Population pharmacokinetic and pharmacogenetic analysis of 6-mercaptopurine in paediatric patients with acute lymphoblastic leukaemia

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT center dot The cytotoxic effects of 6-mercaptopurine (6-MP) were found to be due to drug-derived intracellular metabolites (mainly 6-thioguanine nucleotides and to some extent 6-methylmercaptopurine nucleotides) rather than the drug itself. center dot Current empirical dosing methods for oral 6-MP result in highly variable drug and metabolite concentrations and hence variability in treatment outcome. WHAT THIS STUDY ADDS center dot The first population pharmacokinetic model has been developed for 6-MP active metabolites in paediatric patients with acute lymphoblastic leukaemia and the potential demographic and genetically controlled factors that could lead to interpatient pharmacokinetic variability among this population have been assessed. center dot The model shows a large reduction in interindividual variability of pharmacokinetic parameters when body surface area and thiopurine methyltransferase polymorphism are incorporated into the model as covariates. center dot The developed model offers a more rational dosing approach for 6-MP than the traditional empirical method (based on body surface area) through combining it with pharmacogenetically guided dosing based on thiopurine methyltransferase genotype. To investigate the population pharmacokinetics of 6-mercaptopurine (6-MP) active metabolites in paediatric patients with acute lymphoblastic leukaemia (ALL) and examine the effects of various genetic polymorphisms on the disposition of these metabolites. Data were collected prospectively from 19 paediatric patients with ALL (n = 75 samples, 150 concentrations) who received 6-MP maintenance chemotherapy (titrated to a target dose of 75 mg m(-2) day(-1)). All patients were genotyped for polymorphisms in three enzymes involved in 6-MP metabolism. Population pharmacokinetic analysis was performed with the nonlinear mixed effects modelling program (nonmem) to determine the population mean parameter estimate of clearance for the active metabolites. The developed model revealed considerable interindividual variability (IIV) in the clearance of 6-MP active metabolites [6-thioguanine nucleotides (6-TGNs) and 6-methylmercaptopurine nucleotides (6-mMPNs)]. Body surface area explained a significant part of 6-TGNs clearance IIV when incorporated in the model (IIV reduced from 69.9 to 29.3%). The most influential covariate examined, however, was thiopurine methyltransferase (TPMT) genotype, which resulted in the greatest reduction in the model's objective function (P

Fathers’ Views and Understanding of their Roles in Families with a Child with Acute Lymphoblastic Leukaemia: An Interpretative Phenomenological Analysis

This study explored how fathers of children diagnosed with acute lymphoblastic leukaemia (ALL) perceived and understood the roles they had within their family over the course of their child’s illness and treatment. In-depth semi-structured interviews were conducted with five fathers. Transcripts were analysed using interpretative phenomenological analysis (IPA). The major themes that emerged were: adjusting to the diagnosis; the experience of maternal gate-keeping; striving for normalization; experiences of giving and receiving support. Overall, the fathers perceived themselves as having significant responsibility in helping their child and family cope with the illness experience. Clinical implications, including the need for professionals to recognize and more openly acknowledge the father’s position, are considered.

European development of clofarabine as treatment for older patients with acute myeloid leukemia considered unsuitable for intensive chemotherapy.

PURPOSE:
Treatment options for older patients with acute myeloid leukemia (AML) who are not considered suitable for intensive chemotherapy are limited. We assessed the second-generation purine nucleoside analog, clofarabine, in two similar phase II studies in this group of patients.
PATIENTS AND METHODS:
Two consecutive studies, UWCM-001 and BIOV-121, recruited untreated older patients with AML to receive up to four or six 5-day courses of clofarabine. Patients in UWCM-001 were either older than 70 years or 60 to 69 years of age with poor performance status (WHO > 2) or with cardiac comorbidity. Patients in BIOV-121 were >or= 65 years of age and deemed unsuitable for intensive chemotherapy.
RESULTS:
A total of 106 patients were treated in the two monotherapy studies. Median age was 71 years (range, 60 to 84 years), 30% had adverse-risk cytogenetics, and 36% had a WHO performance score >or= 2. Forty-eight percent had a complete response (32% complete remission, 16% complete remission with incomplete peripheral blood count recovery), and 18% died within 30 days. Interestingly, response and overall survival were not inferior in the adverse cytogenetic risk group. The safety profile of clofarabine in these elderly patients with AML who were unsuitable for intensive chemotherapy was manageable and typical of a cytotoxic agent in patients with acute leukemia. Patients had similar prognostic characteristics to matched patients treated with low-dose cytarabine in the United Kingdom AML14 trial, but had significantly superior response and overall survival.
CONCLUSION:
Clofarabine is active and generally well tolerated in this patient group. It is worthy of further evaluation in comparative trials and might be of particular use in patients with adverse cytogenetics.

Identification of gene networks associated with acute myeloid leukemia by comparative molecular methylation and expression profiling

Around 80% of acute myeloid leukemia (AML) patients achieve a complete remission, however many will relapse and ultimately die of their disease. The association between karyotype and prognosis has been studied extensively and identified patient cohorts as having favourable [e.g. t(8; 21), inv (16)/t(16; 16), t(15; 17)], intermediate [e.g. cytogenetically normal (NK-AML)] or adverse risk [e.g. complex karyotypes]. Previous studies have shown that gene expression profiling signatures can classify the sub-types of AML, although few reports have shown a similar feature by using methylation markers. The global methylation patterns in 19 diagnostic AML samples were investigated using the Methylated CpG Island Amplification Microarray (MCAM) method and CpG island microarrays containing 12,000 CpG sites. The first analysis, comparing favourable and intermediate cytogenetic risk groups, revealed significantly differentially methylated CpG sites (594 CpG islands) between the two subgroups. Mutations in the NPM1 gene occur at a high frequency (40%) within the NK-AML subgroup and are associated with a more favourable prognosis in these patients. A second analysis comparing the NPM1 mutant and wild-type research study subjects again identified distinct methylation profiles between these two subgroups. Network and pathway analysis revealed possible molecular mechanisms associated with the different risk and/or mutation sub-groups. This may result in a better classification of the risk groups, improved monitoring targets, or the identification of novel molecular therapies.

Global down-regulation of HOX gene expression in PML-RAR alpha(+) acute promyelocytic leukemia identified by small-array real-time PCR

Acute promyelocytic leukemia (APL) is associated with a reciprocal and balanced translocation involving the retinoic acid receptor-alpha (RARalpha). All-trans retinoic acid (ATRA) is used to treat APL and is a potent morphogen that regulates HOX gene expression in embryogenesis and organogenesis. HOX genes are also involved in hematopoiesis and leukemogenesis. Thirty-nine mammalian HOX genes have been identified and classified into 13 paralogous groups clustered on 4 chromosomes. They encode a complex net-Work of transcription regulatory proteins whose precise targets remain poorly understood. The overall function of the network appears to be dictated by gene dosage. To investigate the mechanisms involved in HOX gene regulation in hematopoiesis and leukemogenesis by precise measurement of individual HOX genes, a small-array real-time HOX (SMART-HOX) quantitative polymerase chain reaction (PCR) platform was designed and validated. Application of SMART-HOX to 16 APL bone marrow samples revealed a global down-regulation of 26 HOX genes compared with normal controls. HOX gene expression was also altered during differentiation induced by ATRA in the PML-RARalpha(+) NB4 cell line. PML-RARalpha, fusion proteins have been reported to act as part of a repressor complex during myelold cell differentiation, and a model linking HOX gene expression to this PML-RARalpha repressor complex is now proposed.

Clinical Utility of Microarray-Based Gene Expression Profiling in the Diagnosis and Subclassification of Leukemia: Report From the International Microarray Innovations in Leukemia Study Group

The Microarray Innovations in Leukemia study assessed the clinical utility of gene expression profiling as a single test to subtype leukemias into conventional categories of myeloid and lymphoid malignancies. METHODS: The investigation was performed in 11 laboratories across three continents and included 3,334 patients. An exploratory retrospective stage I study was designed for biomarker discovery and generated whole-genome expression profiles from 2,143 patients with leukemias and myelodysplastic syndromes. The gene expression profiling-based diagnostic accuracy was further validated in a prospective second study stage of an independent cohort of 1,191 patients. RESULTS: On the basis of 2,096 samples, the stage I study achieved 92.2% classification accuracy for all 18 distinct classes investigated (median specificity of 99.7%). In a second cohort of 1,152 prospectively collected patients, a classification scheme reached 95.6% median sensitivity and 99.8% median specificity for 14 standard subtypes of acute leukemia (eight acute lymphoblastic leukemia and six acute myeloid leukemia classes, n = 693). In 29 (57%) of 51 discrepant cases, the microarray results had outperformed routine diagnostic methods. CONCLUSION: Gene expression profiling is a robust technology for the diagnosis of hematologic malignancies with high accuracy. It may complement current diagnostic algorithms and could offer a reliable platform for patients who lack access to today's state-of-the-art diagnostic work-up. Our comprehensive gene expression data set will be submitted to the public domain to foster research focusing on the molecular understanding of leukemias

Pim2 cooperates with PML-RAR alpha to induce acute myeloid leukemia in a bone marrow transplantation model

Although the potential role of Pim2 as a cooperative oncogene has been well described in lymphoma, its role in leukemia has remained largely unexplored. Here we show that high expression of Pim2 is observed in patients with acute promyelocytic leukemia (APL). To further characterize the cooperative role of Pim2 with promyelocytic leukemia/retinoic acid receptor alpha (PML/RAR alpha), we used a well-established PML-RAR alpha (PR alpha) mouse model. Pim2 coexpression in PR alpha-positive hematopoietic progenitor cells (HPCs) induces leukemia in recipient mice after a short latency. Pim2-PR alpha cells were able to repopulate mice in serial transplantations and to induce disease in all recipients. Neither Pim2 nor PR alpha alone was sufficient to induce leukemia upon transplantation in this model. The disease induced by Pim2 overexpression in PR alpha cells contained a slightly higher fraction of immature myeloid cells, compared with the previously described APL disease induced by PR alpha. However, it also clearly resembled an APL-like phenotype and showed signs of differentiation upon all-trans retinoic acid (ATRA) treatment in vitro. These results support the hypothesis that Pim2, which is also a known target of Flt3-ITD (another gene that cooperates with PML-RAR alpha), cooperates with PR alpha to induce APL-like disease. (Blood. 2010; 115(22): 4507-4516)