Methodology for the rational development of methotrexate analogs in the clinic

This paper suggests a development plan for antifolate analogs, based upon disease classifications that the National Cancer Institute has successfully utilized for the development of anthracycline and platinum analogs. Diseases are classified according to the role of the parent compound in standard therapy: 1) those in which methotrexate is an important component of standard treatment strategies that have state-of-the-art effectiveness; 2) those in which methotrexate has antitumor activity but no clear role in standard state-of-the-art treatment strategies; and 3) those in which methotrexate has insufficient activity to warrant its use alone or in combination. Developmental plans are specified for each of these disease classes. Trimetrexate is used as a specific example for these plans, although this method of drug development is equally applicable to other methotrexate analogs.     

The effect of malignant effusions on methotrexate disposition

PURPOSE: The purpose of this study was to evaluate the effect of malignant effusions on the pharmacokinetics of methotrexate (MTX). METHODS: Simulated drug concentrations in blood, tissues and effusion fluid spaces were generated using a previously published physiologically based pharmacokinetic (PBPK) model for MTX in humans. The model was expanded to incorporate effusion spaces with permeability rate-limited drug transport. The model was used first to simulate MTX plasma concentrations in patients without effusions. Then the effects of cardiac, peritoneal and pleural effusions on MTX plasma concentrations were investigated followed by an examination of the influence of effusion volume, binding in the effusate, and effusion space permeability clearance (PA) on MTX plasma pharmacokinetics. In addition, the effect of the disposition characteristics (e.g. volume of distribution) of the anticancer drug on the overall influence of an effusate was evaluated. Finally, the simulations were compared with MTX concentrations observed in the plasma and pleural fluid of a patient with a pleural effusion treated with MTX. RESULTS: There was good agreement between the PBPK-simulated MTX plasma concentrations and observed values in patients without effusions. There was also a remarkable similarity between simulated and measured plasma and effusion MTX concentrations in a pediatric patient with a malignant pleural effusion. The physiological characteristics of an effusion, i.e. fluid volume, protein binding and membrane permeability clearance, modulate the influence of an effusion on the drug plasma concentration-time course. In general, effusions cause an increase in the steady-state volume of distribution but no change in the overall clearance of a drug. Malignant effusions were noticeable only in the disposition phase of MTX resulting in an apparent "third space." This was most prominent when the effusion fluid volume was large, the binding of MTX in the effusion fluid was greater than in plasma and the PA value was low. The percentage change in terminal half-life due to an effusion is significant for drugs with small volumes of distribution (332%) but not for those with large volumes of distribution (1.29%). In the case of MTX, and probably other anticancer drugs, the resulting increase in half-life may be associated with unanticipated toxicity.     

Evaluation of the TNM classification of stomach cancer and proposal for its rational stage-grouping

The present TNM Classification with the provisional stage-groupingfor stomach cancer, which was adopted in 1978, was evaluatedfor compatibility in respect to survival by using 15,589 stomachcancer patients registered in Japan from 1969 to 1973. Adequacyand usefulness were shown in all categories of T, N, M, pT andpN, individually. Important irrationality in accordance withthe TNM General Rules was recognized in both the provisionalTNM and p.TNM stage-groupings. More adequate stage-groupingwas searched for and is discussed according to the results ofstatistical analysis of the patients' survival and the principleof the TNM General Rules. New TNM and p.TNM stage-groupingswere proposed as the best ones at present.     

Calculated versus measured creatinine clearance for dosing methotrexate in the treatment of primary central nervous system lymphoma

Background High-dose methotrexate (HDMTX) (≥3 g/m²), the cornerstone of therapy for primary CNS lymphoma (PCNSL), is commonly dosed using a measured 24 h creatinine clearance (CrCl) every 2–4 weeks. Because these collections are cumbersome and at times unreliable, the use of a calculated CrCl was evaluated as a potential alternative. Methods A retrospective analysis was performed on data from all 287 treatment cycles from the 25 patients with PCNSL who participated in a multi-center phase II clinical trial of HDMTX conducted by the New Approaches to Brain Tumor Therapy (NABTT) CNS Consortium. Results The 25 patients had a median age of 61 years (range 32–75). Seventeen (68%) were men. The patients received a median of 14 (range 2–21) HDMTX treatments. For 256 of 287 treatments (89%), data were available to compare the measured and calculated (using the Cockcroft–Gault equation) CrCl. The average measured CrCl was 93 ml/min (95% CI, 89–96 ml/min), and the average calculated CrCl was 107 ml/min (95% CI, 102–112 ml/min). The Pearson correlation coefficient (r) was 0.49 (P < 0.0001) between the measured and calculated CrCl. The average MTX dose determined using measured CrCl was 14.1 g (95% CI, 13.6–14.5 g), and the average MTX dose determined using calculated CrCl was 14.7 g (95% CI, 14.2–15.1 g). MTX doses based on measured and calculated CrCl were significantly correlated (r = 0.72, P < 0.0001). Of the 256 HDMTX treatments evaluated, 158 (62%) had reliable 48 h serum MTX levels documented. Forty-seven levels (30%) were within target range (0.3–1 μmol/l), 99 levels (62%) were below target range (<0.3 μmol/l), 12 levels (8%) were in the range associated with mild toxicity range (>1–3 μmol/l), and no levels were in the range associated with severe toxicity (>3 μmol/l). Of these 158 treatments, the use of a calculated rather than measured CrCl would have yielded an identical MTX dose for 48 treatments (30%), a higher MTX dose for 62 treatments (40%), and a lower MTX dose for 48 treatments (30%). This distribution was not significantly different among the subsets of below target, within target range, and above target MTX levels (P = 0.87). Conclusions In this cohort of patients with PCNSL, there is significant correlation between the calculated and measured CrCl. MTX doses determined using calculated and measured CrCl are not significantly different. For these patients, there is no clear association between the method of determining CrCl and serum MTX levels. As a result, calculated CrCl is a reasonable alternative to measured CrCl in this patient population and would avoid the inconvenience and potential inaccuracies associated with measured CrCl. Presented in abstract format at the Annual Meeting of the American Society of Clinical Oncology, Atlanta, GA, June 2–6, 2006.     

Individualized methotrexate dosing in children with relapsed acute lymphoblastic leukemia.

Although high-dose methotrexate has been extensively studied in children with newly diagnosed acute lymphoblastic leukemia (ALL), there are fewer data in children with relapsed ALL, many of whom have been heavily pretreated and have subclinical kidney dysfunction. We characterized the pharmacokinetics of adaptively controlled methotrexate given as a 24-h infusion during consolidation therapy in 24 children with relapsed ALL. To achieve the target steady-state concentration of 65 microM, dosage adjustments were required in 14 patients, with doses ranging from 2854 to 6700 mg/m2 per course. The mean steady-state plasma concentration (Cpss) of 68.0 microM was different (P = 0.025) than the predicted Cpss (mean = 87.4 microM; range 35.7-184 microM) had no adjustment in dose been made. The coefficient of variation in Cpss was reduced from 41% to 18% by individualizing doses. Predisposing factors that correlated with decreased methotrexate clearance were female sex (P = 0.03), age greater than 6 years (P = 0.01), and prior history of heavy amphotericin B treatment (>30 mg/kg) (P = 0.03), but no factor predicted low clearance as well as the measured initial methotrexate clearance during the infusion (P < 0.0001). There was no life-threatening toxicity with the regimen. We conclude that dosage individualization decreases interpatient variability and avoids potentially toxic methotrexate exposures in heavily pretreated ALL patients.     

Leptomeningeal metastasis from ovarian carcinoma successfully treated by the intraventricular administration of methotrexate

A 60-year-old woman with a history of ovarian carcinoma and complaining of gait instability, dizziness, nausea, and a right temporal headache visited a neurologist. A diagnosis of leptomeningeal metastasis was made, based on the results of a cerebrospinal fluid examination. After the administration of intrathecal methotrexate, her neurological complaints disappeared. An Ommaya intraventricular reservoir was inserted, and methotrexate administration was continued for 11 months, until another recurrence was found in her pelvis. Although uncommon, the possibility of leptomeningeal metastasis from ovarian carcinoma should be considered; in such cases, treatment with intraventricular methotrexate may be effective and feasible and should be considered as a treatment strategy.     

用群体药物动力学方法指导个体化大剂量甲氨蝶呤用药

目的：探讨用群体药物动力学（PPK）方法结合贝叶斯法对急性淋巴细胞性白血病（ALL）患儿的大剂量甲氨蝶呤（HDMTX）的剂量个体化的效果。方法：荧光偏振免疫法（fluorescence polarization immunoassay，FPIA）测定MTX血浆浓度。根据已建立的HDMTX的PPK模型结合MTX开始后第1h和第6h的血浆浓度，用贝叶斯法对11个患者的45个疗程HD—MTX的剂量个体化。结果：3g／m2HDMTX组，预测Cpss在目标值范围内的22个疗程中有20个疗程的实测Cpss在目标范围内；分别有14个和2个疗程的预测Cpss值低于和高于目标范围，经贝叶斯法调整剂量后，仍有1个疗程的实测Cpss低于目标范围。5g／m2HDMTX组，Cpss预测值在目标值范围内的5个疗程，实测Cpss均在目标范围内；预测值高于目标范围的2个疗程经贝叶斯法减少剂量后，实测Cpss也均在Cpss目标范围内。MTX开始静滴后第6h的血药浓度与预测Cpss和MTX的全身清除率有较好的相关性，MTX开始静滴后第1h的血药浓度与第6h的血药浓度及预测Cpss无相关性。结论：通过对45个疗程HDMTX的个体化研究，发现HDMTX的PPK模型预测较准确，个体化效果较好。     

Effect of IV hydration with sodium bicarbonate on high-dose methotrexate disposition kinetics

Following two-compartment kinetic analysis, the effect of loading of transfusion with sodium bicarbonate on methotrexate disposition was investigated in 13 cases with malignant tumor, being treated with high-dose methotrexate. The mean values of total body clearance, when administered at doses 50 mg and 100 mg per kg body weight, were 0.369 and 0.402 (l/h) per kg, respectively. No significant relationship was observed between alpha value and total amount of transfusion, of urine or dosage of sodium bicarbonate. The other kinetic parameters on elimination, beta value, K10 and total body clearance, did not also correlate with those values described above. These results suggest that the elimination profile of methotrexate show linear kinetics, and that massive administration of transfusion with sodium bicarbonate be not necessary if pH value of urine exceeds 7.0.     

Oral leukoplakia: a proposal for uniform reporting

Leukoplakia is the most common precancerous lesion of the oral mucosa. In order to promote uniform reporting of management results, including the event of malignant transformation, recommendations have been made for the various definitions and terminologies, including the application of a certainty factor with which the diagnosis of oral leukoplakia has been established. For reporting purposes there seems to be no rationale for distinguishing "tobacco-associated" leukoplakias from non-tobaccco-associated, so-called idiopathic leukoplakias. The recommendation has been made to use a classification and staging system in which the size and the histopathologic findings are reflected. At present, there seems to be no justification to give a weighting factor to the oral subsite of leukoplakias.     

Variability in the pharmacokinetics of cyclophosphamide,methotrexate and 5-fluorouracil in women receiving adjuvant treatment for breast cancer

A total of 23 women with stage II breast cancer receiving adjuvant cyclophosphamide, methotrexate and 5-fluorouracil had detailed pharmacokinetic monitoring performed on the first and third courses of therapy. The area under the concentration time curve (AUC) of each of these three drugs varied by a factor of 3–4 among patients. No systematic change in pharmacokinetics between the first and third courses was seen for cyclophosphamide, methotrexate or 5-fluorouracil, and the mean AUC for each of the three drugs did not change. However, significant intrapatient variability in drug pharmacokinetics was observed for all three drugs such that the AUC, clearance and half-life in an individual on the third course could not be reliably predicted from data generated on the first course. On the basis of these results, cyclophosphamide, methotrexate, and 5-fluorouracil pharmacokinetic data from one treatment would not be useful information from which the doses for subsequent courses could be determined.This research was supported by the National Cancer Institute of Canada     

Faithful companions: a proposal for neurooncology trials in pet dogs

Although relatively rare, malignant glioma (MG) is frequently used for testing novel cancer treatments. However, human MG trials have often been initiated on the basis of preclinical models that involve numerous discontinuities with the human disease. Below, we discuss various limitations of the mainstay model used in MG preclinical research, the murine orthotopic xenograft. After discussing alternative model systems like transgenic mouse models and canine xenografts, we argue that companion animals with spontaneous brain cancers offer a scientifically and ethically attractive system for preclinical testing of novel MG interventions. Ethical advantages and practical challenges of companion animal brain cancer trials are briefly discussed.     

Distribution and degradation of [3H]methotrexate after intravenous and cerebral intraventricular injection in primates.

Four hr after either a single injection or continuous infusion of methotrexate (MTX) plus purified [3',5',9(n)-3H]MTX in cynomolgus or rhesus monkeys, 80 to 98% of the 3H radioactivity present in the plasma was found not to represent intact MTX. The percentage of 3H-containing MTX products in the urine after 4 hr was considerably less, although more variable. This variability seemed to be related to variability in the amount of the total dose excreted. Non-MTX products were also found in selected tissues and the percentage of intact MTX found 4 hr after i.v. injection varied from 2 to 26%. The percentage of intact MTX was routinely measured by comparing the values obtained using the dihydrofolate reductase assay with values based on the specific activity of [3',5',9(n)-3H]MTX. Results obtained by diethylaminoethyl column chromatography on a few samples, however, showed good agreement with results from the reductase assay. [3',5',9(n)-3H]MTX products appeared in peaks eluting from the diethylaminoethyl column both earlier and later than the MTX peak, with the earlier peaks being present in only small amounts in the urine. After continuous i.v. infusion, only 2% or less of the radioactivity found in the cerebrospinal fluid after 4 hr represented intact MTX, with the remaining radioactivity eluting much earlier than MTX. In contrast, after direct injection into the left lateral ventricel, all the 3H radioactivity in both cerebrospinal fluid and brain tissue represented intact MTX for up to 4 hr after injection. The appearance of MTX products in the plasma and selected tissues of these primates a short time after i.v. injection is compared to other work in experimental animals and man and suggests a greater metabolism of MTX than was previously suspected.     

The ailments of cancer registries: a proposal for remedial education

A study on the ailments of cancer registries, manifested by inaccuracies in data collection and delays in data retrieval, is presented. The etiology is identified as the lack of educational foundation for physicians and medical students. The symptoms are caused by the distance between physicians and the cancer registry. Investigations were carried out by error analysis, problem identification, and comparative and contrast studies. Pathogenesis is described on the basis of lack of bondage between the medical record system and the cancer registry. Educational remedies starting from the patients, medical students, and physicians are prescribed. Newly designed data collection forms that can form a secure link between the hospital medical record and the cancer registry are presented. It is hoped that physicians will perceive the cancer registry not as a burden of paperwork, but as a valuable tool to study cancer, and see it as a reflection of their achievements in cancer control.     

High-dose methotrexate: a critical reappraisal

High-dose methotrexate (HDMTX) with leucovorin (LV) rescue has been used as a therapeutic strategy in oncology for more than a decade. Administration of HDMTX results in tumoricidal plasma concentrations of the drug without significant host toxicity, provided that plasma MTX levels are monitored and LV rescue is properly administered. The original premise of LV rescue was that the provision of reduced folate to normal cells would circumvent the metabolic block produced by MTX and allow resumption of DNA synthesis, although the presumed therapeutic selectivity of leucovorin has not yet been adequately explained. Despite a strong pharmacologic rationale and a vast clinical experience, HDMTX with leucovorin rescue has not been shown to be unequivocally superior to conventional doses of MTX in any clinical situation except, perhaps, for treatment of osteogenic sarcoma and childhood acute leukemia. While HDMTX is an important component of effective treatment regimens for these diseases, its precise contribution to the success of these regimens remains undefined. Although HDMTX can theoretically overcome all known mechanisms of MTX resistance, no data exist to suggest that this can be accomplished in the clinic. Thus, this well-known but poorly understood treatment regimen must remain a subject of clinical investigation rather than a part of routine clinical practice.     

Variability in the pharmacokinetics of epirubicin: a population analysis

Summary Population pharmacokinetic analysis of the anticancer agent epirubicin was carried out using the program NONMEM. Data were available from 36 patients aged 20–73 years, of whom 23 were women. All subjects exhibited normal liver and renal function. Epirubicin was given as a short-term i. v. infusion over the dose range of 25–100 mg/m², and an average of 11 plasma samples/subject were taken for a period of up to 72 h after each dose. A Two compartment model was fitted to the data, characterised by the parameters clearance, volume of the central compartment, alpha and beta. Clearance was tested as a linear function of various demographic and/or biochemical features. A significant proportion of the variability in clearance could be attributed to sex, and also to age in women. For example, a 25-year-old man would display an average clearance of 95 l/h, whereas a 70-year-old woman would exhibit an average clerance of 64 l/h. Such differences in clearance might be important in the selection of epirubicin dose regimens.