The Population Pharmacokinetics of High-Dose Methotrexate in Infants with Acute Lymphoblastic Leukemia Highlight the Need for Bedside Individualized Dose Adjustment: A Report from the Children's Oncology Group

Population pharmacokinetic analyses of methotrexate in pediatric patients: a systematic review

BACKGROUND AND OBJECTIVES

Methotrexate is widely utilized in the chemotherapy of malignant tumors and autoimmune diseases in the pediatric population, but dosing can be challenging. Several population pharmacokinetic models were developed to characterize factors influencing variability and improve individualization of dosing regimens. However, significant covariates included varied across studies. The primary objective of this review was to summarize and discuss population pharmacokinetic models of methotrexate and covariates that influence pharmacokinetic variability in pediatric patients.

METHODS

Systematic searches were conducted in the PubMed and EMBASE databases from inception to 7 July 2023. Reporting Quality was evaluated based on a checklist with 31 items. The characteristics of studies and information for model construction and validation were extracted, summarized, and discussed.

RESULTS

Eighteen studies (four prospective studies and fourteen retrospective studies with sample sizes of 14 to 772 patients and 2.7 to 93.1 samples per patient) were included in this study. Two-compartment models were the commonly used structural models for methotrexate, and the clearance range of methotrexate ranged from 2.32 to 19.03 L/h (median: 6.86 L/h). Body size and renal function were found to significantly affect the clearance of methotrexate for pediatric patients. There were limited reports on the role of other covariates, such as gene polymorphisms and co-medications, in the pharmacokinetic parameters of methotrexate pediatric patients. Internal and external evaluations were used to assess the performance of the population pharmacokinetic models.

CONCLUSION

A more rigorous external evaluation needs to be performed before routine clinical use to select the appropriate PopPK model. Further research is necessary to incorporate larger cohorts or pool analyses in specific susceptible pediatric populations to improve the understanding of predicted exposure profiles and covariate identification.

Therapeutic drug monitoring guidelines in oncology: what do we know and how to move forward? Insights from a systematic review

Background

Compared with anti-infective drugs, immunosuppressants and other fields, the application of therapeutic drug monitoring (TDM) in oncology is somewhat limited.

Objective

We aimed to provide a comprehensive understanding of TDM guidelines for antineoplastic drugs and to promote the development of individualized drug therapy in oncology.

Design

This study type is a systematic review.

Data sources and methods

This study was performed and reported according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses 2020 statement. Databases including PubMed, Embase, the official websites of TDM-related associations and Chinese databases were comprehensively searched up to March 2023. Two investigators independently screened the literature and extracted data. The methodological and reporting quality was evaluated using the Appraisal of Guidelines for Research and Evaluation II (AGREE II) and the Reporting Items for Practice Guidelines in Healthcare (RIGHT), respectively. Recommendations and quality evaluation results were presented by visual plots. This study was registered in PROSPERO (No. CRD42022325661).

Results

A total of eight studies were included, with publication years ranging from 2014 to 2022. From the perspective of guideline development, two guidelines were developed using evidence-based methods. Among the included guidelines, four guidelines were for cytotoxic antineoplastic drugs, three for small molecule kinase inhibitors, and one for antineoplastic biosimilars. Currently available guidelines and clinical practice provided recommendations of individualized medication in oncology based on TDM, as well as influencing factors. With regard to methodological quality based on AGREE II, the average overall quality score was 55.21%. As for the reporting quality by RIGHT evaluation, the average reporting rate was 53.57%.

Conclusion

From the perspective of current guidelines, TDM in oncology is now being expanded from cytotoxic antineoplastic drugs to newer targeted treatments. Whereas, the types of antineoplastic drugs involved are still small, and there is still room for quality improvement. Furthermore, the reflected gaps warrant future studies into the exposure-response relationships and population pharmacokinetics models.

Understanding hemoglobin contribution to high-dose methotrexate disposition-population pharmacokinetics in pediatric patients with hematological malignancies

PURPOSE

The aim of the present study was to develop a population pharmacokinetic model for methotrexate (MTX) during high-dose treatment (HDMTX) in pediatric patients with acute lymphoblastic leukemia (ALL) and non-Hodgkin's lymphoma (NHL) and to describe the influence of variability factors.

METHODS

The study included 50 patients of both sexes (aged 1-18 years) who received 3 or 5 g/m2 of HDMTX. A nonlinear mixed effect modeling approach was applied for data analysis. Parameter estimation was performed by first-order conditional estimation method with interaction (FOCEI), whereas stepwise covariate modeling was used to assess variability factors.

RESULTS

The final model is a two-compartment model that incorporates the effect of body surface area and the influence of hemoglobin and serum creatinine on MTX clearance (CL). Population pharmacokinetic values for a typical subject were estimated at 5.75 L/h/m2 for clearance (CL), 21.3 L/m2 for volume of the central compartment (V1), 8.2 L/m2 for volume of the peripheral compartment (V2), and 0.087 L/h/m2 for intercompartmental clearance (Q). According to the final model, MTX CL decreases with increasing serum creatinine, whereas a positive effect was captured for hemoglobin. A difference of almost 32% in MTX CL was observed among patients' hemoglobin values reported in the study.

CONCLUSION

The developed population pharmacokinetic model can contribute to the therapy optimization during HDMTX in pediatric patients with ALL and NHL. In addition to renal function and body weight, it describes the influence of hemoglobin on CL, allowing better understanding of its contribution to the disposition of HDMTX.

External Evaluation of Population Pharmacokinetic Models for High-Dose Methotrexate in Adult Patients with Hematological Tumors

Currently, numerous population pharmacokinetic (popPK) models for methotrexate (MTX) have been published for estimating PK parameters and variability. However, it is unclear whether the accuracy of these models is sufficient for clinical application. The aim of this study is to evaluate published models and assess their predictive performance according to the standards of scientific research. A total of 237 samples from 74 adult patients who underwent high-dose MTX (HDMTX) treatment at Shanghai Changzheng Hospital were collected. The software package NONMEM was used to perform an external evaluation for each model, including prediction-based diagnosis, simulation-based diagnosis, and Bayesian forecasting. The simulation-based diagnosis includes normalized prediction distribution error (NPDE) and visual predictive check (VPC). Following screening, 7 candidate models suitable for external validation were identified for comparison. However, none of these models exhibited excellent predictive performance. Bayesian simulation results indicated that the prediction precision and accuracy of all models significantly improved when incorporating prior concentration information. The published popPK models for MTX exhibit significant differences in their predictive performance, and none of the models were able to accurately predict MTX concentrations in our data set. Therefore, before adopting any model in clinical practice, extensive evaluation should be conducted.

High-dose methotrexate pharmacokinetics and its impact on prognosis of paediatric acute lymphoblastic leukaemia patients: A population pharmacokinetic study

This study delivers a comprehensive evaluation of the efficacy and pharmacokinetics of high-dose methotrexate (HDMTX) in a large cohort of Chinese paediatric acute lymphoblastic leukaemia patients. A total of 533 patients were included in the prognostic analysis. An association was observed between lower steady-state MTX concentrations (<56 μmol/L) and poorer outcomes in intermediate-/high-risk (IR/HR) patients. Subgroup analysis further revealed that this relationship between concentrations and prognosis was even more pronounced in patients with MLL rearrangements. In contrast, such an association did not emerge within the low-risk patient group. Additionally, utilizing population pharmacokinetic modelling (6051 concentrations from 815 patients), we identified the significant impact of physiological maturation, estimated glomerular filtration rate, sex and concurrent dasatinib administration on MTX pharmacokinetics. Simulation-based recommendations include a reduced dosage regimen for those with renal insufficiency and a specific 200 mg/kg dosage for infants under 1 year. The findings underscore the critical role of HDMTX in treating IR/HR populations and call for a reassessment of its application in lower-risk groups. An individualized pharmacokinetic dosage regimen could achieve the most optimal results, ensuring the largest proportion of steady-state concentrations within the optimal range.

Factors influencing methotrexate pharmacokinetics highlight the need for individualized dose adjustment: a systematic review

PURPOSE

To develop a population pharmacokinetic (PPK) model for methotrexate (MTX) dosage for all ages, assess the association between concentration and clearance, and determine covariates affecting MTX disposition.

METHODS

We compared MTX PK profiles among neonates, children, and adults by performing a systematic literature search for published population MTX models and conducted a Monte Carlo-based meta-analysis. Subsequently, we evaluated study quality and covariates significantly affecting dosage regimens and compared LDMTX and HDMTX PK profiles.

RESULTS

Of the total 40 studies included, 34 were HDMTX, and six were LDMTX studies. For HDMTX, three studies involving neonates reported estimated apparent clearances (median, range) of 0.53 (0.27-0.77) L/kg/h; for 14 studies involving children, 0.23 (0.07-0.23) L/kg/h; and for 13 involving adults, 0.11 (0.03-0.22) L/kg/h. Neonates had a higher volume of distribution than children and adults. For LDMTX studies, apparent clearance was 0.085 (0.05-1.68) L/kg/h, and volume of distribution was 0.25 (0.018-0.47) L/kg, lower than those of HDMTX studies, with large between-subject variability. Bodyweight significantly influenced apparent clearance and volume of distribution, whereas renal function mainly influenced clearance. Mutations in certain genes reduced MTX clearance by 8-35.3%, whereas those in others increased it by 15-48%. Body surface area (BSA) significantly influenced apparent clearance with a median reduction of 51% when BSA increased in pediatric patients.

CONCLUSIONS

Methotrexate dosage regimens were primarily based on body surface area and renal function. Further studies are needed to evaluate MTX pharmacokinetics and pharmacodynamics in both children (especially infants) and adults.

Pharmacogenetic aspects of efficacy and safety of methotrexate treatment in pediatric acute lymphoblastic leukemia

OBJECTIVES

To evaluate the role of ABCB1 (C3435T rs1045642, rs1128503, rs2032582, rs4148738), SLCO1B1 T521C rs4149056 genetic polymorphisms in the development of major types of methotrexate (MTX) toxicities and the occurrence of a terminal event (death, relapse) in pediatric АLL.

METHODS

The study included 124 patients diagnosed with pediatric ALL. All patients treated according to the protocols of the German BFM group (2002/2009) with high-dose (1,000, 2,000 and 5,000 mg/m2) methotrexate. MTX-related toxicities, including hematologic, hepatic and renal, were evaluated according to the common terminology criteria for adverse events version 5.0 (CTCAE v.5.0). Real-time PCR method was used to investigate polymorphisms of ABCB1 and SLCO1B1 genes. The study material was peripheral blood.

RESULTS

A competitive analysis demonstrated significant relationships between MTX ADRs. The results of the study support the existence of relationships between some ADRs and MTX kinetics. An associative analysis showed association with the development of AEs to methotrexate indicating their clinical significance from different genetic polymorphisms protein-transporters. The available results confirm the associations of the studied genes with the increased risk of high doses MTX toxic ADRs and terminal events.

CONCLUSIONS

Complementing the existing criteria for pediatric ALL risk groups with pharmacogenetic indicators will allow further individualization of therapy.

Clinical covariates that improve the description of high dose methotrexate pharmacokinetics in a diverse population to inform MTXPK.org

The MTXPK.org webtool was launched in December 2019 and was developed to facilitate model-informed supportive care and optimal use of glucarpidase following the administration of high-dose methotrexate (HDMTX). One limitation identified during the original development of the MTXPK.org tool was the perceived generalizability because the modeled population comprised solely of Nordic pediatric patients receiving 24-h infusions for the treatment of acute lymphoblastic leukemia. The goal of our study is to describe the pharmacokinetics of HDMTX from a diverse patient population (e.g., races, ethnicity, indications for methotrexate, and variable infusion durations) and identify meaningful factors that account for methotrexate variability and improve the model's performance. To do this, retrospectively analyzed pharmacokinetic and toxicity data from pediatric and adolescent young adult patients who were receiving HDMTX (>0.5 g/m2 ) for the treatment of a cancer diagnosis from three pediatric medical centers. We performed population pharmacokinetic modeling referencing the original MTXPK.org NONMEM model (includes body surface area and serum creatinine as covariates) on 1668 patients, 7506 administrations of HDMTX, and 30,250 concentrations. Our results support the parameterizations of short infusion duration (<8 h) and the presence of Down syndrome on methotrexate clearance, the parameterization of severe hypoalbuminemia (<2.5 g/dL) on the intercompartmental clearance (Q2 and Q3), and the parameterization of pleural effusion on the volume of distribution (V1 and V2). These novel parameterizations will increase the generalizability of the MTXPK.org model once they are added to the webtool.

Population Pharmacokinetic Model of Methotrexate in Brazilian Pediatric Patients with Acute Lymphoblastic Leukemia

OBJECTIVES

Methotrexate (MTX) is subject to therapeutic drug monitoring because of its high pharmacokinetic variability and safety risk outside the therapeutic window. This study aimed to develop a population pharmacokinetic model (popPK) of MTX for Brazilian pediatric acute lymphoblastic leukemia (ALL) patients who attended the Hospital de Clínicas de Porto Alegre, Brazil.

METHODS

The model was developed using NONMEM 7.4 (Icon®), ADVAN3 TRANS4, and FOCE-I. To explain inter-individual variability, we evaluated covariates from demographic, biochemical, and genetic data (single nucleotide polymorphisms [SNPs] related to the transport and metabolism of drugs).

RESULTS

A two-compartment model was built using 483 data points from 45 patients (0.33-17.83 years of age) treated with MTX (0.25-5 g/m2) in different cycles. Serum creatinine (SCR), height (HT), blood urea nitrogen (BUN) and a low BMI stratification (according to the z-score defined by the World Health Organization [LowBMI]) were added as clearance covariates. The final model described MTX clearance as [Formula: see text]. In the two-compartment structural model, the central and peripheral compartment volumes were 26.8 L and 8.47 L, respectively, and the inter-compartmental clearance was 0.218 L/h. External validation of the model was performed through a visual predictive test and metrics using data from 15 other pediatric ALL patients.

CONCLUSION

The first popPK model of MTX was developed for Brazilian pediatric ALL patients, which showed that inter-individual variability was explained by renal function and factors related to body size.

External evaluation and systematic review of population pharmacokinetic models for high-dose methotrexate in cancer patients

Several population pharmacokinetic (PPK) models have been established to optimize the therapeutic regimen and reduce the toxicity of high-dose methotrexate (HDMTX) in patients with cancer. However, their predictive performance when extrapolated to different clinical centers was unknown. In this study, we aimed to externally evaluate the predictive ability of HDMTX PPK models and determine the potential influencing factors. We searched the literature and determined the predictive performance of the selected models using methotrexate concentrations in 721 samples from 60 patients in the First Affiliated Hospital of the Navy Medical University. Prediction-based diagnostics and simulation-based normalized prediction distribution errors (NPDE) were used to evaluate the predictive performance of the models. The influence of prior information was also assessed using Bayesian forecasting, and the potential factors affecting model predictability were investigated. Thirty models extracted from published PPK studies were assessed. Prediction-based diagnostics showed that the number of compartments potentially influenced model transferability, and simulation-based NPDE indicated model misspecification. Bayesian forecasting significantly improved the predictive performance of the models. Various factors, including bioassays, covariates, and population diagnosis, influence model extrapolation. The published models were unsatisfactory for all prediction-based diagnostics, except for the 24 h methotrexate concentration monitoring and simulation-based diagnostics, making them inappropriate for direct extrapolation. Moreover, Bayesian forecasting combined therapeutic drug monitoring could improve the predictive performance of the models.

Precision Oncology by Point-of-Care Therapeutic Drug Monitoring and Dosage Adjustment of Conventional Cytotoxic Chemotherapies: A Perspective

Therapeutic drug monitoring (TDM) of conventional cytotoxic chemotherapies is strongly supported yet poorly implemented in daily practice in hospitals. Analytical methods for the quantification of cytotoxic drugs are instead widely presented in the scientific literature, while the use of these therapeutics is expected to keep going for longer. There are two main issues hindering the implementation of TDM: turnaround time, which is incompatible with the dosage profiles of these drugs, and exposure surrogate marker, namely total area under the curve (AUC). Therefore, this perspective article aims to define the adjustment needed from current to efficient TDM practice for cytotoxics, namely point-of-care (POC) TDM. For real-time dose adjustment, which is required for chemotherapies, such POC TDM is only achievable with analytical methods that match the sensitivity and selectivity of current methods, such as chromatography, as well as model-informed precision dosing platforms to assist the oncologist with dose fine-tuning based on quantification results and targeted intervals.

External Evaluation of Population Pharmacokinetic Models of Methotrexate for Model-Informed Precision Dosing in Pediatric Patients with Acute Lymphoid Leukemia

BACKGROUND

Methotrexate (MTX) is a key immunosuppressant for children with acute lymphoid leukemia (ALL), and it has a narrow therapeutic window and relatively high pharmacokinetic variability. Several population pharmacokinetic (PopPK) models of MTX in ALL children have been reported, but the validity of these models for model-informed precision dosing in clinical practice is unclear. This study set out to evaluate the predictive performance of published pediatric PopPK models of MTX using an independent patient cohort.

METHODS

A PubMed literature search was performed to identify suitable models for evaluation. Demographics and measurements of the validation dataset were retrospectively collected from the medical records of ALL children who had received intravenous MTX. Predictive performance for each model was assessed by visual comparison of predictions to observations, median and mean predicted error (PE), and relative root mean squared error (RMSE).

RESULTS

Six models were identified for external evaluation, carried out on a dataset containing 354 concentrations from 51 pediatrics. Model performance varied considerably from one model to another. Different models had the median PE for population and individual predictions at -33.23% to 442.04% and -25.20% to 6.52%, mean PE for population and individual predictions at -25.51% to 780.87% and 1.33% to 64.44%, and RMSE for population and individual predictions at 62.88% to 1182.24% and 63.39% to 152.25%. All models showed relatively high RMSE.

CONCLUSIONS

Some of the published models showed reasonably low levels of bias but had some problems with imprecision, and extensive evaluation is needed before model application in clinical practice.

Population pharmacokinetics of methotrexate in pediatric patients with acute lymphoblastic leukemia and malignant lymphoma

1. This study aimed to identify physiological and pharmacogenomic covariates and develop a population pharmacokinetic model of high-dose methotrexate (HD-MTX) in Chinese pediatric patients with acute lymphoblastic leukemia (ALL) and malignant lymphoma.2. A total 731 MTX courses and 1658 MTX plasm concentration from 205 pediatric patients with ALL and malignant lymphoma were analyzing using a nonlinear mixed-effects model technique. 47 SNPs in 16 MTX-related gene were genotyped and screened as covariates. A PPK model was established to determine the influence of covariates such as body surface area (BSA), age, laboratory test value, and SNPs on the pharmacokinetic process of HD-MTX.3. Two-compartmental model with allometric scaling using BSA could nicely characterize the in vivo behavior of HD-MTX. After accounting for body size, rs17004785 and rs4148416 were the covariates that influence MTX clearance (CL). The PPK model obtained was: CL =9.33 * (BSA/1.73) ^0.75 * e^{0.13*rs17004785} * e^{0.39*rs4148416} * e^ηCL, Vc =24.98 * (BSA/1.73) * e^ηvc, Q = 0.18 * (BSA/1.73) ^0.75 * e^ηQ and Vp =4.70 * (BSA/1.73) * e^ηvp.4. The established model combined with Bayesian approach could estimate individual pharmacokinetic parameters and optimize personalized HD-MTX therapy for pediatric patients with ALL and malignant lymphoma.

Extracorporeal Treatment for Methotrexate Poisoning: Systematic Review and Recommendations from the EXTRIP Workgroup

Methotrexate is used in the treatment of many malignancies, rheumatological diseases, and inflammatory bowel disease. Toxicity from use is associated with severe morbidity and mortality. Rescue treatments include intravenous hydration, folinic acid, and, in some centers, glucarpidase. We conducted systematic reviews of the literature following published EXtracorporeal TReatments In Poisoning (EXTRIP) methods to determine the utility of extracorporeal treatments in the management of methotrexate toxicity. The quality of the evidence and the strength of recommendations (either "strong" or "weak/conditional") were graded according to the GRADE approach. A formal voting process using a modified Delphi method assessed the level of agreement between panelists on the final recommendations. A total of 92 articles met inclusion criteria. Toxicokinetic data were available on 90 patients (89 with impaired kidney function). Methotrexate was considered to be moderately dialyzable by intermittent hemodialysis. Data were available for clinical analysis on 109 patients (high-dose methotrexate [>0.5 g/m²]: 91 patients; low-dose [≤0.5 g/m²]: 18). Overall mortality in these publications was 19.5% and 26.7% in those with high-dose and low-dose methotrexate-related toxicity, respectively. Although one observational study reported lower mortality in patients treated with glucarpidase compared with those treated with hemodialysis, there were important limitations in the study. For patients with severe methotrexate toxicity receiving standard care, the EXTRIP workgroup: (1) suggested against extracorporeal treatments when glucarpidase is not administered; (2) recommended against extracorporeal treatments when glucarpidase is administered; and (3) recommended against extracorporeal treatments instead of administering glucarpidase. The quality of evidence for these recommendations was very low. Rationales for these recommendations included: (1) extracorporeal treatments mainly remove drugs in the intravascular compartment, whereas methotrexate rapidly distributes into cells; (2) extracorporeal treatments remove folinic acid; (3) in rare cases where fast removal of methotrexate is required, glucarpidase will outperform any extracorporeal treatment; and (4) extracorporeal treatments do not appear to reduce the incidence and magnitude of methotrexate toxicity.

A Systematic Review of Population Pharmacokinetic Models of Methotrexate

BACKGROUND AND OBJECTIVES

Methotrexate (MTX) is widely used for the treatment of a variety of neoplastic and autoimmune diseases. However, its toxicity and efficacy varied greatly among individuals, and they could be predicted by its pharmacokinetics. Many population pharmacokinetic models have been published to describe MTX pharmacokinetics. The objective of this systematic review was to summarize and discuss covariates with significant influence on MTX pharmacokinetics.

METHODS

We searched PubMed and EMBASE databases from their inception to April 2021 for population pharmacokinetic of MTX. The articles were screened by inclusion and exclusion criteria. The characteristics of studies and information for model construction and validation were extracted, summarized and discussed.

RESULTS

Thirty-five articles were included. The two-compartment model well described the pharmacokinetic behavior of MTX. For inter-individual variability, an exponential distribution error model was usually used for high-dose MTX population pharmacokinetic models, while a proportional distribution error model was used for low-dose MTX population pharmacokinetic models. Proportional and combined proportional and additive error models were used to describe residual error. Renal function was an independent indicator of MTX clearance. Body weight, age, gene polymorphisms (SLCO1B1, ABCC2, ABCB1, ABCG2 and MTHFR) and co-medications (proton pump inhibitors, non-steroidal anti-inflammatory drug, dexamethasone, vancomycin, penicillin and salicylic acid) could influence MTX clearance. Body weight, body surface area, age and dosage regimen have significant influence on MTX central compartment volume. Internal bootstrap test, external validation and visual predictive check were used to evaluate model predictive ability.

CONCLUSIONS

Various covariates could affect MTX pharmacokinetics, and their relationships have been summarized and discussed. This review will be helpful for researchers to develop their own population pharmacokinetic models and select appropriate models for individualized therapy of MTX.

Clinical pharmacology of cytotoxic drugs in neonates and infants: Providing evidence-based dosing guidance

Cancer in neonates and infants is a rare but challenging entity. Treatment is complicated by marked physiological changes during the first year of life, excess rates of toxicity, mortality, and late effects. Dose optimisation of chemotherapeutics may be an important step to improving outcomes. Body size–based dosing is used for most anticancer drugs used in infants. However, dose regimens are generally not evidence based, and dosing strategies are frequently inconsistent between tumour types and treatment protocols. In this review, we collate available pharmacological evidence supporting dosing regimens in infants for a wide range of cytotoxic drugs. A systematic review was conducted, and available data ranked by a level of evidence (1–5) and a grade of recommendation (A–D) provided on a consensus basis, with recommended dosing approaches indicated as appropriate. For 9 of 29 drugs (busulfan, carboplatin, cyclophosphamide, daunorubicin, etoposide, fludarabine, isotretinoin, melphalan and vincristine), grade A was scored, indicating sufficient pharmacological evidence to recommend a dosing algorithm for infants. For busulfan and carboplatin, sufficient data were available to recommend therapeutic drug monitoring in infants. For eight drugs (actinomycin D, blinatumomab, dinutuximab, doxorubicin, mercaptopurine, pegaspargase, thioguanine and topotecan), some pharmacological evidence was available to guide dosing (graded as B). For the remaining drugs, including commonly used agents such as cisplatin, cytarabine, ifosfamide, and methotrexate, pharmacological evidence for dosing in infants was limited or non-existent: grades C and D were scored for 10 and 2 drugs, respectively. The review provides clinically relevant evidence-based dosing guidance for cytotoxic drugs in neonates and infants.

•

Treating cancer in neonates and infants is challenging.

•

Dose optimisation of cytotoxic drugs is an important step to improving outcomes.

•

Clinical pharmacological evidence supporting dosing regimens in infants was collated.

•

All available pharmacological evidence was ranked by a level of evidence.

•

A grade of recommendation was derived and a recommended dose per agent provided.

Medication Therapy of High-Dose Methotrexate: An Evidence-Based Practice Guideline of the Division of Therapeutic Drug Monitoring, Chinese Pharmacological Society

OBJECTIVES

A lot of medication risks related to high-dose methotrexate (HDMTX) therapy still remain to be identified and standardized. This study aims to establish an evidence-based practice guideline for individualized medication of HDMTX.

METHODS

The practice guideline was launched by the Division of Therapeutic Drug Monitoring, Chinese Pharmacological Society. The guideline was developed following the WHO handbook for guideline development and the methodology of evidence-based medicine (EBM). The guideline was initially registered in the International Practice Guidelines Registry Platform (IPGRP-2017CN021). Systematic reviews were conducted to synthesis available evidence. A multicenter cross-sectional study was conducted by questionnaires to evaluate patients' perception and willingness on individualized medication of HDMTX. The Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach was used to rate the quality of evidence and to grade the strength of recommendations.

RESULTS

Multidisciplinary working groups were included in this guideline, including clinicians, pharmacists, methodologists, pharmacologists and pharmacoeconomic specialists. A total of 124 patients were involved to integrate patient values and preferences. Finally, the guideline presents 28 recommendations, regarding evaluation prior to administration (renal function, liver function, pleural effusion, comedications, genetic testing), pre-treatment and routine dosing regimen, therapeutic drug monitoring (necessity, method, timing, target concentration), leucovorin rescue (initial timing, dosage regimen and optimization), management of toxicities. Of them, 12 are strong recommendations.

CONCLUSIONS

We developed an evidence-based practice guideline with respect to HDMTX medication using a rigorous and multidisciplinary approach. This guideline provides comprehensive and practical recommendations involving the whole process of HDMTX administration to health care providers.

Population Pharmacokinetics of High-Dose Methotrexate in Chinese Pediatric Patients With Acute Lymphoblastic Leukemia

High-dose methotrexate (HD-MTX) is widely used in pediatric acute lymphoblastic leukemia (ALL) treatment regimens. In this study, we aimed to develop a population pharmacokinetic (PK) model of HD-MTX in Chinese pediatric patients with ALL for designing personalized dosage regimens. In total, 4,517 MTX serum concentration data for 311 pediatric patients with ALL, aged 0.75–15.2 years and under HD-MTX treatment, were retrospectively collected at a tertiary Children’s Hospital in China. The non-linear mixed-effect model was used to establish the population PK model, using NONMEM software. The potential covariate effects of age, body weight, and biochemical measurements (renal and liver function) on MTX PK disposition were investigated. The model was then evaluated using goodness-of-fit, visual predictive check. MTX PK disposition was described using a three-compartment model reasonable well. Body weight, implemented as a fixed allometric function on all clearance and volume of distribution parameters, showed a substantial improvement in model fit. The final population model demonstrated that the MTX clearance estimate in a typical child with body weight of 19 kg was 6.9 L/h and the central distribution of volume estimate was 20.7 L. The serum creatinine significantly affected the MTX clearance, with a 0.97% decrease in clearance per 1 μmol/L of serum creatinine. Other covariates (e.g., age, sex, bilirubin, albumin, aspartate transaminase, concomitant medication) did not significantly affect PK properties of MTX. The proposed population PK model could describe the MTX concentration data in Chinese pediatric patients with ALL. This population PK model combined with a maximum a posteriori Bayesian approach could be used to estimate individual PK parameters, and optimize personalized MTX therapy in target patients, thus aiming to reduce toxicity and improve treatment outcomes.

Effect of SLCO1B1 Polymorphisms on High-Dose Methotrexate Clearance in Children and Young Adults With Leukemia and Lymphoblastic Lymphoma

High-dose (HD) methotrexate (MTX) is a critical component of treatment for hematologic malignancies in children and young adults. Therapeutic drug monitoring is necessary due to substantial interindividual variation in MTX clearance. Common function-altering polymorphisms in SLCO1B1 (encodes OATP1B1, which transports MTX) may contribute to clearance variability. We performed pharmacokinetic modeling using data for 106 children and young adults treated with HD MTX for hematologic malignancies; of 396 total courses of HD MTX, 360 consisted of 5 g/m² over 24 hours. We evaluated the contribution of clinical covariates and SLCO1B1 genotype (388A>G and 521T>C) to MTX clearance variability. Of the clinical covariates studied, patient weight improved the pharmacokinetic model most significantly (P < 0.001). The addition of the SLCO1B1 variants individually further improved the model (P < 0.05 for each). An interaction between these variants was suggested when both were included (P = 0.017). SLCO1B1 genotype should be considered in efforts to personalize HD MTX dosing.

Neurocognitive impairment in Asian childhood cancer survivors: a systematic review

Childhood cancer survivors are at higher risk of developing neurocognitive deficits due to the intensive treatment they received at an early age. Most studies on childhood cancer survivorship have so far focused on the Western populations. Due to the ethnic, genetic, environmental, and cultural differences, clinical data of the Western populations may not be representative of Asian countries. This scoping review systematically summarized the existing clinical evidence of the neurocognitive impairment of Asian childhood cancer survivors. We searched the Embase and Medline databases for studies assessing the neurocognitive functions of survivors in Asia, who were diagnosed with cancer before the age of 19 and completed active treatment. The literature search identified 13 studies involving 2212 participants from five Asian countries: South Korea (n = 4, 30.8%), Taiwan (n = 3, 23.1%), Japan (n = 3, 23.1%), Hong Kong (n = 2, 15.4%), and Thailand (n = 1, 7.7%). The included studies focused on CNS tumors (n = 10, 76.9%), hematological malignancies (n = 7, 53.8%), or heterogeneous cancer diagnoses (n = 3, 23.1%). Collectively, mild-to-moderate impairment in intelligence was observed in 10.0 to 42.8% of survivors, which seemed higher than the reported rate in Western survivors. We speculate that the ethnic and genetic variations in drug responses and susceptibility to adverse chronic toxicities may have contributed to the differences in the prevalence and severity of neurocognitive impairment between these two populations. To better understand the effects of culturally relevant and region-specific environmental risk factors on the post-treatment neurocognitive development in cancer survivors, a holistic approach that addresses the complex interactions between biological, physical, and psychosocial factors is needed. This will aid the development of effective intervention strategies to improve the functional and psychosocial outcomes of cancer survivors in Asian societies.

MTXPK.org: A Clinical Decision Support Tool Evaluating High-Dose Methotrexate Pharmacokinetics to Inform Post-Infusion Care and Use of Glucarpidase

Methotrexate (MTX), an antifolate, is administered at high doses to treat malignancies in children and adults. However, there is considerable interpatient variability in clearance of high‐dose (HD) MTX. Patients with delayed clearance are at an increased risk for severe nephrotoxicity and life‐threatening systemic MTX exposure. Glucarpidase is a rescue agent for severe MTX toxicity that reduces plasma MTX levels via hydrolysis of MTX into inactive metabolites, but is only indicated when MTX concentrations are > 2 SDs above the mean excretion curve specific for the given dose together with a significant creatinine increase (> 50%). Appropriate administration of glucarpidase is challenging due to the ambiguity in the labeled indication. A recent consensus guideline was published with an algorithm to provide clarity in when to administer glucarpidase, yet clinical interpretation of laboratory results that do not directly correspond to the algorithm prove to be a limitation of its use. The goal of our study was to develop a clinical decision support tool to optimize the administration of glucarpidase for patients receiving HD MTX. Here, we describe the development of a novel 3‐compartment MTX population pharmacokinetic (PK) model using 31,672 MTX plasma concentrations from 772 pediatric patients receiving HD MTX for the treatment of acute lymphoblastic leukemia and its integration into the online clinical decision support tool, MTXPK.org. This web‐based tool has the functionality to utilize individualized demographics, serum creatinine, and real‐time drug concentrations to predict the elimination profile and facilitate model‐informed administration of glucarpidase.

Doxorubicin induces cytotoxicity and miR-132 expression in granulosa cells

Doxorubicin (DOX) is one of the most commonly used drugs for the treatment of childhood cancers, including leukemia and lymphomas. Despite the high survival rate, female leukemia survivors are at higher risk of ovarian failure and infertility later in life. Treatment with chemotherapeutic drugs like DOX is associated with damage in ovarian follicles, but the affectation grade of granulosa cells remains unclear. To assess and avoid the possible side-effects of DOX, early biomarkers of ovarian injury and chemotherapy-induced ovarian toxicity should be identified. MicroRNAs (miRNAs) have emerged in recent years as a promising new class of biomarkers for drug-induced tissue toxicity. In this study, the effects of DOX on cell viability, steroidogenesis, and miRNA expression were studied in primary granulosa cells (GCs) and in two cellular models (COV434 and KGN cells). We report that compared to other chemotherapeutic drugs, DOX treatment is more detrimental to granulosa cells as observed by decrease of cell viability. Treatment with DOX changes the expression of the aromatase gene (CYP19A1) and the secretion of 17β-estradiol (E2) in a cell-specific manner. miR-132-3p is dose-dependently increased by DOX in all cellular models. In absence of DOX, miR-132-3p overexpression in COV434 cells has no effect on E2 secretion or CYP19A1 expression. Altogether, these findings contribute to understanding the hormonal disbalance caused by DOX in human ovarian cells and suggest miR-132 as a putative sensor to predict DOX-induced ovarian toxicity.

Pharmacokinetic basis for dosing high-dose methotrexate in infants and young children with malignant brain tumours

AIMS

No population pharmacokinetic studies of high-dose methotrexate (HDMTX) have been conducted in infants with brain tumours, which are a vulnerable population. The aim of this study was to evaluate HDMTX disposition in these children to provide a rational basis for MTX dosing.

METHODS

Patients received 4 monthly courses of HDMTX (5 g/m² or 2.5 g/m² for infants aged ≤31 days) as a 24-h infusion. Serial samples were analysed for MTX by an enzyme immunoassay method. Pharmacokinetic parameters were estimated using nonlinear mixed effects population modelling. Demographics, concomitant medications and genetic polymorphisms were considered as pharmacokinetic covariates while MTX exposure and patient age were considered as covariates for Grade 3 and 4 toxicities.

RESULTS

The population pharmacokinetics of HDMTX were estimated in 178 patients (age range 0.02-4.7 years) in 648 courses. The population clearance and volume were 90 mL/min/m² and 14.4 L/m² , respectively. Significant covariates on body surface area adjusted MTX clearance included estimated glomerular filtration rate and co-treatment with dexamethasone or vancomycin. No significant association was observed between MTX toxicity and MTX exposure, patient age, leucovorin dosage or duration. MTX clearance in infants ≤31 days at enrolment was 44% lower than in older infants, but their incidence of toxicity was not higher since they also received a lower MTX dosage.

CONCLUSIONS

By aggressively following institutional clinical guidelines, HDMTX-related toxicities were low, and using covariates from the population pharmacokinetic model enabled the calculation of a rational dosage for this patient population for future clinical trials.