept=-0.151ng/mL, 95% CI:-0.671 to 0.256ng/mL) and proportional level (slope=0.971, 95% CI: 0.895 to 1.074) with a non-statistically significant combined bias of-3.6% (95% CI:-8.4-1.1%). Based on a concentration of calibrators and controls above the assigned value for both the analytical methods, in the ACMIA/EVRO a correction which was approximately one-third of the correction for the QMS/EVER was observed. ACMIA/EVRO but not QMS/EVER shows a lack of interchangeability with the CE-IVD-certified LC-MS/MS assay. We hypothesize that, as the ACMIA/EVRO uses an anti-sirolimus antibody, the under-corrected assigned value in the assay calibrators was not sufficient to reproduce the everolimus metabolites cross-reactivity occurring in real samples.

Model-Informed Precision Dosing of Everolimus: External Validation in Adult Renal Transplant Recipients

Background and ObjectiveThe immunosuppressant everolimus is increasingly applied in renal transplantation. Its extensive pharmacokinetic variability necessitates therapeutic drug monitoring, typically based on whole-blood trough concentrations (C0). Unfortunately, therapeutic drug monitoring target attainment rates are often unsatisfactory and patients with on-target exposure may still develop organ rejection. As everolimus displays erythrocyte partitioning, haematocrit-normalised whole-blood exposure has been suggested as a more informative therapeutic drug monitoring marker. Furthermore, model-informed precision dosing has introduced options for more sophisticated dose adaptation. We have previously developed a mechanistic population pharmacokinetic model, which described everolimus plasma pharmacokinetics and enabled estimation of haematocrit-normalised whole-blood exposure. Here, we externally evaluated this model for its utility for model-informed precision dosing.MethodsThe retrospective dataset included 4123 pharmacokinetic observations from routine clinical therapeutic drug monitoring in 173 renal transplant recipients. Model appropriateness was confirmed with a visual predictive check. A fit-for-purpose analysis was conducted to evaluate whether the model accurately and precisely predicted a future C0 or area under the concentration–time curve (AUC) from prior pharmacokinetic observations. Bias and imprecision were expressed as the mean percentage prediction error (MPPE) and mean absolute percentage prediction error (MAPE), stratified on 6 months post-transplant. Additionally, we compared dose adaptation recommendations of conventional C0-based therapeutic drug monitoring and C0- or AUC-based model-informed precision dosing, and assessed the percentage of differences between observed and haematocrit-normalised C0 (∆C0) and AUC (∆AUC) exceeding ± 20%.ResultsThe model showed adequate accuracy and precision for C0 and AUC prediction at ≤ 6 months (MPPEC0: 8.1 ± 2.5%, MAPEC0: 26.8 ± 2.1%; MPPEAUC: − 9.7 ± 5.1%, MAPEAUC: 13.3 ± 3.9%) and > 6 months post-transplant (MPPEC0: 4.7 ± 2.0%, MAPEC0: 25.4 ± 1.4%; MPPEAUC: − 0.13 ± 4.8%, MAPEAUC: 13.3 ± 2.8%). On average, dose adaptation recommendations derived from C0-based and AUC-based model-informed precision dosing were 2.91 ± 0.01% and 13.7 ± 0.18% lower than for conventional C0-based therapeutic drug monitoring at ≤ 6 months, and 0.93 ± 0.01% and 3.14 ± 0.04% lower at > 6 months post-transplant. The ∆C0 and ∆AUC exceeded ± 20% on 13.6% and 14.3% of occasions, respectively.ConclusionsWe demonstrated that our population pharmacokinetic model was able to accurately and precisely predict future everolimus exposure from prior pharmacokinetic measurements. In addition, we illustrated the potential added value of performing everolimus therapeutic drug monitoring with haematocrit-normalised whole-blood concentrations. Our results provide reassurance to implement this methodology in clinical practice for further evaluation.Electronic supplementary materialThe online version of this article (10.1007/s40262-020-00925-8) contains supplementary material, which is available to authorized users.

Long-Term Performance of Laboratory-Developed Liquid Chromatography-Tandem Mass Spectrometry Tests and a Food and Drug Administration-Approved Immunoassay for the Therapeutic Drug Monitoring of Everolimus.

Laboratory-developed tests (LDTs) are analytical tests developed and validated "in-house" for clinical diagnosis. Regulatory agencies, such as the United States Food and Drug Administration (FDA), encourage using regulatory-approved assays rather than LDTs. In the ongoing Zortracker everolimus study, samples were provided monthly to participating clinical laboratories that conduct therapeutic drug monitoring of everolimus. This allowed for the long-term (6-year) comparison of the performance of liquid chromatography-tandem mass spectrometry (LC-MS/MS) assays, which are LDTs, to the FDA-approved everolimus Quantitative Microsphere System (QMS). Each laboratory received the same 3 blinded samples. LC-MS/MS and QMS assays were compared using Passing Bablok regression analysis. Data were analyzed in 12-month periods to detect trends over time. The slopes of the Passing Bablok regression curves remained unchanged in 2013 and 2014 (reference LC-MS/MS; test QMS: slope = 0.934 and 1.008). However, by 2016, the slope increased significantly to between 1.111 and 1.320, then dropped to 0.980 in 2017 and 0.912 in 2018, suggestive of changes in QMS bias compared with LC-MS/MS over longer periods. Outliers did not affect these results. The interlaboratory variability of LC-MS/MS and QMS remained unchanged from 2013 to 2015, with coefficients of variation of 15.3%, 18.4%, and 17.2% for LC-MS/MS, and 13.0%, 13.1%, and 15.3% for QMS, respectively, per year. At the end of the observation period, the average coefficients of variation in LC-MS/MS laboratories dropped to 14.3%, 12.6%, and 14.2%, whereas the variability in QMS laboratories was 19.5%, 13.3%, and 19.6% in 2016, 2017, and 2018, respectively. Initially, QMS everolimus concentrations in patient samples were comparable with those detected in LC-MS/MS laboratories. However, concentration bias of the QMS assay significantly changed within 6 years, emphasizing the need for long-term, independent performance tracking of therapeutic drug monitoring assays, including FDA-approved assays.

Comparison of the everolimus concentrations measured in whole blood with everolimus QMS or sirolimus CMIA

Few years ago, it was proposed that everolimus blood levels could be determined with the commercially available sirolimus chemiluminescence magnetic microparticle immunoassay (CMIA). More recently, a highly specific microsphere system (QMS) has been approved by FDA for therapeutic drug monitoring in humans. Aim of the present study was to compare the results of everolimus assay performed with everolimus QMS and with sirolimus CMIA. The two methods were compared with Passing–Bablok regression and Bland–Altman plot analysis. The Passing–Bablok regression analysis showed that although the results obtained with the two techniques were significantly correlated, CMIA-measured differed from QMS-measured everolimus concentrations by both a systematic and a proportional error. Specifically, at blood levels lower than 5 ng/mL CMIA were lower than QMS-measured everolimus concentrations. On the opposite, at everolimus blood concentrations higher than 10 ng/mL CMIA-estimated values became progressively higher than QMS-measured everolimus concentrations. The analysis of the Bland Altman plot showed a less than optimal agreement of the two tests (5.59% of the data point outside the ±1.96 SD interval). Moreover, the relationship between the difference between EveroQMS and EveroCMIA and their average was clearly concentration dependent with positive and negative values at concentration values lower and higher than 5 ng/mL respectively.In conclusion, our finding showed that the values of everolimus concentrations measured with sirolimus CMIA differ from those detected with the FDA-approved everolimus QMS further suggesting that sirolimus CMIA should not be used anymore for everolimus therapeutic drug monitoring.

Towards therapeutic drug monitoring of everolimus in cancer? Results of an exploratory study of exposure-effect relationship

IntroductionTherapeutic drug monitoring (TDM) of everolimus is not performed in oncology and no trough level (C0) target has been yet defined. The aim of this study was to determine everolimus C0 target for toxicity and efficacy. Materials and methodsClinical, biological and radiologic data from 54 patients were collected. Toxicity event was defined by termination, temporary interruption and/or dose reduction of everolimus while efficacy was defined as progression-free survival. C0 values were dichotomized by ROC curve analysis and the association between exposure and outcome was determined using Cox models for repeated events (toxicity) or Cox model censured at the first event (progression free survival). ResultsAmong the 42 patients (77.8%) with breast cancer, 10 (18.5%) kidney cancer and 2 (3.7%) neuroendocrine cancer, adverse events were reported in 75.9% of the patients (everolimus termination in 25.9% patients). C0 everolimus higher than 26.3ng/mL (Sen=0.38,Spe=0.88) were associated with a 4-fold increased risk of toxicity (HR=4.12, IC95%=[1.48–11.5], p=0.0067) whereas C0 lower than 11.9ng/mL were associated with a 3-fold increased risk of progression (HR=3.2, IC95%=[1.33–7.81],p=0.001). DiscussionFurther studies are required to evaluate the everolimus C0 threshold proposed for toxicity (26.3ng/mL) and for progression (11.9ng/mL) especially with a large number of patients and more homogeneous types of cancer. However, these results are in favour of TDM for everolimus in oncology.

Therapeutic Drug Monitoring of Everolimus: Comparability of Concentrations Determined by 2 Immunoassays and a Liquid Chromatography Tandem Mass Spectrometry Method.

Therapeutic drug monitoring is recommended to guide therapy with the immunosuppressant everolimus (EVL) in solid organ transplantation to prevent rejections and to limit toxicity. For therapeutic drug monitoring, predose EVL concentrations are measured in whole blood mainly by liquid chromatography tandem mass spectrometry (LC-MS/MS). In addition, 2 immunoassays [Quantitative Microsphere System (QMS) EVL and Elecsys EVL] are commercially available. The aim of this study was to evaluate the comparability of EVL results determined with the 2 immunoassays and a validated LC-MS/MS test using samples from kidney, liver, and heart transplant (KT, LT, and HT, respectively) recipients. Analysis of predose samples from KT (n = 56), LT (n = 60), and HT (n = 59) recipients, obtained at variable time points after transplantation, was performed by LC-MS/MS and with the 2 immunoassays. The QMS EVL assay was applied on Dimension Xpand Plus and the Elecsys EVL assay on cobas e 411 analyzer. Results were compared by the Spearman's rank correlation coefficient, unbiased Passing and Bablok linear regression test, and Bland-Altman plot. Results generated with both immunoassays correlated well with those of LC-MS/MS. An overestimation of EVL concentrations by the Elecsys EVL compared with LC-MS/MS was observed (mean bias: 34.2%). Using the QMS EVL, a small but significant negative deviation (mean bias: -8.0%) was found. Looking at KT, HT, and LT samples separately, the bias to LC-MS/MS seen with the Elecsys EVL was similar. With the QMS EVL, the best agreement was observed with the KT samples followed by LT and HT. Results generated by the 3 methods are not consistent regarding their diagnostic value. Both laboratories and manufacturers should take care to inform their costumers about the between-method differences to avoid misinterpretation of the results in clinical practice.

1552P - Toward therapeutic drug monitoring of everolimus? Results of an exploratory study of the dose-exposure relationships

1552P - Toward therapeutic drug monitoring of everolimus? Results of an exploratory study of the dose-exposure relationships

Long-term cross-validation of everolimus therapeutic drug monitoring assays: the Zortracker study.

This ongoing academic collaboration was initiated for providing support to set up, validate, and maintain everolimus therapeutic drug monitoring assays and to study long-term interlaboratory performance. This study was based on EDTA whole blood samples collected from transplant patients treated with everolimus in a prospective clinical trial. Samples were handled under controlled conditions during collection, storage and were shipped on dry ice to minimize freeze-thaw cycles. For more than 1.5 years, participating laboratories received a set of 3 blinded samples on a monthly basis. Among others, these samples included individual patient samples, patient sample pools to assess long-term performance, and patient samples pools enriched with isolated everolimus metabolites. The results between liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) and the everolimus Quantitative Microsphere System (QMS, Thermo Fisher) assay were comparable. The monthly interlaboratory variability (coefficient of variation %) for cross-validation samples ranged from 6.5% to 23.2% (average of 14.8%) for LC-MS/MS and 4.2% to 26.4% (average of 11.1%) for laboratories using the QMS assay. A blinded long-term pool sample was sent to the laboratories for 13 months. The result was 5.31 ± 0.86 ng/mL (range, 2.9-7.8 ng/mL) for the LC-MS/MS and 5.20 ± 0.54 ng/mL (range, 4.0-6.8 ng/mL) for QMS laboratories. Enrichment of patient sample pools with 5-25 ng/mL of purified everolimus metabolites (46-hydroxy everolimus and 39-O-desmethyl everolimus) did not affect the results of either LC-MS/MS or QMS assays. Both LC-MS/MS and QMS assays gave similar results and showed similar performance, albeit with a trend toward higher interlaboratory variability among laboratories using LC-MS/MS than the QMS assay.

Reply

Everolimus was approved for the prevention of organ rejection of kidney transplants in adult patients in April 2010 by the US Food and Drug Administration. Therapeutic drug monitoring of everolimus is recommended for all patients receiving this immunosuppressant. The goal of this study was to improve and revalidate our previously published high-performance liquid chromatography tandem mass spectrometry method for the measurement of everolimus and to assess the performance of the recently introduced isotopically labeled internal standard (IS). For this method, the following innovative changes were incorporated: (1) sample preparation includes the addition of water to hemolyze red blood cells; (2) a separate extraction column is added to the system; (3) different settings of the switching valve are used to minimize dead volume; (4) a more sensitive mass spectrometer is used (API 5000) for drug detection; (5) isotopically labeled everolimus is used as the IS. The addition of water to blood before adding ZnSO4 with methanol improves absolute recovery of everolimus from 77.3% ± 6.18% to 82.3% ± 6.3%. The use of the more sensitive mass spectrometer permitted the use of a smaller sample volume and lowered the lower limit of quantification from 1.0 to 0.5 ng/mL. Between-day precision for quality control samples is below 9%, and the accuracy ranged from 94.8% to 106.4%. Neither carryover nor matrix effects were observed. A comparison study showed very good agreement between the results obtained by our laboratory and those obtained by a reference laboratory (r = 0.93). The performance of the new IS, [13c2d4] RAD001, was compared with that of SDZ RAD 223-756. Everolimus concentration results obtained using the isotopically labeled IS agreed more closely with the results from the reference laboratory (using 13c2d4) as compared with everolimus concentration results obtained using the analog (SDZ RAD 223-756). This revised methodology together with the comparison study data proved that our novel method for the measurement of everolimus is sensitive, precise, reliable, and robust.

Therapeutic drug monitoring of everolimus using the dried blood spot method in combination with liquid chromatography–mass spectrometry

An assay of everolimus based on finger prick sampling and consecutive application as a blood spot on sampling paper has been developed. We explored several methods [K. Hoogtanders, J. van der Heijden, M. Christiaans, P. Edelbroek, J. van Hooff, L. Stolk, J. Pharm. Biomed. Anal. 44 (2006) 658–664; A. Allanson, M. Cotton, J. Tettey, et al., J. Pharm. Biomed. Anal. 44 (2007) 963–969] and developed a new method, namely the impregnation of sampling paper with a solution of plasma–protein, formic acid and ammonium acetate, in combination with the extraction of the blood spot by filter filtration. This kind of sample preparation provides new possibilities for blood spot sampling especially if analytes are adsorbed to the paper. The dried blood spot was analysed using the HPLC–electrospray-tandem mass spectrometry method, with 32-desmethoxyrapamycin as the internal standard. The working range of our study was 2–30 μg/l. Within this range, intra-and inter-assay variability for precision and accuracy was <15%. Everolimus blood spot samples proved stable for 3 days at 60 °C and for 32 days at 4 °C. Everolimus concentrations of one stable out-patient were compared after both blood spot sampling and conventional venous sampling on various occasions. Results indicate that this new method is promising for therapeutic drug monitoring in stable renal transplant patients.

Comparison between a liquid chromatography‐tandem mass spectrometry assay and a fluorescent polarization immunoassay to measure whole blood everolimus concentration in heart and renal transplantations

Various methods [fluorescent polarization immunoassay (FPIA) and liquid chromatography-tandem mass spectrometry (LC-MS/MS) assay] are used for therapeutic drug monitoring of everolimus. The aim of this study is to compare these assays in renal and heart transplantation. The correlation between results was investigated by linear regression in 44 patients (24 heart recipients and 20 renal recipients--137 samples). The comparison between assays was performed by a paired t-test. A highly significant correlation was found between FPIA and LC-MS/MS in heart and renal recipients [FPIA=0.851 x LC-MS/MS+1.773r(2)=0.8738 (P<0.001)]. Paired t-tests did not show a significant difference between everolimus whole blood concentrations in the populations of heart and renal recipients or heart recipients or renal recipients. FPIA and LC-MS/MS assays gave consistent overall results although some significant differences were observed in some samples between these methods indicating that FPIA assay has limitations that deserve further investigations.

A HPLC–mass spectrometric method suitable for the therapeutic drug monitoring of everolimus

We report here the validation of an HPLC–electrospray–tandem mass spectrometry method for the quantification of everolimus, an immunosuppressant drug. Whole blood samples (100 μl) were extracted by protein precipitation which involved sample pre-treatment with zinc sulphate followed by acetonitrile (containing internal standard, 40- O-(3′-hydroxy)propyl-rapamycin). HPLC was performed using a step-gradient at a flow rate of 0.6 ml/min on a Waters TDM C 18 column (10 mm × 2.1 mm I.D.) with a resultant chromatographic analysis time of 2 min. Mass spectrometric detection by selected reaction monitoring (everolimus m/ z 975.5 → 908.3; internal standard m/ z 989.5 → 922.3). The assay was linear from 0.5 to 40 μg/l ( r 2 > 0.994, n = 11). The inter- and intra-day analytical recovery and imprecision for quality control samples (1.25, 12.5 and 30 μg/l) were 93.4–98.2% and <10.7%, respectively ( n = 10). At the lower limit of quantification (0.5 μg/l) the inter- and intra-day analytical recovery was 94.4–95.8% with imprecision of <14.1% ( n = 10). The absolute recovery of everolimus (6.5 μg/l) and internal standard (12.5 μg/l) was 96.5 and 88.3%, respectively ( n = 3). A comparison of our method against the mean of all HPLC methods for a series of samples from an external proficiency testing scheme revealed good correlation as shown by the regression analysis: y = 0.973 x + 0.301 ( r 2 = 0.986, n = 71). In conclusion, the method described is suited to the current requirements for therapeutic drug monitoring of everolimus.

Comparison of the Innofluor® certican assay with HPLC-UV for the determination of everolimus concentrations in heart transplantation

Objectives: Therapeutic monitoring of everolimus with chromatographic methods (HPLC) enabled effective immunosuppression while limiting the incidence of drug-related adverse events. A fluorescence polarization immunoassay (FPIA) has been recently developed for the assessment of everolimus levels. The present study was designed to evaluate FPIA performance and to compare it to HPLC. Design and methods: The performance of HPLC and FPIA was initially tested using drug-free whole blood spiked with different amount of everolimus concentrations and, subsequently, by analyzing 113 trough blood samples from heart transplant recipients chronically given everolimus as part of their immunosuppressive regimen. Results: Inaccuracy and imprecision of both methods were below 15%. The correlation between everolimus concentrations and measured FPIA and HPLC was good, with a Pearson coefficient of 0.9118. The FPIA gave a mean overestimation of 24.3% as compared with HPLC. As additional analysis, cross-reactivity ranging from 85.4% to 138.0% was found with sirolimus, an immunosuppressant with a chemical structure close to everolimus. Conclusion: The FPIA demonstrated acceptable performance for therapeutic drug monitoring of everolimus, and is a viable alternative to HPLC-based methods.

Everolimus drug interactions: application of a classification system for clinical decision making

More than half of all drugs used in medical practice are metabolized by cytochrome CYP3A. Coadministration of drugs that share this elimination pathway may lead to pharmacokinetic drug interactions. Efforts are underway by clinical, drug development and regulatory scientists to classify CYP3A-related drug interactions with the ultimate goal of improving guidance for clinical intervention. The CYP3A inhibitory classification system ranks inhibitors according to the fold-increase in area-under-the-curve (AUC) of a probe substrate as: strong (> or =5-fold), moderate (>2.0- to 4.9-fold), or weak (< or =2.0-fold). This classification system was applied to characterize everolimus as a CYP3A substrate.Methods. Five open-label crossover drug interaction studies were performed in 12-16 healthy subjects each. Subjects received a single 2 mg dose of everolimus alone and again during single- or multiple-dose treatment with the probe inhibitors ketoconazole, erythromycin, verapamil, cyclosporine and atorvastatin.Results. The fold-increase in everolimus AUC was: 15.0 with the strong inhibitor ketoconazole; 4.4, 3.5 and 2.7 with the moderate inhibitors erythromycin, verapamil and cyclosporine; and no change with the weak inhibitor atorvastatin. Subjects with low baseline AUCs when everolimus was given alone tended to have AUC increases of a higher magnitude (more potent interaction) in the presence of an inhibitor.Conclusions. Strong CYP3A inhibitors should be avoided when possible during everolimus treatment as compensatory everolimus dose reductions could be difficult to manage. Everolimus therapeutic drug monitoring should be used to guide individualized dose adjustments when moderate CYP3A inhibitors are added to or withdrawn from the regimen. Routine everolimus therapeutic drug monitoring should be sufficient to determine whether dose adjustments are needed when weak CYP3A inhibitors are coadministered. This rational and systematic approach to drug interactions on everolimus yielded clinically useful, structured guidelines for dose adjustment.

The Role of Therapeutic Monitoring of Everolimus in Solid Organ Transplantation

Everolimus is a novel proliferation signal inhibitor used in immunosuppressive therapies for the prevention of acute and chronic rejection. A role for everolimus drug monitoring has been suggested because of the potential for improving efficacy and reducing adverse effects. Everolimus has proven efficacy for prevention of rejection in adult de novo renal and cardiac transplant recipients. Similar effects have been shown in pediatric renal transplant patients. Several analytic methods are available to quantify everolimus concentrations. A good relationship exists between everolimus concentration and pharmacological response. Mere clinical monitoring of efficacy is insufficient because clinical presentations of graft rejection vary for each patient and are nonspecific. Thus, the authors have used a previously published 9-step decision-making algorithm to evaluate the utility of therapeutic drug monitoring for everolimus. The recommended therapeutic range for everolimus is a trough concentration of 3 to 8 ng/mL, as concentrations over 3 ng/mL have been associated with a decreased incidence of rejection, and concentrations >8 ng/mL with increased toxicity. Everolimus exhibits interindividual pharmacokinetic variability. African American patients have higher apparent clearance, whereas patients with hepatic dysfunction or those on concomitant medications with potent cytochrome P450 (CYP) 3A4 inhibitor or inducer properties have lower or higher apparent clearance, respectively. Solid organ transplant recipients will likely be maintained on immunosuppressant therapy for the life of the graft and/or recipient and thus are likely to benefit from clinical pharmacokinetic monitoring. Based on the available evidence, therapeutic drug monitoring for everolimus may provide additional information on efficacy and safety than sound clinical judgment alone. Patients on everolimus who have problems with absorption, who take concurrent cytochrome P450 inhibitors or inducers, or are noncompliant will attain the greatest benefit from drug monitoring.

Therapeutic drug monitoring for everolimus in kidney transplantation using 12‐month exposure, efficacy, and safety data

The aims of the current study were to determine whether therapeutic drug monitoring (TDM) might benefit kidney transplant recipients receiving everolimus, and to establish dosage recommendations when everolimus is used in combination with cyclosporine and corticosteroids. The analysis was based on data from 779 patients enrolled in two 12-month trials. Everolimus trough concentrations >/=3 ng/mL were associated with a reduced incidence in biopsy-proven acute rejection (BPAR) in the first month (p = 0.0001) and the first 6 months (p = 0.0001), and reduced graft loss compared with lower concentrations (4% vs. 20%, respectively). By contrast, cyclosporine in the standard concentration range had no impact on BPAR within the same timeframes. Most patients receiving everolimus 1.5 or 3 mg/d achieved trough concentrations above the therapeutic threshold of 3 ng/mL, regardless of reductions in cyclosporine dose. TDM simulation showed that just two dose adjustments would achieve median everolimus trough values >/=3 ng/mL in 95% of patients during the first 6 months. This investigation indicates that improved efficacy is likely when TDM is considered as an integral component of the immunosuppressive strategy of everolimus.

Effect of multiple-dose erythromycin on everolimus pharmacokinetics

We sought to quantify the influence of the CYP3A inhibitor erythromycin on the pharmacokinetics of everolimus, a CYP3A substrate. This was a two-period, single-sequence, crossover study in 16 healthy subjects. In period 1, subjects received the reference treatment of a single 2-mg dose of everolimus. In period 2, they received the test treatment of erythromycin 500 mg three times daily for a total of 9 days and a single 2-mg dose of everolimus coadministered on the fifth day of erythromycin therapy. The test/reference ratio and 90% confidence interval (CI) were derived for everolimus C (max) and AUC. During erythromycin coadministration, everolimus C (max) increased 2.0-fold (90% CI, 1.8-2.3) from 20+/-5 ng/ml to 40+/-10 ng/ml. Everolimus AUC increased 4.4-fold (90% CI, 3.5-5.4) from 116+/-37 ng h/ml to 524+/-225 ng h/ml. Everolimus half-life was prolonged by 39% from 32+/-6 h to 44+/-6 h. Erythromycin predose concentrations were not changed after single-dose administration of everolimus. Multiple-dose erythromycin increased single-dose everolimus blood levels by an average 4.4-fold (range, 2.0-12.6). During erythromycin treatment, a compensatory everolimus dose reduction should be made guided by everolimus therapeutic drug monitoring.

Therapeutic Drug Monitoring for Everolimus in Heart Transplant Recipients Based on Exposure–Effect Modeling

Everolimus, a proliferation signal inhibitor, is an immunosuppressant that targets the primary causes of progressive allograft dysfunction, thus improving the long-term outcome after heart transplantation. The present study investigated whether therapeutic drug monitoring (TDM) of everolimus would benefit heart transplant patients. Data from a twelve-month phase III trial comparing everolimus (1.5 or 3 mg daily) with azathioprine were used to evaluate everolimus pharmacokinetics, exposure-efficacy/safety and TDM prognostic simulations. Everolimus trough levels were stable in the first year post-transplant and averaged 5.2 +/- 3.8 and 9.4 +/- 6.3 ng/mL in patients treated with 1.5 and 3 mg/day, respectively. Cyclosporine trough levels were similar in all treatment groups. Biopsy-proven acute rejection (BPAR) was reduced with everolimus trough levels > or =3 ng/mL. Intravascular ultrasound (IVUS) analysis showed evidence of reduced vasculopathy at 12 months with increasing everolimus exposure. Unlike cyclosporine, increasing everolimus exposure was not related to a higher rate of renal dysfunction. The TDM simulation, which was based on two everolimus dose adjustments and an initial starting dose of 1.5 mg/day, showed that the simulated BPAR rate (with TDM) was 21% versus 26% in the group with fixed dosing. Therefore, TDM in heart transplantation could optimize immunosuppressive efficacy and reduce treatment-related toxicity.