Resumption of high-dose methotrexate after acute kidney injury and glucarpidase use in pediatric oncology patients

Methotrexate-induced neurotoxicity in oncology: Current issues for a classic drug

Methotrexate (MTX) is an antimetabolite with immunosuppressive and antineoplastic properties extensively used in cancer treatment. It is administered through various routes, including intravenous and intrathecal. MTX inhibits the dihydrofolate reductase, thereby disrupting folic acid metabolism and impending DNA synthesis. Despite its efficacy, MTX administration can result in significant toxicity, affecting multiple organs and leading to potential side effects like myelosuppression, hepatotoxicity, renal failure, mucositis and neurotoxicity. MTX-induced neurotoxicity is a critical problem, with manifestations varying from hours to years post-administration, ranging from transient and reversible to severe presentations. Several risk factors may contribute to MTX-induced neurotoxicity, including genetic predisposition, drug interactions, renal impairment and concurrent radiotherapy. Management strategies in preventing and mitigating neurotoxicity are based on supportive measures such as hydration, leucovorin rescue and the use of glucarpidase. This review focusses on the neurotoxic effects of MTX, a global health issue in the growing cancer population.

Navigating methotrexate toxicity: Examining the therapeutic roles of folinic acid and glucarpidase

Methotrexate (MTX) toxicity varies depending on factors such as dosing frequency (acute or repeated), dosage (low or high) and the administration route (oral, parenteral or intrathecal). Renal impairment can trigger or exacerbate MTX toxicity. Acute oral low-dose MTX (LDMTX) overdoses seldom lead to toxicity due to the saturable maximal bioavailable dose, but toxicity risks increase with repeated low doses (>3 days), high-dose MTX (HDMTX) or intrathecal poisoning. Folinic acid shares MTX transporters in the gut and cells and bypasses the MTX-induced dihydrofolate reductase inhibition. The required folinic acid dosage differs for low-dose and high-dose MTX toxicities. Acute LDMTX poisoning rarely requires folinic acid, while chronic LDMTX poisoning needs low-dose folinic acid until cellular function is restored. In HDMTX toxicities, early intravenous folinic acid administration is recommended, with dose and duration being guided by MTX concentrations and clinical improvement. In intrathecal MTX poisoning, folinic acid should be administered intravenously. Glucarpidase, a recombinant bacterial enzyme, has a high affinity for MTX and folate analogues in the intravascular or intrathecal systems. It decreases serum MTX concentrations by 90%-95% within 15 min. Its primary indication is for intrathecal MTX poisoning. It is rarely indicated in HDMTX toxicity unless patients have renal injury. However, there is no literature evidence supporting its use in HDMTX poisoning. Its use is limited by its significant cost and lack of availability. Haemodialysis can be potentially useful for MTX removal in cases where glucarpidase is not available. Additionally, fluid hydration, renal support and urine alkalinization are important adjunctive therapies for managing MTX toxicities.

PAX3-FOXO1 drives targetable cell state-dependent metabolic vulnerabilities in rhabdomyosarcoma

PAX3-FOXO1, an oncogenic transcription factor, drives a particularly aggressive subtype of rhabdomyosarcoma (RMS) by enforcing gene expression programs that support malignant cell states. Here we show that PAX3-FOXO1 + RMS cells exhibit altered pyrimidine metabolism and increased dependence on enzymes involved in de novo pyrimidine synthesis, including dihydrofolate reductase (DHFR). Consequently, PAX3-FOXO1 + cells display increased sensitivity to inhibition of DHFR by the chemotherapeutic drug methotrexate, and this dependence is rescued by provision of pyrimidine nucleotides. Methotrexate treatment mimics the metabolic and transcriptional impact of PAX3-FOXO1 silencing, reducing expression of genes related to PAX3-FOXO1-driven malignant cell states. Accordingly, methotrexate treatment slows growth of multiple PAX3-FOXO1 + tumor xenograft models, but not fusion-negative counterparts. Taken together, these data demonstrate that PAX3-FOXO1 induces cell states characterized by altered pyrimidine dependence and nominate methotrexate as an addition to the current therapeutic arsenal for treatment of these malignant pediatric tumors.

A European consensus recommendation on the management of delayed methotrexate elimination: supportive measures, leucovorin rescue and glucarpidase treatment

High-dose methotrexate (HDMTX) is used in the treatment of a range of adult and childhood cancers. Although HDMTX can provide effective anti-tumor activity with an acceptable safety profile for most patients, delayed methotrexate elimination (DME) develops in a minority of patients receiving HDMTX and may be accompanied by renal dysfunction and potentially life-threatening toxicity. A panel of European physicians with experience in the use of HDMTX as well as of glucarpidase convened to develop a series of consensus statements to provide practical guidance on the prevention and treatment of DME, including the use of glucarpidase. Robust implementation of supportive measures including hyperhydration and urine alkalinization emerged as critical in order to reduce the risk of DME with HDMTX treatment, with leucovorin rescue critical in reducing the risk of DME complications. Early recognition of DME is important to promptly implement appropriate treatment including, intensified hydration, high-dose leucovorin and, when appropriate, glucarpidase.

Rechallenge With High-Dose Methotrexate After Treatment With Glucarpidase in Adult Patients With Lymphoma

PURPOSE

Limited evidence exists regarding methotrexate (MTX) resumption after patients with lymphoma receive glucarpidase for toxic MTX levels and acute kidney injury (AKI).

METHODS

This retrospective review included adults with lymphoma treated with glucarpidase after MTX at Mayo Clinic between January 31, 2020, and October 10, 2022. Descriptive statistics summarize patient characteristics and clinical outcomes.

RESULTS

Of 11 patients treated with glucarpidase after MTX, seven (64%) were rechallenged with MTX. Indications for MTX rechallenge included confirmed CNS disease (n = 6, 86%) and intravascular lymphoma (n = 1, 14%). Compared with the nonrechallenged subgroup, before receiving MTX that required glucarpidase rescue, the rechallenged patients had lower median pretreatment serum creatinine (Scr; 0.7 v 1.2 mg/dL), and none had AKI with previous MTX doses, n = 0 (0%) versus n = 2 (50%). During the MTX dose requiring glucarpidase rescue, the rechallenged group had lower median peak Scr (1.26 v 3.32 mg/dL) and lower incidence of AKI stage III (n = 1 [14%] v n = 3 [75%]), and none of the rechallenged patients required renal replacement therapy (RRT; n = 0 [0%] v n = 1 [25%]). At the first rechallenge after glucarpidase administration, the median MTX dose reduction was 56% (range, 46%-75%), and the lowest used dose when prescribed according to each treatment protocol schedule was 1.5 g/m2. Two (29%) patients experienced AKI (n = 1 stage I, n = 1 stage II) after MTX rechallenge. Zero patients required RRT, and zero required another glucarpidase administration. Six (86%) patients completed all recommended MTX doses.

CONCLUSION

In selected adults with lymphoma who required glucarpidase for toxic MTX levels after administration of high-dose MTX, resumption of MTX therapy at lower doses is safe. Patients selected for MTX resumption had experienced less severe AKI during the previous cycle compared with those not selected for MTX resumption.

Methotrexate level discrepancy post-glucarpidase: A pediatric case series and review of literature

Methotrexate is a common component of pediatric oncology treatment and delayed clearance increases risk of significant toxicities. Glucarpidase is indicated for patients with toxic plasma methotrexate concentrations with renal toxicity. Laboratory interference with immunoassay measurement post-glucarpidase administration is well established, with current product labeling indicating this persists for 48 h. However, recent experience in pediatric patients supports this discrepancy persists beyond 48 h. Three cases experienced delayed methotrexate clearance and received glucarpidase with subsequent measurement of methotrexate levels by liquid chromatography tandem mass spectrometry (LC-MS/MS) and/or immunoassay. Within this case series, discrepancies between LC-MS/MS and immunoassay levels persisted significantly longer than 48 h.

Diagnostic, Pathologic, and Therapeutic Considerations for Primary CNS Lymphoma

Primary CNS lymphoma (PCNSL) is a rare lymphoma representing 3% of CNS malignancies. The diagnosis is complicated by the unique risks associated with brain biopsy, and the treatment is similarly complicated by the restriction of effective therapeutics able to cross the blood-brain barrier. Currently, the majority of individuals diagnosed with this disease are immunocompetent although immune deficiency related to HIV or immunosuppressive therapy remains an important risk factor. Improvements in both frontline therapy and consolidation options, including the use of hematopoietic stem-cell transplantation, have translated to improved survival. Unfortunately, patients experiencing relapsed or refractory disease often fare poorly. Here, we review key clinical, pathologic, and therapeutic aspects of PCNSL and highlight challenging clinical scenarios that may be encountered by the treating oncologist.

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.

Use of glucarpidase (carboxypeptidase-G2) in pediatric cancer patients: 11-year experience of a tertiary center

Methotrexate is an essential drug in the treatment of childhood cancer that is not exempt from toxicities. Glucarpidase is a drug used to reduce the toxic concentration of plasma methotrexate in patients with delayed elimination or at risk of toxicity. We describe the characteristics of a cohort of pediatric patients that received glucarpidase and analyze its role in the treatment of toxicity induced by high doses of methotrexate (HDMTX). Retrospective observational study of all pediatric cancer patients who received glucarpidase between 2012 and 2022 at a single center. Fifteen patients were treated with a single dose of glucarpidase, eleven of them presented with acute lymphoblastic leukemia and received HDMTX at 5 g/m2 in 24-hour infusion. In eight patients, glucarpidase was administered during the first cycle of HDMTX. The indication in thirteen cases was acute renal failure with delayed elimination of plasma methotrexate. The median maximum creatinine was 1.22 mg/dl (0.68 2.01 mg/dl), with a median increase over its baseline level of 313%. All patients normalized renal function after glucarpidase administration, with a median methotrexate excretion time of 193 hours (42-312 hours). No grade ≥2 adverse events derived from carboxypeptidase administration. Eleven patients received new doses of HDMTX in subsequent cycles, without new episodes of serious toxicity. The use of glucarpidase is effective and safe in the treatment of acute renal failure and methotrexate elimination delay in pediatric cancer patients. Further HDMTX doses may be prescribed without additional toxicities.

Engineered biomaterial delivery strategies are used to reduce cardiotoxicity in osteosarcoma

Osteosarcoma (OS) is the most common malignant bone tumor in children and adolescents. Chemotherapy drugs play an integral role in OS treatment. Preoperative neoadjuvant chemotherapy and postoperative conventional adjuvant chemotherapy improve survival in patients with OS. However, the toxic side effects of chemotherapy drugs are unavoidable. Cardiotoxicity is one of the common side effects of chemotherapy drugs that cannot be ignored. Chemotherapy drugs affect the destruction of mitochondrial autophagy and mitochondria-associated proteins to cause a decrease in cardiac ejection fraction and cardiomyocyte necrosis, which in turn causes heart failure and irreversible cardiomyopathy. Biomaterials play an important role in nanomedicine. Biomaterials act as carriers to deliver chemotherapy drugs precisely around tumor cells and continuously release carriers around the tumor. It not only promotes anti-tumor effects but also reduces the cardiotoxicity of chemotherapy drugs. In this paper, we first introduce the mechanism by which chemotherapy drugs commonly used in OS cause cardiotoxicity. Subsequently, we introduce biomaterials for reducing cardiotoxicity in OS chemotherapy. Finally, we prospect biomaterial delivery strategies to reduce cardiotoxicity in OS.

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.

The use of glucarpidase as a rescue therapy for high dose methotrexate toxicity - a review of pharmacological and clinical data

INTRODUCTION

This review aims to summarize recent data on the pharmacodynamic, pharmacokinetic, and safety of glucarpidase. This is an enzymatic agent that catalyzes the conversion of methotrexate (MTX) into inactive metabolites. Glucarpidase is used to manage high-dose MTX (HDMTX) toxic plasma concentration, especially in patients with impaired renal function.

AREAS COVERED

In this review, studies on glucarpidase clinical efficacy as a therapeutic option for patients suffering from MTX kidney toxicity were presented. Pharmacodynamic and pharmacokinetic properties of glucarpidase were included. Moreover, potential interactions and safety issues were discussed.

EXPERT OPINION

The use of glucarpidase is an effective therapeutic strategy in both adults and children treated with high doses of MTX for various types of cancer who have developed acute renal failure. Glucarpidase causes MTX to be converted to nontoxic metabolites and accelerates the time for its complete elimination. After administration of glucarpidase, it is possible to resume HDMTX.

A pooled subgroup analysis of glucarpidase treatment in 86 pediatric, adolescent, and young adult patients receiving high-dose methotrexate therapy in open-label trials

BACKGROUND

Delayed methotrexate elimination can occur in patients undergoing high-dose methotrexate cancer treatment. Effectiveness of glucarpidase for rapidly reducing methotrexate concentrations was shown in compassionate-use trials in patients aged 0-84 years.

METHODS

We performed post hoc analyses of infants (≥28 days to <2 years), children (≥2 to <12 years), adolescents (≥12 to <15 years), and young adults (≥15 to <25 years) from four multicenter, open-label, single-arm, glucarpidase compassionate-use trials. Patients had toxic methotrexate levels due to delayed methotrexate elimination and/or renal dysfunction, and received glucarpidase (50 U/kg). The primary endpoint was clinically important reduction (CIR) in plasma methotrexate (methotrexate ≤1 μmol/L at all post-glucarpidase measurements) based on high-performance liquid chromatography.

RESULTS

Among 86 patients included in efficacy analyses, CIR was achieved by zero of one infant (0.0%), five of 16 children (31.3%), seven of 24 adolescents (29.2%), and 26/45 young adults (57.8%). Median methotrexate reduction was 98.7% or higher in each group 15 minutes post-glucarpidase. Patients with pre-glucarpidase methotrexate less than 50 μmol/L (35/42, 83.3%) were more likely to achieve CIR than those with methotrexate 50 μmol/L or higher (1/37, 2.7%). The most common treatment-related adverse event was paresthesia, occurring in three adolescents (4.5%) and six young adults (5.2%). No other treatment-related adverse event occurred in 5% or higher of any age group.

CONCLUSION

After accounting for pre-glucarpidase methotrexate levels, glucarpidase efficacy at inducing CIR in pediatric/young adult patients was consistent, with efficacy observed in the overall study population (i.e., patients aged 0-84), and no unexpected safety findings were observed. These findings demonstrate glucarpidase (50 U/kg) is an effective and well-tolerated dose for pediatric, adolescent, and young adult patients.

Rescue Therapies for AKI in Onconephrology: Rasburicase and Glucarpidase

Tumor lysis syndrome (TLS) and high-dose methotrexate (HD MTX) toxicity can present with potentially severe complications, including acute kidney injury, in patients with malignancy. Guidelines for using rasburicase and glucarpidase as rescue therapies for TLS and HD MTX toxicity, respectively, are widely used by clinicians intending to mitigate organ toxicity and decrease morbidity and mortality as a consequence of cancer therapy. This review discusses the pathogenesis of TLS and HD MTX-associated toxicity, to understand the mechanism of action of these therapeutic agents and to review the currently available evidence supporting their use.

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.

Insights from a pharmacometric analysis of HDMTX in adults with cancer: Clinically relevant covariates for application in precision dosing

AIMS

High-dose methotrexate (HDMTX) is an essential part of the treatment of several adult and paediatric malignancies. Despite meticulous supportive care during HDMTX administration, severe toxicities, including acute kidney injury (AKI), may occur contributing to patient morbidity. Population pharmacokinetics provide a powerful tool to predict time to clear HDMTX and adjust subsequent doses. We sought to develop and validate pharmacokinetic models for HDMTX in adults with diverse malignancies and to relate systemic exposure with the occurrence of severe toxicity.

METHODS

Anonymized, de-identified data were provided from 101 US oncology practices that participate in the Guardian Research Network, a non-profit clinical research consortium. Modelled variables included clinical, laboratory, demographic and pharmacological data. Population pharmacokinetic analysis was performed by means of nonlinear mixed effects modelling using MonolixSuite.

RESULTS

A total of 693 HDMTX courses from 243 adults were analysed, of which 62 courses (8.8%) were associated with stage 2/3 acute kidney injury (43 stage 2, 19 stage 3). A three-compartment model adequately fitted the data. Time-dependent serum creatinine, baseline serum albumin and allometrically scaled bodyweight were clinically significant covariates related to methotrexate clearance. External evaluation confirmed a satisfactory predictive performance of the model in adults receiving HDMTX. Dose-normalized methotrexate concentration at 24 and 48 hours correlated with AKI incidence.

CONCLUSION

We developed a population pharmacometric model that considers weight, albumin and time-dependent creatinine that can be used to guide supportive care in adult patients with delayed HDMTX elimination.

High-Dose Methotrexate in Patients With Lymphoma: Predictors of a Complicated Course

PURPOSE

High-dose methotrexate (HDMTX; > 500 mg/m²) is an important component of lymphoma therapy. Serum MTX monitoring at 48 hours is the standard approach to identify those at increased risk of developing MTX toxicity. Our aim was to characterize the incidence of complications and their association with MTX levels.

METHODS

A retrospective review of our institutional electronic medical record was conducted to identify patients with lymphoma who received HDMTX between January 1, 2002, and December 31, 2018. We characterized the incidence of acute kidney injury (AKI), intensive care unit (ICU) admission, length of hospital stay (LOS), and 30-day mortality across 48-hour MTX levels. To establish an association between 48-hour MTX levels and the complications listed, we performed chi-square analysis for dichotomous variables and Kruskal-Wallis for nonparametric data. Receiver operator characteristic curve analysis was performed to identify the MTX level where AKI grade ≥ 2 was more likely. Multivariate logistic regression analysis was performed to identify risk factors for this MTX level.

RESULTS

We identified 642 patients with 2,804 cycles of HDMTX. The incidence of AKI was 19.1% with AKI grade ≥ 2 making up 21% of cases. Rates of AKI, ICU admission, and 30-day mortality are associated with elevated 48-hour MTX levels. There was a significant increase in median LOS with elevated MTX levels (P < .001). Receiver operator characteristic curve analysis for AKI grade ≥ 2 demonstrated a 48-hour MTX level threshold of 1.28 μmol/L. Multivariate logistic regression analysis revealed age, male sex, elevated body surface area, higher MTX dose, monotherapy, and first cycle as independent factors.

CONCLUSION

Elevated MTX levels are associated with a significant increased rate of AKI, ICU admission, prolonged LOS, and 30-day mortality. Elevated 48-hour MTX levels, particularly > 1.28 μmol/L, should alert clinicians for complications and to initiate measures to reduce MTX levels.

Massively parallel, computationally guided design of a proenzyme

Confining the activity of a designed protein to a specific microenvironment would have broad-ranging applications, such as enabling cell type-specific therapeutic action by enzymes while avoiding off-target effects. While many natural enzymes are synthesized as inactive zymogens that can be activated by proteolysis, it has been challenging to redesign any chosen enzyme to be similarly stimulus responsive. Here, we develop a massively parallel computational design, screening, and next-generation sequencing-based approach for proenzyme design. For a model system, we employ carboxypeptidase G2 (CPG2), a clinically approved enzyme that has applications in both the treatment of cancer and controlling drug toxicity. Detailed kinetic characterization of the most effectively designed variants shows that they are inhibited by ∼80% compared to the unmodified protein, and their activity is fully restored following incubation with site-specific proteases. Introducing disulfide bonds between the pro- and catalytic domains based on the design models increases the degree of inhibition to 98% but decreases the degree of restoration of activity by proteolysis. A selected disulfide-containing proenzyme exhibits significantly lower activity relative to the fully activated enzyme when evaluated in cell culture. Structural and thermodynamic characterization provides detailed insights into the prodomain binding and inhibition mechanisms. The described methodology is general and could enable the design of a variety of proproteins with precise spatial regulation.

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.

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.

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.

Relationship Between the Free and Total Methotrexate Plasma Concentration in Children and Application to Predict the Toxicity of HD-MTX

High-dose methotrexate (HD-MTX) can be highly effective as well as extremely toxic. Many drug molecules can bind to plasma proteins to different extents in vivo, whereas only the free drug can reach the site of action to exert a pharmacological effect and cause toxicity. However, free MTX concentrations in plasma have not been reported. Traditional analyses of free drugs are both cumbersome and inaccurate. We collected 92 plasma samples from 52 children diagnosed with ALL or NHL or other lymphomas that were treated with HD-MTX. The hollow fiber centrifugal ultrafiltration (HFCF-UF) was used to prepare plasma samples for analysis of the free MTX concentration. Protein precipitation was employed to measure the total MTX concentration. The HFCF-UF is a simple method involving a step of ordinary centrifugation; the validation parameters for the methodological results were satisfactory and fell within the acceptance criteria. A linearity coefficient r² of 0.910 was obtained for the correlation between the free and total MTX plasma concentrations in 92 plasma samples. However, the free and total MTX concentrations was only weakly correlated in 16 clinical plasma specimens with total MTX concentrations >2 μmol L⁻¹ (r² = 0.760). Both the free and total MTX concentrations at 42 h were negatively correlated with the creatinine clearance (CCr) level (P = 0.023, r = −0.236 for total MTX and P = 0.020, r = −0.241for free MTX, respectively). The free MTX concentration could not be accurately estimated from the total MTX concentration for patients with high MTX levels which are conditions under which toxic reactions are more likely to occur. High plasma MTX levels could become a predictor of the occurrence of MTX nephrotoxicity to draw people's attention. The proposed HFCF-UF method is a simple and accurate way to evaluate efficacy and toxicity in clinical therapeutic drug monitoring.

Standardized Supportive Care Documentation Improves Safety of High-Dose Methotrexate Treatment

BACKGROUND

High-dose (HD) methotrexate (MTX) is an essential component of treatment protocols in acute lymphoblastic leukemia, aggressive lymphoma, and osteosarcoma. However, delayed MTX clearance may lead to life-threatening toxicities. Administration of supportive therapy for HD-MTX is complex, and insufficient supportive care increases the risk of MTX toxicity. To improve patient safety, we investigated the implementation of a checklist and urine alkalinization protocol in addition to standard supportive care during HD-MTX therapy.

MATERIALS AND METHODS

The intervention included individualized patient checklists for control of adequate supportive care for every HD-MTX treatment cycle and a urine alkalinization protocol for documentation and guidance during urine alkalinization therapy. The impact of these tools on the rate of adverse events (acute renal injury, delayed MTX clearance) was retrospectively assessed in patients treated from April 2017 to April 2019 (intervention group) and compared with patients treated from January 2015 to March 2017 who received standard supportive care for HD-MTX according to a standard operating procedure (SOP).

RESULTS

In total, 118 patients received 414 HD-MTX cycles in the intervention group compared with 108 patients with 332 treatment cycles in the SOP group. Delayed MTX clearance was observed in 2.6% of treatment cycles in the intervention cohort opposed to 15.2% of cycles in the SOP group. The rate of acute kidney injury was also significantly reduced in the intervention group (6.2%. vs. 0.7%). The use of carboxypeptidase as rescue treatment for severe renal impairment and insufficient MTX clearance was necessary in five cases in the SOP group and in only two cycles within the intervention group.

CONCLUSION

The use of standardized documentation for supportive care during HD-MTX therapy is recommended to minimize the risk of adverse events.

IMPLICATIONS FOR PRACTICE

High-dose methotrexate (HD-MTX) is a commonly used treatment in several cancer types. Distinct supportive measures are necessary to minimize the risk of HD-MTX side effects, which can be life-threatening. Supportive care consists of certain examinations and interventions before starting HD-MTX and permanent alkalinization of the urine, as this greatly increases the elimination of MTX and decreases the risk of kidney injury. After implementing a checklist for control of supportive care and a urine alkalinization protocol to optimize urine alkalinization, a significant decrease of side effects was observed in comparison to the standard of care; therefore, the use of a safety checklist and alkalinization protocol is recommended for all patients who receive HD-MTX.

Charcoal Hemoperfusion for Methotrexate Toxicity: A Safe and Effective Life-Rescue Alternative When Glucarpidase Is Not Available

Background: High dose methotrexate (HDMTX) is used for the treatment of pediatric hemato-oncological diseases. HDMTX can induce acute kidney injury in cases of delayed elimination. The use of leucovorin remains the most effective rescue action. Further treatment options are of difficult access in the rare cases where leucovorin fails to prevent renal failure from occurring. Glucarpidase is an effective treatment in cases of methotrexate (MTX) delayed elimination, but cost is high and availability is limited. Charcoal hemoperfusion (CHP) is a very efficient procedure to remove protein-bound drugs, promoting fast MTX elimination, but is rarely considered as a treatment option. Methods: We present three pediatric cases with prolonged exposure to MTX after HDMTX and delayed elimination in which hemoperfusion was performed as rescue treatment for methotrexate intoxication. Results: Charcoal hemoperfusion was performed with positive results and no complications as bridging until glucarpidase was available in two cases and in one case where two doses of glucarpidase led to insufficient reduction of MTX levels. Conclusions: CHP can be considered as a rescue treatment option in MTX intoxication, since it is an effective and safe extracorporeal method for removing MTX, in cases where rescue with leucovorin is insufficient and glucarpidase is not available or while waiting for delivery.

Zingerone protects liver and kidney tissues by preventing oxidative stress, inflammation, and apoptosis in methotrexate-treated rats

The clinical use of drugs used in the treatment of diseases is limited due to the toxic side effects, and many studies have been conducted to benefit from herbal adjuvant therapies recently to eliminate these effects. In this study, the protective effect of zingerone against liver and kidney damage generated in rats through methotrexate (MTX). Histopathological investigations were performed to determine tissue damage caused by MTX and the healing effect of zingone and liver function markers such as serum alanine transaminase (ALT), aspartate transaminase (AST), alkaline phosphatase (ALP), and renal function markers such as urea, creatine, and aquaporin-1 (AQP-1) were measured. The effects of MTX and protective properties of zingerone on oxidative stress were investigated through the measurement of malondialdehyde and reduced glutathione (GSH) levels, catalase (CAT), and glutathione peroxidase (GPx) enzyme activities. The anti-inflammatory effect of zingerone was determined by measuring the cytokine levels causing inflammation such as nuclear factor-kappa B (NF-κB), tumor necrosis factor-α (TNF-α), and interleukin-1β (IL-1β), and its effects on apoptosis were determined by immunohistochemical analysis of caspase-3 and B-cell lymphoma-2 (Bcl-2) expression levels. According to the results obtained within the scope of the study, it was determined that zingerone treatment prevented the increase in MTX-induced liver and kidney function markers, showed healing effects on antioxidant parameters degraded in both tissues, and decreased the inflammation parameters. It was determined that it also prevented apoptosis and possessed a protective effect on disrupted tissue architecture by decreasing the increased caspase-3 expression and increasing the decreased Bcl-2 level.

A second administration of glucarpidase in a different cycle of high-dose methotrexate: Is it safe and effective in adults?

INTRODUCTION

Methotrexate intoxication following high-dose methotrexate-induced acute kidney injury is a life-threatening complication. Glucarpidase can quickly reduce extracellular methotrexate to safe levels, but the effectiveness and safety of its use in different episodes of nephrotoxicity remain an unknown area.

CASE REPORT

A 30-year-old male diagnosed with acute lymphoblastic T-cell lymphoma received methotrexate 5 g/m2 intravenous (IV) as part of the first consolidation cycle. On Consolidation 3, he restarted methotrexate at a dose of 3 g/m2 IV showing slow methotrexate elimination, associated myelosuppression, and hepatic toxicity. Glucarpidase was administered (total dose of 2000 International Units (IU)). No adverse events were observed, and his renal function returned to normal. One hundred and six days later, he was diagnosed with leptomeningeal and cerebellar relapse and treatment with methotrexate 3,5 g/m2 IV day 1 and cytosine arabinoside (Ara-C) 2 g/m2 IV twice per day days 1, 3, and 5 was started. At 36 h from methotrexate infusion, serum creatinine increased up to 1.89 mg/dL and methotrexate concentration was 100 µmol/L.Management and Outcome: Ara-C was suspended, and a second administration of glucarpidase (2000 IU) was dispensed. No adverse events were noticed, methotrexate levels decreased and renal function progressively improved, recovering completely three weeks later.

DISCUSSION

The effectiveness and safety of the use of glucarpidase in different episodes of nephrotoxicity remain an unknown area, and the rate and consequences of antiglucarpidase antibody formation remain poorly understood. This case report is, to our knowledge, the first case of a second administration of glucarpidase in a different cycle of high-dose methotrexate in an adult patient.

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.

Plasma creatinine as predictor of delayed elimination of high-dose methotrexate in childhood acute lymphoblastic leukemia: A Danish population-based study

BACKGROUND

Severely delayed elimination of methotrexate (MTX) is difficult to predict in patients treated with high-dose MTX (HD-MTX), but it may cause life-threatening toxicity. It has not been defined how an increase in plasma creatinine can be best used as a predictor for severely delayed MTX elimination, thus providing a guide for therapeutic interventions to minimize renal toxicity.

METHODS

Pharmacokinetic data were retrospectively collected on 218 Danish children with acute lymphoblastic leukemia treated with HD-MTX 5 or 8 g/m² on the NOPHO2000 protocol. Moderately delayed MTX elimination was defined as 42-hour plasma MTX ≥ 4.0-9.9 μM, and severely delayed elimination was defined as 42-hour plasma MTX ≥ 10 μM.

RESULTS

Median 42-hour plasma MTX was 0.61 μM (interquartile range, 0.4-1.06 μM). Of 1295 MTX infusions with 5 g/m² (n = 140 patients) or 8 g/m² (n = 78 patients), 5.1% were severely (1.5%) or moderately (3.6%) delayed. The risk of having delayed elimination was highest in the first of eight infusions with MTX 5 g/m² (7.4% vs 0.0 to 4.1% for subsequent MTX infusions) (P < 0.02). A 25 μM increase or a 1.5-fold increase in plasma creatinine within 36 hours from start of the MTX infusion had a sensitivity of 92% (95% CI, 82%-97%) and a specificity of 85% (95% CI, 83%-87%) for predicting 42-hour MTX ≥4.0 μM.

CONCLUSIONS

A 25 μM increase or a 1.5-fold in plasma creatinine within 36 hours after start of an HD-MTX infusion can predict delayed MTX elimination, thus allowing intensification of hydration and alkalization to avoid further renal toxicity and promote the elimination of MTX.

Delayed methotrexate clearance in patients with acute lymphoblastic leukemia concurrently receiving dasatinib

We aimed to determine whether patients receiving dasatinib or imatinib concurrently with high-dose methotrexate (HDMTX) had slower methotrexate clearance than patients not receiving a tyrosine kinase inhibitor (TKI) during the HDMTX infusion. Patients concurrently receiving dasatinib and HDMTX (N = 7) had significantly slower MTX clearance (P = 0.008) than patients not receiving a TKI (N = 111). Two patients receiving a TKI during a HDMTX infusion required glucarpidase. In vitro studies showed that dasatinib significantly inhibited methotrexate uptake by SLCO1B1-expressing cells (P = 0.009). There may be an interaction between dasatinib and HDMTX, mediated by the transporter SLCO1B1, that causes a delay in MTX clearance.

Puerarin improves methotrexate-induced renal damage by up-regulating renal expression of Oat1 and Oat3 in vivo and in vitro

The regulation of renal transporters such as organic anion transporter (OATs) is a new target for treatment of acute renal failure. The purpose of this study was to investigate whether the effect of puerarin (Pur) on renal damage induced by methotrexate (MTX) is related to the expression of renal Oat1/3 in vivo and in vitro, and to explore the related mechanisms. Effect of Pur on the renal damage caused by MTX was evaluated by assessment of the changes of endogenous metabolites, toxins and H&E staining. Furthermore, Real-time PCR and western blot methods were taken to evaluate the modulation of Oat1/3 in rats. Then, the regulation of Oat1/3 by B-cell CLL/lymphoma (BCL)6 was explored by siRNA assay using NRK-52E cells in vitro. Pur reduced levels of endogenous metabolites and toxins, like creatinine, urea nitrogen and indoxyl sulfate in plasma in MTX-treated rats. Moreover, plasma concentration of MTX was significantly decreased, while the cumulative urinary excretion of MTX and the uptake of MTX by kidney slices were strongly increased after administration of multiple-dose of Pur via up-regulation of renal Oat1/3 expression. Knockdown of BCL6 by siRNA abrogated the Pur-induced Oat1/3 expression in NRK-52E cells. Pur improved MTX-induced renal toxicity through promotion of renal excretion of toxins by up-regulating renal Oat1/3 via BCL6. Pur was beneficial for the improvement of MTX-induced renal toxicity.

Management of Patients with Acute Methotrexate Nephrotoxicity with High-Dose Leucovorin

BACKGROUND

Acute kidney injury complicating high-dose methotrexate (HDMTX) therapy increases the risk for severe mucositis, myelosuppression, and death. It is unclear whether high-dose leucovorin and supportive therapy without the use of glucarpidase can reduce toxicity from HDMTX.

STUDY DESIGN

The charts of all patients at Memorial Sloan Kettering Cancer Center whose methotrexate (MTX) drug levels at 48 or 72 hours after administration were 10 times or more the toxic level were reviewed between January 2000 and December 2011.

RESULTS

Eighty-eight patients (median age 51 years, range 9-90 years) who received 100 courses of HDMTX were identified. Serum creatinine increased by 2-fold from baseline (median, range 1- to 10-fold), but all patients recovered kidney function. Serum levels of MTX were 69 μmol/L (median, range 2.2-400), 6.9 μmol/L (1.3-64), and 2.0 μmol/L (0.05-26) at 24, 48, and 72 hours, respectively, after administration. A statistically significant correlation existed between MTX levels at 48, 72, 96, and 120 hours after administration but not between 24 and 72 hours or subsequent time points. High-dose leucovorin was given in 81% of courses in accordance with institutional protocols in most cases. Myelosuppression was present in 42%; grade III or higher neutropenia in 29%, and thrombocytopenia in 25%. Infectious complications, oral mucositis, and diarrhea occurred in 21%, 17%, and 6% of patients, respectively. Five deaths occurred, none directly attributed to complications from MTX administration. Seven additional patients received glucarpidase at the discretion of a treating physician during the study period, and results are reported separately.

CONCLUSION

Patients who had 100 episodes of HDMTX-associated acute kidney injury were treated with a strategy that only included usual supportive measures and high-dose leucovorin. No deaths were directly attributed to complications related to HDMTX. Glucarpidase, an expensive drug, may not be necessary for a significant number of patients.

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.

Delayed Methotrexate Clearance Despite Carboxypeptidase-G2 (Glucarpidase) Administration in 2 Patients With Toxic Methotrexate Levels

High-dose methotrexate has been a treatment for osteosarcoma; however, its nephrotoxic effects are considerable. Carboxypeptidase-G2 (glucarpidase) was approved by the US Food and Drug Administration in 2012 for treatment of toxic methotrexate levels. We report our experience using glucarpidase under compassionate use before Food and Drug Administration approval in 2 patients who had delayed methotrexate clearance and prolonged kidney injury despite glucarpidase administration. Our results show that patients with methotrexate toxicity may require repeated doses of glucarpidase in addition to supportive measures, such as dialysis.

Consensus Guideline for Use of Glucarpidase in Patients with High-Dose Methotrexate Induced Acute Kidney Injury and Delayed Methotrexate Clearance

An expert panel was convened to provide specific, expert consensus guidelines for the use of glucarpidase in patients who develop high‐dose methotrexate (HDMTX)‐induced nephrotoxicity and delayed methotrexate excretion. This guideline provides recommendations to identify the population of patients who would benefit from glucarpidase rescue by more precisely defining the absolute methotrexate concentrations associated with risk for severe or life‐threatening toxicity at several time points after the start of a HDMTX infusion.

Acute kidney injury due to high‐dose methotrexate (HDMTX) is a serious, life‐threatening toxicity that can occur in pediatric and adult patients. Glucarpidase is a treatment approved by the Food and Drug Administration for high methotrexate concentrations in the context of kidney dysfunction, but the guidelines for when to use it are unclear. An expert panel was convened to provide specific, expert consensus guidelines for the use of glucarpidase in patients who develop HDMTX‐induced nephrotoxicity and delayed methotrexate excretion. The guideline provides recommendations to identify the population of patients who would benefit from glucarpidase rescue by more precisely defining the absolute methotrexate concentrations associated with risk for severe or life‐threatening toxicity at several time points after the start of an HDMTX infusion. For an HDMTX infusion ≤24 hours, if the 36‐hour concentration is above 30 µM, 42‐hour concentration is above 10 µM, or 48‐hour concentration is above 5 µM and the serum creatinine is significantly elevated relative to the baseline measurement (indicative of HDMTX‐induced acute kidney injury), glucarpidase may be indicated. After a 36‐ to 42‐hour HDMTX infusion, glucarpidase may be indicated when the 48‐hour methotrexate concentration is above 5 µM. Administration of glucarpidase should optimally occur within 48–60 hours from the start of the HDMTX infusion, because life‐threatening toxicities may not be preventable beyond this time point.

Implications for Practice.

Glucarpidase is a rarely used medication that is less effective when given after more than 60 hours of exposure to high‐dose methotrexate, so predicting early which patients will need it is imperative. There are no currently available consensus guidelines for the use of this medication. The indication on the label does not give specific methotrexate concentrations above which it should be used. An international group of experts was convened to develop a consensus guideline that was specific and evidence‐based to identify the population of patients who would benefit from glucarpidase.

Delayed elimination of high-dose methotrexate and use of carboxypeptidase G2 in pediatric patients during treatment for acute lymphoblastic leukemia

BACKGROUND

Carboxypeptidase G2 (CPDG₂ ) can be used as rescue treatment in cases of delayed methotrexate elimination (DME) and Mtx-induced nephrotoxicity.

PROCEDURE

Between July 2008 and December 2014, all children (1.0-17.9 years) in the Nordic countries diagnosed with Philadelphia chromosome negative acute lymphoblastic leukemia (ALL) were treated according to the Nordic Organization for Pediatric Hematology and Oncology (NOPHO) ALL 2008 protocol, including administration of six to eight high-dose (5 g/m² /24 hr) Mtx (HDMtx) courses. The protocol includes recommendations for CPDG₂ administration in cases of DME (clinicaltrials.gov NCT01305655).

RESULTS

Forty-seven of the 1,286 children (3.6%) received CPDG₂ during 50 HDMtx courses at a median dose of 50 IU/kg. In 49% of the cases, CPDG₂ was used during the first HDMtx course. Within a median of 6 hr from CPDG₂ administration, the Mtx concentration decreased by 75% when measured with immune-based methods, and by 100% when measured with high-performance liquid chromatography. The median time from the start of Mtx infusion to plasma levels ≤ 0.2 μM was 228 hr (range: 48-438). The maximum increase in plasma creatinine was 375% (range: 100-1,310). Creatinine peaked after a median of 48 hr (range: 36-86). Mtx elimination time was shorter in patients with body surface area < 1 m² (median 198.5 vs. 257 hr; P = 0.004) and was inversely correlated to the maximum creatinine increase (209 vs. 258 hr; P = 0.034). All patients normalized their renal function as measured with s-creatinine.

CONCLUSIONS

CPDG₂ administration is highly effective as rescue in case of delayed Mtx clearance. Subsequent HDMtx courses could be administered without events in most of the patients.

Non-infectious chemotherapy-associated acute toxicities during childhood acute lymphoblastic leukemia therapy

During chemotherapy for childhood acute lymphoblastic leukemia, all organs can be affected by severe acute side effects, the most common being opportunistic infections, mucositis, central or peripheral neuropathy (or both), bone toxicities (including osteonecrosis), thromboembolism, sinusoidal obstruction syndrome, endocrinopathies (especially steroid-induced adrenal insufficiency and hyperglycemia), high-dose methotrexate-induced nephrotoxicity, asparaginase-associated hypersensitivity, pancreatitis, and hyperlipidemia. Few of the non-infectious acute toxicities are associated with clinically useful risk factors, and across study groups there has been wide diversity in toxicity definitions, capture strategies, and reporting, thus hampering meaningful comparisons of toxicity incidences for different leukemia protocols. Since treatment of acute lymphoblastic leukemia now yields 5-year overall survival rates above 90%, there is a need for strategies for assessing the burden of toxicities in the overall evaluation of anti-leukemic therapy programs.

Engineering carboxypeptidase G2 circular permutations for the design of an autoinhibited enzyme

Carboxypeptidase G2 (CPG2) is an Food and Drug Administration (FDA)-approved enzyme drug used to treat methotrexate (MTX) toxicity in cancer patients receiving MTX treatment. It has also been used in directed enzyme-prodrug chemotherapy, but this strategy has been hampered by off-site activation of the prodrug by the circulating enzyme. The development of a tumor protease activatable CPG2, which could be achieved using a circular permutation of CPG2 fused to an inactivating 'prodomain', would aid in these applications. We report the development of a protease accessibility-based screen to identify candidate sites for circular permutation in proximity of the CPG2 active site. The resulting six circular permutants showed similar expression, structure, thermal stability, and, in four cases, activity levels compared to the wild-type enzyme. We rationalize these results based on structural models of the permutants obtained using the Rosetta software. We developed a cell growth-based selection system, and demonstrated that when fused to periplasm-directing signal peptides, one of our circular permutants confers MTX resistance in Escherichia coli with equal efficiency as the wild-type enzyme. As the permutants have similar properties to wild-type CPG2, these enzymes are promising starting points for the development of autoinhibited, protease-activatable zymogen forms of CPG2 for use in therapeutic contexts.

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.

Evaluation of a Methotrexate Chemiluminescent Microparticle Immunoassay: Comparison to Fluorescence Polarization Immunoassay and Liquid Chromatography-Tandem Mass Spectrometry

OBJECTIVES

For most laboratories, methotrexate (MTX) concentrations are routinely monitored by fluorescence polarization immunoassay (FPIA). In anticipation of an announced withdrawal of the FPIA reagent on the Abbott TDxFLx (Abbott Diagnostics, Abbott Park, IL), we have evaluated a new reagent kit developed by Abbott on the Architect i1000, based on chemiluminescent microparticle immunoassay (CMIA).

METHODS

Precision, inaccuracy, and selectivity were assessed. Interassay variability was established using 75 plasma patient samples treated with MTX and analyzed by two methods: FPIA and liquid chromatography-tandem mass spectrometry (LC-MS/MS). RESULTS FOR MTX,: the intraday inaccuracy was between -6.37% and +3.52%, while interday performance was between -3.70% and 7.90%. Intraday and interday imprecision was less than 2.65% and less than 2.22%, respectively. The correlation coefficient between CMIA and FPIA or LC-MS/MS was 0.9969 and 0.9985, respectively.

CONCLUSIONS

These results comparing CMIA vs FPIA and LC-MS/MS indicate that CMIA is a suitable alternative to the FPIA method.

Comparable efficacy with varying dosages of glucarpidase in pediatric oncology patients

BACKGROUND

Glucarpidase rapidly reduces methotrexate plasma concentrations in patients experiencing methotrexate-induced renal dysfunction. Debate exists regarding the role of glucarpidase in therapy given its high cost. The use of reduced-dose glucarpidase has been reported, and may allow more institutions to supply this drug to their patients. This report explores the relationship between glucarpidase dosage and patient outcomes in pediatric oncology patients.

METHODS

The authors evaluated data from 26 patients who received glucarpidase after high-dose methotrexate. Decrease in plasma methotrexate concentrations and time to renal recovery were evaluated for an association with glucarpidase dosage, which ranged from 13 to 90 units/kg.

RESULTS

No significant relationship was found between glucarpidase dosage (units/kg) and percent decrease in methotrexate plasma concentrations measured by TDx (P > 0.1) or HPLC (P > 0.5). Patients who received glucarpidase dosages <50 units/kg had a median percent reduction in methotrexate plasma concentration of 99.4% (range, 98-100) measured by HPLC compared to a median percent reduction of 99.4% (range, 77.2-100) in patients who received ≥50 units/kg. Time to SCr recovery was not related to glucarpidase dosage (P > 0.8).

CONCLUSIONS

The efficacy of glucarpidase in the treatment of HDMTX-induced kidney injury was not dosage-dependent in this retrospective analysis of pediatric oncology patients.

Evaluation of serum and urine fetuin-A levels in children with acute lymphoblastic leukemia during and after high-dose methotrexate therapy: Relation to toxicity

BACKGROUND/OBJECTIVES

Fetuin-A is a multifunctional protein with its urine level was considered as a marker of acute kidney injury. We investigated the serum and urine fetuin-A in acute lymphoblastic leukemia (ALL) children during and after high-dose methotrexate (HDMTX).

METHODS

Twenty-two ALL children and 20 matched healthy controls were included. Liver transaminases, serum creatinine, estimated glomular filtration rate (eGFR), creatinine clearance (CrCl), serum β2 microglobulin (B2M), and serum and urine fetuin-A levels were assayed pre and 4 months after the consolidation. Among a subgroup of 15 patients, the investigations were performed 42 hours after the start of the second and the fourth HDMTX infusions.

RESULTS

HDMTX was well tolerated. During HDMTX, there was significant decline in serum fetuin-A together with significant rise of urine fetuin-A and B2M levels compared to the control and to the pre-consolidation levels, changes that persisted 4 months after the consolidation despite recovery of the significantly altered renal functions. The second HDMTX-related serum fetuin-A level directly correlated with eGFR and CrCl (r = 0.86, P < 0.0001 and r = 0.67, P = 0.016, respectively). Four months after consolidation, urine fetuin-A directly correlated with serum creatinine (r = 0.54, P = 0.004) and inversely correlated with the eGFR (r = -0.66, P < 0.0001).

CONCLUSION

Significant disturbance in serum and urinary fetuin-A levels, which was related to renal functions, had occurred during HDMTX and persisted for at least 4 months after the consolidation. Serum and urine fetuin-A could be sensitive markers for subtle renal dysfunction in ALL children.

MDR1 and OAT1/OAT3 mediate the drug-drug interaction between puerarin and methotrexate

PURPOSE

To conduct in vivo and in vitro experiments to investigate puerarin (PUR), an isoflavone C-glyoside, and elucidate its ability to alter methotrexate (MTX) transport and pharmacokinetics.

METHODS

In vivo absorption studies, in vitro everted intestinal sac preparation, kidney slices in rats and bi-directional transport assay with mock-/MDCK-MDR1 cells, uptake studies in HEK293-OAT1/3 cells were employed to evaluate the interaction.

RESULTS

In vivo and in vitro MTX absorption in rats were enhanced in combination with PUR. PUR inhibited digoxin efflux transport in MDCK-MDR1 monolayers with an IC50 value of 1.6 ± 0.3 μM, suggesting that the first target of drug interaction was MDR1 in the intestine during the absorption process. MTX renal clearance decreased significantly after simultaneous intravenous administration. MTX uptake in rat kidney slices and HEK293-OAT1/3 cells were markedly inhibited by PUR, suggesting that the second target of drug interaction was OATs located in the kidney. Moreover, concomitant administration of PUR reduced renal MTX accumulation and plasma levels of creatinine and BUN.

CONCLUSIONS

Co-administration of PUR enhanced MTX exposure by inhibition of intestinal MDR1 and renal OAT1/3. Although the renal damage of MTX was improved by PUR, the high level exposure of MTX should be cautious in the clinical usage.

Glucarpidase Intervention for Delayed Methotrexate Clearance

Objective: To review and evaluate the current published literature on the effectiveness and safety of glucarpidase and to determine its potential role in clinical practice. Data Sources: A PubMed literature search from 1946 to January 2014 was performed using the search terms carboxypeptidase G2, glucarpidase, high-dose methotrexate, and leucovorin rescue. Additional references were identified by reviewing the references from the PubMed search articles. Study Selection and Data Extraction: English-language clinical trials and retrospective studies assessing the safety and effectiveness of glucarpidase were included. Case reports were excluded. Data Synthesis: A total of 5 non-randomized, prospective studies and 1 retrospective study evaluated the effectiveness and safety of glucarpidase in patients receiving high-dose methotrexate. In these studies, glucarpidase conferred a >87% reduction in serum methotrexate concentrations (sMTX) and was well tolerated. Although a substantial reduction in sMTX was observed, clinically significant outcomes such as the need for dialysis, time to administration of next chemotherapy cycle, and methotrexate toxicity-related mortality were not consistently evaluated. Conclusions: Glucarpidase is effective in lowering sMTX in patients with delayed methotrexate clearance and renal dysfunction. Considering the relatively high cost of glucarpidase, it should be reserved for specific patients who have not responded to standard supportive care measures.

Hypersensitivity reaction to high-dose methotrexate and successful rechallenge in a pediatric patient with osteosarcoma

Hypersensitivity reactions to methotrexate are rare, but have been reported. Methotrexate has shown activity against many malignancies, and omission of methotrexate therapy may increase the risk of cancer-related death in some patients. Therefore, rechallenging patients with methotrexate following hypersensitivity may be beneficial. We report a case of a child with metastatic osteosarcoma who experienced a hypersensitivity reaction to high-dose methotrexate and was successfully rechallenged with methotrexate using a 6-hour infusion. Using this regimen, adequate peak methotrexate plasma concentrations were achieved and no further hypersensitivity reactions were noted.