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PubMed1985

Methotrexate analogues. 25. Chemical and biological studies on the gamma-tert-butyl esters of methotrexate and aminopterin.

gamma-tert-Butylaminopterin (gamma-tBAMT), the first example of an aminopterin (AMT) gamma-monoester, was synthesized, and new routes to the known N10-methyl analogue gamma-tert-butyl methotrexate (gamma-tBMTX) were developed. The inhibitory effects of gamma-tBAMT on the activity of purified dihydrofolate reductase (DHFR) from L1210 murine leukemia cells, the growth of L1210 cells and CEM human leukemic lymphoblasts in suspension culture, and the growth of several lines of human squamous cell carcinoma of the head and neck in monolayer culture were compared with the effects of gamma-tBMTX and the parent acids AMT and methotrexate (MTX). Patterns of cross-resistance to gamma-tBAMT, gamma-tBMTX, and AMT among several MTX-resistant cell lines were examined. In vivo antitumor activities of gamma-tBAMT and gamma-tBMTX were compared in mice with L1210 leukemia. While the activity of gamma-tBAMT was very close to that of gamma-tBMTX in the DHFR inhibition assay, the AMT ester was more potent than the MTX ester against cells in culture and against L1210 leukemia in vivo. Only partial cross-resistance was shown against gamma-tBMTX and gamma-tBAMT in cultured cells that were resistant to MTX by virtue of a transport defect or a combination of defective transport and elevated DHFR activity.

Aminopterin↗

PubMed1973

Studies concerned with overcoming resistance to methotrexate: a comparison of the effects of methotrexate and 2,4-diamino-5-(3',4'-dichlorophenyl)-6-methylpyrimidine (BW50197) on the colony forming ability of L5178Y cells.

The effects of methotrexate (MTX) and 2,4-diamino-5-(3',4'-dichlorophenyl)-6-methylpyrimidine (BW50197) on the colony forming ability of L5178Y cells were compared. Two sub-lines of cells were used, one sensitive to methotrexate and the other resistant. In addition, the inhibitory effects of BW50197 against dihydrofolate reductase (DHFR) extracted from the MTX resistant cells were compared with those of MTX and pyrimethamine. It was found that although BW50197 was a less effective inhibitor of DHFR than MTX, it was superior to MTX at high concentrations in killing MTX resistant cells, and this superiority increased with the time of exposure to the drugs. These findings suggest that (a) when antifolate compounds are screened for antitumour activity it is insufficient simply to assess them on the basis of their ability to inhibit DHFR and (b) BW50197 should be given clinically so as to achieve the highest possible tissue concentration for the longest possible time consistent with the safety of the patient.

Animals↗

PubMed1999

Randomized trial to compare the efficacy and toxicity of cyclophosphamide, methotrexate and 5-fluorouracil (CMF) with methotrexate mitoxantrone (MM) in advanced carcinoma of the breast.

One hundred and sixteen patients with locally advanced or metastatic breast cancer were randomized to receive CMF (cyclophosphamide 600 mg m(-2) day 1 and 8 i.v., 5-fluorouracil 600 mg m(-2) day 1 and 8 i.v., methotrexate 40 mg m(-2) day 1 and 8 i.v., monthly for 6 cycles) or MM (methotrexate 30 mg m(-2), mitoxantrone 6.5 mg m(-2), both i.v. day 1 3-weekly for 8 cycles) as first line treatment with chemotherapy. Objective responses occurred in 17 patients out of 58 (29%) who received CMF and nine out of 58 (15%) who received MM; 95% confidence interval for difference in response rates (-1%-29%), P = 0.07. No statistically significant differences were seen in overall survival or time to progression between the two regimes although a tendency towards a shorter progression time on the MM regime must be acknowledged. There was, however, significantly reduced haematological toxicity (P < 0.001) and alopecia (P < 0.001) and fewer dose reductions and delays in patients randomized to MM. No statistically significant differences were seen between the two regimes in terms of quality of life (QOL). However, some association between QOL and toxicity was apparent overall with pooled QOL estimates tending to indicate a worsening in psychological state with increasing maximum toxicity over treatment. Despite the fact that results surrounding response rates and time to progression did not reach statistical significance, their possible compatibility with an improved outcome on CMF treatment must be borne in mind. However, MM is a well-tolerated regimen with fewer side-effects than CMF, which with careful patient management and follow-up, therefore, may merit consideration as a first-line treatment to palliate patients with metastatic breast cancer who are infirm or elderly.

Adult↗

PubMed2005

Accumulation of methotrexate and methotrexate polyglutamates in lymphoblasts and treatment outcome in children with B-progenitor-cell acute lymphoblastic leukemia: a Pediatric Oncology Group study.

We reported that children with B-progenitor-cell acute lymphoblastic leukemia (BpALL) treated in the early 1980s whose lymphoblasts accumulated high levels of methotrexate (MTX) and of methotrexate polyglutamates (MTXPGs) in vitro had an improved 5-year event-free survival (EFS) (65% (standard error (s.e.) 12%) vs 22% (s.e. 9%)). We repeated this study in children with BpALL treated in the early 1990s. The major change in treatment was the addition of 12 24-h infusions of 1 g/M2 MTX with leucovorin rescue (IDMTX). In 87 children treated on Pediatric Oncology Group (POG) study 9005 and POG 9006, the 5-year EFS for those whose lymphoblasts accumulated high levels of MTX and MTXPGs (79.2%, s.e. 8.3%) was not significantly different from that of patients with lesser accumulation of MTX and MTXPGs (77.7%, s.e. 5.4%). These findings support the notion that higher dose MTX therapy has contributed to increased cure, particularly for patients whose lymphoblasts accumulate the drug less well.

Antimetabolites, Antineoplastic↗

PubMed2002

Carboxypeptidase-G2 rescue in cancer patients with delayed methotrexate elimination after high-dose methotrexate therapy.

High-dose methotrexate (HDMTX) is a component of many cancer treatment regimens. Despite careful management, delayed renal clearance, followed by extremely high serum levels with potentially life-threatening toxicity can occur. In the present study, we report our results of carboxypeptidase-G2 (CPDG2) rescue in 8 patients with delayed methotrexate elimination and renal impairment after HDMTX therapy for lymphoma or osteosarcoma. A dose of 50 U/kg CPDG2 was administered. MTX plasma levels decreased rapidly and recovery of renal function was observed in all patients. No patient developed severe WHO grade 4 MTX toxicity. CPDG2 provides an alternative route of MTX elimination by converting it to inactive and non-toxic metabolites. CPDG2 rescue was well tolerated, safe and very effective in preventing severe or life-threatening MTX toxicity.

Adult↗

PubMed1998

Efficacy of dose-intensified MEC (methotrexate, epirubicin and cisplatin) chemotherapy for advanced urothelial carcinoma: a prospective randomized trial comparing MEC and M-VAC (methotrexate, vinblastine, doxorubicin and cisplatin). Japanese Urothelial Cancer Research Group.

BACKGROUND: To evaluate the antitumor activity in patients with T3b, T4 or metastatic urothelial carcinoma treated with MEC or M-VAC chemotherapy, by performing a multi-center randomized prospective study. METHODS: From 1991 to 1995, 89 patients with T3b, T4 or metastatic urothelial carcinoma were randomly allocated to a methotrexate, epirubicin and cisplatin chemotherapy group (arm 1: S-MEC therapy; n = 29), a dose-intensified MEC therapy combined with G-CSF group (arm 2: I-MEC therapy; n = 30) or a methotrexate, vinblastine, doxorubicin and cisplatin chemotherapy (arm 3: M-VAC therapy; n = 30). At the registration center, the patients were stratified into previously untreated patients and patients with recurrence after radical operation and then randomly allocated to the treatment groups. In each arm, two or more courses of chemotherapy (4-week cycles) were performed. RESULTS: Of the 88 eligible patients, four treated with S-MEC therapy and two treated with I-MEC therapy showed CR. The response rates (CR + PR) were 52% (15/29) with S-MEC therapy, 76% (22/29) with I-MEC therapy and 47% (14/30) with M-VAC therapy. The response rate with I-MEC therapy was significantly higher than that with M-VAC therapy (P = 0.02). Although the incidence of leukopenia was low with I-MEC therapy, the incidence of thrombocytopenia was high with this therapy. CONCLUSION: MEC therapy used in this study is promising in terms of the antitumor effects.

Adult↗

PubMed2005

Bendamustine prolongs progression-free survival in metastatic breast cancer (MBC): a phase III prospective, randomized, multicenter trial of bendamustine hydrochloride, methotrexate and 5-fluorouracil (BMF) versus cyclophosphamide, methotrexate and 5-fluorouracil (CMF) as first-line treatment of MBC.

Two i.v. regimens, bendamustine, methotrexate and 5-fluorouracil (BMF) and cyclophosphamide, methotrexate and 5-fluorouracil (CMF) were compared as first-line therapy in a randomized, open, multicenter phase III trial including 364 patients with metastatic breast cancer (MBC). Bendamustine is an anti-neoplastic agent with alkylating, but also additional, so far unclear, mechanisms of action. We wanted to show the superiority of BMF over CMF in terms of time to progression (TTP) (primary endpoint), overall response, response duration, toxicity and quality of life (QoL). TTP was significantly longer in the BMF group (8.2 versus 6.7 months for CMF) (p=0.0071). The effect of BMF on TTP was more pronounced in the stratum 'prior adjuvant therapy, no visceral metastases' (p=0.034). Overall response rates and QoL did not significantly differ between the regimens. BMF caused more mucositis and leukopenias. Thus, bendamustine, when replacing cyclophosphamide in the CMF combination, can be expected to produce longer progression-free survival in first-line treatment of MBC.

Adolescent↗

PubMed2005

Understanding the role of Leu22 variants in methotrexate resistance: comparison of wild-type and Leu22Arg variant mouse and human dihydrofolate reductase ternary crystal complexes with methotrexate and NADPH.

Structural data are reported to 2.5 A resolution for the first full analysis of the methotrexate-resistant Leu22Arg (L22R) variant of mouse dihydrofolate reductase (mDHFR) crystallized as a ternary complex with methotrexate (MTX) and the cofactor NADPH. These results are compared with the MTX and NADPH ternary complexes of L22R human DHFR (hDHFR) and those of mouse and human wild-type DHFR enzymes. The conformation of mDHFR Arg22 is such that it makes hydrogen-bonding contacts with Asp21, Trp24 and a structural water molecule, observations which were not made in the L22R hDHFR ternary complex. These data show that there is little difference between the structures of the wild type and L22R variant for either mouse or human DHFR; however, there are significant differences between the species. Comparison of these structures reveals that the active site of mDHFR is larger than that in the hDHFR structure. In mDHFR, the position of MTX is shifted 0.6 A toward helix C (residues 59-65), which in turn is shifted 1.2 A away from the active site relative to that observed in the hDHFR ternary complexes. In the L22R variant mDHFR structure, MTX makes shorter contacts to the conserved residues Ile7, Val115 and Tyr121 than in the L22R variant human DHFR structure. These contacts are comparable in both wild-type enzymes. The unexpected results from this comparison of the mouse and human DHFR complexes bound with the same ligand and cofactor illustrate the importance of detailed study of several species of enzyme, even when there is a high sequence homology between them. These data suggest that the differences in binding interactions of the L22R variant are in agreement with the weaker binding affinity for MTX in the variant enzymes; the larger size of the binding site in mDHFR supports the observation that the binding affinity of MTX for L22R mDHFR is significantly weaker than that of the L22R hDHFR enzyme.

Amino Acid Sequence↗

PubMed2006

Determinants of the elimination of methotrexate and 7-hydroxy-methotrexate following high-dose infusional therapy to cancer patients.

AIMS: To characterize determinants of the elimination of methotrexate (MTX) and 7-hydroxy-methotrexate (7-OH-MTX) in patients receiving high-dose MTX therapy (HDMTX). METHODS: 24 and 48-h blood samples from 76 patients receiving HDMTX (dose range 300 mg m-2 to 12 g m-2) were analysed, and concentration-time data were subjected to population pharmacokinetic and covariate analysis using nonlinear mixed-effect modelling (NONMEM). RESULTS: Treatment-related mortality was 1.3% (one patient with renal failure). Values for MTX clearance (CLMTX) and 7-OH-MTX clearance (CL7-OH-MTX) were estimated at 8.85 and 2 L-1, respectively. Baseline creatinine clearance correlated with CLMTX and CL7-OH-MTX. Concurrent administration of benzimidazoles led to a 27% decrease in CLMTX and a 39% decrease in CL7-OH-MTX. Prior administration of nonsteroidal anti-inflammatory drugs (NSAIDs) resulted in a 16% decrease in CLMTX and a 38% decrease in CL7-OH-MTX. Plasma MTX concentrations were significantly higher in patients also receiving benzimidazoles at 24 h (2.01 micromol L-1vs. 0.66 micromol L-1, P<10(-4)) and at 48 h (0.25 micromol L-1vs. 0.12 micromol L-1, P<10(-4)). 7-OH-MTX plasma concentrations were also significantly higher in patients with concurrent benzimidazoles as compared with patients without benzimidazoles at 24 h (4.47 micromol L-1vs. 2.52 micromol L-1, P=0.0009) and at 48 h (1.11 micromol L-1vs. 0.72 micromol L-1, P=0.031). CONCLUSIONS: In patients receiving HDMTX, concurrent administration of benzimidazoles was associated with a significant decrease of CLMTX and CL7-OH-MTX, resulting in significantly higher plasma concentrations of MTX and 7-OH-MTX. The data suggest that benzimidazole treatment should be seen as a relative contraindication for HDMTX.

Antimetabolites, Antineoplastic↗

PubMed1988

Pharmacokinetics of 7-hydroxy-methotrexate and methotrexate in the rat.

To investigate the pharmacokinetics of the active metabolite of methotrexate (MTX), 7-hydroxy-methotrexate (7-OH-MTX), 1 mg/kg of the compound was administered as single intravenous bolus injections to 6 unanaesthetized rats. For comparison, 1 mg/kg of the parent drug MTX was given to the same number of animals. Venous blood samples were drawn at intervals for a total of 120 min., and thereafter the rats were sacrificed and tissue samples were obtained from the brain, lungs, liver, kidneys, testes, fat, and muscle. Pharmacokinetics of 7-OH-MTX and MTX were biphasic, with a significantly (P less than 0.05) smaller central compartment of distribution (Vc) and a longer second phase half-life (t1/2(beta)) for 7-OH-MTX. MTX tissue concentrations exceeded those of 7-OH-MTX in all tissues examined. The highest 7-OH-MTX concentrations were found in renal tissue. It is implied that 7-OH-MTX is less extensively distributed than the parent compound.

Animals↗

PubMed1994

Blast cell methotrexate-polyglutamate accumulation in vivo differs by lineage, ploidy, and methotrexate dose in acute lymphoblastic leukemia.

High-dose methotrexate (HDMTX) is a component of most treatment protocols for childhood acute lymphoblastic leukemia (ALL), yet recent studies of receptor-mediated transport and saturable polyglutamylation have questioned its rationale. To investigate this in vivo, methotrexate and its active polyglutamated metabolites (MTX-PG) were measured in bone marrow blasts obtained from 101 children randomized to single-agent therapy with either HDMTX (1 g/m2 per 24 h i.v., n = 47) or low-dose MTX (LDMTX, 30 mg/m2 by mouth every 6 h x 6, n = 54), before remission induction therapy. Blast concentrations of total MTX-PGs (median 460 vs 1380 pmol/10(9) cells) and of long-chain MTX-glu4-6 were both significantly higher after HDMTX (P < 0.001). With either treatment, MTX-PGs were significantly higher in B-lineage blasts than in T-lineage blasts (LDMTX P = 0.001, HDMTX P = 0.03). In a multiple regression analysis of B-lineage ALL, blast MTX-PG was significantly related to MTX dose (or plasma MTX concentration), lymphoblast ploidy (hyperdiploid > nonhyperdiploid), and percentage S-phase. This is the first evidence that HDMTX achieves higher MTX-PG concentrations in ALL blasts in vivo, establishing a rationale for HDMTX in the treatment of childhood ALL, especially T-lineage or nonhyperdiploid B-lineage ALL, disease characteristics associated with a poor prognosis on conventional therapy.

Adolescent↗

PubMed1994

Neuropsychologic effects of cranial irradiation, intrathecal methotrexate, and systemic methotrexate in childhood cancer.

PURPOSE: To investigate the neuropsychologic effects of cranial irradiation (CRT), intrathecal methotrexate (IT-MTX), and systemic methotrexate (SYS-MTX) in a cohort of pediatric patients with cancer who had either received no, moderate, or high doses of these treatments alone or in various combinations. PATIENT AND METHODS: Data were collected on 120 pediatric cancer patients from a large variety of diagnostic groups. Patients completed a comprehensive neuropsychologic test battery designed to assess most areas of cognitive functioning. In analyzing cancer treatment effects, the following variables were statistically controlled: (1) age, (2) socioeconomic status (SES), (3) age at diagnosis, (4) months since both onset and cessation of CNS treatments, (5) time missed from schooling, and (6) presence/type of CNS cancer. RESULTS: CRT, largely in combination with IT-MTX, was significantly associated with deficits in several, primarily nondominant, hemispheric neuropsychologic functions, even after control and other treatment variables were addressed. This relationship was somewhat, but not highly, dose-dependent at CRT doses greater than approximately 18 Gy, at least over the first several years posttreatment. While there was statistically significant evidence for cognitive impairment, absence from school during treatment and age at diagnosis were more predictive of reading and spelling academic achievement than having received CRT. IT-MTX and SYS-MTX alone were not associated with significant degrees of neuropsychologic involvement. CONCLUSION: CRT, especially when administered with IT-MTX, at currently used dosages was associated with significant neuropsychologic impairment in children. These impairments are most likely to be reflected in nonverbal intelligence, perceptual abilities, and susceptibility to distraction. IT-MTX and SYS-MTX did not result in a consistent pattern of cognitive deficit.

Absenteeism↗

PubMed2005

Adjuvant cisplatin plus methotrexate versus methotrexate, vinblastine, epirubicin, and cisplatin in locally advanced bladder cancer: results of a randomized, multicenter, phase III trial (AUO-AB 05/95).

PURPOSE: Radical cystectomy as standard treatment of muscle-invasive urothelial carcinoma of the urinary bladder cures less than 50% of patients with locally advanced bladder cancer. We compared two adjuvant combination chemotherapies in patients with stage pT3a-4a and/or pathologic node-positive transitional-cell carcinoma of the bladder after radical cystectomy. PATIENTS AND METHODS: A total of 327 patients were randomly assigned to either adjuvant systemic chemotherapy with three cycles of cisplatin 70 mg/qm(2) on day 1 and methotrexate 40 mg/qm(2) on days 8 and 15 of a 21-day cycle (CM) or three cycles of methotrexate 30 mg/qm(2) on days 1, 15, and 22, vinblastine 3 mg/qm(2) on days 2, 15, and 22, epirubicin 45 mg/qm(2) on day 2, and cisplatin 70 mg/qm(2) on day 2 of a 28-day cycle (M-VEC). RESULTS: The hazard ratio for progression-free survival as the primary end point was 1.13 (90% CI, 0.86 to 1.48) for 163 CM patients compared with 164 M-VEC patients whose right-hand limit remained below the upper bound compatible with the noninferiority hypothesis (alpha = .0403). The 5-year progression-free, tumor-specific, and overall survival rates (point estimates +/- SE) for CM versus M-VEC were 46.3% +/- 4.6% v 48.8% +/- 4.5%, 52.0% +/- 4.6% v 52.3% +/- 4.8%, and 46.1% +/- 4.3% v 45.1% +/- 4.6%, respectively. WHO grade 3 and 4 leukopenia occurred in 7.0% of patients treated with CM and 22.2% of patients treated with M-VEC (P < .0001). CONCLUSION: CM cannot be considered inferior to M-VEC with regard to progression-free survival of patients with locally advanced bladder cancer after radical cystectomy. Moreover, patients receiving adjuvant CM combination therapy experienced significantly less grade 3 and 4 leukopenia than patients treated with M-VEC.

Adult↗

PubMed2003

HPLC determination of erythrocyte methotrexate polyglutamates after low-dose methotrexate therapy in patients with rheumatoid arthritis.

BACKGROUND: Methotrexate (MTX) may produce antiarthritic effects through polyglutamation to methotrexate polyglutamates (MTXPGs), a process that covalently attaches sequential gamma-linked glutamic residues to MTX. We sought to develop an innovative HPLC method for the quantification of these metabolites in erythrocytes. METHODS: Two alternative approaches were developed. In the first approach, MTXPGs from 50 micro L of packed erythrocytes were converted to MTX in the presence of plasma gamma-glutamyl hydrolase and mercaptoethanol at 37 degrees C. In the second approach, MTXPG species (up to the hepta order of glutamation) from 100 micro L packed erythrocytes were directly quantified in a single run. In both methods, the MTXPGs were extracted from the biological matrix by a simple perchloric acid deproteinization step with direct injection of the extract into the HPLC. The chromatography used a C(18) reversed-phase column, an ammonium acetate/acetonitrile buffer, and postcolumn photo-oxidation of MTXPGs to fluorescent analytes. RESULTS: Intra- and interday imprecision (CVs) were <10% at low and high concentrations of analytes for both methods. The limit of quantification was 5 nmol/L. In 70 patients with rheumatoid arthritis receiving weekly low-dose MTX, the mean (SD) total MTXPG concentration measured after conversion of MTXPGs to MTX was similar to the total MTXPG concentration calculated from the sum of individual MTXPG species [117 (56) vs 120 (59) nmol/L; r = 0.97; slope = 1.0]. The triglutamate predominated over all other MTXPG species (36% of total), the pentaglutamate was the highest order of glutamation detected, and a stability study revealed no change in the polyglutamation pattern in erythrocytes 48 h after phlebotomy when the specimen was stored at 2-8 degrees C. CONCLUSION: The proposed method for quantification of erythrocyte MTXPGs is rapid, sensitive, and accurate and can be applied to the routine monitoring of MTX therapy.

Antirheumatic Agents↗

PubMed2000

Cyclosporine, methotrexate, and methylprednisolone compared with cyclosporine and methotrexate for the prevention of graft-versus-host disease in bone marrow transplantation from HLA-identical sibling donor: a prospective randomized study.

The role of corticosteroids in the prophylaxis of graft-versus-host disease (GVHD) is not well established. We have conducted a prospective, randomized, open-label, single-center study about the effect of adding methylprednisolone (MP) to the widely used prophylactic regimen consisting of cyclosporine A and methotrexate. A total of 108 consecutive patients treated with allogeneic bone marrow transplantation from an HLA-identical sibling donor for malignant blood disease were entered into the study; 53 patients were randomized to receive and 55 were randomized not to receive prophylactic MP. The dose of MP was 0.5 mg/kg on days 14 to 20, 1 mg/kg on days 21 to 34, 0.5 mg/kg on days 35 to 48, and thereafter the dose was slowly tapered and the administration discontinued on day 110. In the group given prophylactic MP, the incidence of acute GVHD was lower (19% vs 56%, P =.0001), there was a trend toward a lower incidence of chronic GVHD among low-risk patients (P =.06), and during the first 4 months the time spent at hospital was shorter and there were fewer infections. The total amount of MP given was similar in the study groups because of a higher incidence of acute GVHD and its treatment in the group of patients not given prophylactic MP. There were no significant differences between the study groups in relapse rate or survival. In conclusion, the addition of MP to the combination of cyclosporine and methotrexate markedly reduced the incidence of acute GVHD without causing untoward effects. The timing of corticosteroid administration is probably important for the efficacy.

Acute Disease↗

PubMed1990

In vivo methotrexate kinetics and metabolism in human hematopoietic cells. Clinical significance of methotrexate concentrations in erythrocytes.

The author has performed in vivo investigations of the methotrexate (MTX) accumulation, kinetics and polyglutamate metabolism in erythrocytes, neutrophils and myeloid bone marrow cells during clinical MTX therapy of patients with acute lymphoblastic leukemia (ALL), non-Hodgkin lymphoma and psoriasis. On the basis of these studies the clinical applicability of monitoring erythrocyte MTX concentrations in children with ALL and adult psoriasis patients have been evaluated. To accomplish this task a set of methods has been developed: 1) An automated enzymatic assay adapted for a centrifugal analyzer was used to measure MTX concentrations between 10 and 60 nmol/l in erythrocytes and serum. 2) For the study of MTX kinetics in myeloid cells, age fractionated erythrocytes and HPLC fractionated methotrexate polyglutamates a sequential radioligand binding assay with a range of 1-8 (and 1-16) nmol/l was employed. 3) Discontinuous Percoll gradients of increasing densities were used to separate myeloid cells and erythrocytes of increasing mean cell age. Declining reticulocyte counts and erythrocyte-aspartate aminotransferase activity were taken as parameters of increasing mean erythrocyte age. 4) In order to study MTX polyglutamate metabolism a high performance liquid chromatography (HPLC) procedure was set up using tetrabutylammonium phosphate in acetonitrile in an automatically generated gradient buffer system. The MTX polyglutamates were separated, and the concentrations determined by the radioligand binding assay. The individual polyglutamates were identified by comparisons with the retention times of MTX polyglutamate standards (MTX-glu1+2+3+4+6+7) which were detected spectrophotometrically at 304 nm. During 24 hour infusions MTX was incorporated predominantly in the proliferating myeloid bone marrow cells before appearing in circulating neutrophils about seven days later. Evidence for MTX incorporation in the erythroid precursors of the bone marrow was provided by demonstrating high MTX content in density fractionated reticulocyte enriched erythrocyte populations. During weekly low dose MTX treatment the erythrocyte MTX concentration reached a constant level (steady state ery-MTX) after 4-6 weeks. MTX concentrations in age fractionated red blood cells and the terminal decline of the ery-MTX and its polyglutamate forms after cessation of MTX administration revealed that maintenance of the steady state ery-MTX depended on three conditions: 1) The amount of MTX added to the circulation via MTX containing reticulocytes. 2) The in vivo efflux of MTX from circulating erythrocytes, and 3) The loss of MTX with age dependent destruction of red blood cells. The in vivo efflux of MTX accounted for a loss of MTX which was 3-4 times greater than the amount that was lost with age dependent erythrocyte destruction.(ABSTRACT TRUNCATED AT 400 WORDS)

Erythrocytes↗

PubMed1990

The use of protein as a carrier of methotrexate for experimental cancer chemotherapy. V. Alternative method for preparation of serum albumin-methotrexate derivative.

An alternative method for the preparation of human serum albumin-methotrexate derivative (HSA-MTX) using N-hydroxysuccinimide ester of methotrexate (MTX) was compared with that using the water-soluble carbodiimide (WSC) assistance. The prepared derivative was tested to find the advantages and drawbacks of this method. The N-hydroxysuccinimide ester method is more laborious than that using WSC but some reasons speak in favor of this method. The formation of protein-protein conjugates during the reaction was negligible and under specific conditions more MTX molecules could be bound to protein than by the WSC method. However, some disadvantages of this method were found: A laborious preparation, a small degree of denaturation of protein during the synthesis and, moreover, the binding of MTX to protein did not always take place through NH2-groups of protein but through some other groups (--OH, --SH) as well. These couplings were not so stable as an amidic (or peptidic) bond. In water environment they were hydrolyzed and MTX was slowly released. If there is no difference in a small fraction of protein-protein conjugates, the WSC-assisted method possesses evident advantages over the active MTX ester one, mainly because of the simple preparation of the stable derivative.

Animals↗

PubMed1989

Wild-type and drug-resistant Leishmania major hydrolyze methotrexate to N-10-methyl-4-deoxy-4-aminopteroate without accumulation of methotrexate polyglutamates.

We have examined the metabolism of the folate analog methotrexate (MTX) in the human parasite Leishmania major. These cells readily hydrolyzed MTX to N-10-methyl-4-deoxy-4-aminopteroate (MAPA), such that following a 24-h incubation in 1 microM [3H]MTX approximately 30% of the cell-associated radioactivity was MAPA. MAPA also accumulated in the culture medium, exceeding the concentration of MTX after 24 h. Neither 7-hydroxy-methotrexate nor MTX polyglutamates were observed in cells or medium, even after a 72-h incubation with MTX. In contrast to MTX, folate is extensively polyglutamylated in L. major (Santi, D. V., Nolan, P., and Shane, B. (1987) Biochem. Biophys. Res. Commun. 146, 1089-1092). MAPA was found to be 190-fold less potent than MTX as an inhibitor of leishmanial growth and to bind less tightly than MTX to leishmanial dihydrofolate reductase-thymidylate synthase. We therefore examined the possibility that MTX resistance is mediated by increased MTX hydrolysis to MAPA in drug-resistant Leishmania. However, enzymatic assays show that the rate of MTX hydrolysis was unaltered in the MTX-resistant R1000-3 line and the primaquine-resistant PQ-R30 line (which is 24-fold cross-resistant to MTX). In addition to MAPA, several minor unidentified metabolites were observed in the LT252, R1000-5B, and PQR30 cells but no consistent differences in the amounts of these metabolites were evident among these lines. These data indicate that alterations in the rate of MTX hydrolysis in vitro, or in the characteristics of MTX metabolites formed in vivo, do not underly the MTX resistance displayed by the H region-amplified R1000-5B and PQ-R30 lines.

Animals↗