Population Pharmacokinetics of High-Dose Methotrexate in Children with Acute Lymphoblastic Leukaemia

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.

Whole blood multiplex measurements using electrochemical aptamer-based biosensors

Simultaneous measurements of various molecules ("multiplex") using electrochemical biosensors typically require multiple electrode implementations, which for neonates, hemophiliacs, etc. is problematic. Here, we introduce the oxazine ATTO 700 into electrochemical aptamer-based biosensors to achieve "true" multiplex, continuous and real-time measurements of two different molecules in undiluted whole blood using a single electrode.

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.

A Delphi study to determine the epidemiology and clinical management of patients treated with HDMTX who develop methotrexate (MTX) delayed elimination in France, Germany, Italy, and the UK

Introduction

High-dose methotrexate (HDMTX) is administered for the treatment of some malignancies. Serious complications after the administration of HDMTX are rare, but occasionally MTX may precipitate in the renal tubes causing a delayed elimination leading to renal, multiorgan toxicities and to life-threatening complications. This study aims to estimate the incidence and clinical management of delayed MTX elimination in France, Germany, Italy, and the UK.

Methods

Twelve haemato-oncology and pediatric oncology clinical experts from leading European hospitals participated in the study. A two-round Delphi methodology was used to gather data on different variables relevant to evaluate the HDMTX induced-toxicity impact. For quantitative data, median and interquartile ranges were calculated. Data on prevalence was calculated considering the number of patients in each hospital and the population they cover, and then, extrapolated to the country population.

Results

The total number of patients treated annually with HDMTX in France, Germany, Italy, and the UK is estimated in 7155. Of these, 16% are estimated to develop delayed MTX elimination and around 9% may develop HDMTX-induced acute kidney injury (AKI). Leucovorin, hyperhydration and urine alkalinization are applied to prevent MTX toxicity and precipitation whilst glucarpidase, hemofiltration and hemodialysis are being used for persisting toxic MTX serum levels. Grade 3 systemic toxicities are common in these patients, hematologic and gastrointestinal being the most common ones.

Conclusions

This report provides expert clinical practice experience and opinion of the incidence and management of HDMTX-delayed elimination in France, Germany, Italy and the UK, thereby contributing to the evidence available on this relevant medical condition which can be life-threatening.

A new pharmacokinetic model of urinary methotrexate to assess adherence in rheumatoid arthritis

BACKGROUND AND OBJECTIVES

Methotrexate (MTX) is the first-line therapy for rheumatoid arthritis (RA). While therapeutic adherence is essential to successful management, no objective MTX assay is currently available. Using population pharmacokinetic modelling (PopPK), our objective was to describe the urinary MTX (MTXu) kinetics in treated patients and to evaluate its abilities to assess the MTX-adherence.

METHODS

The association between urinary methotrexate level and methotrexate administration was assessed using a generalized linear model. Then, a population pharmacokinetic model was developed based on data from 59 patients using with Monolix 2021. R2. Simulations were run to establish a reference kinetic profile and evaluate the proportion of samples predicted as true positives.

RESULTS

Compared to the control group, multivariate analysis showed that MTXu was independently associated with methotrexate administration (p < 0.0001) with a sensitivity and specificity greater than 99%. The final PopPK model selected was a two-compartment model with first-order absorption and elimination. Internal and external validation of the model met all predefined criteria. When using an analytical assay with a LOQ equal to 1 nM, the proportion of samples predicted as true positives is over 90%, as a function of MTX dose (7.5-25 mg/week) and post-administration sampling days (1-7 days).

CONCLUSION

We developed a pharmacokinetic model able to describe expected patterns of urinary methotrexate. This allowed us to propose a new objective test of MTX adherence, which could help in routine practice to differentiate patients who are truly unresponsive to methotrexate from those who are unresponsive because of non-adherence.

Association of microRNA Polymorphisms with Toxicities Induced by Methotrexate in Children with Acute Lymphoblastic Leukemia

Methotrexate (MTX), a structurally related substance to folic acid, is an important chemotherapeutic agent used for decades in the treatment of pediatric acute lymphoblastic leukemia (ALL) and other types of cancer as non-Hodgkin lymphomas and osteosarcomas. Despite the successful outcomes observed, the primary drawback is the variability in the pharmacokinetics and pharmacodynamics between patients. The main adverse events related to its use are nephrotoxicity, mucositis, and myelosuppression, especially when used in high doses. The potential adverse reactions and toxicities associated with MTX are a cause for concern and may lead to dose reduction or treatment interruption. Genetic variants in MTX transport genes have been linked to toxicity. Pharmacogenetic studies conducted in the past focused on single nucleotide polymorphisms (SNPs) in the coding and 5'-regulatory regions of genes. Recent studies have demonstrated a significant role of microRNAs (miRNAs) in the transport and metabolism of drugs and in the regulation of target genes. In the last few years, the number of annotated miRNAs has continually risen, in addition to the studies of miRNA polymorphisms and MTX toxicity. Therefore, the objective of the present study is to investigate the role of miRNA variants related to MTX adverse effects.

Early clinical indicators of acute kidney injury caused by administering high-dose methotrexate therapy to juvenile pigs

Introduction

Early identification of compromised renal clearance caused by high-dose methotrexate (HDMTX) is essential for initiating timely interventions that can reduce acute kidney injury and MTX-induced systemic toxicity.

Methods

We induced acute kidney injury (AKI) by infusing 42 juvenile pigs with 4 g/kg (80 g/m2) of MTX over 4 hours without high-volume alkalinizing hydration therapy. Concentrations of serum creatinine and MTX were measured at 15 time points up to 148 hours, with 10 samples collected during the first 24 hours after the start of the HDMTX infusion.

Results

During the first 28 hours, 81% of the pigs had increases in the concentrations of serum creatinine in one or more samples indicative of AKI (i.e., > 0.3g/dL increase). A rate of plasma MTX clearance of less than 90% during the initial 4 hours after the HDMTX infusion and a total serum creatinine increase at 6 and 8 hours after starting the infusion greater than 0.3 g/dL were predictive of AKI at 28 hours (p < 0.05 and p < 0.001, respectively). At conclusion of the infusion, pigs with a creatinine concentration more than 0.3 g/dL higher than baseline or serum MTX greater than 5,000 μmol/L had an increased risk of severe AKI.

Conclusions

Our findings suggest that serum samples collected at conclusion and shortly after HDMTX infusion can be used to predict impending AKI. The pig model can be used to identify biological, environmental, and iatrogenic risk factors for HDMTX-induced AKI and to evaluate interventions to preserve renal functions, minimize acute kidney injury, and reduce systemic toxicity.

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.

Novel and replicated clinical and genetic risk factors for toxicity from high-dose methotrexate in pediatric acute lymphoblastic leukemia

STUDY OBJECTIVE

Methotrexate (MTX) is a key component of treatment for high-risk pediatric acute lymphoblastic leukemia (ALL) but may cause acute kidney injury and prolonged hospitalization due to delayed clearance. The purpose of this study is to identify clinical and genetic factors that may predict which children are at risk for creatinine increase and prolonged MTX clearance.

DESIGN

We conducted a single-center, retrospective cohort study of pediatric patients with ALL who received 4000-5000 mg/m2 of MTX. Measurements We performed germline genotyping to determine genetic ancestry and allele status for 49 single nucleotide polymorphisms (SNPs) identified from the literature as related to MTX disposition. Bayesian hierarchical ordinal regression models for creatinine increase and for prolonged MTX clearance were developed.

MAIN RESULTS

Hispanic ethnicity, body mass index (BMI) < 3%, BMI between 85%-95%, and Native American genetic ancestry were found to be associated with an increased risk for creatinine elevation. Older age, Black race, and use of the intensive monitoring protocol were associated with a decreased risk for creatinine elevation. Older age, B- compared to T-ALL, and the minor alleles of rs2838958/SLC19A1 and rs7317112/ABCC4 were associated with an increased risk for delayed clearance. Black race, MTX dose reduction, and the minor allele of rs2306283/SLCO1B1 were found to be associated with a decreased risk for delayed clearance.

CONCLUSIONS

These predictors of MTX toxicities may allow for more precise individualized toxicity risk prediction.

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.

Feasibility of Delivering High-Dose Methotrexate in Adolescent and Adult All Patients: A Retrospective Study

Introduction HD-MTX is a key drug in the treatment protocols for ALL. The regimen needs to be administered with appropriate supportive measures and serum methotrexate level monitoring. A limited testing strategy is relevant in resource constraint settings since it allows a shorter duration of hospitalization. We report our experience with this strategy and its impact on the patient safety outcomes. Methods This is a retrospective study of all patients ≥ 15 years of age with newly diagnosed ALL or Lymphoblastic lymphoma (LBL) who were administered HDMTX (part of BFM-90 ALL protocol) at our institute between March 2013 to November 2013.The medical records were reviewed for clinical characteristics, disease-related details, HDMTX dose and cycles administered, leucovorin rescue and toxicities. Results A total of 423 cycles of HD-MTX were administered to 106 patients during the study period. The median duration for completion of all 4 cycles of HDMTX was 53 (IQR 49-60) days. The grade 3 or higher toxicities were anemia in 9.6%, neutropenia 19.4%, febrile neutropenia 5.7%, thrombocytopenia 4.4% and mucositis in 0.7%. There was statistically significant correlation between the levels at 42 h (≤ 1 mmol/L vs > 1 mmol/L) and toxicity- anemia, FN and mucositis observed more in the late clearance group. With limited sampling strategy whereby if the 42- hour level MTX level are < 1 mmol/L, 57% of patients could be discharged early. Conclusion HD-MTX can be safely administered to adolescent and adult ALL patients. A limited methotrexate level monitoring is a safe strategy that can optimize the resources better.

Leucovorin (folinic acid) rescue for high-dose methotrexate: A review

High-dose methotrexate (HDMTX) is active against various malignancies; it possesses serious toxicities and is associated with patient characteristics, dosage regimens, comedications, and physiological status. There are many strategies to overcome HDMTX-induced toxicities, such as hydration, alkalization, leucovorin rescue, and haemodialysis. Leucovorin rescue is a cornerstone for toxicity prevention in HDMTX treatment. However, the leucovorin dose adjustment and the existence of leucovorin overrescue are still controversial. At present, various methods for calculating leucovorin doses in different tumour types have been proposed, including empirical calculations based on MTX plasma concentration, the Bleyer nomogram, and other methods. Nonetheless, leucovorin rescue protocols differ greatly across tumour types and medical institutions. Further studies are needed to investigate the optimal dosage regimen for leucovorin rescue in various tumours using HDMTX.

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.

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.

Incidence and management of patients with methotrexate delayed elimination in the clinical practice: A Delphi study

INTRODUCTION

High-dose methotrexate (HDMTX) is administered for the treatment of some cancers. HDMTX is usually safe but may crystallize in renal tubules causing acute kidney injury (AKI). Consequently, MTX elimination is delayed, resulting in a severe and life-threatening condition. No studies have been published about the impact of MTX toxicity in Spain. This study aims to estimate the incidence and management of MTX delayed elimination and toxicity.

METHODS

A two-round Delphi study was performed to reach consensus between 10 medical experts on haemato-oncology and paediatric oncology with experience in the management of HDMTX treated patients from leading Spanish hospitals. An online questionnaire was developed based on national and international guidelines and previous evidence regarding HDMTX-related toxicity. Consensus was established at 80% agreement. Median and interquartile ranges were calculated, and incidence data were extrapolated to the Spanish general population.

RESULTS

Out of 1.475 patients estimated to receive HDMTX treatment annually in Spain, 27.5% present MTX delayed elimination and 11.6% develop HDMTX-induced AKI (35.4% with severe systemic toxicities (>grade 3) and 18.8% develop chronic renal disease). Mortality is estimated in 4.2%. Immuno-enzymatic assay is used in most of the hospitals (90%) for MTX serum level monitoring. All experts use increased supportive care and high leucovorin as first-line treatment. Available treatments in experts' hospitals in case toxicity persists are haemodialysis (90% of hospitals), glucarpidase (60%) and hemofiltration (50%). Most prevalent non-renal systemic toxicities are haematologic and mucositis (21-40% of patients). Patients with HDMTX-induced AKI require from intensive care (5% of patients), more than 3 sessions and 4 days of dialysis, and about 8.5 days of hospitalization (non-ICU patients) and 12 days in case of patients requiring ICU.

CONCLUSIONS

These results are the first evidence regarding HDMTX-induced AKI in Spain. Incidence and mortality results are in line with previous studies. Clinical management is based on preventive measures and the treatment depend on the availability in the hospital. The need for effective, safe and rapid treatment for the reduction of MTX toxic levels and the improvement of monitoring methods were noted by experts as urgent needs. Further observational studies to validate these results would be needed.

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.

Utility of repeated drug level measurements after high dose methotrexate infusion for treatment planning in pediatric leukemia

Introduction: Although high-dose Methotrexate (MTX) is a successful chemotherapeutic agent used in the treatment of acute lymphoblastic leukemia in childhood, life-threatening toxic effects are rarely seen. Therefore, frequent follow-up of drug levels is recommended. The study researched the necessity of drug level measurement and a minimum safe number of measurements. Materials and Methods: The files of pediatric patients with Acute Lymphoblastic Leukemia receiving high-dose MTX treatment in a single center between 2018 and 2021 were retrospectively reviewed. The treatment protocol was: 3000 mL/m2 alkaline hydration fluid was continued until the 72nd hour together with 2 gr/m2 continuous MTX infusion in the low-risk group and 5 gr/m2 in moderate and high-risk groups, and 15 mg/m2 /dose folinic acid was given at the 42nd, 48thand 54th hours. Findings: 456 MTX treatments were evaluated in 114 patients. Similar results (p>0.05) were obtained in the MTX level measurements performed at the 24th, 42nd, 48th, and 54th hours after MTX administration. In the repeated measurements, the data at the 42nd hour were similar (p=0.021). The number of cases that were >150 µmol/L at the 24th hour of methotrexate infusion and above 1 µmol/L at the 42nd, 48th, and 52nd hours were found to be similar in the repeated measurements. Conclusion: Although recommended, frequent follow-up of MTX levels might not always indicate toxicity. In centers with limited laboratory facilities, the MTX level measured at the 42nd hour in the first treatment might be a practical approach to guide the management of other MTX treatments.

High dose methotrexate in adult Egyptian patients with hematological malignancies: impact of ABCB1 3435C > T rs1045642 and MTHFR 677C > T rs1801133 polymorphisms on toxicities and delayed elimination

High dose methotrexate (HDMTX) is an essential agent in chemotherapeutic regimens used in various hematological malignancies in Egyptian adults. The research for the impact of gene polymorphism on HDMTX induced toxicities and delayed elimination is an important ongoing objective in many studies, variable and conflicting results produced in the past years to clarify that impact. This study aimed to investigate the role of ABCB1 3435 C > T rs1045642 and MTHFR 677 C > T rs1801133 polymorphisms on HDMTX induced toxicity outcomes and delayed elimination in Egyptian adult patients with hematological malignancies. A prospective, observational cohort study was conducted on a total of 62 Egyptian adult patients with hematological malignancies age ≥ 18-years-old. All demographic, medical, and laboratory data were continuously collected from the patients' medical files in an up-to-date follow-up in selected clinics during the period from April 2018 to March 2020. Venous blood samples were collected for the purpose of genotyping, DNA extraction, and measurement of MTX levels. All the relevant data were statistically analyzed. The studied patients' median age was 25 years old with a range of (18-62) years. Forty-six patients were males with about 74%, and 16 were females with about 26%. Eighty-nine percent of the patients diagnosed with acute lymphoblastic leukemia 'ALL', 5% of the patients had B cell non-hodgkin lymphoma 'B-NHL' and 3% diagnosed with primary central nervous system lymphoma 'PCNSL' and Burkitt's lymphoma 'BL' Hematological, hepatic, renal and gastrointestinal toxicities observed post-HDMTX were recorded with the hematological toxicities toping on all the others, also patients with delayed elimination at 72 hours post the HDMTX dose were determined. Statistical analysis revealed a significant association between ABCB1 3435 C > T rs1045642 and HDMTX delayed elimination with about 10 times higher risk among the minor allele 'T' carriers (p-value = 0.006) (odds ratio [OR]: 10.470; 95% CI: 1.961-55.904). No significant association observed between the studied gene polymorphisms: MTHFR 677 C > T rs1801133, ABCB1 3435 C > T rs1045642, and different toxicity outcomes. According to our best knowledge, this study is the first to conclude a significant association between ABCB1 3435 C > T rs1045642 gene polymorphism and HDMTX delayed elimination at 72 hours post HDMTX infusion; also, it is the first study to analyze the association between ABCB1 3435 C > T rs1045642 polymorphism with HDMTX toxicity and delayed elimination in adult Egyptian patients with hematological malignancies.

A Risk Scoring Model for High-Dose Methotrexate-Induced Liver Injury in Children With Acute Lymphoblastic Leukemia Based on Gene Polymorphism Study

A study on 70 acute lymphoblastic leukemia (ALL) children (age ≤16 years) treated with high-dose methotrexate (HD-MTX) in Sichuan Provincial People’s Hospital was conducted. The aim of the study was to establish a risk-scoring model to predict HD-MTX-induced liver injury, considering gene polymorphisms’ effects. Data screening was performed through t-test, chi-square test, and ridge regression, and six predictors were identified: age, MTRR_AA, MTRR_AG, SLCO1B1_11045879_CC, albumin_1 day before MTX administration, and IBIL_1 day before MTX administration (p < 0.1). Then, the risk-scoring model was established by ridge regression and evaluated the prediction performance. In a training cohort (n = 49), the area under the curve (AUC) was 0.76, and metrics including accuracy, precision, sensitivity, specificity, positive predictive value, and negative predictive value were promising (0.86, 0.81, 0.76, 0.91, 0.81, 0.88, respectively). In a test cohort (n = 21), the AUC was 0.62 and negative predictive value was 0.80; other evaluation metrics were not satisfactory, possibly due to the limited sample size. Ultimately, the risk scores were stratified into three groups based on their distributions: low- (≤48), medium- (49–89), and high-risk (>89) groups. This study could provide knowledge for the prediction of HD-MTX-induced liver injury and reference for the clinical medication.

Novel risk factors for glucarpidase use in pediatric acute lymphoblastic leukemia: Hispanic ethnicity, age, and the ABCC4 gene

BACKGROUND

Carboxypeptidase G₂ (CPDG₂ ; glucarpidase) is a rescue drug for patients at risk for kidney injury from high-dose methotrexate (MTX). As there are no strategies for predicting patients who will require CDPG₂ , we evaluated the role of demographic, clinical, and genetic factors for CPDG₂ use.

PROCEDURE

Cases who received CPDG₂ and controls who did not were identified by chart review of acute lymphoblastic leukemia (ALL) patients who received MTX doses between 1000 and 5000 mg/m² between 2010 and 2017. We used multivariable Bayesian logistic regression to evaluate the association of CPDG₂ use with demographic and clinical variables and, on a subset of patients, with genetic ancestry and 49 single nucleotide variants previously associated with MTX toxicity.

RESULTS

We identified 423 patients who received 1592 doses of MTX. Of the 18 patients who received CPDG₂ , 17 (94%) were Hispanic. No patients who received 1000 or 2000 mg/m² of MTX received CPDG₂ . Hispanic ethnicity (odds ratio: 4.68; 95% compatibility interval: 1.63-15.06) and older age (1.87 [1.17-3.17]) were associated with receiving CPDG₂ . Of the 177 patients in the genomic cohort, 11 received CPDG₂ . Each additional G allele of rs7317112 in ABCC4 increased the odds of requiring CPDG₂ (3.10 [1.12-6.75]). Six other loci (NTRK1/rs10908521, TSG1/rs9345389, STT3B/rs1353327, SCLO1B1/rs4149056, GATA3/rs3824662, ARID5B/rs10821936) demonstrated probabilities of association between 88% and 97%.

CONCLUSION

We demonstrated that demographic characteristics, including Hispanic ethnicity and age, are associated with CPDG₂ use. Additionally, we provide evidence that inherited genetic variation is associated with risk of requiring CPDG₂ . If validated in independent populations, this information could be leveraged to develop targeted toxicity prevention strategies for children with ALL.

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.

Evaluation of body-surface-area adjusted dosing of high-dose methotrexate by population pharmacokinetics in a large cohort of cancer patients

Background

The aim of this study was to identify sources of variability including patient gender and body surface area (BSA) in pharmacokinetic (PK) exposure for high-dose methotrexate (MTX) continuous infusion in a large cohort of patients with hematological and solid malignancies.

Methods

We conducted a retrospective PK analysis of MTX plasma concentration data from hematological/oncological patients treated at the University Hospital of Cologne between 2005 and 2018. Nonlinear mixed effects modeling was performed. Covariate data on patient demographics and clinical chemistry parameters was incorporated to assess relationships with PK parameters. Simulations were conducted to compare exposure and probability of target attainment (PTA) under BSA adjusted, flat and stratified dosing regimens.

Results

Plasma concentration over time data (2182 measurements) from therapeutic drug monitoring from 229 patients was available. PK of MTX were best described by a three-compartment model. Values for clearance (CL) of 4.33 [2.95–5.92] L h^− 1 and central volume of distribution of 4.29 [1.81–7.33] L were estimated. An inter-occasion variability of 23.1% (coefficient of variation) and an inter-individual variability of 29.7% were associated to CL, which was 16 [7–25] % lower in women. Serum creatinine, patient age, sex and BSA were significantly related to CL of MTX. Simulations suggested that differences in PTA between flat and BSA-based dosing were marginal, with stratified dosing performing best overall.

Conclusion

A dosing scheme with doses stratified across BSA quartiles is suggested to optimize target exposure attainment. Influence of patient sex on CL of MTX is present but small in magnitude.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-021-08443-x.

Genetic factors involved in delayed methotrexate elimination in children with acute lymphoblastic leukemia

BACKGROUND

Delayed excretion of methotrexate can lead to life-threatening toxicity that may result in treatment cessation, irreversible organ damage, and death. Various factors have been demonstrated to influence the pharmacokinetic process of methotrexate, including genetic and nongenetic factors.

METHODS

We investigated the genetic factors primarily related to the metabolic pathway of methotrexate in children with acute lymphoblastic leukemia with delayed elimination, defined as C_44-48h ≥ 1.0μmol/L in this study. A total of 196 patients (delayed excretion group: 98; normal excretion group: 98) who received CCCG-ALL-2015 protocol after propensity score-matched analysis were included in the study. Twenty-eight target single-nucleotide polymorphisms (SNPs) were analyzed by multiplex polymerase chain reaction and sequencing, and 25 SNPs were finally included in the study.

RESULTS

The genotype distribution of SLCO1B1 rs2306283 SNP was different between the delayed and normal excretion groups. SLCO1B1 rs2306283 AA carriers had a significantly lower methotrexate C_44-48h /D ratio than GG carriers in both groups. Furthermore, compared with the normal excretion group, SLCO1B1 rs2306283 AG and GG were risk factors for developing oral mucositis (odds ratio [OR]: 2.13; 95% confidence interval [CI]: 1.11-4.08; P < .001), hepatotoxicity (OR: 2.12; 95% CI: 1.26-3.56; P < .001), and myelosuppression (OR: 1.21; 95% CI: 1.04-1.41; P = .005) in delayed excretion group.

CONCLUSIONS

The results from this study indicate the potential role of SLCO1B1 rs2306283 as a pharmacogenomic marker to guide and optimize methotrexate treatment for delayed elimination in children with acute lymphoblastic leukemia.

Influence of Methylenetetrahydrofolate Reductase C677T and A1298C Polymorphism on High-Dose Methotrexate-Related Toxicities in Pediatric Non-Hodgkin Lymphoma Patients

Purpose

This retrospective study aimed to investigate the relationships between the methylenetetrahydrofolate reductase (MTHFR) C677T/A1298C and high-dose methotrexate (HD-MTX)-related toxicities in pediatric non-Hodgkin lymphoma (NHL) patients.

Patients and Methods

We reviewed the medical records of 93 NHL patients aged under 18 years who received HD-MTX therapy at the dose of 5 g/m² with 24-h infusion at Sun Yat-sen University Cancer Center between 2014 and 2019.

Results

There were 61 males and 32 females, with a median age of 8.8 years (0.9–15.8 years). The tumor types included lymphoblastic lymphoma (n = 38), Burkitt’s lymphoma (n = 31), anaplastic large cell lymphoma (n = 18), diffuse large B-cell lymphoma (n = 6). Overall, 355 courses of HD-MTX therapy were prescribed. All patients were rescued with calcium folinate 12 h after the end of MTX infusion. We found that plasma MTX levels > 0.2 μmol/L at 48 h post-infusion increased the risk of developing oral mucositis (2.4% VS. 9.5%, P = 0.018). Also, patients carrying the C677T and T677T genotypes had tendencies to be more susceptible to oral mucositis (P = 0.034). Patients harboring mutant 677T allele were more likely to develop leucopenia (38.5 vs. 50.3%, P = 0.025) and thrombocytopenia (22.0 vs. 32.4%, P = 0.028). For polymorphism A1298C, the mutant genotype played a protective role in vomiting (11.1 vs. 4.3%, P = 0.018) but increased the risk of anemia (23.8 vs. 41.7%, P < 0.001) and leucopenia (38.1 vs. 50.3%, P = 0.021).

Conclusion

Childhood NHL patients harboring C677T genotype were more vulnerable to oral mucositis, leucopenia, and thrombocytopenia, while those with A1298C genotype were at a decreased risk of vomiting and more likely to develop anemia and leucopenia.

The Application of 99mTc-DTPA Renal Dynamic Imaging to Measuring Renal Function of Children with Acute Lymphoblastic Leukemia after Induction Therapy

Purpose

The study was aimed at assessing renal functions of children with acute lymphoblastic leukemia (ALL) after induction therapy by ^99mTc-DTPA renal dynamic imaging Gates method (GFR_Gates) and investigating whether renal function after induction therapy will affect the occurrence of high-dose methotrexate- (HDMTX-) induced acute kidney injury (AKI).

Methods

Children with newly diagnosed ALL were enrolled. Renal functions before the administration of HDMTX were assessed by estimated glomerular filtration rate (eGFR) and GFR_Gates, respectively, before the first cycle of HDMTX after induction therapy. The areas under the ROC curve were used to assess covariates' ability to predict HDMTX-induced AKI.

Results

102 children with ALL were included in the study. A stepwise backward binary logistic regression showed that only standardized GFR_Gates was an independent risk factor for HDMTX-induced AKI (p = 0.018, odds ratio 0.985, 95% CI 0.972-0.997). The area under the ROC of standardized GFR_Gates was 0.679 (p = 0.012, 95% CI 0.554-0.804).

Conclusion

Standardized GFR_Gates showed that the normal renal function of children is not enough to be used as a cutoff point to predict HDMTX-induced AKI in ALL children receiving HDMTX. More attention and supportive care should be given to the children with standardized GFR_Gates lower than the cutoff value to avoid the HDMTX-induced AKI.

Pediatric randomized trial EORTC CLG 58951: Outcome for adolescent population with acute lymphoblastic leukemia

Over the years, the prognosis of adolescents treated for acute lymphoblastic leukemia (ALL) has improved. However, this age group still represents a challenge with an overall survival (OS) of 60% compared to 85% in younger children. Herein, we report the outcome of adolescents treated in the European Organisation for Research and Treatment of Cancer (EORTC) 58951 clinical trial. EORTC 58951 clinical trial included patients with de novo ALL between 1998 and 2008. For this study, we analyzed data of all adolescents between 15 and under 18. Data from 97 adolescents were analyzed, 70 had B-lineage and 27 had T-lineage ALL. The 8-year event-free survival (EFS) and OS for the B-cell precursor ALL cases were 72.3% (59.4%-81.7%) and 80.8% (67.4%-89.1%), respectively. For the T-lineage, the 8-year EFS and OS were 57.4% (36.1%-74.0%) and 59.0% (36.1%-76.2%), respectively. "B-other" ALL, defined as BCP-ALL lacking any known recurrent genetic abnormalities were more frequent in our adolescent population (52.8%) than in younger children (27.1%). Outcome of adolescents in the EORTC 58951 study is supporting the findings that adolescents have better outcome in pediatric compared to adults' trials. Nevertheless, in pediatric studies, adolescents still have a worse prognosis than younger children. Despite the fact that specific unfavorable characteristics may be linked to the adolescent population, a careful study and characterization of adolescents "B-other" genetic abnormalities in ALL is critical to improve the outcome of this population.

Development and Validation of UHPLC-MS/MS Assay for Therapeutic Drug Monitoring of High-dose Methotrexate in Children with Acute Lymphoblastic Leukemia

Purpose

Precise and timely detection of methotrexate (MTX) concentration played a key role in high-dose MTX individualization therapy in acute lymphoblastic leukemia (ALL) children to avoid serious adverse effects or nonresponse. This report described a sensibility and validation of ultra-high performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) method for therapeutic drug monitoring (TDM) of methotrexate concentration in children's plasma.

Methods

One-step protein precipitation of samples was accomplished by adding 200 μL of acetonitrile to 100 μL of plasma sample. The separation of plasma samples was carried out on a ZORBAX Eclipse Plus C18 Rapid Resolution HD column with gradient elution using a mobile phase constituted of acetonitrile and 1% formic acid. The detection was executed by electrospray ionization (ESI) of triple quadrupole tandem mass spectrometer (TQMS) in the multiple reaction monitoring (MRM) mode with the transitions m/z 455.2 → 307.9 for methotrexate and m/z 458.2 → 311.2 for IS, separately. Linear concentration range of the calibration curve was 44-11,000 nmol/L and 44 nmol/L was the lower limit of quantification.

Results

The methotrexate elution time was at 1.577 min, and the overall running time was only 3.3 min. The intra- and interday precision for all the analysis results was within 11.24%, and mean recoveries rate of methotrexate exceeded 87.98%.

Conclusion

The described and fully validated UHPLC-MS/MS method was successfully applied in clinical TDM after infusion of high-dose methotrexate 1-5 g/m² to 41 childpatients.

Safe administration of high-dose methotrexate with minimal drug level monitoring: Experience from a center in north India

BACKGROUND

High-dose methotrexate (HDMTX) is recommended to be administered with serial monitoring of methotrexate (MTX) levels, which may not be universally feasible in resource-limited settings. In this study, we evaluated the overall experience of administration of HDMTX at our center by monitoring a single drug level at 54 h from the start of MTX infusion.

METHODS

This retrospective study was performed at a tertiary level hospital in north India, over a 5-year period (2011-2015). All patients <18 years of age with newly diagnosed acute lymphoblastic leukemia (ALL) and T-non-Hodgkin lymphoma (T-NHL) were enrolled in the study. Details of HDMTX and all significant toxicities requiring prolonged or repeat hospitalization were retrieved from the medical records. All eligible patients received HDMTX as per the recommendations followed by at least three doses of leucovorin rescue, before drug levels were sent at 54 h. Subsequent leucovorin doses were adjusted accordingly.

RESULTS

The records of 598 cycles of HDMTX in 184 patients were reviewed. A total of 531 of 598 cycles (88.7%) were managed with monitoring only a single plasma drug level at 54 h from the beginning of infusion. Delayed MTX clearance was seen in 260 of 598 cycles (43.5%). Only three episodes (0.5%) were associated with significant toxicity. There were no deaths.

CONCLUSIONS

The strategy of monitoring MTX concentration at 54 h was safe in our cohort. Although recommended, dynamic monitoring of plasma drug levels may not always predict toxicity.

Do intravenous fluid substitutions influence methotrexate clearance? An unanticipated impact of an intravenous sodium bicarbonate drug shortage

BACKGROUND

National drug shortages of essential medications for childhood cancer have increasingly posed a challenge in the treatment of patients. The efficacy of standardized supportive care practices to avoid treatment-related toxicities may be limited during these drug shortages. High-dose methotrexate (HDMTX) plays a critical role in modern treatment protocols for acute lymphoblastic leukemia and requires stringent supportive care measures to mitigate toxicity. As the result of a national intravenous (IV) sodium bicarbonate shortage, institutional standard HDMTX supportive care guidelines had to be modified. We describe the unanticipated consequences on HDMTX clearance.

METHODS

We performed a retrospective chart review assessing the impact of alternative compositions of IV fluids on the mean 24-h methotrexate levels (Cp_ss ) of 25 patients receiving 76 total HDMTX infusions at Texas Children's Hospital Cancer Center from March to October 2017. During the sodium bicarbonate drug shortage, all patients received IV hydration consisting of either dextrose 5%, 0.45% normal saline (D5 ½ NS-Group A) or dextrose 5%, 0.2% normal saline (D5 ¼ NS-Group B).

RESULTS

Patients receiving a higher total sodium dose demonstrated significantly lower Cp_ss (25.36 ± 16.6 μMol) compared to patients receiving less sodium (53.9 ± 37.9 μMol; P < .001).

CONCLUSIONS

Our report shows that in the setting of IV sodium bicarbonate shortage, the composition of hydration IV fluids may affect methotrexate clearance. Patient who received a higher sodium load had a lower 24-h methotrexate level. This demonstrates the potential for unanticipated outcomes resulting from national drug shortages.

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.

Pharmacokinetics and pharmacogenetics of high-dose methotrexate in Chinese adult patients with non-Hodgkin lymphoma: a population analysis

PURPOSE

High-dose methotrexate (HD-MTX) is widely used in the treatment of non-Hodgkin lymphoma (NHL), but the pharmacokinetic properties of HD-MTX in Chinese adult patients with NHL have not yet been established through an approach that integrates genetic covariates. The purposes of this study were to identify both physiological and pharmacogenomic covariates that can explain the inter- and intraindividual pharmacokinetic variability of MTX in Chinese adult patients with NHL and to explore a new sampling strategy for predicting delayed MTX elimination.

METHODS

A total of 852 MTX concentrations from 91 adult patients with NHL were analyzed using the nonlinear mixed-effects modeling method. FPGS, GGH, SLCO1B1, ABCB1 and MTHFR were genotyped using the Sequenom MassARRAY technology platform and were screened as covariates. The ability of different sampling strategies to predict the MTX concentration at 72 h was assessed through maximum a posteriori Bayesian forecasting using a validation dataset (18 patients).

RESULTS

A two-compartment model adequately described the data, and the estimated mean MTX clearance (CL) was 6.03 L/h (9%). Creatinine clearance (CrCL) was identified as a covariate for CL, whereas the intercompartmental clearance (Q) was significantly affected by the body surface area (BSA). However, none of the genotypes exerted a significant effect on the pharmacokinetic properties of MTX. The percentage of patients with concentrations below 0.2 µmol/L at 72 h decreased from 65.6 to 42.6% when the CrCL decreased from 90 to 60 ml/min/1.73 m² with a scheduled dosing of 3 g/m², and the same trend was observed with dose regimens of 1 g/m² and 2 g/m². Bayesian forecasting using the MTX concentrations at 24 and 42 h provided the best predictive performance for estimating the MTX concentration at 72 h after dosing.

CONCLUSIONS

The MTX population pharmacokinetic model developed in this study might provide useful information for establishing personalized therapy involving MTX for the treatment of adult patients with NHL.

Population pharmacokinetics of high-dose methotrexate in Chinese pediatric patients with medulloblastoma

Methotrexate (MTX) pharmacokinetics has substantial inter-individual variability and toxicity. In children with medulloblastoma treated with high-dose methotrexate (HD-MTX), the pharmacokinetic properties of methotrexate have not been established. A total of 660 serum samples from 105 pediatric patients with medulloblastoma were included in a population pharmacokinetic (PPK) analysis of methotrexate by using the nonlinear mixed-effects modeling method. The basic one-compartment population pharmacokinetic model was established by NONMEM software and the first-order conditional estimation (FOCE) method, and the final covariate model was obtained by the stepwise regression method. Weight (WT), creatinine clearance (CrCL), and whether the treatment was combined with dexamethasone (DEX) were covariates that had significant effects on the clearance rate (CL) of the model. The pharmacokinetic equation of CL in the final covariate model was as follows: CL_i = 9.23× (1 + 0.0005× (θ_CrCL -105.78)) × (1 + 0.0017× (θ_WT -16)) × e^ηcl,i (L/h), IF (θ_DEX ) CL_i = 1.19× CL_i (L/h). The estimation accuracy of all pharmacokinetic parameters were acceptable (relative standard error < 14.74%). The goodness-of-fit diagram and bootstrap tests indicated that the final PPK model was stable with acceptable predictive ability. The PPK model may be useful for determining personalized medication levels in pediatric medulloblastoma patients undergoing HD-MTX therapy.

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

BACKGROUND

Infants with acute lymphoblastic leukemia (ALL) treated with high-dose methotrexate may have reduced methotrexate clearance (CL) due to renal immaturity, which may predispose them to toxicity.

OBJECTIVE

The aim of this study was to develop a population pharmacokinetic (PK) model of methotrexate in infants with ALL.

METHODS

A total of 672 methotrexate plasma concentrations were obtained from 71 infants enrolled in the Children's Oncology Group (COG) Clinical Trial P9407. Infants received methotrexate 4 g/m2 intravenously for four cycles during weeks 4-12 of intensification. A population PK analysis was performed using NONMEM® version 7.4. The final model was evaluated using a non-parametric bootstrap and a visual predictive check. Simulations were performed to evaluate methotrexate dose and the utility of a bedside algorithm for dose individualization.

RESULTS

Methotrexate was best characterized by a two-compartment model with allometric scaling. Weight was the only covariate included in the final model. The coefficient of variation for interoccasion variability (IOV) on CL was relatively high at 25.4%, compared with the interindividual variability for CL and central volume of distribution (10.7% and 13.2%, respectively). Simulations identified that 21.1% of simulated infants benefitted from bedside dose adjustment, and adjustment of methotrexate doses during infusions can avoid supratherapeutic concentrations.

CONCLUSION

Infants treated with high-dose methotrexate demonstrated a relatively high degree of IOV in methotrexate CL. The magnitude of IOV in the CL of methotrexate suggests that use of a bedside algorithm may avoid supratherapeutic methotrexate concentrations resulting from high IOV in methotrexate CL.

Quantification of Methotrexate in Human Serum and Plasma by Liquid Chromatography Tandem Mass Spectrometry

Mass spectrometry (MS) is a highly specific and sensitive technique that is used for the detection of many different analytes with diverse chemical characteristics. It has been adopted by clinical laboratories for the quantification of small molecules and, by extension, has been widely used for therapeutic drug monitoring. It is an attractive alternative to immunoassay methods, because it is not subject to the same interferences. A limitation of MS (relative to immunoassays) is the turnaround time. However, this can be addressed by workflow parallelization with other assays. Herein we describe a tandem LC-MS/MS method for the detection and quantification of methotrexate in human plasma with a lower limit of quantification of 0.01 μM and within-assay and between-assay coefficients of variation of less than 15%. This method lacks interference from high-abundance metabolites and utilizes kindred chromatography to improve turnaround time in the therapeutic drug monitoring laboratory.

Population Pharmacokinetic Study and Individual Dose Adjustments of High-Dose Methotrexate in Chinese Pediatric Patients With Acute Lymphoblastic Leukemia or Osteosarcoma

High-dose methotrexate (>0.5 g/m² ) is among the first-line chemotherapeutic agents used in treating acute lymphoblastic leukemia (ALL) and osteosarcoma in children. Despite rapid hydration, leucovorin rescue, and routine therapeutic drug monitoring, severe toxicity is not uncommon. This study aimed at developing population pharmacokinetic (popPK) models of high-dose methotrexate for ALL and osteosarcoma and demonstrating the possibility and convenience of popPK model-based individual dose optimization using R and shiny, which is more accessible, efficient, and clinician-friendly than NONMEM. The final data set consists of 36 ALL (354 observations) and 16 osteosarcoma (585 observations) patients. Covariate model building and parameter estimations were done using NONMEM and Perl-speaks-NONMEM. Diagnostic Plots and bootstrapping validated the models' performance and stability. The dose optimizer developed based on the validated models can obtain identical individual parameter estimates as NONMEM. Compared to calling a NONMEM execution and reading its output, estimating individual parameters within R reduces the execution time from 8.7-12.8 seconds to 0.4-1.0 second. For each subject, the dose optimizer can recommend (1) an individualized optimal dose and (2) an individualized range of doses. For osteosarcoma, recommended optimal doses by the optimizer resemble the final doses at which the subjects were eventually stabilized. The dose optimizers developed demonstrated the potential to inform dose adjustments using a model-based, convenient, and efficient tool for high-dose methotrexate. Although the dose optimizer is not meant to replace clinical judgment, it provides the clinician with the individual pharmacokinetics perspective by recommending the (range of) optimal dose.

Evaluation of the Novel Methotrexate Architect Chemiluminescent Immunoassay: Clinical Impact on Pharmacokinetic Monitoring

BACKGROUND

Fluorescence polarization immunoassay (FPIA) has probably been the most widely used technique for the determination of methotrexate (MTX) concentrations in clinical laboratories. After its replacement by a novel architect chemiluminescent microparticle immunoassay (CMIA), it is essential to verify that there are no differences between the methods that can induce an error in leucovorin rescue with dire consequences for the patient. The objective of our study was to compare plasma/serum MTX measurements between CMIA and FPIA (reference method in this study) in the work conditions of a clinical pharmacokinetics unit to determine whether any difference would affect clinical decisions on the management of this drug.

METHODS

FPIA on TDx/FLx and CMIA on Architect ci8200 were simultaneously used to evaluate 127 clinical samples. Within-run (20 repetitions on same day) and between-run (20 repetitions on different days) imprecision was evaluated using 6 control samples provided by the manufacturer and diluting 2 of them by 50% for 0.03 and 0.22 μmol/L, respectively. The Passing-Bablok regression method, Bland-Altman plot, and concordance correlation coefficient (CCC) were used in the statistical analysis.

RESULTS

Within-run imprecision was <5% (3.6%-4.39%) and between-run imprecision <11% (2.42%-10.65%). Between-assay correlation for the studied concentration range (0.05-250 μmol/L) was CMIA = -0.026 + 1.033 FPIA (n = 127), r = 0.9963, and CCC = 0.9946. For samples <1.5 μmol/L (nondiluted) included in the assay calibration curve, the correlation was CMIA = -0.009 + 0.955 FPIA (n = 54), r = 0.9819, and CCC = 0.9807. No significant difference was observed between the measurements by the 2 assays, given that the 95% confidence interval of the ordinate at the origin included "0" (-0.020 to 0.0007), and the 95% confidence interval of the slope included 1 (0.923-1.020). The interchangeability of these assays was confirmed by Bland-Altman plot results, which showed a mean difference insignificant at concentrations <10 μmol/L.

CONCLUSIONS

The correlation between methods was excellent, and Passing-Bablok regression analysis detected no virtually difference in their results. Utilization of the CMIA-Architect assay to measure MTX concentrations would therefore not affect clinical decisions on MTX management, supporting its employment in routine MTX monitoring.

Population Pharmacokinetics of High-Dose Methotrexate in Patients With Primary Central Nervous System Lymphoma

The intra- and inter-individual variances of methotrexate (MTX) pharmacokinetics are extremely large, and the pharmacokinetic property of MTX in patients with primary central nervous system lymphoma (PCNSL) is unestablished. A total of 701 MTX plasma concentrations from 98 patients with PCNSL under high-dose MTX therapy were used to develop the population pharmacokinetic (popPK) model of MTX by using the nonlinear mixed-effects modeling method. A 2-compartment model was employed to describe the pharmacokinetic property of MTX. In the final popPK model, inclusion of serum creatinine and body surface area significantly reduced objective function value for clearance over the base model (p <0.001), and inclusion of age significantly reduced objective function value for distribution volume of central compartment (V_c) over the base model (p <0.001). In the final popPK model, the inter-individual clearance = 6.67 × (SCR/68.1)^-0.48 × (BSA/1.75)^1.17; V_c = 24.46 × (age/57.16)^0.81. The precision of all parameters was acceptable (relative standard error <28.61%). Bootstrap and visual predictive check results indicated that the final popPK model was stable with acceptable predictive ability. The popPK model may be useful for personalized medication in PCNSL patients under high-dose MTX therapy. Further studies are warranted to confirm the results.

Population Pharmacokinetics: Some Observations in Pediatric Modeling for Drug Clearance

The objective of this study is to evaluate the predictive performance of several models to predict drug clearance in preterm and term neonates. Five models using different types of allometric and linear models were developed. Two sets of data were used to develop these models (data from preterm neonates to adults and data from preterm and term neonates). Models were also developed with (normalized to 70 kg) or without body weight normalization (body weight 1 kg). From the literature, clearance values for four drugs from neonates to adults were obtained. External data were used to evaluate the predictive performance of these models in preterm and term neonates. The results of the study indicated that (1) normalization to a standard body weight had no impact on the predictive performance of the models, (2) the model developed from preterm neonates to adults using fixed exponent 0.75 provided inaccurate estimate (overestimation) of drug clearance in neonates, (3) a far superior prediction of clearance was observed with the model when the exponents of allometry were estimated than the model using exponent 0.75, (4) linear models with the exception of the model with intercept provided comparable results to the estimated exponent model and were superior in their predictive performance to the model using exponent 0.75, and (5) when the models were developed from neonate data, the predictive performance of all models were similar. Overall, the study indicated that body weight normalization had no impact on the performance of model prediction, the exponents of allometry in pharmacostatistical models should be estimated rather than fixed, and more studies are needed to evaluate the suitability of linear models for the prediction of drug clearance in neonates.

Using a Bedside Algorithm to Individually Dose High-dose Methotrexate for Patients at Risk for Toxicity

We developed a bedside algorithm for individually adjusting the high-dose methotrexate (HDMTX) dose (5 g/m) given to patients with acute lymphoblastic leukemia at high risk for methotrexate toxicity. Data were reviewed for 8 patients receiving 21 cycles of HDMTX as per our algorithm. Eleven cycles began with 5 g/m, 10 cycles began with a preinfusion 20% to 25% dose reduction. Neither mean MTX AUC (2320.5±179.1 vs. 2080.4±161.7 μmol×h/L), mean Cpss (64.3±7.9 vs. 60.8±6.1 μM), nor toxicities were statistically different between groups. Our algorithm allowed the safe administration of HDMTX to patients at risk of MTX toxicities and obviated the need for preinfusion dose reduction.

Preventing and Managing Toxicities of High-Dose Methotrexate

: High-dose methotrexate (HDMTX), defined as a dose higher than 500 mg/m2, is used to treat a range of adult and childhood cancers. Although HDMTX is safely administered to most patients, it can cause significant toxicity, including acute kidney injury (AKI) in 2%-12% of patients. Nephrotoxicity results from crystallization of methotrexate in the renal tubular lumen, leading to tubular toxicity. AKI and other toxicities of high-dose methotrexate can lead to significant morbidity, treatment delays, and diminished renal function. Risk factors for methotrexate-associated toxicity include a history of renal dysfunction, volume depletion, acidic urine, and drug interactions. Renal toxicity leads to impaired methotrexate clearance and prolonged exposure to toxic concentrations, which further worsen renal function and exacerbate nonrenal adverse events, including myelosuppression, mucositis, dermatologic toxicity, and hepatotoxicity. Serum creatinine, urine output, and serum methotrexate concentration are monitored to assess renal clearance, with concurrent hydration, urinary alkalinization, and leucovorin rescue to prevent and mitigate AKI and subsequent toxicity. When delayed methotrexate excretion or AKI occurs despite preventive strategies, increased hydration, high-dose leucovorin, and glucarpidase are usually sufficient to allow renal recovery without the need for dialysis. Prompt recognition and effective treatment of AKI and associated toxicities mitigate further toxicity, facilitate renal recovery, and permit patients to receive other chemotherapy or resume HDMTX therapy when additional courses are indicated.

IMPLICATIONS FOR PRACTICE

High-dose methotrexate (HDMTX), defined as a dose higher than 500 mg/m2, is used for a range of cancers. Although HDMTX is safely administered to most patients, it can cause significant toxicity, including acute kidney injury (AKI), attributable to crystallization of methotrexate in the renal tubular lumen, leading to tubular toxicity. When AKI occurs despite preventive strategies, increased hydration, high-dose leucovorin, and glucarpidase allow renal recovery without the need for dialysis. This article, based on a review of the current associated literature, provides comprehensive recommendations for prevention of toxicity and, when necessary, detailed treatment guidance to mitigate AKI and subsequent toxicity.

Naked-eye nanobiosensor for therapeutic drug monitoring of methotrexate

Sensing of methotrexate at clinically-relevant concentrations was achieved with a plasmon-coupling assay.

Methotrexate Associated Renal Impairment Is Related to Delayed Elimination of High-Dose Methotrexate

Although Methotrexate (MTX) is an effective drug for the treatment of acute lymphoblastic leukemia (ALL), the toxicity remains a significant problem. In this prospective study, fifty-four patients with ALL were enrolled. 3 g or 5 g MTX/m² was administered over 24 hours. Serum MTX concentrations were determined in 24, 48, and 96 hours after MTX infusion. Serum creatinine concentrations and creatinine clearance rate (CCR) were determined before and 24 and 48 hours after MTX infusion. A total of 173 courses of MTX infusion were administered. The serum creatinine concentrations did not change much after MTX infusion while the CCR was gradually decreased. MTX clearance status was independently related to CCR decrease, with the risk of 8.07 to develop renal impairment in patients with delayed MTX elimination. Serum creatinine concentration, serum creatinine ratio, CCR, and CCR ratio at 24 hours were all related to MTX elimination delay. Patients with serum creatinine level >35.0 μmol/L, creatinine ratio >1.129, or CCR <100.0 mL/min were more likely to undergo MTX elimination delay. In conclusion, MTX could induce transient renal impairment and compromised renal function will delay MTX clearance. The serum creatinine concentration and the ratio and CCR are useful tools for evaluating MTX elimination status.

Toxicity of Cancer Therapy in Adolescents and Young Adults (AYAs)

OBJECTIVES

To identify treatment-related toxicities that are either more frequent or more severe in the adolescent and young adult (AYA) oncology population. To explore differences in drug pharmacology and patient physiology that contribute to toxicities in the AYA population and to describe the impact of treatment-related toxicities on outcomes for AYA patients.

DATA SOURCES

A PubMed search was undertaken using the key words Adolescent Young Adult Oncology, AYA, toxicity, bone marrow transplant, late effects, and chemotherapy. Additional toxicity information was also obtained from recent publications from cancer cooperative groups treating AYA patients.

CONCLUSION

AYA patients often experience more severe toxicities than children when treated with identical chemotherapy regimens, which can interfere with successful administration of planned treatment, as well as have profound effects on quality of life. AYA patients with cancer face the dual challenge of disease biology associated with inferior response to treatment, thus necessitating treatment intensification, while at the same time suffering higher rates of specific toxicities such as vincristine-induced neuropathy, osteonecrosis, and treatment-related mortality caused by infection.

IMPLICATIONS FOR NURSING PRACTICE

AYA patients are at a higher risk for toxicities from regimens that may be tolerated by younger patients. Staff should be aware of toxicities facing this population so that appropriate supportive care measures can be utilized. Future research on the pharmacology of drugs in adolescence, hormonal effects on drug-metabolizing enzymes, cumulative exposure to different drugs in combination, and risk and severity of specific toxicities will be critical to improving the treatment of AYA patients.

Delayed methotrexate excretion in infants and young children with primary central nervous system tumors and postoperative fluid collections

PURPOSE

High-dose methotrexate (HD-MTX) has been used to treat children with central nervous system tumors. Accumulation of MTX within pleural, peritoneal, or cardiac effusions has led to delayed excretion and increased risk of systemic toxicity. This retrospective study analyzed the association of intracranial post-resection fluid collections with MTX plasma disposition in infants and young children with brain tumors.

METHODS

Brain MRI findings were analyzed for postoperative intracranial fluid collections in 75 pediatric patients treated with HD-MTX and for whom serial MTX plasma concentrations (MTX) were collected. Delayed plasma excretion was defined as (MTX) ≥1 μM at 42 hours (h). Leucovorin was administered at 42 h and then every 6 h until (MTX) <0.1 μM. Population and individual MTX pharmacokinetic parameters were estimated by nonlinear mixed-effects modeling.

RESULTS

Fifty-eight patients had intracranial fluid collections present. Population average (inter-individual variation) MTX clearance was 96.0 ml/min/m² (41.1 CV %) and increased with age. Of the patients with intracranial fluid collections, 24 had delayed excretion; only 2 of the 17 without fluid collections (P < 0.04) had delayed excretion. Eleven patients had grade 3 or 4 toxicities attributed to HD-MTX. No significant difference was observed in intracranial fluid collection, total leucovorin dosing, or hydration fluids between those with and without toxicity.

CONCLUSIONS

Although an intracranial fluid collection is associated with delayed MTX excretion, HD-MTX can be safely administered with monitoring of infants and young children with intracranial fluid collections. Infants younger than 1 year may need additional monitoring to avoid toxicity.