Therapeutic Drug Monitoring in Oncology No abstract available

Pharmacokinetics of Anticancer Drugs Used in Treatment of Older Adults With Colorectal Cancer: A Systematic Review Purpose: Older adults with cancer experience more toxicity from anticancer therapy, possibly because of age-related changes in the pharmacokinetic (PK) profile of anticancer drugs. We aimed to evaluate studies investigating the effect of aging on the PK of anticancer therapies used in the treatment of colorectal cancer (CRC). Methods: A systematic literature search of EMBASE and PubMed was performed to find eligible studies that assessed the effect of age on the PK of anticancer therapies used in the treatment of CRC. Results: The 21 eligible studies included 17 prospective studies and 4 pooled analyses of prospective studies. Of these, PK of 5-fluorouracil (5-FU) was determined in 7 studies, oxaliplatin in 2 studies, capecitabine in 3 studies, irinotecan in 4 studies, bevacizumab in 1 study, cetuximab in 3 studies, and panitumumab in 1 study. Studies included a median of 44 patients and had varying definitions for older adults: 65 years or older (3 studies), older than 70 years (3 studies), or older than 75 years (1 study). Increasing age significantly affected the PK parameters of irinotecan with a 7%–8% reduction in CL (P < 0.001) for every 10 years in patients older than 60 years and an increase in area under the curve (r = 0.44, P = 0.007) and Cmax (r = 0.42, P = 0.009). Conclusions: Older age mainly influences PK of irinotecan and, to some extent, that of capecitabine, 5-FU, and panitumumab, but there is limited evidence for age-related changes in PK of other anticancer therapies used in the management of older adults with CRC. Factors other than PK may be responsible for the greater toxicity of these agents experienced by older adults.

Therapeutic Drug Monitoring of Oral Anticancer Drugs: The Dutch Pharmacology Oncology Group–Therapeutic Drug Monitoring Protocol for a Prospective Study Background: Oral anticancer drugs show a high interpatient variability in pharmacokinetics (PK), leading to large differences in drug exposure. For many of these drugs, exposure has been linked to efficacy and toxicity. Despite this knowledge, these drugs are still administered in a one-size-fits-all approach. Consequently, individual patients have a high probability to be either underdosed, which can lead to decreased antitumor efficacy, or overdosed, which could potentially result in increased toxicity. Therapeutic drug monitoring (TDM), personalized dosing based on measured drug levels, could be used to circumvent underdosing and overdosing and thereby optimize treatment outcomes. Methods: In this prospective clinical study (www.trialregister.nl; NL6695), the feasibility, tolerability, and efficacy of TDM of oral anticancer drugs will be evaluated. In total, at least 600 patients will be included for (at least) 23 different compounds. Patients starting regular treatment with one of these compounds at the approved standard dose can be included. PK sampling will be performed at 4, 8, and 12 weeks after the start of treatment and every 12 weeks thereafter. Drug concentrations will be measured, and trough concentrations (Cmin) will be calculated. In cases where Cmin falls below the predefined target and acceptable toxicity, a PK-guided intervention will be recommended. This could include emphasizing compliance, adapting concomitant medication (due to drug–drug interactions), instructing to take the drug concomitant with food, splitting intake moments, or recommending a dose increase. Discussion: Despite a strong rationale for the use of TDM for oral anticancer drugs, this is currently not yet widely adopted in routine patient care. This prospective study will be a valuable contribution to demonstrate the additional value of dose optimization on treatment outcome for these drugs.

Therapeutic Drug Monitoring of Everolimus in Oncology: Evidences and Perspectives Abstract: Everolimus is a mammalian target of rapamycin (m-TOR) inhibitor that has been approved for the treatment of hormone receptor-positive advanced breast cancer, metastatic renal cancer, and neuroendocrine tumors. Although therapeutic drug monitoring (TDM) of everolimus is well established in the transplantation field, it is not currently performed in oncology. The last consensus conference about the TDM of everolimus states that for the use of everolimus in oncology, “further studies are required to determine the clinical utility of TDM for everolimus in oncology settings.” In this review, the authors will discuss the current evidences and perspectives, based on observational studies available, in favor of the TDM of everolimus in oncology focusing on (1) the management of everolimus in routine practice, (2) the prerequisites for TDM of everolimus in oncology, (3) the pharmacodynamics (including a description of the biomarker of resistance and mutations in m-TOR), and (4) a general outlook.

Evaluation of Medication Adherence and Pharmacokinetics of Dasatinib for Earlier Molecular Response in Japanese Patients With Newly Diagnosed Chronic Myeloid Leukemia: A Pilot Study Background: Tyrosine kinase inhibitors markedly improve the survival for patients with chronic myeloid leukemia (CML). However, a decrease in adherence leads to undesired therapeutic outcomes. In this study, the relationships among adherence, pharmacokinetics, response, and adverse effects for dasatinib treatment were prospectively investigated. Methods: This study was a prospective cohort study of patients with newly diagnosed CML at 4 general hospitals and 1 university hospital. Patients started to receive dasatinib 100 mg once daily. A Medication Event Monitoring System was used to assess medication adherence and the medication possession ratio during the 12 months. Plasma concentrations of dasatinib were measured using liquid chromatograph-tandem mass spectrometry (LC-MS/MS), and therapy responses were assessed at 3, 6, and 12 months after treatment. Results: Ten patients were included. An extremely high medication adherence for dasatinib was observed; the median medication possession ratio was 99.4%. All 9 CML patients with breakpoints in the major BCR-ABL achieved major molecular response (MMR; major BCR-ABL transcript level below 0.1% on the International Scale) within 12 months, and 5 achieved MMR within 6 months. The receiver operating characteristic curve analysis revealed that the cutoff value for the dasatinib area under the concentration–time curve was 336.1 ng × h/mL (accuracy 88.9%, sensitivity 80.0%, specificity 100%, and receiver operating characteristic curve–area under the concentration–time curve 0.800) for achieving MMR within 6 months. Two patients had interrupted dasatinib treatment because of pleural effusion and diarrhea with intestinal edema, respectively. These edematous adverse events developed after plasma dasatinib Cmin surpassed 3.0 ng/mL. Conclusions: A Medication Event Monitoring System was applied for the direct evaluation of oral dasatinib adherence for the first time, and the clinical effect of dasatinib was investigated under the strict monitoring of patient adherence. Although this study had a small sample size, the plasma concentration monitoring of dasatinib is considered to be useful to predict an earlier molecular response with fewer edematous adverse events.

Association of Hepatic Nuclear Factor 4 Alpha Gene Polymorphisms With Free Imatinib Plasma Levels and Adverse Reactions in Chinese Gastrointestinal Stromal Tumor Patients Background: As the first-line treatment of gastrointestinal stromal tumor (GIST), the pharmacokinetic and pharmacodynamic of imatinib (IM) were characterized by marked interindividual variability. Pharmacogenetics of IM involved metabolic enzymes and transporters have been extensively reported, but the results remained inconsistent. This study investigated the effect of genetic variants in hepatocyte nuclear factor 4 alpha (HNF4α, encoded by gene NR2A1), a pivotal transcriptional regulator of drug disposition genes, on dose-adjusted IM-free plasma levels and related adverse reactions in Chinese GIST patients. Methods: Five common polymorphisms of NR2A1 (rs3818247, rs1884613, rs2071197, rs2425640, and rs736824) were genotyped in 70 Chinese GIST patients who had been administered IM 300–600 mg/d. The free IM trough plasma levels were determined based on a method of ultrafiltration coupled with high performance liquid chromatography-tandem mass spectrometry. Results: There were wide interpatient variations in free plasma levels of IM (range, 9.50–67.50 ng/mL), in which significant sex differences were observed (P < 0.01). The dose-adjusted IM-free plasma levels showed a significant negative correlation with body surface area (r = −0.302, P = 0.012). Although there were no significant effects of NR2A1 polymorphisms on dose-adjusted IM-free plasma levels among the study population, polymorphism in rs736824 was found to be significantly associated with dose-adjusted IM-free plasma levels in male subjects (P = 0.031). For the IM-related adverse reaction, polymorphisms in rs3818247 were found to be significantly associated with periorbital edema (P = 0.032). In addition, no significant correlations were found between IM-free plasma levels and IM-related adverse reactions, except for the correlation of IM-free plasma levels with periorbital edema among male patients (P = 0.013). Conclusions: The research demonstrated that NR2A1 polymorphisms may act as contributors of IM pharmacokinetics and responses in Chinese GIST patients. This represents an attractive opportunity for IM therapy optimization, worth testing in clinical trials.

Impact of Cachexia and Opioid Analgesic Cotreatment on Pregabalin Pharmacokinetics and Central Nervous System Symptoms in Cancer Patients Background: Patients with cancer receiving pregabalin potentially have a high incidence of central nervous system (CNS) symptoms. The purpose of this study was to explore clinical factors influencing the incidence of CNS symptoms, including plasma pregabalin exposure, cancer cachexia, and opioid analgesic cotreatment. Methods: Sixty-eight patients with cancer receiving twice-daily pregabalin were enrolled. Plasma concentrations of pregabalin, clinical laboratory data, opioid analgesic cotreatment, and the Glasgow Prognostic Score, which is an inflammation-based cachexia score, were considered as clinical factors. The incidence of CNS symptoms was collected from the patients' medical records. The predose plasma concentrations of pregabalin at steady state were determined by ultra-high-performance liquid chromatography. Results: The steady-state trough plasma pregabalin concentrations showed a large variability with an interquartile range of 0.43–1.2 mg/L per mg/kg and were negatively correlated with an estimated glomerular filtration rate (eGFR). C-reactive protein (standardized partial regression coefficient, β = 0.31) and opioid analgesic cotreatment (β = 0.24) were also identified in addition to eGFR (β = −0.60) in the multiple regression analysis. The incidence of CNS symptoms was significantly increased with opioid analgesic cotreatment and a higher Glasgow Prognostic Score but not with the absolute value of plasma pregabalin concentrations, eGFR, or other clinical laboratory data. Conclusions: In patients with cancer, steady-state trough plasma pregabalin concentrations were altered with renal function, systemic inflammation, and opioid analgesic cotreatment. However, a higher incidence of CNS symptoms observed in patients with cancer on pregabalin was more related to cachexia and opioid analgesic cotreatment than to altered pregabalin concentrations.

Development and Validation of a Sensitive UHPLC-MS/MS–Based Method for the Analysis of Folylpolyglutamate Synthetase Enzymatic Activity in Peripheral Blood Mononuclear Cells: Application in Rheumatoid Arthritis and Leukemia Patients Background: Folylpolyglutamate synthetase (FPGS) is a crucial enzyme in both cellular folate homeostasis and the intracellular retention of folate analogue drugs such as methotrexate (MTX), which is commonly used for the treatment of (pediatric) leukemia and the anchor drug in rheumatoid arthritis (RA) treatment. To date, assessment of FPGS catalytic activity relies on assays using radioactive substrates that are labor-intensive and require relatively large numbers of cells. Here, we describe a nonradioactive, ultra–high-performance liquid chromatography–tandem mass spectrometer (UHPLC-MS/MS)–based method allowing for sensitive and accurate measurements of FPGS activity in low cell numbers (ie, 1–2 × 106) of biological specimens, including leukemic blast cells of acute lymphoblastic leukemia patients and peripheral blood mononuclear cells of patients with RA. Methods: The UHPLC-MS/MS assay was validated with 2 CCRF-CEM human leukemia cells, one proficient and one deficient in FPGS activity. Linearity of time and protein input were tested by measuring FPGS activity at 30–180 minutes of incubation time and 10–300 mcg protein extract. In addition, FPGS enzyme kinetic parameters were assessed. Results: The FPGS enzymatic assay showed a linear relation between FPGS activity and protein input (R2 ≥ 0.989) as well as incubation time (R2 ≥ 0.996). Moreover, the UHPLC-MS/MS method also allowed for evaluation of FPGS enzyme kinetic parameters revealing Km values for the substrates MTX and L-glutamic acid of 64 µmol/L and 2.2 mmol/L, respectively. The mean FPGS activity of acute lymphoblastic leukemia blast cells (n = 4) was 3-fold higher than that of CCRF-CEM cells and 44-fold and 88-fold higher than that of peripheral blood mononuclear cells from MTX-naive (n = 9) and MTX-treated RA patients (n = 6), respectively. Conclusions: Collectively, given its sensitivity with low cell numbers and avoidance of radioactive substrates, UHPLC-MS/MS–based analysis of FPGS activity may be eligible for routine therapeutic drug monitoring of MTX in RA and leukemia for therapy (non)response evaluations.

Tacrolimus Can Be Reliably Measured With Volumetric Absorptive Capillary Microsampling Throughout the Dose Interval in Renal Transplant Recipients Background: Therapeutic drug monitoring is standard practice for the immunosuppressant tacrolimus (Tac). Venous blood sampling at outpatient clinics is time-consuming and impractical with regard to obtaining trough concentrations on clinical visit days. Home-based blood sampling may be patient friendly and pave the way for limited sampling strategies for the prediction of total drug exposure. The aim was to establish a Tac assay for dried capillary microsamples, ensuring reliable measurements during the full dose interval in renal transplant recipients. Methods: An assay based on volumetric absorptive microsampling and liquid chromatography tandem mass spectrometry was validated. The agreement between capillary microsamples and liquid venous samples was investigated in stable renal recipients on twice-daily Tac dosing. Sampling throughout the 12-hour dose interval was examined at 2 separate days, at least 1 week apart, for each participant. Two sets of samples were obtained at each time point, one delivered directly to the laboratory and one sent through mail. Results: Twenty-seven renal transplant recipients were included, of whom 26 were investigated twice. Tac was efficiently extracted from the dried microsamples (mean recovery 94%–103%). The between-series mean accuracy was 88%–98% with coefficients of variation ≤5.0% (≤11% at the lower limit of quantification), measurement range 0.70–60 mcg/L. The mean difference between parallel microsamples was 5%–7%. Overall, the mean differences between dried microsamples and liquid samples were −3.1% when mailed (n = 679) and −4.2% when directly delivered (n = 682). Less than 8% were outside ±20%. The microsamples were stable for 1 month at ambient temperature. Conclusions: The microsample method demonstrated acceptable performance. Tac concentrations can be reliably quantified throughout the dose interval by using volumetric absorptive microsampling in renal transplant recipients, and the results are not influenced by postal shipment.

Estimation of Blood Sirolimus Concentration Based on Tacrolimus Concentration/Dose Normalized by Body Weight Ratio in Lung Transplant Patients Background: Sirolimus and tacrolimus require accurate drug dosing based on their target blood levels to produce better clinical outcomes, specifically, the avoidance of drug-induced adverse effects and the maintenance of efficacy. However, because the ideal dose of sirolimus and the schedule for measuring its blood levels are unclear in lung transplant patients, an index is required for estimating sirolimus blood concentrations. The aim of this work is to study the correlation between the trough concentration/dose normalized by body weight (C0/D) ratios of sirolimus and tacrolimus in lung transplant patients. Methods: Thirteen lymphangiomyomatosis patients who underwent lung transplantation and were treated with sirolimus and tacrolimus from February 2015 to July 2018 were divided into 2 groups, one receiving twice-daily (TD, n = 6) and the other once-daily (OD, n = 7) tacrolimus formulations. The correlation between the C0/D ratio of sirolimus and patient background was evaluated using Spearman's rank correlation coefficient. Correlations between sirolimus and tacrolimus C0/D ratios or doses were analyzed by single regression analysis. Results: Significant correlations were found between the C0/D ratios of sirolimus and tacrolimus. The regression equations from the initial data of TD and OD groups at steady state were y = 1.880x + 32.636 (adjusted R2 = 0.743, P = 0.017) and y = 1.684x + 38.816 (adjusted R2 = 0.919, P < 0.001), respectively. In addition, the regression equations from all data of TD and OD groups were y = 1.883x + 4.170 (adjusted R2 = 0.546, P < 0.001) and y = 1.950x + 43.188 (adjusted R2 = 0.898, P < 0.001), respectively. A significant correlation between the dosage of sirolimus and tacrolimus was observed only in the OD group, with relatively low accuracy. Conclusions: Blood sirolimus concentrations can be estimated using the C0/D ratio of tacrolimus, suggesting that the C0/D ratio of tacrolimus is an index of required sirolimus dosage and the frequency of blood sirolimus concentration measurements.