Pharmacodynamic Model-Based Safety Management of Eribulin-Induced Myelosuppression in Patients With Breast Cancer.

BACKGROUND: Neutropenia is a major dose-limiting toxicity of cancer chemotherapy. Semimechanistic mathematical models have been applied to describe the time course of neutrophil counts. The objectives of this study were to develop a mathematical model describing changes in neutrophil counts during eribulin treatment, to apply the empirical Bayes method to predict the probability of developing neutropenia ≥ grade 3 during eribulin treatment in each patient, and to propose the implementation of this mathematical tool in clinical practice for individual safety management. METHODS: The present model analysis and subsequent external evaluation were performed using the data of 481 patients with breast cancer, previously obtained from a postmarketing surveillance (training set) and a phase 2 clinical study (validation set). The model we previously reported (Kawamura et al 2018) was modified to improve its predictive capability. The individual time course of neutrophil changes during the treatment period was predicted by the empirical Bayes method using the observed neutrophil counts at baseline and the first measurement after the first eribulin dose. To evaluate the predictability of this method, the predicted neutrophil counts were compared with those of the observed values. RESULTS: The developed model provided good individual predictions, as indicated by the goodness-of-fit plots between the predicted and observed neutrophil counts, especially for a lower neutrophil count range. Days required to reach the nadir after the dose were also well-predicted. The sensitivity, specificity, and accuracy of the prediction of neutropenia grade ≥3 were 76%, 53%, and 71%, respectively. CONCLUSIONS: We developed a mathematical method for predicting and managing the risk of neutropenia during eribulin treatment. This method is generally applicable to other cases of chemotherapy-induced neutropenia and can be a new practical tool for individual safety management.

Prospective evaluation of the relationship between response and exposure of total and unbound erlotinib in non-small cell lung cancer patients.

PURPOSE: To evaluate the relationship between treatment efficacy and exposure of total and unbound erlotinib in patients with non-small cell lung cancer (NSCLC) harboring epidermal growth factor receptor (EGFR)-activating mutations. PATIENTS AND METHODS: EGFR-tyrosine kinase inhibitor naïve NSCLC patients were enrolled, and erlotinib was started at 150 mg/day. Total and unbound exposure of erlotinib were prospectively evaluated. RESULTS: Of the 70 enrolled patients, 61 had EGFR-activating mutations (30 patients with exon 19 deletions, 31 patients with L858R). The median area under the concentration-time curve from 0 to 24 h (AUC0-24) of total and unbound erlotinib on day 1 was 37,004 ng·h/mL (range, 9683-63,257 ng·h/mL) and 2338 ng·h/mL (581-5904 ng·h/mL), respectively. The median progression-free survival (PFS) was 10.9 months, and PFS did not differ between each tertile of total and unbound AUC0-24 on day 1 in 59 patients with EGFR-activating mutations. The worst grade of skin toxicities was significantly correlated with total trough concentration at steady state (Ctrough,ss) at each visit for 3 months after the initiation of erlotinib treatment (P < 0.0001). Total and unbound Ctrough,ss on day 7-15 in 20 patients whose dose was reduced due to intolerable toxicities was significantly higher than those in 48 patients whose dose was unchanged for 3 months (P = 0.0046, 0.0008). CONCLUSION: The lack of relationship between efficacy and exposure of total and unbound erlotinib demonstrates that the standard dose of 150 mg/day is sufficient for the treatment of NSCLC harboring EGFR-activating mutations, despite wide inter-individual variability in exposure and dose reduction. CLINICAL TRIALS REGISTRATION NUMBER: UMIN000012862.

Evaluation of clinical validity of an S-1 dosage formula based on renal function using data of the SPIRITS and the G-SOX trials.

BACKGROUND: The aim of this study was to evaluate clinical validity of the S-1 dosage formula based on body surface area (BSA) and creatinine clearance (CLcr) to achieve the target area under the concentration-time curve of 5-FU, which we had developed and refined in each prospective pharmacokinetic study. METHODS: The recommended dose determined by the refined formula was assessed using data of the SPIRITS (S-1 vs. S-1 plus cisplatin [SP]) and the G-SOX (SP vs. S-1 plus oxaliplatin [SOX]) trials. Nine hundred and thirty-eight patients in these trials were classified into three groups according to their actual S-1 starting doses compared with the recommended doses (under-dosed, recommended dose). RESULTS: The patients in the under-dosed group in both trials showed similar tendencies: male, younger, higher BSA, and higher CLcr. The incidence of any grade neutropenia was significantly greater in the over-dosed group compared with the equal-dosed group in the S-1 and the SOX arms. The hazard ratios (HR) of overall survival (OS) (under-dosed vs. equal-dosed) were 1.361 (S-1 arm), 1.259 (SP arm) in the SPIRITS trial, and 1.381 (SOX arm), 0.999 (SP arm) in the G-SOX trial. Multivariate analysis in all the patients demonstrated that OS of the over-dosed group was equivalent (HR 1.002, 95% confidence interval [CI] 0.850-1.182, p = 0.980) and that of the under-dosed group was inferior (HR 1.267, 95% CI 1.005-1.597, p = 0.045) to the equal-dosed group. CONCLUSIONS: It is suggested that the refined S-1 dosage formula can recommend optimal dose in terms of safety and efficacy.

Pharmacometric analysis of seasonal influenza epidemics and the effect of vaccination using sentinel surveillance data.

The identification of influenza epidemics and assessment of the efficacy of vaccination against this infection are major challenges for the implementation of effective public health strategies, such as vaccination programs. In this study, we developed a new pharmacometric model to evaluate the efficacy of vaccination based on infection surveillance data from the 2010/2011 to 2018/2019 influenza seasons in Japan. A novel susceptible-infected-removed plus vaccination model, based on an indirect response structure with the effect of vaccination, was applied to describe seasonal influenza epidemics using a preseasonal collection of data regarding serological H1 antibody titer positivity and the fraction of virus strains. Using this model, we evaluated Kin (a parameter describing the transmission rate of symptomatic influenza infection) for different age groups. Furthermore, we defined a new parameter (prevention factor) showing the efficacy of vaccination against each viral strain and in different age groups. We found that the prevention factor of vaccination against influenza varied among age groups. Notably, children aged 5-14 years showed the highest Kin value during the 10 influenza seasons and the greatest preventive effect of vaccination (prevention factor = 70.8%). The propagation of influenza epidemics varies in different age groups. Children aged 5-14 years most likely play a leading role in the transmission of influenza. Prioritized vaccination in this age group may be the most effective strategy for reducing the prevalence of influenza in the community.

Pharmacodynamic analysis of hypertension caused by lenvatinib using real-world postmarketing surveillance data.

Lenvatinib is a tyrosine kinase inhibitor of the vascular endothelial growth factor receptor used against nonoperative thyroid cancer; however, hypertension is a major dose-limiting side effect. In this study, hypertension caused by lenvatinib was described through a novel population pharmacodynamic model using postmarketing surveillance data obtained in Japan. The model consists of two maximum effect model components based on the (1) concentration of lenvatinib in plasma and (2) cumulative area under the curve of lenvatinib. In addition, antihypertensive drug of either an angiotensin-converting enzyme inhibitor/angiotensin receptor blocker or calcium channel blocker accounted for by lowering effect on diastolic blood pressure. Based on virtual simulations, the combination of antihypertensive drug and dose adjustment of lenvatinib showed a reduction in the probability of grade greater than or equal to 3 hypertension. The present model provides useful guidance in managing hypertension during treatment with lenvatinib in the real-world setting.

Prospective evaluation and refinement of an S-1 dosage formula based on renal function for clinical application.

In patients with impaired renal function, S-1-related toxicities increase due to higher exposure of 5-fluorouracil (5-FU). Our previous pharmacokinetic study in 16 cancer patients with various renal functions developed an S-1 dosage formula based on individual creatinine clearance (CLcr) and body surface area (BSA). To evaluate and refine the formula, this prospective study was conducted. Thirty-three patients with various renal functions received S-1 for 4 weeks at doses determined by the nomogram derived from the previously developed formula. A series of blood samples were collected after the first dose to calculate the area under the concentration-time curve (AUC) of 5-FU. Thirty patients with BSA of 1.14-1.84 m2 and CLcr of 23.8-96.4 mL/min were assessable for pharmacokinetics. The observed daily AUC ranged from 712.6 to 2868.7 ng·h/mL, and 18 patients achieved the target AUC (1447.8 ± 545.4 ng·h/mL). Three patients experienced S-1-related grade 3 adverse events during the first course. In the population pharmacokinetic analysis from the combined data of 46 patients in this study and the previous study, sex was identified as a statistically significant covariate for 5-FU clearance. Hence, the refined formula includes sex as an additional factor: Recommended daily dose = target AUC × (14.5 + 8.23 × SEX [0 for female and 1 for male] + 0.301 × CLcr) × BSA. Revised nomograms for recommended daily doses derived from the refined formula can be used in clinical practice to achieve the target AUC ensuring efficacy and safety of S-1.

Prediction of Fracture Risk From Early-Stage Bone Markers in Patients With Osteoporosis Treated With Once-Yearly Administered Zoledronic Acid.

The prevention of fractures is the ultimate goal of osteoporosis treatments. To achieve this objective, developing a method to predict fracture risk in the early stage of osteoporosis treatment would be clinically useful. This study aimed to develop a mathematical model quantifying the long-term fracture risk after 2 annual doses of 5 mg of once-yearly administered zoledronic acid or placebo based on the short-term measurement of bone turnover markers or bone mineral density (BMD). The data used in this analysis were obtained from a randomized, placebo-controlled, double-blind, 2-year study of zoledronic acid that included 656 patients with primary osteoporosis. Two-year individual bone resorption marker (tartrate-resistant acid phosphatase 5b [TRACP-5b]) and lumbar spine (L2-L4) BMD profiles were simulated using baseline values and short-term measurements (at 3 months for TRACP-5b and 6 months for BMD) according to the pharmacodynamic model. A new parametric time-to-event model was developed to describe the risk of clinical fractures. Fracture risk was estimated using TRACP-5b or BMD and the number of baseline vertebral fractures. As a result, the fracture risk during the 2 years was successfully predicted using TRACP-5b or BMD. The 90% prediction intervals well covered the observed fracture profiles in both models. Therefore, TRACP-5b or BMD is useful to predict the fracture risk of patients with osteoporosis, and TRACP-5b would be more useful because it is an earlier marker. Importantly, the developed model allows clinicians to inform patients of their predicted response at the initial stage of zoledronic acid treatment.

Population Pharmacokinetics of Voriconazole in Patients With Invasive Aspergillosis: Serum Albumin Level as a Novel Marker for Clearance and Dosage Optimization.

BACKGROUND: Voriconazole (VRCZ) is an antifungal triazole recommended as an effective first-line agent for treating invasive aspergillosis. OBJECTIVES: To develop a population pharmacokinetic model of VRCZ and trough concentration-based dosing simulation for dynamic patient conditions. METHODS: The authors combined plasma VRCZ data from intensive sampling, and retrospective trough concentration monitoring for analysis. Nonlinear mixed-effects modeling with subsequent model validation was performed. The recommended dosage regimens were simulated based on the developed model. RESULTS: The study participants included 106 patients taking oral VRCZ. A linear one-compartment model with first-order elimination and absorption best described the observed data. The CYP2C19 phenotypes did not influence the pharmacokinetic parameters. Serum albumin (SA) levels and gamma-glutamyl transferase significantly correlated with the VRCZ clearance rate, whereas the actual body weight influenced the volume. A visual predictive check showed good consistency with the observed data, whereas SA levels across the treatment course correlated with linear clearance, irrespective of the CYP2C19 phenotype. Patients with SA levels ≤30 g/L had lower linear clearance than that in patients with SA levels >30 g/L. Dosing simulation based on the developed model indicated that patients with SA levels of ≤30 g/L required a lower daily maintenance dose to attain the therapeutic trough level. CONCLUSIONS: SA level was identified as a novel marker associated with VRCZ clearance. This marker may be a practical choice for physicians to perform therapeutic drug monitoring and optimize VRCZ dosage.

Pharmacokinetic and pharmacodynamic analysis of neutropenia following nab-paclitaxel administration in Japanese patients with metastatic solid cancer.

PURPOSE: To develop a pharmacokinetic (PK) and pharmacodynamic (PD) model for neutropenia following nab-paclitaxel administration and identify factors associated with drug disposition and changes in neutrophil counts in patients with solid cancer. METHODS: PK/PD analysis by nonlinear mixed effects approach was performed using the data from 27 patients who participated in phase I studies of nab-paclitaxel monotherapy conducted in Japan. The patients were treated with either weekly (80, 100, or 125 mg/m2) or every 3 weeks (200, 260, or 300 mg/m2). The observed paclitaxel concentrations in whole blood and neutrophil counts in the first cycle were used for PK/PD analysis. Covariate analysis was performed to identify factors affecting PK and the decrease in neutrophil counts. RESULTS: The developed 3-compartment, non-linear PK model described relationships of body surface area with total body clearance and volume of distribution for the peripheral compartment. Covariate factors affecting neutrophil counts were age and serum albumin level. Simulation based on the developed PK/PD model showed a substantial impact of age and serum albumin level on the time course of neutrophil counts after nab-paclitaxel administration. Advanced age was related to greater decrease in neutrophil counts, and serum albumin level, inversely related to change in neutrophil counts. CONCLUSION: We have developed a novel PK/PD model for nab-paclitaxel in which age and serum albumin level were considered clinically important covariate factors. This model needs to be further validated using a larger patient population.

Evaluation of gefitinib systemic exposure in EGFR-mutated non-small cell lung cancer patients with gefitinib-induced severe hepatotoxicity.

PURPOSE: Severe hepatotoxicity induced by the standard dose of gefitinib (250 mg daily) often becomes manageable by dose reduction to 250 mg every other day. Thus, we hypothesized that systemic exposure of standard-dose gefitinib in patients with experience of severe hepatotoxicity might be higher than that in patients without severe hepatotoxicity. METHODS: Patients with advanced epidermal growth factor receptor-mutated non-small cell lung cancer who were receiving gefitinib either at a reduced dose (250 mg every other day) because of intolerable severe toxicity or at a standard dose (250 mg daily) were enrolled. A series of blood samples were collected to estimate pharmacokinetic parameters and calculate systemic exposure of standard-dose gefitinib (area under the concentration-time curve from 0 to 24 h at steady state, AUC0-24,ss). Systemic exposure of unbound gefitinib (fu·AUC0-24,ss) was also assessed, because gefitinib is extensively bound to serum proteins. RESULTS: Of the 38 enrolled patients, 34 (23 patients without experience of severe hepatotoxicity, 11 patients with experience of severe hepatotoxicity) were evaluable. There was no significant differences in total AUC0-24,ss or unbound fu·AUC0-24,ss between patients with and without experience of severe hepatotoxicity. Analysis of the time to severe hepatotoxicity indicated no difference between patients with a high AUC0-24,ss and those with a low AUC0-24,ss of either total or unbound gefitinib. CONCLUSION: This study suggests that reversible severe hepatotoxicity is not caused by high systemic exposure of gefitinib.

CYP2D6 Genotype-Guided Tamoxifen Dosing in Hormone Receptor-Positive Metastatic Breast Cancer (TARGET-1): A Randomized, Open-Label, Phase II Study.

PURPOSE: In patients taking tamoxifen, the CYP2D6 genotype causes different exposure of active metabolite endoxifen. The objective of this randomized, open-label, multicenter, phase II study was to prospectively evaluate whether CYP2D6 genotype-guided tamoxifen dosing in patients with hormone receptor-positive metastatic breast cancer could have an impact on the clinical outcome. METHODS: Patients who needed first-line tamoxifen therapy were enrolled. Based on individual CYP2D6 genotype, patients heterozygous (wild type [wt]/variant [V]) or homozygous (V/V) for variant alleles of decreased or no function were randomly assigned to receive tamoxifen at an increased dose (ID arm; 40 mg daily) or regular dose (RD arm; 20 mg daily), and patients homozygous for wild-type alleles (wt/wt) received tamoxifen at 20 mg daily. The primary endpoint was the progression-free survival (PFS) rate at 6 months. The secondary endpoints included PFS and correlation of Z-endoxifen concentration with clinical outcomes. RESULTS: Between December 2012 and July 2016, 186 patients were enrolled in Japan. Of 184 evaluable patients, 136 carried wt/V or V/V (ID arm, 70; RD arm, 66), and 48 carried wt/wt. PFS rates at 6 months were not significantly different between the ID and RD arms (67.6% v 66.7%). The serum trough concentrations of Z-endoxifen in the ID arm were significantly higher than those in the RD arm (median, 89.2 nM v 51.1 nM; P < .0001) and were also higher compared with wt/wt patients (72.0 nM; P = .045). No significant difference in Z-endoxifen concentrations was observed between patients with disease progression and those who were progression free at 6 months (P = .43). CONCLUSION: In patients with CYP2D6-variant alleles, increasing tamoxifen dosing did not achieve a higher PFS rate at 6 months. The CYP2D6 genotype solely cannot explain individual variability in the efficacy of tamoxifen.

Cerebrospinal pharmacokinetic and pharmacodynamic analysis of efficacy of meropenem in paediatric patients with bacterial meningitis.

BACKGROUND: Meropenem is widely used for the treatment of paediatric patients with bacterial meningitis, but the pharmacodynamic (PD) basis for this has not been fully elucidated. OBJECTIVES: A cerebrospinal pharmacokinetic (PK) and PD analysis was performed to identify the optimal dosage regimen for paediatric patients with inflamed central nervous system disease (bacterial men-ingitis). PATIENTS AND METHODS: Paediatric data from three clinical studies were used to build a novel population PK model with a cerebrospinal fluid (CSF) compartment, assuming CSF clearance of 0.021 L/h from a physical-anatomical perspective. The bactericidal target attainment rates in CSF [50%T>MIC(CSF)], after various dosage regimens, were simulated on the basis of reported or observed minimum inhibitory concentration (MIC) distributions and a newly developed population PK model including CSF concentrations. The effects of increased dose and/or prolonged infusion on target attainment were investigated. RESULTS: Clinical data from 154 patients {mean age 30.6 [standard deviation (SD) 34.4] months, mean body weight 12.4 (SD 7.6) kg} were used for the population PK analysis. The flat profile of the CSF concentration-time curve and attainment of 50%T>MIC(CSF) did not change markedly when the duration of infusion was increased, whereas attainment of 50%T>MIC(CSF) was improved by increasing the dose from 20 to 40 mg/kg q8h for penicillin-resistant Streptococcus pneumoniae and Pseudomonas aeruginosa. Thirty-six patients who achieved satisfactory clinical cure showed at least 75.3%T>MIC(CSF). CONCLUSIONS: A high dose of meropenem (40 mg/kg q8h) is necessary to achieve clinical efficacy in paediatric patients with bacterial meningitis.

Gefitinib exposure and occurrence of interstitial lung disease in Japanese patients with non-small-cell lung cancer.

PURPOSE: A prospective, multicenter, large-scale cohort with a nested case-control study (NCT00252759) was conducted to identify and quantify risk factors for interstitial lung disease (ILD) in Japanese patients with non-small-cell lung cancer who received gefitinib. This study reports the association between gefitinib exposure and the occurrence of ILD. METHODS: A total of 1891 gefitinib plasma concentrations from 336 patients were measured after first dose, at steady state, and at time of ILD occurrence. Influences of demographic and pathophysiological factors on pharmacokinetics were investigated by non-linear mixed-effect modeling. The exposure to gefitinib was compared between patients without and with ILD occurrence to explore risks associated with gefitinib-induced ILD. Intra-patient comparison of exposure was also conducted between times at ILD development and normal states. RESULTS: In the population pharmacokinetic analysis for gefitinib, α1-acid glycoprotein (AGP), age, body weight, and concomitant use of cytochrome P450 3A4 inducers were significant covariates on oral clearance (CL/F). AGP and body weight were also identified as factors affecting the volume of distribution. CL/F was significantly lower at the time of ILD occurrence than normal states. Patients who developed ILD tended to show higher exposure to gefitinib than those without ILD; however, these differences were not statistically significant. On the other hand, exposure at the time of ILD occurrence was significantly elevated compared to the time of normal state within the same patients. CONCLUSIONS: Significant elevation of exposure of gefitinib was observed at the time of ILD occurrence, suggesting reduction of CL/F could be associated with ILD-induced AGP elevation. Increase in exposure of gefitinib is unlikely to be a robust predictor of ILD and does not warrant any dose modifications.

Therapeutic Drug Monitoring in Oncology: International Association of Therapeutic Drug Monitoring and Clinical Toxicology Recommendations for 5-Fluorouracil Therapy.

5-Fluorouracil (5-FU) is dosed by body surface area, a practice unable to reduce the interindividual variability in exposure. Endorsed by the International Association of Therapeutic Drug Monitoring and Clinical Toxicology (IATDMCT), we evaluated clinical evidence and strongly recommend TDM for the management of 5-FU therapy in patients with colorectal or head-and-neck cancer receiving common 5-FU regimens. Our systematic methodology provides a framework to evaluate published evidence in support of TDM recommendations in oncology.

Individualized Dosing of Axitinib Based on First-Dose Area Under the Concentration-Time Curve for Metastatic Renal-Cell Carcinoma.

BACKGROUND: Previous studies have revealed that higher exposure of axitinib leads to better prognosis in metastatic renal-cell carcinoma. We thus assessed individualized dosing of axitinib on the basis of the first-dose area under the concentration-time curve from 0 to 12 hours (AUC0-12) for sunitinib-pretreated metastatic renal-cell carcinoma patients. PATIENTS AND METHODS: In this prospective single-arm trial, the starting dose of axitinib was 5 mg twice daily. A series of blood samples were taken at predetermined times after the first dose to calculate AUC0-12. On day 15 of axitinib administration, the dose was adjusted to ensure ≥ 150 ng·h/mL AUC0-12 at steady state according to first-dose AUC0-12. The primary end point was the 6-month progression-free survival rate. RESULTS: Twenty-six Japanese patients were enrolled. The median recommended dose based on the first-dose AUC0-12 was 2.5 mg (range, 1-16 mg) twice daily. The 6-month progression-free survival rate for all enrolled patients and per-protocol set, from which 3 patients were excluded for not adjusting to the recommended dose on day 15, was 84.6% (95% confidence interval, 65.5-94.1) and 82.6% (95% confidence interval, 61.8-93.3), respectively. The most common nonhematologic adverse events were hypertension, hand-foot syndrome, fatigue, and decreased appetite. Eighteen patients (75%) developed grade 3 hypertension; however, actual blood pressure could be controlled using antihypertensive agents. Other adverse events were manageable during the protocol treatment. CONCLUSION: Individualized dosing of axitinib based on the first-dose AUC0-12 might have promising efficacy and manageable toxicity.

Pharmacodynamic analysis of eribulin safety in breast cancer patients using real-world postmarketing surveillance data.

Postmarketing surveillance is useful to collect safety data in real-world clinical settings. In this study, we applied postmarketing real-world data on a mechanistic model analysis for neutropenic profiles of eribulin in patients with recurrent or metastatic breast cancer. Demographic and safety data were collected using an active surveillance method from eribulin-treated recurrent or metastatic breast cancer patients. Changes in neutrophil counts over time were analyzed using a mechanistic pharmacodynamic model. Pathophysiological factors that might affect the severity of neutropenia were investigated, and neutropenic patterns were simulated for different treatment schedules. Clinical and laboratory data were collected from 401 patients (5199 neutrophil count measurements) who had not received granulocyte colony-stimulating factor and were eligible for pharmacodynamic analysis. The estimated mean parameters were as follows: mean transit time = 104.5 h, neutrophil proliferation rate constant = 0.0377 h-1 , neutrophil elimination rate constant = 0.0295 h-1 , and linear coefficient of drug effect = 0.0413 mL/ng. Low serum albumin levels and low baseline neutrophil counts were associated with severe neutropenia. The probability of grade ≥3 neutropenia was predicted to be 69%, 27%, and 27% for patients on standard, biweekly, and triweekly treatment scenarios, respectively, based on virtual simulations using the developed pharmacodynamic model. In conclusion, this is the first application of postmarketing surveillance data to a model-based safety analysis. This analysis of safety data reflecting authentic clinical settings will provide useful information on the safe use and potential risk factors of eribulin.

Application of PBPK Modeling and Virtual Clinical Study Approaches to Predict the Outcomes of CYP2D6 Genotype-Guided Dosing of Tamoxifen.

The Tamoxifen Response by CYP2D6 Genotype-based Treatment-1 (TARGET-1) study (n = 180) was conducted from 2012-2017 in Japan to determine the efficacy of tamoxifen dosing guided by cytochrome P450 2D6 (CYP2D6) genotypes. To predict its outcomes prior to completion, we constructed the comprehensive physiologically based pharmacokinetic (PBPK) models of tamoxifen and its metabolites and performed virtual TARGET-1 studies. Our analyses indicated that the expected probability to achieve the end point (demonstrating the superior efficacy of the escalated tamoxifen dose over the standard dose in patients carrying CYP2D6 variants) was 0.469 on average. As the population size of this virtual clinical study (VCS) increased, the expected probability was substantially increased (0.674 for n = 260). Our analyses also informed that the probability to achieve the end point in the TARGET-1 study was negatively impacted by a large variability in endoxifen levels. Our current efforts demonstrate the promising utility of the PBPK modeling and VCS approaches in prospectively designing effective clinical trials.

Clinical Factors Predicting Detection of T790M Mutation in Rebiopsy for EGFR-Mutant Non-small-cell Lung Cancer.

BACKGROUND: T790M, a secondary epidermal growth factor receptor (EGFR) mutation, accounts for approximately 50% of acquired resistance to EGFR-tyrosine kinase inhibitors (TKIs). To facilitate the use of third-generation EGFR-TKIs to potentially overcome T790M-mediated resistance, we evaluated the clinical factors influencing the incidence of T790M mutation. PATIENTS AND METHODS: We retrospectively screened patients with non-small-cell lung cancer harboring EGFR mutations with progressive disease who were rebiopsied between January 2013 and December 2016. Factors influencing T790M status were evaluated by univariate and multivariate analysis. RESULTS: Among 131 rebiopsied patients for whom EGFR mutation status was available, 58 (44%) had T790M mutations. Patient characteristics at rebiopsy were not significantly different between T790M-positive and -negative groups, except for surgical history (postsurgery recurrence). Total duration of EGFR-TKI treatment before rebiopsy, TKI-free interval, EGFR-TKI treatment history immediately before rebiopsy, continuation of initial EGFR-TKI beyond progressive disease, progression-free survival after initial TKI treatment, and rebiopsy site (other than fluid samples) significantly influenced T790M status. The incidence of T790M mutation was shown by multivariate analysis to be significantly higher in patients with postsurgery recurrence and total duration of EGFR-TKI treatment ≥ 1 year before rebiopsy (odds ratio, 4.2; 95% confidence interval, 1.3-15.7 and odds ratio, 4.4; 95% confidence interval, 1.1-19.8, respectively). CONCLUSION: Postsurgery recurrence and longer total duration of EGFR-TKI treatment before rebiopsy may represent useful predictive markers for T790M detection. In patients with these clinical factors, rebiopsies are more recommended to detect T790M mutation.

Effect of everolimus on the glucose metabolic pathway in mouse skeletal muscle cells (C2C12).

INTRODUCTION: Everolimus selectively inhibits mammalian target of rapamycin complex 1 (mTORC1) and exerts an antineoplastic effect. Metabolic disturbance has emerged as a common and unique side effect of everolimus. OBJECTIVES: We used targeted metabolomic analysis to investigate the effects of everolimus on the intracellular glycometabolic pathway. METHODS: Mouse skeletal muscle cells (C2C12) were exposed to everolimus for 48 h, and changes in intracellular metabolites were determined by capillary electrophoresis time-of-flight mass spectrometry. mRNA abundance, protein expression and activity were measured for enzymes involved in glycometabolism and related pathways. RESULTS: Both extracellular and intracellular glucose levels increased with exposure to everolimus. Most intracellular glycometabolites were decreased by everolimus, including those involved in glycolysis and the pentose phosphate pathway, whereas no changes were observed in the tricarboxylic acid cycle. Everolimus suppressed mRNA expression of enzymes related to glycolysis, downstream of mTOR signaling enzymes and adenosine 5'-monophosphate protein kinases. The activity of key enzymes involved in glycolysis and the pentose phosphate pathway were decreased by everolimus. These results show that everolimus impairs glucose utilization in intracellular metabolism. CONCLUSIONS: The present metabolomic analysis indicates that everolimus impairs glucose metabolism in muscle cells by lowering the activities of glycolysis and the pentose phosphate pathway.

Population Pharmacokinetics of Diazoxide in Children with Hyperinsulinemic Hypoglycemia.

BACKGROUND: Diazoxide is the first-line treatment for pediatric hyperinsulinemic hypoglycemia (HI). This study aimed to elucidate the pharmacokinetics of diazoxide in children with HI. METHODS: We obtained 81 blood samples from 22 children with HI. Measured serum diazoxide concentrations were used for population pharmacokinetic analysis. Patient factors influencing pharmacokinetics were estimated using nonlinear mixed-effects model analysis. Relationships between drug exposure and adverse drug reactions were also investigated. RESULTS: Diazoxide disposition in the body was described by a 1-compartment model. Oral clearance (CL/F) and the volume of distribution were proportional to body weight (WT), as expressed by CL/F in males (liters/h) = 0.0358 + 0.00374 × WT (kg). CL/F in females was 39% greater than that in males. Steady-state concentrations of diazoxide were similar following twice- and 3 times-daily dosing when the total daily doses were comparable. A patient whose serum diazoxide concentration exceeded 100 µg/mL over a 4-month period developed hyperglycemia. No significant correlation was observed between severity of hirsutism and diazoxide concentration. CONCLUSION: We have proposed for the first time a population pharmacokinetic model for diazoxide in children with HI. The potential risk of diabetes mellitus and/or hyperglycemia increases when serum concentrations of diazoxide exceed 100 µg/mL.