Daily profiles of plasma phenylalanine and tyrosine in patients with osteogenic sarcoma during treatment with high-dose methotrexate-citrovorum rescue

Three adolescents and one child with osteosarcoma were studied during multiple courses of high-dose methotrexate, citrovorum factor rescue (HDMTX-CFR), with one adolescent treated intermittently over a period of 6 years. Plasma phenylalanine (Phe) and tyrosine (Tyr) were measured immediately before the infusion of MTX and then daily until serum MTX fell below 10(-7) M. At 24 hours, all showed marked increases in Phe and in the Phe/Tyr ratio. This suggests inhibition of dihydropteridine reductase (DHPR) which, in association with hepatic Phe hydroxylase, controls plasma concentrations of Phe. Inhibition of this enzyme system is not relieved by CFR. In the adolescent patients, although MTX levels in plasma declined steadily, Phe concentrations, which fell between 24 and 48 hours, rose to a new peak at 4-7 days. Possible reasons for this secondary increase are discussed. The patient with the longest exposure to HDMTX showed an increase in pretreatment Phe/Tyr ratios with time, suggesting damage to liver parenchymal cells not indicated by standard tests of liver function. Evaluation of plasma Phe during the course of HDMTX-CFR may permit assessment of intracellular concentrations of MTX or its metabolites in the liver without interference by CFR.     

Pharmacokinetics and toxicity of methotrexate in children with Down syndrome and acute lymphocytic leukemia

Children with Down syndrome and acute lymphocytic leukemia (ALL) have poor tolerance to antineoplastic drugs, including methotrexate (MTX). We evaluated MTX pharmacokinetics and toxicity in five patients with Down syndrome and ALL who had received multiple high doses of MTX (1 g/m2). Three control patients without Down syndrome were matched to each case according to sex, race, age, and initial leukocyte count. Median MTX plasma concentrations, measured 42 hours after infusion, were significantly higher in patients with Down syndrome versus control patients (average 0.47 vs 0.24 mumol/L, respectively, P = 0.03). When a 42-hour MTX concentration of 0.5 mumol/L was used to identify patients at risk for toxicity, more courses were considered at high risk for toxicity among patients with Down syndrome (31 of 62, 50%) than in control patients (13 of 214, 6.1%, P less than 0.0001). The average MTX clearance was 64.1 mL/min/m2 in Down syndrome vs an average control value of 80.6 mL/min/m2 (P = 0.13). Toxicity after each high-dose MTX course was graded according to standardized criteria. Grades 2 through 4 gastrointestinal toxicity and grades 3 and 4 hematologic toxicity occurred more frequently in the patients with Down syndrome (36% and 13.4% of courses, respectively) vs the control patients (3.6% and 0.9% respectively, P less than 0.0001 for both). This higher frequency of toxicity occurred despite higher doses and prolonged duration of leucovorin given to all patients with Down syndrome. We conclude that altered MTX pharmacokinetics may contribute to the higher incidence of MTX-induced toxicity seen in patients with Down syndrome.     

Serum Creatinine Versus Plasma Methotrexate Levels to Predict Toxicities in Children Receiving High-dose Methotrexate

Facilities for measuring methotrexate (MTX) levels are not available everywhere, potentially limiting administration of high-dose methotrexate (HDMTX). We hypothesized that serum creatinine alteration after HDMTX administration predicts MTX clearance. Overall, 122 cycles in 50 patients of non-Hodgkin lymphoma or acute lymphoblastic leukemia aged ≤18 years receiving HDMTX were enrolled prospectively. Plasma MTX levels were measured at 12, 24, 36, 48, 60, and 72 hours; serum creatinine was measured at baseline, 24, 48, and 72 hours. Correlation of plasma MTX levels with creatinine levels and changes in creatinine from baseline (Δ creatinine) were evaluated. Plasma MTX levels at 72 hours showed positive correlation with serum creatinine at 48 hours (P = .011) and 72 hours (P = .013) as also Δ creatinine at 48 hours (P = .042) and 72 hours (P = .045). However, cut-off value of either creatinine or Δ creatinine could not be established to reliably predict delayed MTX clearance. Greater than 50% Δ creatinine at 48 and 72 hours significantly predicted grade 3/4 leucopenia (P = .036 and P = .001, respectively) and thrombocytopenia (P = .012 and P = .009, respectively) but not mucositis (P = .827 and P = .910, respectively). Delayed MTX elimination did not predict any grade 3/4 toxicity. In spite of demonstration of significant correlation between serum creatinine and Δ creatinine with plasma MTX levels at 72 hours, cut-off value of either variable to predict MTX delay could not be established. Thus, either of these cannot be used as a surrogate for plasma MTX estimation. Interestingly, Δ creatinine effectively predicted hematological toxicities, which were not predicted by delayed MTX clearance.     

Biopterin derivatives in normal and phenylketonuric patients after oral loads of L-phenylalanine, L-tyrosine, and L-tryptophan

Plasma biopterin derivatives studied in 10 normal and 21 phenylketonuric children showed a significantly high concentration in the latter group. Biopterin derivatives correlated with plasma phenylalanine concentration, but in normal adults given an oral phenylalanine load the rate of increase with phenylalanine differed from that in phenylketonuric patients. A patient with hyperphenylalaninaemia, not due to phenylketonuria, had an abnormal biopterin derivatives response to phenylalanine distinct from that of patients with classical phenylketonuria. This may be a useful investigation to differentiate some variants of phenylketonuria.     

Biopterin derivatives in normal and phenylketonuric patients after oral loads of L-phenylalanine,L-tyrosine,and L-tryptophan.

Plasma biopterin derivatives studied in 10 normal and 21 phenylketonuric children showed a significantly high concentration in the latter group. Biopterin derivatives correlated with plasma phenylalanine concentration, but in normal adults given an oral phenylalanine load the rate of increase with phenylalanine differed from that in phenylketonuric patients. A patient with hyperphenylalaninaemia, not due to phenylketonuria, had an abnormal biopterin derivatives response to phenylalanine distinct from that of patients with classical phenylketonuria. This may be a useful investigation to differentiate some variants of phenylketonuria.     

High dose methotrexate treatment in childhood ALL: pilot study on the impact of the MTHFR 677C>T and 1298A>C polymorphisms on MTX-related toxicity

Methotrexate (MTX) is commonly administered in high doses for treatment of childhood acute lymphoblastic leukemia (ALL). The aim of this analysis was to study the influence of 2 common MTHFR polymorphisms (MTHFR 677C>T and 1298 A>C) on MTX toxicity in children with ALL.Retrospective analysis of 129 MTX courses in 34 pediatric patients with ALL.677C>T variants (CT or TT) were found in 19 (14 heterozygous, 5 homozygous) and 1298A>C variants (AC or CC) in 20 (16 heterozygous, 4 homozygous) patients. The MTHFR 677C>T wild type was associated with an increased frequency of grade III and IV leukopenia (60% vs. 31%, p<0.05) compared to the variants. The rate of severe infections (21% vs. 0%, p<0.05) and grade III-IV anemia (26% vs. 5%, p<0.05) was increased in carriers of the MTHFR 677C>T wild type compared to patients with the TT variant. Grade III-IV anemia was more frequent in patients with the MTHFR 1298A>C CC variant compared to the wild type (56% vs. 21%, p<0.05). The differences were not significant in a patient-based analysis.MTX related toxicity might be influenced by the MTHFR 677C>T or the MTHFR 1298A>C polymorphisms. Differences in MTX toxicity are only partially explainable by these 2 polymorphisms.     

Limited Tolerance of Intensified Conditioning Regimens in Children Receiving Methotrexate/Cyclosporin A for Graft-Versus-Host Disease Prophylaxis

Twenty-one patients with a median age of 9 years (0.5-19) underwent intensifid myeloblative therapy: 1800 mg/m² etoposide (VP) was added to 120 mg/kg cyclophosphamide (CY) and 12 Gy fractionated total body irradiation (FTBI) or 12-16 mg/kg busulfan (BU) for treatment of acute lymphoblastic leukemia (11 patients), acute myeloid leukemia (8 patients), non-Hodgkin's lymphoma (1 patient), or myelodysplastic syndrome (1 patient). Severe liver toxicity occurred in 5 of 7 children (71 %) receiving short-term methotrexate (MTX) and additional cyclosporin A (CSA) for prophylaxis of graft versus-host disease (GVHD). Three of them died of subsequent acute renal failure on days 8, 13, and 34.

In contrast, acute severe organ toxicity occurred in only 1 of 14 children (7%) receiving the same intensified regimens who were autografted (7 pts) or received MTX alone for GVHD prophylaxis (7 pts). These observations suggest that GVHD prophylaxis with MTX and CSA may adversely influence the tolerance of intensified antileukemic regimens in children.     

Degradation and clearance of methotrexate in children with osteosarcoma receiving high-dose infusion

Plasma methotrexate (MTX) concentrations were quantitated in 34 patients after 127 high-dose (35–350 mg/kg) infusions with citrovorum factor rescue. Significant linear correlations have been obtained between methotrexate dosage and concentrations in plasma at 6 and 24 hours after the initiation of the therapy. However, similar trends have not been observed when 48- and 72-hour samples were analyzed. Clinical toxicity was not serious when the methotrexate level in plasma was < 4.5 × 10^?6 M at 48 hours after the start of a six-hour infusion in children. A minimal four-hour steady-state methotrexate plasma level can be maintained during a six-hour infusion. Children excrete methotrexate at a faster rate than adults; the half-life of MTX during the first phase of plasma clearance curve is one hour shorter in children. Urinary analyses have indicated that substantial methotrexate is metabolized. The chemical nature of these components has not been identified. Further, the urinary metabolic profiles varied among patients.     

Sequential chemotherapy of advanced colorectal cancer with standard or high-dose methotrexate followed by 5-fluorouracil

Thirty patients with advanced measurable colorectal cancer were randomized to receive either methotrexate (MTX) 200 mg/m² or 40 mg/m², followed in four hours by 5-fluorouracil (5-FU) 600 mg/m². Patients receiving the higher dose MTX were given leucovorin rescue 24 hours later. Eight of 13 patients treated with 200 mg/m² MTX + 5-FU developed severe hematologic toxicity, leading to two toxic deaths. In addition, 9/13 developed mild azotemia, and three patients had severe gastrointestinal toxicity. No patients with prior chemotherapy responded to either regimen. Among those without prior chemotherapy, there were two of six and three of eight partial responses, respectively, in the 200 mg/m² and 40 mg/m² MTX regimens. Sequential 200 mg/m² MTX followed by 5-FU after four hours has unacceptable toxicity. Sequential treatment with standard dose MTX + 5-FU is tolerable and merits further study.     

Cerebrospinal Fluid and Plasma Methotrexate Levels Following High-Dose Regimen Given as a 3-Hour Intravenous Infusion in Children with Nonhodgkin's Lymphoma

In the French non Hodgkin's lymphoma protocols, central nervous system prophylaxis is provided by high-dose methotrexate (HD-MTX), given as a 3-hour IV infusion of 3 g/m² MTX along with intrathecal MTX injection. The incidence of CNS relapse is less than 3%. We designed a study to evaluate the MTX transfer across the blood brain barrier in terms of cytotoxic concentrations, during these short-term infusions. Cerebrospinal fluid and plasma MTX levels were measured during 61 courses in 29 children with non Hodgkin's lymphoma; none of them had central nervous system disease. Samples were obtained either 4, 12, 18, or 24 hours after the start of HD-MTX IV infusion. A potentially cytotoxic MTX level (10^-6 M) was reached in all courses at 4 hours (median: 2.3 × 10^-6 M) and remained available in 8/16 courses at 12 hours (median: 1.0 × 10^-6 M) and in only 2/17 courses at 18 hours (median: 0.29 × 10^-6 M). Twenty-four hours after the start of HD-MTX IV infusion, CSF MTX level was always less than 10^-6 M. The plasma MTX levels were 260, 1.3, 1.0, and 1.7 × 10^-6 M at 4, 12, 18, and 24 hours, respectively. There was no correlation between plasma and CSF MTX levels. These data show that potentially cytotoxic MTX concentrations can be reached in CSF after a 3-hour IV infusion of 3 g/m² in every patient and remain available for at least 8 hours in half of them.     

Degradation and clearance of methotrexate in children with osteosarcoma receiving high-dose infusion.

Plasma methotrexate (MTX) concentrations were quantitated in 34 patients after 127 high-dose (35--350 mg/kg) infusions with citrovorum factor rescue. Significant linear correlations have been obtained between methotrexate dosage and concentrations in plasma at 6 and 24 hours after the initiation of the therapy. However, similar trends have not been observed when 48- and 72-hour samples were analyzed. Clinical toxicity was not serious when the methotrexate level in plasma was less than 4.5 X 10(-6) M at 48 hours after the start of a six-hour infusion in children. A minimal four-hour steady-state methotrexate plasma level can be maintained during a six-hour infusion. Children excrete methotrexate at a faster rate than adults; the half-life of MTX during the first phase of plasma clearance curve is one hour shorter in children. Urinary analyses have indicated that substantial methotrexate is metabolized. The chemical nature of these components has not been identified. Further, the urinary metabolic profiles varied among patients.     

The Course of Biological Parameters and 6-Mercaptopurine Pharmacokinetics during Maintenance Treatment of Children with Acute Lymphoblastic Leukaemia

ABSTRACT. Twenty patients on maintenance therapy (MT) for acute lymphoblastic leukaemia (ALL) with oral 6-mercaptopurine (6-MP) and methotrexate (MTX) were studied. White cell and red cell indices and platelets counts were monitored every second week as were drug levels. Mean values for 6-MP and MTX doses, and blood component parameters were calculated for each 6-month period for the whole patient group. 6-MP plasma concentrations and liver-function tests were determined once every six months and mean values calculated. 6-MP and MTX mean doses did not change significantly during MT. The mean area under the concentration versus time curve (AUC) 0-4 hours varied slightly from the start to the end of the MT (257 and 296 ng/ml-h, respectively). The mean plasma peak concentration increased from 98 ng/ml to 195 ng/ml ( p <0.01) during the same period. There were significant decreases betwen the initial white blood cell counts (WBC) and red blood cell counts (RBC) as compared to levels at the end of therapy ( p <0.01 and 0.02, respectively). A linear correlation was found between 6-MP peak concentrations and both WBC ( r =0.96) and RBC ( r =0.87). At the end of MT liver function tests became normal in all except 6 patients. In conclusion, MT have moderate effects on bone marrow and liver and monitoring 6-MP plasma concentration might be of value for determination of the optimal WBC levels during MT.     

The course of biological parameters and 6-mercaptopurine pharmacokinetics during maintenance treatment of children with acute lymphoblastic leukaemia

Twenty patients on maintenance therapy (MT) for acute lymphoblastic leukaemia (ALL) with oral 6-mercaptopurine (6-MP) and methotrexate (MTX) were studied. White cell and red cell indices and platelets counts were monitored every second week as were drug levels. Mean values for 6-MP and MTX doses, and blood component parameters were calculated for each 6-month period for the whole patient group. 6-MP plasma concentrations and liver-function tests were determined once every six months and mean values calculated. 6-MP and MTX mean doses did not change significantly during MT. The mean area under the concentration versus time curve (AUC) 0-4 hours varied slightly from the start to the end of the MT (257 and 296 ng/ml.h, respectively). The mean plasma peak concentration increased from 98 ng/ml to 195 ng/ml (p less than 0.01) during the same period. There were significant decreases between the initial white blood cell counts (WBC) and red blood cell counts (RBC) as compared to levels at the end of therapy (p less than 0.01 and 0.02, respectively). A linear correlation was found between 6-MP peak concentrations and both WBC (r = 0.96) and RBC (r = 0.87). At the end of MT liver function tests became normal in all except 6 patients. In conclusion, MT have moderate effects on bone marrow and liver and monitoring 6-MP plasma concentration might be of value for determination of the optimal WBC levels during MT.     

Dietary management of oculocutaneous tyrosinemia in an 11-year-old child

An 11-year-old girl with keratitis and plantar keratosis had tyrosinemia. The concentration of tyrosine in the plasma was 16.5 mg/dL. Dietary intake of phenylalanine and tyrosine was systematically varied, and the plasma concentrations of tyrosine and nitrogen balance were studied. It was necessary to achieve a total intake of phenylalanine and tyrosine less than 100 mg/kg/day to obtain plasma concentrations of tyrosine of less than 10 mg/dL. After dietary therapy was started, the keratitis resolved promptly, and the patient remained asymptomatic during a period of 16 months in which the mean plasma concentration of tyrosine was 11.1 mg/dL. The dietary management of a child at this age presents a different problem from that of a young infant. It can be successfully pursued at home, as well as in the carefully regulated environment of a clinical research center.     

Graft‐versus‐host disease (GVHD) prophylaxis by using methotrexate decreases pre‐engraftment syndrome and severe acute GVHD,and accelerates engraftment after cord blood transplantation

GVHD and graft failure are serious problems in CBT. PES after CBT also occurs frequently and is associated with transplantation‐related complications such as acute GVHD. We reviewed medical records for 70 consecutive child CBT recipients between December 1997 and April 2015. Forty‐nine patients received prophylaxis against GVHD with CsA or Tac in combination with mPSL from day +7 (mPSL group), and 21 patients received CsA or Tac with MTX on day +1 and day +3 (MTX group). Neutrophil engraftment was detected in 59 patients (84.3%). Neutrophil engraftment rate in the MTX group was significantly higher than that in the mPSL group (21/21 (100%) and 38/49 (77.6%), respectively, p = 0.027). PES developed in 35 patients, and the incidence of PES in the mPSL group was significantly higher than that in the MTX group (p = 0.036). The incidence of severe acute GVHD (grade III or IV) in the MTX group was significantly lower than that in the mPSL group (p = 0.049). Although this study was a small‐scale study, the results showed that increase in the rate of engraftment and decrease in the incidence of early immune reactions such as PES and severe acute GVHD could be achieved by early commencement of immunosuppression using MTX.     

The Effect of Cranial Irradiation on Blood-Brain Barrier Permeability to Methotrexate

Seshadri, R. S., Ryall, R. G., Rice, M. S., Leahy, Margaret, and Ellis, R. (1979). Aust. Paediatr. J. , 15, 184–186. The Effect of cranial irradiation on blood-brain barrier permeability to methotrexate. Methotrexate (MTX) was given orally (30 mg/m²) to 14 patients with leukaemia/lymphoma before and soon after cranial irradiation (Cl). The MTX levels in plasma and cerebrospinal fluid were measured three hours after the administration of MTX. Markedly increased blood-brain barrier (BBB) permeability of MTX was found in both asymptomatic and symptomatic patients with central nervous system (CNS) disease even before Cl. Successful treatment of the CNS disease decreased the BBB permeability to MTX. Cl per se did not increase the BBB permeability.     

LEUCOVORIN AND MAXIMUM TOLERATED DOSE TOXICITY OF METHOTREXATE IN RATS

High-dose methotrexate (HD-MTX) is widely used in combination chemotherapy and can be handled without life-threatening toxicity in combination with leucovorin (LV) rescue. However, in an experimental animal modelfortesting of short-term HD-MTX effects in anesthetized rats, the authors previously demonstrated intolerable toxicity and death within a few hours in some animals. Serum levels were below levels routinely found in patients on HD-MTX treatment. This study was aimed at disclosure of possible mechanisms for acute toxicity of MTX in rats. The previously determined maximum tolerated dose of 5 g/kg MTX was used as the test dose. The animals that died showed sudden reduction in heart rate and blood pressure. LV, 1 g/kg infused immediately prior to MTX, changed MTX elimination kinetics, but did not change the acute toxicity. The data of this study together with additional evidence obtained in the experimental model, suggest that MTX acute toxicity may not be related to its antiproliferative effect, but rather to perturbation of endothelial cell and platelet function.     

Leucovorin and maximum tolerated dose toxicity of methotrexate in rats

High-dose methotrexate (HD-MTX) is widely used in combination chemotherapy and can be handled without life-threatening toxicity in combination with leucovorin (LV) rescue. However, in an experimental animal modelfortesting of short-term HD-MTX effects in anesthetized rats, the authors previously demonstrated intolerable toxicity and death within a few hours in some animals. Serum levels were below levels routinely found in patients on HD-MTX treatment. This study was aimed at disclosure of possible mechanisms for acute toxicity of MTX in rats. The previously determined maximum tolerated dose of 5 g/kg MTX was used as the test dose. The animals that died showed sudden reduction in heart rate and blood pressure. LV, 1 g/kg infused immediately prior to MTX, changed MTX elimination kinetics, but did not change the acute toxicity. The data of this study together with additional evidence obtained in the experimental model, suggest that MTX acute toxicity may not be related to its antiproliferative effect, but rather to perturbation of endothelial cell and platelet function.     

The metabolic effects of cold exposure in the newborn rabbit.

Blood glucose, lactate, plasma free fatty acid and plasma and tissue individual free amino acid levels were followed in newborn rabbits exposed for 10 h to an environmental temperature of 25 degrees C. Severe hypothermia developed with an increase of blood lactate and accumulation of total free amino acids in plasma and liver. Alanine, isoleucine, leucine, valine, phenylalanine, tyrosine, ornithine and taurine were elevated in the plasma; alanine and ornithine in the liver; leucine and isoleucine in the muscle.     

Tyrosine supplementation in phenylketonuria: diurnal blood tyrosine levels and presumptive brain influx of tyrosine and other large neutral amino acids

Tyrosine supplementation has not consistently been found to improve neuropsychologic function in phenylketonuria (PKU), possibly because of failure to achieve adequate levels of tyrosine in the brain. OBJECTIVES: To evaluate blood levels achieved after tyrosine supplementation in treated PKU and calculate brain influxes of tyrosine and other large neutral amino acids before and with tyrosine supplementation. STUDY DESIGN: Ten subjects with PKU receiving a phenylalanine-restricted diet were studied over 48 hours; each received tyrosine supplementation (300 mg/kg) on day 2. Plasma phenylalanine and tyrosine were measured every 2 hours, and all free amino acids were measured every 6 hours. Brain influxes of tyrosine and other large neutral amino acids were calculated. RESULTS: Plasma tyrosine levels were low normal at baseline. With supplementation there was a substantial but unsustained rise in plasma tyrosine. Calculated brain influx of tyrosine was 27% +/- 19% of normal before supplementation, increasing to 90% +/- 58% of normal with supplementation. Nevertheless, calculated influx remained less than 70% of normal at 50% of the time points. The calculated brain influxes of all other large neutral amino acids except tryptophan were 20% to 40% of normal before and with tyrosine supplementation. CONCLUSIONS: Tyrosine supplementation in the diet for PKU produces marked but nonsustained increases in plasma tyrosine levels, with calculated brain influx that often remains suboptimal. This could explain the lack of consistent neuropsychologic benefit with tyrosine supplementation.