Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.1.1.67 (thiopurine methyltransferase)
 551 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

6-Mercaptopurine (6MP) and methotrexate are the backbone of continuation therapy for childhood acute lymphoblastic leukemia (ALL). In studies of oral 6MP and methotrexate, indices of chronic systemic exposure to active metabolites of these agents, namely, red blood cell (RBC) concentrations of methotrexate polyglutamates (MTXPGs) and thioguanine nucleotides (TGNs) have positively correlated with event-free survival (EFS). Our objective was to evaluate whether MTXPGs, TGNs, and the dose intensity of administered methotrexate and 6MP were prognostic in the setting of a treatment protocol in which all treatment was coordinated through a single center, and the weekly doses of methotrexate were given parenterally. On protocol Total XII, 182 children achieved remission and received weekly methotrexate 40 mg/m2 parenterally and daily oral 6MP, interrupted every 6 weeks during the first year by pulse chemotherapy. A total of 709 TGN, 418 MTX-PG, and 267 thiopurine methyltransferase (TPMT) measurements, along with complete dose intensity information (dose received divided by protocol dose per week) for 19,046 weeks of 6MP and methotrexate, were analyzed. In univariate analyses, only higher dose intensity of 6MP and of weekly methotrexate were significant predictors of overall EFS (P =.006 and. 039, respectively). The occurrence of neutropenia was associated with worse outcome (P =.040). In a multivariate analysis, only higher dose intensity of 6MP (P =.020) was a significant predictor of EFS, with lower TPMT activity (P =.096) tending to associate with better outcome. 6MP dose intensity was also associated (P =.007) with EFS among patients with homozygous wild-type TPMT phenotype. Lower 6MP dose intensity was primarily due to missed weeks of therapy and not to reductions in daily dose. We conclude that increased dose-intensity of oral 6MP is an important determinant of EFS in ALL, particularly among those children with a homozygous wild-type TPMT phenotype. However, increasing intensity of therapy such that neutropenia precludes chemotherapy administration may be counterproductive.
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PMID:Prognostic importance of 6-mercaptopurine dose intensity in acute lymphoblastic leukemia. 1021 75

Of 1614 Nordic children with ALL that were treated according to the NOPHO ALL92 protocol, 20 developed an SMN (cumulative risk at 12 years: 1.6%). Sixteen of the twenty SMNs were acute myeloid leukemias or myelodysplasias, and 9 of these had either monosomy 7 (n=7) or 7q deletions (n=2). In Cox multivariate analysis longer duration of oral MTX/6MP maintenance therapy (p=0.02; being longest for standard risk patients) and presence of high-hyperdiploidy (p=0.07) were related to an increased risk of SMN. In 524 patients we determined the erythrocyte activity of thiopurine methyltransferase (TPMT), which methylates 6MP and its metabolites, and thus reduces cellular levels of cytotoxic 6-thioguanine nucleotides. The TPMT activity was significantly lower in those that did compared to those that did not develop an SMN (Median: 12.1 vs 18.1 IU/ml; p=0.02). Among 427 TPMT wild type patients, those who developed SMN received higher 6MP doses than the remaining (69.7 vs 60.4 mg/m(2), p=0.03), which may reflect increased levels of methylated metabolites that inhibit purine de novo synthesis and thus enhance incorporation of 6-thioguanine nucleotides into DNA. In conclusion, the duration and intensity of 6MP/MTX maintenance therapy of childhood ALL may influence the risk of SMN.
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PMID:Epidemiology of therapy-related myeloid neoplasms after treatment for pediatric acute lymphoblastic leukemia in the nordic countries. 2171 78