Reasons for non-feasibility of therapeutic drug monitoring of oral targeted therapies in oncology - an analysis of the closed cohorts of a multicentre prospective study.

BACKGROUND: Therapeutic drug monitoring (TDM) - performing dose adjustments based on measured drug levels and established pharmacokinetic (PK) targets - could optimise treatment with drugs that show large interpatient variability in exposure. We evaluated the feasibility of TDM for multiple oral targeted therapies. Here we report on drugs for which routine TDM is not feasible. METHODS: We evaluated drug cohorts from the Dutch Pharmacology Oncology Group - TDM study. Based on PK levels taken at pre-specified time points, PK-guided interventions were performed. Feasibility of TDM was evaluated, and based on the success and practicability of TDM, cohorts could be closed. RESULTS: For 10 out of 24 cohorts TDM was not feasible and inclusion was closed. A high incidence of adverse events resulted in closing the cabozantinib, dabrafenib/trametinib, everolimus, regorafenib and vismodegib cohort. The enzalutamide and erlotinib cohorts were closed because almost all PK levels were above target. Other, non-pharmacological reasons led to closing the palbociclib, olaparib and tamoxifen cohort. CONCLUSIONS: Although TDM could help personalising treatment for many drugs, the above-mentioned reasons can influence its feasibility, usefulness and clinical applicability. Therefore, routine TDM is not advised for cabozantinib, dabrafenib/trametinib, enzalutamide, erlotinib, everolimus, regorafenib and vismodegib. Nonetheless, TDM remains valuable for individual clinical decisions.

Real-world pharmacokinetics and pharmacodynamics of everolimus in metastatic breast cancer.

Purpose This study investigated the relationship between the pharmacokinetics and pharmacodynamics of everolimus in patients with metastatic breast cancer (mBC) in real-world practice.Methods Twenty-two patients with mBC treated with everolimus plus exemestane were enrolled. Blood everolimus concentrations were measured at outpatient visits. The inhibition of the mammalian target of rapamycin (mTOR) activity in peripheral blood mononuclear cells (PBMCs) was examined. The efficacy and safety endpoints were progression-free survival (PFS) and the cumulative incidence of dose-limiting toxicities (DLTs), respectively. Results Blood samples were obtained from 19 consenting patients. Everolimus did not completely inhibit mTOR activity in PBMCs at therapeutic concentrations (~ 56 % maximal inhibition). The most common adverse event was stomatitis (any grade 77 %). The trough concentration (Ctrough) was significantly higher in patients experiencing DLTs than in those without any DLTs (P = 0.030). The optimal Ctrough cutoff predicting DLT development was 17.3 ng/mL. The cumulative incidence of DLTs was significantly higher in patients with Ctrough ≥17.3 ng/mL than in other patients (sub-hazard ratio 4.87, 95 % confidence interval [CI] 1.53-15.5; P = 0.007). Furthermore, the median PFS was numerically longer in patients who maintained a steady-state Ctrough below the threshold than in those who did not (327 days [95 % CI 103-355 days] vs. 194 days [95 % CI 45 days-not estimable]; P = 0.35). Conclusions The suggested upper threshold for the therapeutic window of everolimus Ctrough was 17.3 ng/mL. Pharmacokinetically guided dosing may improve the efficacy and safety of everolimus for mBC, warranting further investigation in a larger study.Clinical trial registry: Not applicable.

A POETIC Phase II study of continuous oral everolimus in recurrent, radiographically progressive pediatric low-grade glioma.

BACKGROUND: To evaluate efficacy, pharmacokinetics (PK) and pharmacodynamics of single-agent everolimus in pediatric patients with radiographically progressive low-grade glioma (LGG). METHODS: Everolimus was administered at 5 mg/m2 once daily as a tablet or liquid for a planned 48-week duration or until unacceptable toxicity or disease progression. Patients with neurofibromatosis type 1 were excluded. PK and pharmacodynamic endpoints were assessed in consenting patients. RESULTS: Twenty-three eligible patients (median age 9.2 years) were enrolled. All patients received prior chemotherapy (median number of prior regimens two) and/or radiotherapy (two patients). By week 48, two patients had a partial response, 10 stable disease, and 11 clinical or radiographic progression; two discontinued study prior to 1 year (toxicity: 1, physician determination: 1). With a median follow up of 1.8 years (range 0.2-6.7 years), the 2-, 3-, and 5-year progression-free survivals (PFS) were 39 ± 11%, 26 ± 11%, and 26 ± 11%, respectively; two patients died of disease. The 2-, 3-, and 5-year overall survival (OS) were all 93 ± 6%. Grade 1 and 2 toxicities predominated; two definitively related grade 3 toxicities (mucositis and neutropenia) occurred. Grade 4 elevation of liver enzymes was possibly related in one patient. Predose blood levels showed substantial variability between patients with 45.5% below and 18.2% above the target range of 5-15 ng/mL. Pharmacodynamic analysis demonstrated significant inhibition in phospho-S6, 4E-BP1, and modulation of c-Myc expression. CONCLUSION: Daily oral everolimus provides a well-tolerated, alternative treatment for multiple recurrent, radiographically progressive pediatric LGG. Based on these results, everolimus is being investigated further for this patient population.

Lack of everolimus diffusion in pleural fluid during pleural progression of breast cancer: A case report.

BACKGROUND: We report here a case where no everolimus pleural diffusion was evidenced at the same time of pleural progression of a metastatic breast cancer treated with everolimus and exemestane. CASE DESCRIPTION: A 69-year-old woman was diagnosed in October 2006 with stage III invasive ductal breast adenocarcinoma. After nine months of everolimus and exemestane treatment, she presented with a pleural progression. Everolimus concentration was measured in blood and in pleural fluid. Residual blood concentration was at 9.1 ng/mL, while no everolimus was observed in the pleural fluid. MANAGEMENT AND OUTCOME: Due to inefficacy of everolimus in this patient, she was switched to palbociclib and fulvestrant. CONCLUSION: Everolimus seems to have a poor diffusion in the pleural fluid.

Severe COVID-19 in a renal transplant recipient: A focus on pharmacokinetics.

The current coronavirus disease 2019 (COVID-19) pandemic requires extra attention for immunocompromised patients, including solid organ transplant recipients. We report on a case of a 35-year-old renal transplant recipient who suffered from a severe COVID-19 pneumonia. The clinical course was complicated by extreme overexposure to the mammalian target of rapamycin inhibitor everolimus, following coadministration of chloroquine and lopinavir/ritonavir therapy. The case is illustrative for dilemmas that transplant professionals may face in the absence of evidence-based COVID-19 therapy and concurrent pressure for exploration of experimental pharmacological treatment options. However, the risk-benefit balance of experimental or off-label therapy may be weighed differently in organ transplant recipients than in otherwise healthy COVID-19 patients, owing to their immunocompromised status and potential drug interactions with immunosuppressive therapy. With this case report, we aimed to achieve increased awareness and improved management of drug-drug interactions associated with the various treatment options for COVID-19 in renal transplant patients.

Effect of genetic polymorphisms in CYP3A4, CYP3A5, and m-TOR on everolimus blood exposure and clinical outcomes in cancer patients.

Genetic variations in CYP3A4, CYP3A5, and m-TOR could contribute to interpatient variability regarding m-TOR inhibitors pharmacokinetics or cellular effects. The purpose of this study was to evaluate the influence of selected candidate variations in these genes on everolimus pharmacokinetics, efficacy, and toxicity in cancer patients. Thirty-four patients receiving everolimus for breast (n = 22) or renal (n = 10) cancers, or neuroendocrine tumors of pancreatic origin (n = 2) were included in the study. Six variants in genes related to everolimus pharmacokinetics (CYP3A4*22 and CYP3A5*3) or pharmacodynamics (m-TOR rs2295079, rs2295080, rs2024627 and rs1057079) were genotyped. Associations with trough concentrations (C0), dose reductions, or treatment interruptions due to toxicity and progression-free survival were investigated using generalized estimating equations and Cox models. CYP3A5 nonexpressers had significantly higher C0 as compared with expressers (ßGG vs AG = + 6.32 ± 2.22 ng/mL, p = 0.004). m-TOR rs2024627 was significantly associated with an increased risk of cancer progression studied alone or as part of an haplotype (T vs C: HR = 2.60, 95% CI [1.16-5.80], p = 0.020; CTCG vs other haplotypes HR = 2.29, 95% CI [1.06-4.95], p = 0.035, respectively). This study showed that CYP3A5 expression impacts everolimus pharmacokinetics in cancer patients and identified a genetic variation in m-TOR associated with the risk of cancer progression.

Flucloxacillin decreases tacrolimus blood trough levels: a single-center retrospective cohort study.

PURPOSE: Tacrolimus and everolimus are widely used to prevent allograft rejection. Both are metabolized by the hepatic cytochrome P450 (CYP) enzyme CYP3A4 and are substrate for P-glycoprotein (P-gp). Drugs influencing the activity or expression of CYP enzymes and P-gp can cause clinically relevant changes in the metabolism of immunosuppressants. Several case reports have reported that flucloxacillin appeared to decrease levels of drugs metabolized by CYP3A4 and P-gp. The magnitude of this decrease has not been reported yet. METHODS: In this single-center retrospective cohort study, we compared the tacrolimus and everolimus blood trough levels (corrected for the dose) before, during, and after flucloxacillin treatment in eleven transplant patients (tacrolimus n = 11 patients, everolimus n = 1 patient, flucloxacillin n = 11 patients). RESULTS: The median tacrolimus blood trough level decreased by 37.5% (interquartile range, IQR 26.4-49.7%) during flucloxacillin treatment. After discontinuation of flucloxacillin, the tacrolimus blood trough levels increased by a median of 33.7% (IQR 22.5-51.4%). A Wilcoxon signed-rank test showed statistically significantly lower tacrolimus trough levels during treatment with flucloxacillin compared with before (p = 0.009) and after flucloxacillin treatment (p = 0.010). In the only available case with concomitant everolimus and flucloxacillin treatment, the same pattern was observed. CONCLUSIONS: Flucloxacillin decreases tacrolimus trough levels, possibly through a CYP3A4 and/or P-gp-inducing effect. It is strongly recommended to closely monitor tacrolimus and everolimus trough levels during flucloxacillin treatment and up to 2 weeks after discontinuation of flucloxacillin.

Marcromolecular Architecture and Encapsulation of the Anticancer Drug Everolimus Control the Self-Assembly of Amphiphilic Polypeptide-Containing Hybrids.

Macromolecular architecture plays an important role in the self-assembly process of block copolymer amphiphiles. Herein, two series of stimuli-responsive amphiphilic 3-miktoarm star hybrid terpolypeptides and their corresponding linear analogues were synthesized exhibiting the same overall composition and molecular weight but different macromolecular architecture. The macromolecular architecture was found to be a key parameter in defining the morphology of the nanostructures formed in aqueous solutions as well as to alter the self-assembly behavior of the polymers independently of their composition. In addition, it was found that the assemblies prepared from the star-shaped polymers showed superior tolerance against enzymatic degradation due to the increased corona block density on the outer surface of the nanoparticles. Encapsulation of the hydrophobic anticancer drug Everolimus resulted in the formation of intriguing non-spherical and non-symmetric pH-responsive nanostructures, such as "stomatocytes" and "multi-compartmentalized suprapolymersomes", while the pH-triggered release of the drug was also investigated. Owing to the similarities of the developed "stomatocytes" with red blood cells, in combination with their pH-responsiveness and superior stability over enzymatic degradation, they are expected to present advanced drug delivery properties and have the ability to bypass several extra- and intracellular barriers to reach and effectively treat cancer cells.

Pharmacodynamic Monitoring of mTOR Inhibitors.

Pharmacodynamic (PD) monitoring may complement routine pharmacokinetic monitoring of mTOR inhibitors (mTORis) in an attempt to better guide individualized sirolimus (SRL) or everolimus (EVR) treatment after organ transplantation. This review focuses on current knowledge about PD biomarkers for personalized mTORi therapies. Different strategies have already been used in the evaluation of the pharmacodynamics of SRL and EVR as a proxy for their effects on the immune response after transplantation. These include measuring p70S6K (70 kDa ribosomal protein S6 kinase) activity, p70S6K phosphorylation (P-p70S6K), or P-S6 protein expression. Compared with Western blot and ELISA, phosphoflow cytometry can detect phosphorylated proteins and differentiate activation-induced changes of signaling molecules inside the cell from unstimulated populations of identical cells in the same sample. Alternatively, in patients receiving a combined therapy, the other PD approach is to consider biomarkers such as NFAT residual expression for calcineurin inhibitors or to evaluate nonspecific effects of the drugs such as lymphocyte proliferation, interleukin synthesis, specific peripheral blood T regulatory subsets, or lymphocyte surface antigens, which have the advantage to reflect the overall immunosuppressive status achieved. Although limited, the available data on mTOR pathway biomarkers seem promising. Before clinical implementation, the analytical methodologies must be standardized and cross-validated, and the selected biomarkers will have to demonstrate their clinical utility for SRL or EVR dose individualization in multicenter clinical trials.

Cannabidiol Interacts Significantly with Everolimus-Report of a Patient with Tuberous Sclerosis Complex.

A 6.5-year-old female patient with a TSC2 mutation had been given everolimus (EVE) for 3 years for pharmacoresistant focal epilepsy and for life-threatening, severe ventricular dysrhythmia. EVE had been started with daily dose of 0.15 mg/kg/day and was increased up to 0.6 mg/kg/day. Target blood trough levels of around 9 µg/L had been documented. Although EVE therapy revealed no effect on seizure activity, cardiac rhythm normalized completely. Thus, EVE was reduced to a dose of 0.3 mg/kg/day leading to stable blood trough levels of 4 to 5 µg/L. Due to refractory tonic seizures with a frequency of 1 to 4 per day, we initiated cannabidiol (CBD) treatment, raising it to a daily dose of 200 mg. After 6 weeks, the EVE blood trough levels rose to 12.0 µg/L. Although we halved the EVE dose, her EVE blood trough level continued increasing up to 16.0 µg/L.The CBD dose was increased to 500 mg/day (20.4 g/kg/day), but EEG parameters and seizures failed to respond. Serum concentrations of EVE were unstable under the co-medication with CBD. Depending on the CBD dose, they varied between 1.7 and 12.3 µg/L, while EVE was always administered at the same dose.Although never before reported, CBD and EVE appear to interact, due to the metabolic pathway through CYP 450 3A4. Although we detected no side effects in our patient, we strongly recommend drug monitoring using the combination of CBD with EVE to prevent harmful overdosing.

Lenvatinib plus everolimus or pembrolizumab versus sunitinib in advanced renal cell carcinoma: study design and rationale.

AIM: Lenvatinib plus everolimus is approved for the treatment of advanced renal cell carcinoma (RCC) after one prior vascular endothelial growth factor-targeted therapy. Lenvatinib plus pembrolizumab demonstrated promising antitumor activity in a Phase I/II trial of RCC. METHODS: We describe the rationale and design of the CLEAR study, a three-arm Phase III trial comparing lenvatinib plus everolimus and lenvatinib plus pembrolizumab versus sunitinib monotherapy for first-line treatment of RCC. Eligible patients must have advanced clear cell RCC and must not have received any prior systemic anticancer therapy. The primary end point is progression-free survival; secondary end points include objective response rate, overall survival, safety, health-related quality of life and pharmacokinetics. Biomarker evaluations are included as exploratory end points.

Effects of MDR1 1236C > T-2677G > T-3435C > T polymorphisms on the intracellular accumulation of tacrolimus, cyclosporine A, sirolimus and everolimus.

1. Overexpression of P-glycoprotein (P-gp, encoded by MDR1) mediates resistance to multiple immunosuppressors. Several common MDR1 variants (1236C > T, 2677G > T, 3435C > T) impact the efflux activity of P-gp-mediated substrates. We assessed the effect of these polymorphisms on the sensitivity, intracellular accumulation, and efflux of tacrolimus, cyclosporine A, sirolimus and everolimus in transfected LLC-PK1 cells. 2. LLC-PK1 cell lines were transfected with empty vector (pcDNA3.1) and recombinant MDR1T-T-T, MDR1C-T-T, MDR1C-G-T and MDR1C-G-C vectors, respectively and further screened in the presence of puromycin. The IC50 values, intracellular accumulation, and apparent permeability ratios of tacrolimus, cyclosporine A, sirolimus and everolimus were evaluated. 3. MDR1 overexpression increased the resistance of LLC-PK1 cells to tacrolimus, cyclosporine A, sirolimus and everolimus. The resistance of cells expressing MDR1C-G-C wild-type haplotypes to tacrolimus were increased compared to MDR1T-T-T, MDR1C-T-T, MDR1C-G-T variant haplotypes. The efflux ability of P-gp-mediated tacrolimus in cells transfected with MDR1C-G-C was higher than cells overexpressing MDR1T-T-T, MDR1C-T-T, MDR1C-G-T variant haplotypes. In addition, the resistance of cells expressing MDR1C-G-C wild-type haplotypes to sirolimus were increased compared to MDR1C-T-T, MDR1C-G-T variant haplotypes. The efflux ability of P-gp-mediated sirolimus in cells overexpressing MDR1C-G-C was higher than cells transfected with MDR1C-T-T, MDR1C-G-T variant haplotypes. 4. These findings indicate that wild-type MDR1 exports tacrolimus and sirolimus more efficiency than the MDR1T-T-T, MDR1C-T-T, MDR1C-G-T variant protein. This observation indicates that 1236C > T, 2677G > T, 3435C > T variant haplotypes drastically decrease the efflux ability of P-gp-mediated tacrolimus and sirolimus in a substrate-specific manner.

A phase Ib study of everolimus combined with metformin for patients with advanced cancer.

Background The efficacy to monotherapy with the mTOR inhibitor everolimus in advanced cancer is often limited due to therapy resistance. Combining everolimus with metformin may decrease the chance of therapy resistance. Methods Patients received everolimus and metformin in a 3 + 3 dose-escalation scheme. Objectives were to determine the dose-limiting toxicities (DLTs), maximum tolerated dose, toxic effects, pharmacokinetics and anti-tumour efficacy. Results 9 patients received study treatment for a median duration of 48 days (range: 4-78). 6 patients discontinued due to toxicity and 3 patients because of progressive disease. At the starting dose level of 10 mg everolimus qd and 500 mg metformin bid, 3 out of 5 patients experienced a DLT. After de-escalation to 5 mg everolimus qd and 500 mg metformin bid, considerable toxicity was still observed and patient enrollment was terminated. In pharmacokinetic analyses, metformin was eliminated slower when co-administered with everolimus than as single-agent. After 9 weeks of treatment, 3 patients were still on study and all had stable disease. Conclusion The combination of everolimus and metformin is poorly tolerated in patients with advanced cancer. The pharmacokinetic interaction between everolimus and metformin may have implications for diabetic cancer patients that are treated with these drugs. Our results advocate for future clinical trials with combinations of other mTOR inhibitors and biguanides.

Everolimus dosing recommendations for tuberous sclerosis complex-associated refractory seizures.

OBJECTIVE: The present analysis examined the exposure-response relationship by means of the predose everolimus concentration (Cmin ) and the seizure response in patients with tuberous sclerosis complex-associated seizures in the EXIST-3 study. Recommendations have been made for the target Cmin range of everolimus for therapeutic drug monitoring (TDM) and the doses necessary to achieve this target Cmin . METHODS: A model-based approach was used to predict patients' daily Cmin . Time-normalized Cmin (TN-Cmin ) was calculated as the average predicted Cmin in a time interval. TN-Cmin was used to link exposure to efficacy and safety end points via model-based approaches. A conditional logistic regression stratified by age subgroup was used to estimate the probability of response in relation to exposure. A multiplicative linear regression model was used to estimate the exposure-response relationship for seizure frequency (SF). An extended Cox regression model was used to link exposure to the time to first adverse event. RESULTS: There was a strong, consistent, and highly significant relationship between everolimus exposure and efficacy, measured by TN-Cmin and SF, regardless of patient's age and concomitant use of cytochrome P450 3A4 (CYP3A4) inhibitors/inducers. Results of an extended Cox regression analyses indicated that twofold increases in TN-Cmin were not associated with statistically significant increases in the risk of stomatitis or infections. SIGNIFICANCE: The recommended TDM is to target everolimus Cmin within a range of 5-7 ng/mL initially and 5-15 ng/mL in the event of an inadequate clinical response, and safety is consistent with previous reports. Starting doses depend on age and the concomitant use of CYP3A4/P-glycoprotein inducers/inhibitors.

A pharmacological rationale for improved everolimus dosing in oncology and transplant patients.

AIMS: Everolimus is a drug from the class of mammalian target of rapamycin inhibitors used for both immunosuppressant and oncological indications. We postulate that there is room for improvement of dosing, as the optimal immunosuppressive dose in calcineurin-free regimens is unknown and since the once daily dosing regimen for oncological indications is often associated with treatment-limiting toxicity. METHODS: We developed a mechanistic population pharmacokinetic model for everolimus in cancer and transplant patients and explored alternative dosing regimens. RESULTS: We found that formulation did not influence bioavailability and that use of >20 mg prednisolone daily increased everolimus clearance. In transplant patients, the approved dose of 0.75-1 mg twice daily (BID) results in subtherapeutic trough levels (<6 µg l-1 ) and that a higher starting dose of 2.25-3 mg BID is required. CONCLUSION: For oncological indications, our results encourage the investigation of dosing everolimus 3.75 mg BID in terms of superiority in safety and noninferiority in efficacy.

Adequacy of Initial Everolimus Dose, With and Without Calcineurin Inhibitors, in Kidney Transplant Recipients.

BACKGROUND: This study investigates the adequacy of initial everolimus (EVR) dose, with and without calcineurin inhibitors (CNI), in kidney transplant recipients. METHODS: This retrospective cohort analysis involved data from 305 kidney transplant recipients participating in 3 randomized trials receiving reduced dose cyclosporin A (CsA) combined with EVR 0.75 mg BID (CSA/EVR0.75, N = 32) or 1.5 mg BID (CSA/EVR1.5, N = 31), reduced dose tacrolimus (TAC) combined with EVR 1.5 mg BID (TAC0.05/EVR1.5, N = 83), standard dose TAC combined with EVR 1.5 mg BID (TAC0.1/EVR1.5, N = 93), and EVR 1.5 mg BID (EVR1.5, N = 66) with TAC introduction after day 5. The adequacy of the initial EVR dose, based on EVR whole blood trough between 3 and 8 ng/mL, was compared using first EVR blood concentrations obtained at day 3 after transplantation. RESULTS: Recipient age, proportion of patients with diabetes mellitus, and proportion of grafts from living donors were different among the groups. Dose-corrected EVR concentrations were higher in patients receiving CsA than in those receiving TAC or no calcineurin inhibitors (6.7 ± 5.9 versus 5.4 ± 2.2 versus 2.4 ± 0.8 versus 2.5 ± 0.9 versus 2.2 ± 0.7, P = 0.000). No differences were observed comparing dose adjusted EVR concentrations combined with TAC or alone (P = 0.073). The proportion of patients with EVR concentration below <3 ng/mL was lower when EVR was combined with CsA (25 versus 3 versus 43 versus 33 versus 50%, P = 0.000). Later introduction of TAC did not influence EVR concentrations. There were no differences in mean CsA concentrations comparing patients receiving EVR 0.75 or 1.5 mg BID (240 ± 143 versus 213 ± 105 ng/mL). On the other hand, mean TAC concentrations were higher according to the initial TAC dose regimen (6.4 ± 3.9 versus 9.8 ± 5.9 ng/mL). CONCLUSIONS: In de novo kidney transplant recipients, the choice of the initial dose of EVR should consider the type of calcineurin inhibitor to reach target EVR concentration within the first week in a higher proportion of patients, maximizing the efficacy/toxicity profile.

Clinical validation study of dried blood spot for determining everolimus concentration in patients with cancer.

PURPOSE: Everolimus treatment is seriously hampered by its toxicity profile. As a relationship between everolimus exposure and effectiveness and toxicity has been established, early and ongoing concentration measurement can be key to individualize the dose and optimize treatment outcomes. Dried blood spot (DBS) facilitates sampling at a patients' home and thereby eases dose individualization. The aim of this study is to determine the agreement and predictive performance of DBS compared to whole blood (WB) to measure everolimus concentrations in cancer patients. METHODS: Paired DBS and WB samples were collected in 22 cancer patients treated with everolimus and analyzed using UPLC-MS/MS. Bland-Altman and Passing-Bablok analysis were used to determine method agreement. Limits of clinical relevance were set at a difference of ± 25%, as this would lead to a different dosing advice. Using DBS concentration and Passing-Bablok regression analysis, WB concentrations were predicted. RESULTS: Samples of 20 patients were suitable for analysis. Bland-Altman analysis showed a mean ratio of everolimus WB to DBS concentrations of 0.90, with 95% of data points within limits of clinical relevance. Passing-Bablok regression of DBS compared to WB revealed no constant bias (intercept 0.02; 95% CI 0.93-1.35) and a small proportional bias (slope 0.89; 95% CI 0.76-0.99). Predicted concentrations showed low bias and imprecision and 90% of samples had an absolute percentage prediction error of < 20%. CONCLUSIONS: DBS is a valid method to determine everolimus concentrations in cancer patients. This can especially be of value for early recognition of over- or underexposure to enable dose adaptations.

Effect of fluconazole on the pharmacokinetics of everolimus and tacrolimus in a heart transplant recipient: Case report.

OBJECTIVE: Everolimus is an inhibitor of the mammalian target of rapamycin (mTOR) and has been used in combination with calcineurin inhibitors (tacrolimus and cyclosporine) to prevent allograft rejection following organ transplantation. In heart transplant recipients, everolimus should be maintained at a target blood concentration of 3 - 8 ng/mL, in combination with reduced-dose calcineurin inhibitors and therefore, requires strict monitoring. Fluconazole, an azole antifungal agent, affects blood concentration of tacrolimus by inhibiting the cytochromes P450 (CYP) 3A4 and 3A5. Therefore, to avoid overexposure during everolimus-azole cotreatment, the dose of everolimus should be reduced. However, the mechanism of interaction between everolimus and fluconazole remains unclear. CASE REPORT: We report the case of a heart transplant recipient who experienced a 2.8-fold increase in everolimus clearance and a 3.5-fold increase in everolimus dosage, following withdrawal of fluconazole therapy. The clearance and dosage of tacrolimus increased 4.7- and 3.0-fold, respectively. CONCLUSION: The concentrations of everolimus and tacrolimus should be carefully monitored when administered concomitantly with fluconazole to heart transplant recipients. The patient in this case had a CYP3A5*1/*3 genotype, and CYP3A5 constituted the metabolic pathway. Therefore, concomitant use of fluconazole might have a relatively small impact on everolimus and tacrolimus pharmacokinetics in this case.
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Population pharmacokinetics-pharmacodynamics of oral everolimus in patients with seizures associated with tuberous sclerosis complex.

Everolimus is approved in Europe and in the USA for the adjunctive treatment of patients aged 2 years and older whose refractory partial-onset seizures, with or without secondary generalization, are associated with tuberous sclerosis complex. The objective of this analysis was to establish a population pharmacokinetic (PK)/pharmacodynamic model describing the relationship between seizure frequency and everolimus exposure to confirm the recommended target concentration range of 5-15 ng/mL. The PK model was a two-compartment model with first order absorption and clearance. CYP3A and P-gp inducers and body-surface area were shown to impact everolimus exposure, justifying dose adjustments. A Poisson distribution was found to adequately describe the random nature of daily seizure counts during the screening phase. A placebo effect on the Poisson seizure mean was implemented as an asymptotic exponential function of time leading to a new steady-state seizure mean. The everolimus effect was implemented as an inhibitory Emax function of Cmin on the seizure mean, where Emax exhibited an asymptotic exponential increase over time to a higher steady-state value. Increasing age was found to decrease the baseline seizure mean and to prolong the half-life of the increase in Emax. The dependence of seizure frequencies on Cmin was explored by simulation. The responder rate increased with increasing Cmin. As Cmin decreased below 5 ng/mL, variability in response became larger and responder rates decreased more rapidly. The results supported the recommended target concentration range for everolimus of 5-15 ng/mL to ensure treatment efficacy.

Lenvatinib in combination with everolimus in patients with advanced or metastatic renal cell carcinoma: A phase 1 study.

OBJECTIVES: To assess the tolerability, safety, pharmacokinetics and antitumor activities of lenvatinib, an oral inhibitor of multiple receptor tyrosine kinases, in combination with everolimus, an inhibitor of mammalian target of rapamycin, in Japanese patients with advanced or metastatic renal cell carcinoma after disease progression with vascular endothelial growth factor-targeted therapy. METHODS: Lenvatinib 18 mg and everolimus 5 mg once daily were administered on 28-day continuous cycles until disease progression or unacceptable toxicity. Adverse events were evaluated according to the Common Terminology Criteria for Adverse Events version 4.03, and tumor response was assessed according to the Response Evaluation Criteria in Solid Tumor version 1.1. Pharmacokinetics sampling was carried out during the first cycle. RESULTS: Seven patients with clear cell renal cell carcinoma received this combination treatment. Dose-limiting toxicity was not observed. The most commonly observed adverse events were thrombocytopenia and decreased appetite (100%), followed by hypertriglyceridaemia and palmar-plantar erythrodysesthesia syndrome (86%). The most common grade 3 adverse event was lymphopenia (43%). No grade 4 or 5 adverse events occurred. The steady-state mean areas under the concentration-time curves of lenvatinib and everolimus were 3220 and 401 ng·h/mL, respectively. Five patients (71%) had partial response, and one (14%) had stable disease. CONCLUSIONS: Lenvatinib 18 mg and everolimus 5 mg once daily are well tolerated and manageable, and their combined administration has no significant effect on either drug's pharmacokinetics. Overall, this combination therapy shows encouraging antitumor activity in Japanese patients with renal cell carcinoma.