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Pharmacology of 5-Aza-2'-deoxycytidine (decitabine).

The preclinical pharmacology of 5-aza-2'-deoxycytidine (decitabine, 5AZA-CdR) is reviewed. 5AZA-CdR, an analogue of deoxycytidine, is a prodrug that requires metabolic activation by deoxycytidine kinase. The active inhibitor in the cell is its triphosphate form (5AZA-dCTP), which incorporates very readily into DNA to produce an inhibition of DNA methyltransferase. The mechanism responsible for the antileukemic action of 5AZA-CdR is related to its reversal of epigenetic silencing by aberrant DNA methylation of genes that suppress leukemiogenesis. 5AZA-CdR is an S-phase-specific agent. At concentrations in the range of micromolars this analogue can induce terminal differentiation and loss of clonogenicity of human leukemic cells. Drug resistance to 5AZA-CdR occurs primarily by reduction in deoxycytidine kinase activity or increase in the activity of cytidine deaminase, the enzyme that inactivates this analogue. 5AZA-CdR is a very potent antileukemic agent in animal models, more effective than the related antileukemic drug, cytosine arabinoside. In humans, 5AZA-CdR has a short half-life of 15 to 25 minutes due to rapid inactivation by liver cytidine deaminase. The major toxicity produced by 5AZA-CdR is myelosuppression. Preliminary clinical studies in patients with hematologic malignancies indicate that 5AZA-CdR is an active chemotherapeutic agent. The optimal dose-schedule for this interesting epigenetic agent with a novel mechanism of action remains to be determined. Translation of the pharmacology of 5AZA-CdR into therapeutic regimens based on scientific rationale can be used to obtain this objective.

Animals↗

Decitabine in acute myeloid leukemia.

Standard induction chemotherapy, depending on patient tolerability, is at present the treatment of choice in patients with acute myeloid leukaemia (AML) under the age of 75 years. Since AML is a disease primarily of the elderly, a large proportion of patients do not receive this therapy; therefore, novel treatment modalities are warranted. In addition, younger patients with poor-risk cytogenetics often have unsatisfactory results with conventional chemotherapy, so novel treatment options would represent a significant advancement in the management of this disease. The encouraging results of low-dose schedules of demethylating agents in myelodysplastic syndromes (MDS) have stimulated interest in the use of these agents in patients with AML. The DNA methylator phenotype of MDS and AML offers a biological rationale for treating these patients with doses of demethylating agents which act by reverting the hypermethylated state to an unmethylated state rather than by "classic" cytotoxicity mechanisms typically associated with higher doses. However, many issues surrounding this therapy need to be unravelled, including the role of different target genes that may become demethylated, and the potential use of combination therapy of hypomethylating agents with other drugs. This review will provide a summary of epigenetic processes in AML and the role of the demethylating agent 5-aza-2'-deoxycytidine (decitabine; Dacogen, MGI Pharma, Inc, Bloomington, MN).

Acute Disease↗

Epigenetic therapy of cancer with 5-aza-2'-deoxycytidine (decitabine).

Epigenetic events, such as aberrant DNA methylation, have been demonstrated to silence the expression of many genes that suppress malignancy. Since the event is reversible, it is an interesting target for intervention with specific inhibitors of DNA methylation, such as 5-aza-2'-deoxycytidine (5-AZA-CdR, decitabine). 5-AZA-CdR is a prodrug that requires activation via phosphorylation by deoxcytidine kinase. The nucleotide analog is incorporated into DNA, where it produces an irreversible inactivation of DNA methyltransferase. 5-AZA-CdR is an S-phase-specific agent. The demethylation of DNA by this analog in neoplastic cells can lead to the reactivation of silent tumor-suppressor genes, induction of differentiation or senescence, growth inhibition, and loss of clonogenicity. 5-AZA-CdR was demonstrated to be a potent antineoplastic agent against leukemia and tumors in animal models. Preliminary clinical trials of 5-AZA-CdR using different dose-schedules have shown interesting antineoplastic activity in patients with leukemia, myelodysplastic syndrome (MDS), and non-small cell lung cancer (NSCLC). Pharmacokinetic studies have shown that 5-AZA-CdR has a short in vivo half-life of 15 to 25 minutes. The major toxicity produced by this analog is granulocytopenia. To exploit the full chemotherapeutic potential of 5-AZA-CdR for the treatment of cancer, its optimal dose-schedule has to be found. This will require a good understanding of the pharmacology of this analog and its action on both normal and neoplastic cells.

Alleles↗

Pilot phase I-II study on 5-aza-2'-deoxycytidine (Decitabine) in patients with metastatic lung cancer.

5-Aza-2'-deoxycytidine (5-AZA-CdR, Decitabine) is a nucleoside analog and an active drug for the therapy of acute leukemia. The incorporation of 5-AZA-CdR into DNA blocks DNA methylation and can result in the activation of specific genes, such as tumor suppressor genes. This novel mechanism of action of 5-AZA-CdR stimulated our interest in its potential for cancer therapy in patients with lung cancer. Using a colony assay we observed that 5-AZA-CdR showed a potent antineoplastic effect against two human lung carcinoma cell lines. The objective of this preliminary phase I-II study was to evaluate the toxicity and clinical efficacy of 5-AZA-CdR in patients with stage IV non-small cell lung carcinoma. There were 15 patients that entered the clinical study. For nine assessable patients that received 5-AZA-CdR by a single 8 h i.v. infusion of 200-660 mg/m2 for one or more cycles, the median survival duration was 6.7 months, with three patients surviving more than 15 months. The steady-state plasma concentration of 5-AZA-CdR during the infusion was estimated in some patients and was in the same range that produced activation of a tumor suppressor gene in human lung tumor cell lines as reported by other investigators. The major side effect of 5-AZA-CdR was hematopoietic toxicity which required a 5-6 week recovery period before the next cycle of therapy. This study suggests that 5-AZA-CdR may have some clinical activity against metastatic lung carcinoma using this type of dose schedule.

Adult↗

Epigenetic therapy with decitabine for myelodysplasia and leukemia.

New therapeutic approaches are being developed for the treatment of cancer patients. Increasingly, drugs are being produced based on new insight into the intracellular processes in the cancer cell. Recently the typical epigenetic changes in the tumor cell have been considered as a therapeutic target. Several drugs have shown potential epigenetic activity. Decitabine (5-aza-2 -deoxycytidine, Dacogen) is one of the drugs that is able to induce changes in the methylation status of DNA. In this article the authors present an overview of this drug with regard to the chemistry, pharmacokinetics and the data that support its role as the new therapeutic agent in leukemia and myelodysplastic syndrome.

Animals↗

Decitabine: development of a DNA methyltransferase inhibitor for hematological malignancies.

Decitabine (DAC) is a small molecule nucleotide analog that is incorporated into DNA and traps human DNA methyltransferases. Although initially developed as a cytotoxic agent, low-dose DAC is enjoying a revival as a specific inhibitor of hypermethylation in cancer. DAC has activity in several hematological diseases, especially myelodysplastic syndrome, chronic myelogenous leukemia and acute myeloid leukemia. Clinical and preclinical advances are presented in this review.

Animals↗

Decitabine. MGI Pharma Inc/SuperGen Inc.

Decitabine is a DNA methyltransferase inhibitor under development by SuperGen Inc and MGI Pharma Inc for the potential treatment of a range of hematological malignancies, including myelodysplastic syndrome, solid tumors and sickle cell disease.

Animals↗

Pharmacological approach for optimization of the dose schedule of 5-Aza-2'-deoxycytidine (Decitabine) for the therapy of leukemia.

5-Aza-2'-deoxycytidine (5-Aza-CdR; Decitabine) is an active antineoplastic agent in patients with leukemia. Since 5-Aza-CdR is an S phase specific agent and has a short plasma half-life, its antileukemic activity is dose schedule-dependent. Leukemia patients who are candidates for 5-Aza-CdR therapy following relapse after therapy with cytosine arabinoside are at greater risk for the problem of drug resistance since these cytosine nucleoside analogues are metabolized by the same enzymes. Due to its unique mechanism of action of demethylating DNA, 5-Aza-CdR has the potential to activate tumor (growth) suppressor and differentiation genes that have been accidentally silenced by DNA methylation in leukemic cells. All these factors should be taken into account in the design of the optimal dose schedule of this analogue. The optimal dose schedule of 5-Aza-CdR should be based on the kinetic parameters of deoxycytidine kinase, its pharmacokinetics, its effects on DNA methylation and the cell cycle parameters of the leukemic cells and the normal hematopoietic stem cells. Since granulocytopenia is the major toxic effect produced by 5-Aza-CdR, the use of hematopoietic growth factors to shorten the duration of leukopenia should be investigated. Another approach which we are investigating is to use the methods of gene therapy to insert the cytidine deaminase gene into normal hematopoietic progenitor cells so as to make them drug resistant to 5-Aza-CdR. The use of other agents that can induce the differentiation of leukemic cells in combination with 5-Aza-CdR may have the potential to increase the clinical effectiveness of this analogue for the therapy of leukemia.

Animals↗

The effects of 5-aza-2'-deoxycytidine (Decitabine) on the platelet count in patients with intermediate and high-risk myelodysplastic syndromes.

5-Aza-2'-deoxycytidine, a DNA-hypomethylating agent, can induce clinical remissions in patients with high-risk myelodysplastic syndromes (MDS). During treatment an increase in platelet count is frequently the first positive event to be seen. In this study, we analyzed the platelet response of patients with high-risk MDS on low-dose 5-aza-2'-deoxycytidine therapy. We evaluated 162 from the 170 patients entered in three consecutive Phase II studies. One hundred twenty-six of them were thrombocytopenic at start of the therapy. All patients had an IPSS risk score of Intermediate I or higher. A rise in platelet count preceded a good trilineage response. In 58% of the thrombocytopenic patients a platelet response was already seen after one cycle of therapy. During therapy 69% of the patients with a low platelet count showed a response. Due to disease progression the final response rate was 63% in thrombocytopenic patients. No correlation was found between the platelet response and either the presence or absence of an adequate number of megakaryocytes or serum thrombopoietin levels. However, platelet response strongly predicted for overall survival (P < 0.0001). 5-Aza-2'-deoxycytidine has a clinically significant, often long lasting, effect on the platelet count in a substantial number of high-risk MDS patients.

Adult↗

Potential of 5-aza-2'-deoxycytidine (Decitabine) a potent inhibitor of DNA methylation for therapy of advanced non-small cell lung cancer.

Although new agents and drug combinations have increased the response rate in advanced non-small cell lung cancer (NSCLC), long-term survivors are rare. There is an urgent need to develop new chemotherapeutic approaches for disease. In a previous pilot phase I-II study on 5-aza-2'-deoxycytidine (5-AZA-CdR) in patients with stage IV NSCLC, we observed several interesting responses, including one patient that was still alive (68 months) at the time of publication of our results. In the present report, we want to point out the long-term follow up of this patient, who survived 81 months, and discuss the interesting mechanism of action of 5-AZA-CdR that may have been responsible for this interesting response. 5-AZA-CdR is a potent inhibitor of DNA methylation. Recent progress in this field has shown that aberrant methylation of the promoter region of tumor suppressor genes inhibits their expression. This epigenetic event can contribute to tumorigenesis. Since 5-AZA-CdR can reactivate these genes by blocking DNA methylation, it has the potential to reverse tumorigenesis. This novel mode of action makes it an interesting agent to investigate for the chemotherapy of malignant disease, including lung cancer.

Antimetabolites, Antineoplastic↗

Decitabine.

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Antimetabolites, Antineoplastic↗

Phase I study of decitabine-mediated gene expression in patients with cancers involving the lungs, esophagus, or pleura.

PURPOSE: The DNA methylation paradox, manifested as derepression of cancer-testis antigens, and silencing of tumor suppressors during malignant transformation, provides the rationale for the utilization of chromatin remodeling agents for cancer therapy. A phase I trial was done to examine pharmacokinetics, toxicities, and gene expression mediated by 5-aza-2'-deoxycytidine (DAC) in patients with thoracic malignancies. EXPERIMENTAL DESIGN: Thirty-five patients with cancers refractory to standard therapy received continuous 72-hour DAC infusions using a phase I dose-escalation schema. Each full course of therapy consisted of two identical 35-day cycles. Plasma DAC levels were evaluated by liquid chromatography-mass spectrometry techniques. Quantitative reverse transcription-PCR, methylation-specific PCR, and immunohistochemical techniques were used to evaluate NY-ESO-1, MAGE-3, and p16 expression in tumor biopsies. Long oligonucleotide arrays were used to evaluate gene expression profiles in laser-captured tumor cells before and after DAC exposure. RESULTS: Thirty-five patients were evaluable for toxicities; 25 were evaluable for treatment response. Myelosuppression constituted dose-limiting toxicity. The maximum tolerated dose of DAC was 60 to 75 mg/m(2) depending on the number of prior cytotoxic chemotherapy regimens. No objective responses were observed. Plasma DAC concentrations approximated thresholds for gene induction in cultured cancer cells. Target gene induction was observed in 36% of patients. Posttreatment antibodies to NY-ESO-1 were detected in three patients exhibiting NY-ESO-1 induction in their tumor tissues. Complex, heterogeneous gene expression profiles were observed in pretreatment and posttreatment tissues. CONCLUSION: Prolonged DAC infusions can modulate gene expression in primary thoracic malignancies. These findings support further evaluation of DNA-demethylating agents alone or in combination with other regimens targeting induced gene products for the treatment of these neoplasms.

Adult↗

Activation of expression of p15, p73 and E-cadherin in leukemic cells by different concentrations of 5-aza-2'-deoxycytidine (Decitabine).

BACKGROUND: Inactivation of genes that suppress neoplasia by aberrant DNA methylation is a key event that occurs during the development of leukemia. The inhibitor of DNA methylation, 5-aza-2'-deoxycytidine (5AZA), which can re-activate these genes, is under clinical investigation for therapy of leukemia. The objective of this study was to determine the concentrations of 5AZA that will re-activate target silent genes in human leukemic cell lines. MATERIALS AND METHODS: RT-PCR was used to evaluate the effect of concentrations of 1 to 100 ng/ml of 5AZA on the re-activation of p15 and p73 in KG1a myeloid leukemic cells and E-cadherin in HL-60 myeloid leukemic cells. The effect of 5AZA on inhibition of growth, DNA synthesis and colony formation in these cell lines was also investigated. RESULTS: The extent of activation of the target genes was dependent on the concentration of 5AZA. For p15, pronounced activation was observed at 10 ng/ml or greater. For p73 and E-cadherin significant activation was observed at 100 ng/ml of 5AZA. Maximal inhibition of growth, DNA synthesis and colony formation occurred at 100 ng/ml. CONCLUSION: The in vitro antineoplastic and gene re-activation activity of 5AZA is dependent on the concentration of this analog. These data may be helpful in the design of the optimal dose-schedule of 5AZA for the clinical therapy of leukemia.

Antimetabolites, Antineoplastic↗