- Email: [email protected]
Decitabine in Myelodysplastic Syndromes
Decitabine in Myelodysplastic Syndromes Hussain I. Sabaa and Pierre W. Wijermansb Myelodysplastic syndromes (MDS) are a heterogenous group of hematopoietic stem cell disorders that are multifactorial in their etiology. Aberrant DNA hypermethylation is now thought to be involved in MDS, as numerous tumor-suppressor genes have been identified that are silenced in these patients. Thus, the use of DNA methyltransferase inhibitors, such as 5-aza-2=-deoxycytidine (decitabine, Dacogen™, MGI Pharma Inc, Bloomington, MN), for reversal of this process appears to be a rational intervention that may influence the course of the disease. Several phase I/II studies have been conducted using a low-dose schedule of decitabine in MDS patients. Based on these studies, decitabine appears to be effective and generally well tolerated, especially in those patients with worse prognostic indicators. Recent results of a phase III study also confirmed that patients treated with decitabine compared to standard supportive care had higher overall response rates and longer time to AML transformation. Decitabine appears to be a promising new therapy for the treatment of MDS; however, defining the optimal dosing schedule and exploring the possible use in combination with other agents such as the histone deacetylase inhibitors need further evaluation. Semin Hematol 42:S23-31 © 2005 Elsevier Inc. All rights reserved.
M
yelodysplastic syndromes (MDS) are a heterogenous spectrum of hematopoietic stem cell disorders affecting older adults, with a median age of 60 to 80 years at the time of diagnosis.28,43 The incidence of MDS is estimated to be between 10,000 and 20,000 cases per year in the United States.4 As the population ages, the incidence of MDS may be expected to increase.4 MDS is characterized by ineffective hematopoiesis; thus, cytopenias with dysplastic morphology of peripheral blood cells and bone marrow are hallmarks in most MDS cases. The clinical course can vary significantly among patients. MDS was originally thought to be synonymous with “preleukemia”; however, many patients die from complications of bone marrow failure (ie, infection, hemorrhage, or iron overload from frequent transfusions) rather than acute leukemia. Nonetheless, 20% of cases will still evolve into acute myeloid leukemia (AML). Clinical management is dependent on the patient’s age, MDS subtype, International Prognostic Scoring System (IPSS) score, and performance status.55 Currently, standard therapy includes sup-
aDepartment
of Internal Medicine, University of South Florida College of Medicine/James A. Haley Veterans Hospital / H. Lee Moffitt Cancer Center and Research Institute, Tampa, FL. bDepartment of Haematology, Leyenburg Hospital, The Hague, The Netherlands. Address correspondence to Hussain I. Saba, MD, PhD, Department of Internal Medicine, University of South Florida College of Medicine/James A. Haley Veterans Hospital / H. Lee Moffitt Cancer Center and Research Institute, Hematology/Oncology #111R, 13000 Bruce B. Downs Blvd, Tampa, FL 33612. E-mail: [email protected]
0037-1963/05/$-see front matter © 2005 Elsevier Inc. All rights reserved. doi:10.1053/j.seminhematol.2005.05.009
portive care, generally aimed at alleviating symptoms related to anemia, thrombocytopenia, or neutropenia, with no impact on disease progression or survival expected. The only curative treatment at this time is allogeneic stem cell transplantation with dose-intensive chemotherapy conditioning regimens, which is too toxic for the majority of elderly patients diagnosed with MDS. Low-dose chemotherapy may be used to treat intermediate-risk patients, but response rates are low and relapse rates are high.7,19,32 A review on low-dose cytarabine concluded that this was not an effective therapeutic approach,9 a conclusion supported by the fact that no survival improvement was observed in a phase III study.32 Based on these various treatment options, the current 5-year overall survival rate for MDS patients ranges from less than 10% to 60%.10 Therefore, identification of other pharmacologic interventions is warranted.
Classification and Prognostic Factors of MDS The classification of MDS is based on criteria from the French-American-British (FAB) group. These criteria became the framework for comparing all MDS studies. The FAB classification recognizes five distinct subgroups of MDS based on cell morphology and the percentage of blasts6 (Table 1). According to this classification, patients with less than 30% blasts in the bone marrow and peripheral blood along with evidence of ineffective hematopoiesis are considered to have MDS. On the other hand, when the blast percentage exceeds S23
H.I. Saba and P.W. Wijermans
S24 Table 1 MDS Classification: Comparison of FAB and WHO Classifications FAB Subtype6 RA RARS
RAEB CMML RAEB-T
WHO Subtypes17 RA RARS*, refractory cytopenias with multilineage dysplasia†, 5qⴚ syndrome RAEB MDS unclassifiable CMML <13,000 leukocytes/L AML
Blasts in Bone Marrow Peripheral Blood Blasts (%) (%) <5 <5 <5 <5 5–20 <1–20 <1–20 21–30
Monocytes Ringed >1,000/L in Sideroblasts Peripheral Blood >15% — — — — — — ⴙ ⴙ/ⴚ
<1 <1 <1 <1 <5 <5 <1–20
— ⴙ ⴙ/ⴚ ⴙ/ⴚ ⴙ/ⴚ ⴙ/ⴚ ⴙ/ⴚ ⴙ/ⴚ
Abbreviations: AML, acute myeloid leukemia; CMML, chronic myelomonocytic leukemia; RA, refractory anemia; RAEB, refractory anemia with excess of blasts; RAEB-T, refractory anemia with excess of blasts in transformation; RARS, refractory anemia with ringed sideroblasts; ⴙ, positive; ⴚ, negative; ⴙ/ⴚ, equivocal. *Only erythroid lineage. ††At least two lineages involved. Data from Verbeek et al.54
In order to develop a better prognostic system, the cytogenetic, morphologic, and clinical data from 816 patients with MDS were used to develop the IPSS (Table 2).15 This study determined that the most important prognostic variables were the percentage of blasts in the bone marrow and the number of cytopenias present. In this prognostic scoring system the upper limit of blast cell count used as a risk parameter is 30%. This information is used in order to determine the “IPSS score” for each patient. The IPSS scoring system subdivides MDS into four different risk groups for predicting survival and risk of transformation to AML (Table 2). This system appears to be the most practical and validated MDS classification system.
30%, patients are considered to have progressed to AML. The World Health Organization (WHO) recently modified this classification system to provide increased prognostic discrimination.18 This classification system was validated in a larger German patient cohort by Germing et al.13 The major changes in this classification included: (1) lowering the blast threshold for defining AML from 30% to 20%; (2) eliminating the categories of refractory anemia with excess blasts in transformation (RAEB-t) and chronic myelomonocytic leukemia (CMML); (3) subdividing refractory anemia with excess blasts (RAEB) into two categories based on the number of blasts in the bone marrow; (4) splitting refractory anemia (RA) into pure refractory anemia (PRA) and refractory cytopenia with multilineage dysplasia (RCMD); and (5) placing refractory anemia with ringed sideroblasts (RARS) in the pure sideroblastic anemia group with the exception of those with dysplastic features. Pure sideroblastic anemia with dysplastic features was placed into the RCMD category along with refractory anemias without ringed sideroblasts.28 The advantages and disadvantages of the WHO classification are still a matter of much debate.
Overview of MDS Pathophysiology The pathophysiology of MDS is multifactorial, leading to abnormal bone marrow morphology (myelodysplasia) and hypercellular bone marrow with decreased numbers of circu-
Table 2 International Prognostic Scoring System Score
Calculation of Prognostic Score
0
0.5
1.0
1.5
2.0
Bone marrow blasts % Cytogenetics* Cytopenias†
<5 Good 0/1
5–10 Intermediate 2/3
11–20 Poor
21–30
>30
Estimation of Prognosis Overall Score
IPSS Subgroup
Median Survival (yr)
0 0.5–1.0 1.5–2.0 >2.5
Low Intermediate-1 Intermediate-2 High
5.7 3.5 1.2 0.4
*Good risk [ⴚY, del(5q), NI]; intermediate risk (8ⴙ, other); poor risk (chromosome 7 abnormal, >3 abnormal). †Cytopenias: absolute neutrophil count <1.5, hemoglobin <10.0 g/dL, platelets <100,000. Data from Greenberg et al.15
Decitabine in myelodysplastic syndromes lating blood cells (ineffective hematopoiesis). The etiology of this ineffective hematopoiesis is probably primary, or secondary as a result of chemotherapy, radiation, or exposure to environmental toxins. Ineffective hematopoiesis has been attributed to an abnormal bone marrow microenvironment that results in premature apoptotic death of blood cell precursors. Apoptosis in bone marrow cells of patients with MDS has been established.2,26,40,47 Patients with high apoptotic activity in the bone marrow have been associated with poor response to therapy.2 In addition, clonal cytogenetic abnormalities can be present in up to 30% to 70% of patients, although a specific associated chromosomal abnormality has not yet been identified.16 The type (eg, chromosome 7 abnormalities) and number of chromosomal abnormalities may correlate with the risk of progression to AML.21,44 Some of the most frequent chromosomal abnormalities include: loss of chromosomes 5, 7, and 20; gain of chromosome 8; del(5q); monosomy 7; trisomy 8; del(20q); and loss of Y chromosome. Mutations in oncogenes such as Ras, p53, PDGF, and CSF-1 receptor, may also contribute to the development of MDS.1 In addition, there may also be an immune-mediated mechanism for this bone marrow failure as there is an association between autoimmune diseases and MDS.33 The expression and functional significance of VEGF in MDS has also been considered.5 Dysregulation of cytokines like tumor necrosis factor-␣ in the bone marrow has been linked to ineffective hematopoiesis. Finally, the role of DNA hypermethylation has also been identified in MDS. DNA hypermethylation is thought to contribute to the development and progression of cancer by inactivation of gene expression. The increased understanding of the pathophysiology of MDS has led to the development of new therapeutic interventions, including epigenetic therapies.
Genes Hypermethylated in MDS Aberrant DNA hypermethylation is thought to be involved in MDS. The silencing of numerous tumor-suppressor genes has been linked to the development of a growth advantage of malignant cells. Some of the most frequently evaluated genes are the cyclin-dependent kinase inhibitors, p15, p16, p21, and p57. Hypermethylation of the calcitonin gene has also been found in 65% of patients with MDS.12 The p15INK4B and P16INK4A genes encode the cyclin-dependent kinases 4 and 6 and control the progression of the cell cycle from G1 to the S phase.46 Inactivation of these genes has been detected in many cancers, leading to inappropriate cell cycle progression.24,37 DNA hypermethylation of CpG islands of the p15 promoter region has been reported in MDS and is associated with loss of p15 expression.11,39,52 There has also been a close association between the percentage of bone marrow blasts and p15 hypermethylation.11,39,52 Prognosis of MDS patients has been linked to p15INK4B. Patients with hypermethylation at the time of diagnosis were found to have significantly shorter survival than those patients with normal methylation.50 The investigators also assessed p15 methylation patterns in “low-risk” disease (RA and RARS) without excess blasts versus those seen in “high-risk” MDS (RAEB, RAEB-T,
S25 and CMML). p15 methylation was not detectable throughout the course of low-risk disease; however, in high-risk MDS, the incidence ranged from 23% at diagnosis to 30% at advanced states. In AML that previously evolved from MDS, p15 hypermethylation is as high as 60% to 75%.50 This suggests that p15 hypermethylation is a marker of leukemic transformation in MDS.
Rationale for Epigenetic Therapy Based on our knowledge that DNA hypermethylation occurs in bone marrow cells of patients with MDS, it would appear that pharmacologic reversal of this process may influence the course of the disease. DNA methyltransferase 1 (DNMT1) is considered to be an excellent target for intervention with pharmacologic agents, since it acts to induce DNA methylation and contains two domains that can recruit histone deacetylase 1 and 2.41 The use of demethylating agents, 5-azacytidine (Vidaza, Pharmion Corp, Boulder, CO) and 5-aza-2=-deoxycytidine (decitabine, Dacogen™, MGI Pharma, Inc, Bloomington, MN) can restore the normal demethylated state of several tumor suppressor genes, including p16, p15, E-cadherin, hMLH1, and VHL in vitro and in vivo.11,14,20,35,36,59 At low doses, these agents deplete the cell of DNA methylating activity, which subsequently results in hypomethylation after several rounds of DNA replication. Decitabine, at concentrations necessary for inhibiting DNA methylation, is 30 times more active than azacytidine.3 Following the first course of decitabine therapy in 21 high-risk MDS patients, reversal of p15INK4B hypermethylation with generation of partially demethylated p15 alleles and induction of p15 protein has been reported.11 This decrease in hypermethylation was correlated to clinical response. At this early time point, persistence of the abnormal karyotype was found, which is indicative of demethylation in clonal MDS cells. With continued treatment, however, there was emergence of fully demethylated p15 alleles and reversion to normal karyotype, indicating suppression of clonal MDS cells.11 Responses were also seen in patients lacking p15 hypermethylation, which suggests that there are mechanisms other than demethylation of this gene that are responsible for clinical responses. Issa et al22 did not find any correlation between clinical response and p16INK4b methylation status in patients given low doses of decitabine. It may be that demethylation of other genes is more critical for induction of a response or that technical limitations of methylation testing may provide explanations for the lack of effect. A recent report based on data obtained by microarray studies also indicates that there may be benefit of decitabine in MDS outside of its effects on methylation.45 Decitabine appears to preferentially alter gene expression in malignant myeloid cells; however, only 50% of the induced genes contained CpG islands in the 5= region and hypermethylation was only detectable in a small number of the inducible genes.45 In addition, in vivo results with decitabine illustrate an early and sometimes massive increase in platelet counts.53 Hypotheses for the observed increases in platelet counts include outgrowth of normal megakaryocytes, differentiation of the megakaryocytes that belong to the
H.I. Saba and P.W. Wijermans
S26 Table 3 Response Rates of Azacytidine in MDS Response Treatment
CR
PR
Overall
Aza C (n ⴝ 89) Observation before crossover* (n ⴝ 83)
5.6% 0%
10.1% 0%
15.7% 0%
Table 3 describes the clinical response of azacitidine based on information in the package insert. It was expected that clinical trials of decitabine in MDS patients would produce similar results.
Early Phase I/II Trials
Abbreviations: Aza C, azacitidine; CR, complete response; PR, partial response. *Patients in the observation group who crossed over to received azacitidine (47 patients) had a response rate of 12.8%. Data from azacitidine (Vidaza) Package insert. Boulder, CO: Pharmion Corporation, August 31, 2004.
pathologic clone, and stimulation of platelet production from the (ab)normal megakaryocytes or combinations of these possible explanations.53 In comparison, following treatment with azacytidine, MDS CD34⫹ cells only poorly differentiate into the megakaryocytic lineage.49 The mechanism of decitabine’s therapeutic effect is undergoing extensive current investigation. A report from December 2004 suggests that, in vitro, decitabine could significantly downregulate the expression of the gene DNMT3A, which encodes a de novo methyltransferase at the mRNA level in a dose-dependent manner.51 Interestingly, they reported that it had no effects on the DNMT3B gene or the DNMT1 gene, which encodes maintenance methyltransferase.51
Review of Clinical Experience of Decitabine in MDS Decitabine entered clinical trials over 20 years ago, before the unique pharmacology of this agent was completely understood. Since that time, our increased understanding of DNA methylation and the complexity of its pharmacology has allowed us to be able to capitalize on the potential benefits in patients with hematologic malignancies. Some of the most exciting data with demethylating agents is in the treatment of high-risk MDS patients. The interest for these patients was further strengthened by positive results of a phase III trial of a related compound, 5-azacitidine.48 This study compared azacitidine to supportive care and found that azacitidine treatment resulted in greater overall response, improved quality of life and reduced risk of leukemic transformation.48
Decitabine appears to display dual, dose-related, mechanisms. At high concentrations cytotoxicity has been reported and at low concentrations demethylation has been observed.3,8,23,27,34,38,49,58 Phase I and II trials established that decitabine has activity in patients with MDS.55-57,60 The first study, reported in 1993, included 10 patients affected by advanced MDS (two RAEB, eight RAEB-T) who were treated with a daily decitabine dose of 45 mg/m2 divided into three 4-hour infusions for 3 days (n ⫽ 6) or 50 mg/m2 given as a continuous infusion for 3 days (n ⫽ 4).60 More than 50% of patients enrolled showed increases in circulating neutrophils, platelets, and hemoglobin, accompanied by improvement in the bone marrow myeloid cells relative differentiation index and myeloid-to-erythroid cell ratio compared to pretreatment values. Complete hematologic response was reported in 40% of patients. A slow reduction of early leukemic progenitors was also observed. Most of the data on decitabine in MDS come from the Netherlands/Belgium/Germany based research group, who reported their first results in 199757 and a second phase II study in 200056 (Table 4). The response criteria used were defined by Cheson et al.9 Complete response (CR) criteria in these studies included recovery of hemoglobin greater than 11 g/dL, granulocytes greater than 1.0 ⫻ 109/L, platelets greater than 100 ⫻ 109/L, and blast percentage in bone marrow less than 5%. Partial response (PR) was defined by more than a 50% decrease in the number of bone marrow myeloblasts, and a trilineage response or at least an increase in hemoglobin by more than 2 g/dL, platelet count greater than 50 ⫻ 109/L, and a granulocyte count greater than 1.0 ⫻ 109/L. An improvement was defined as a decrease of at least 50% in the transfusion requirement together with improvement in one or two peripheral cell lineage counts by not significant enough increases to qualify for a PR. Stable disease was defined by the absence of CR, PR, or improvement but without disease progression. Progression was defined as a deterioration of blood counts leading to increased transfu-
Table 4 All Available Data of the Phase II Studies on Low-Dose Decitabine in MDS Patients Study No. N CR PR HI SD PD Toxic death Not evaluable
88-0160
91-0157
95-1155
97-06unpublished
97-19unpublished
Total (%)
10 4 1 1 3 1 — —
29 8 5 2 3 4 5 2
66 14 5 9 13 16 4 5
7 1 — 1 4 — 1 —
75 20 8 13 16 12 2 4
187 47 (25) 19 (10) 26 (14) 39 (16) 33 (18) 12 (6) 11 (6)
Abbreviations: CR, complete response; PR, partial response; HI, hematologic improvement; SD, stable disease; PD, progressive disease.
Decitabine in myelodysplastic syndromes
S27
Table 5 Low-Dose Decitabine Phase II Response Data IPSS Risk Groups
Overall Response n (%)56
IPSS Risk Groups
Major Cytogenetic Response n (%)30
Low risk Intermediate-1 Intermediate-2 High
— 4/16 (25%) 12/25 (48%) 16/25 (64%)
Low (NI, 5qⴚ, 20qⴚ, -Y) Intermediate (ⴙ8, other abnormality) — High (chromosome 7 abnormality, >3 abnormalities)
3/5 (60%) 6/30 (20%) — 10/26 (38%)
sion requirement or an increase in the number of myelobasts by more than 10%.55,57 A low-dose 72-hour continuous infusion schedule (120 – 225 mg/m2 total dose) was first evaluated in 29 elderly patients with high-risk MDS.57 The overall response rate was 52%, including eight patients with CR. The median survival from the start of therapy was 46 weeks. The majority of complications were related to myelosuppression. The same group also confirmed these results later in a multicenter trial in 66 patients.55 Patients received decitabine 45 mg/m2/d for 3 days every 6 weeks. Patients who achieved CR after two courses received two further courses as consolidation therapy. For others, a maximum of six cycles was administered. The overall response rate was 42% with a 64% response rate in patients classified as IPSS high-risk (Table 5). The median response duration was 31 weeks (95% confidence interval, 22.6 to 37.4 weeks) with a median survival time of 14 months in the high-risk patients. A significant effect on megakaryopoiesis was reported, with increases in platelet count occurring after one cycle of decitabine in the majority of patients. The most significant toxicity was myelosuppression with a 7% treatment-related mortality. Based on the results of these studies, decitabine has been found to be an effective therapeutic option for MDS patients, especially for those MDS patients with the worst prognosis. In 2002, this research group also presented an update of this study in elderly (median age, 70 years) MDS patients.56 This evaluation included 162 patients with IPSS score intermediate-1 (n ⫽ 45), intermediate-2 (n ⫽ 47), and high-risk (n ⫽ 70). The overall response rate was similar to that previously reported (49%). The response rate based on IPSS groups was as follows: intermediate-1, 44%; intermediate-2, 51%; and highrisk, 51%. Age was not found to be a determinant of response rate or survival. Like in the previous report, 63% of the patients who received at least two cycles of decitabine showed a significant increase in platelets. This platelet response was a strong predictor for overall survival.53 Median survival in this study was 15 months with a 2-year survival of 34%. Survival
was inferior in patients with a blast count greater than 20% and high-risk cytogenetic abnormalities (median survival, 11 months). Decitabine has been shown to result in hematologic and cytogenetic response in patients with MDS, but the mechanism of correction of neutropenia is not clearly understood. Patients who were enrolled in two of the European decitabine studies (in press) were evaluated to determine the ratio of clonal and nonclonal peripheral blood granulocytes.29 The conclusion was that restoration of nonclonal hematopoiesis may be the predominant effect in both early and late stages of decitabine treatment. This indicated that the effect of decitabine was not due to decreased apoptosis and/or differentiation of the malignant clone with the outgrowth of abnormal neutrophils.
Cytogenetic Responses It was previously shown that, clinically, decitabine ameliorates cytopenias, including an induction of trilineage responses in approximately 50% of patients. Lubbert et al30 sought: (1) to evaluate the ability of low-dose decitabine to suppress the abnormal cytogenetic clone in patients with high-risk MDS and chromosomal abnormalities; (2) to determine whether the type of cytogenetic abnormality had an effect on the cytogenetic response; and (3) to determine whether patients achieving major cytogenetic responses had better survival than those in whom the cytogenetic abnormality persisted despite treatment.30 A total of 124 patients from the three Netherlands/Belgium/Germany clinical trials were evaluated, and 115 were successfully karyotyped prior to treatment with follow up data available. An abnormal clone was defined by the presence of at least two cells with the same structural rearrangement or extra chromosome or at least three cells with the same missing chromosome. Cytogenetic responses were defined as follows: PR involved 1% to 35% abnormal metaphases; minor response was defined as the presence of 36% to 95% abnormal metaphases; and no re-
Table 6 Cytogenetic Response to Low-Dose Decitabine in MDS Patients Cytogenetic Classification Low risk Intermediate risk High risk Significance Data from Wijermans et al.56
N 91 40 38
Response Rate 54% 43% 47% P ⴝ .464
N 49 16 18
Response Duration, wk (range) 39 (35–43) 36 (18–54) 32 (22–42) P ⴝ .917
H.I. Saba and P.W. Wijermans
S28
Figure 1 Kaplan-Meier curve for time to AML progression or death in all patients42 (n ⫽ 170) showed early and clinically meaningful separation, consistent with clinical benefit in favor of decitabine in all MDS patients.
sponse, the presence of 96% to 100% abnormal metaphases. CRs and PRs were scored as major response. Of the 115 patients evaluated, 65 had abnormal metaphases and, in 61, the chromosomal abnormalities were clonal. Major cytogenetic responses were observed in 19 patients (31% of those with abnormal cytogenetics, 17% of all patients) after a median of three courses. The median duration of cytogenetic responses was 7.5 months. The analysis of response by IPSS cytogenetic risk groups of all 169 patients of whom cytogenetic data were available prior to therapy is described in Table 6. The relative risk of death in patients achieving a major cytogenetic response was 0.38 (95% confidence interval, 0.17– 0.88) compared to patients where the abnormal clone persisted. This study revealed that repeated doses of decitabine induces cytogenetic remissions in MDS patients with pre-existing chromosomal abnormalities.30
Low-Dose Phase I Trial A phase I, low-dose, prolonged exposure study was conducted in order to determine the optimal dose and duration of decitabine.22 Of the 60 patients enrolled, seven (14%) had MDS. Patient cohorts received decitabine at 5, 10, 15, or 20 mg/m2 intravenously over 1 hour daily, 5 days per week for 2 consecutive weeks. In addition, there were two groups that received 15 mg/m2 daily for 15 or 20 days. The overall response rate for all patients in the study was 32%; four of seven MDS patients had a response (two of seven CRs, two of seven PRs). Responses were observed at all dosing levels; however, it was determined that 15 mg/m2 for 10 days induced the most responses.22
Phase III Trials Two phase III trials have been done in MDS patients comparing decitabine with the current standard of care (growth factors, antibiotics, and/or transfusions). The results of the
North American trial were first reported in December 2004.43 This study randomized 170 patients (89 to decitabine [15 mg/m2 over 3 hours every 8 hours for 3 days every 6 weeks for up to 10 cycles] plus supportive care and 81 to supportive care alone). According to the IPSS scoring system criteria, 69% had intermediate-2 or high-risk MDS. Twenty-one percent of the patients had received prior therapy, and 14% had secondary MDS. Patients treated with decitabine had an overall (CR ⫹ PR) higher response rate (17% v 0%, P ⬍.001) based on International Working Group MDS criteria (Table 7). Responses were seen in patients of all IPSS risk groups. Kaplan-Meier curves for time to AML progression and death showed clinical benefit, especially for high-risk patients and the combined high-risk ⫹ intermediate-2 patients who received decitabine (Figs 1 through 3). The probability of progression to AML or death was 1.72 times greater in those patients who received supportive care. Red blood cell transfusion dependence was reduced from about 70% pretreatment to 35% after six cycles of decitabine, while patients in
Table 7 Phase III Study Results of Low-Dose Decitabine Versus Supportive Care in High-Risk MDS Patients42
N Responses (CR ⴙ PR) CR PR HI Response duration, d (range) Time to response, d (range)
Decitabine
Supportive Care
89 17% 9% 8% 13% 266 (131–346)
81 0% 0% 0% 7% —
89 (55–153)
—
Abbreviations: CR, complete response; PR, partial response; HI, hematologic improvement.
Decitabine in myelodysplastic syndromes
S29
Figure 2 Kaplan-Meier curve for time to AML progression or death in high-risk patients42 (n ⫽ 44) showed early and clinically meaningful separation, consistent with clinical benefit in favor of decitabine in all MDS patients.
the supportive care group did not show a reduction in transfusion requirements. All responders were transfusion-independent during the time of their response. They also had a longer median survival time than nonresponders (17.5 months v 9.8 months). As expected, grade 3 to 4 toxicity (febrile neutropenia and hematologic toxicity) occurred more frequently in the decitabine patients.42 The results of this study are the basis for the New Drug Application submission to the US Food and Drug Administration, currently under review. An ongoing European study is expected to enroll 220 elderly patients with MDS and compare low-dose decitabine to standard supportive care (www.clinicaltrials. gov).
Re-treatment in Previously Responsive Patients Even though there is a considerable body of evidence for the beneficial effects of decitabine in MDS, the optimal treatment duration and the utility in patients who have relapsed following an initial treatment response are still unknown. Luebbert et al31 evaluated 22 MDS patients who received decitabine initially and at relapse. Using the IPSS system, 23% were intermediate-1, 18% intermediate-2, and 59% were high risk. Patients had initially received six decitabine courses, which resulted in CR in 55%, PR in 27%, and HI in 18%. Re-treatment was initiated after the last course of the initial treatment for a median of 11 months
Figure 3 Kaplan-Meier curve for time to AML progression or death in high- plus intermediate-risk patients42 (n ⫽ 118) showed early and clinically meaningful separation, consistent with clinical benefit in favor of decitabine in all MDS patients.
H.I. Saba and P.W. Wijermans
S30 (range, 3 to 7). A median of three courses (range, one to six) was received during re-treatment with an overall response rate of 45% (one CR, two PR, and seven HI). The median time from second response to another relapse was 4 months (range, 1 to 16). Interestingly, more than half of the patients did not show a response to decitabine upon re-treatment. The investigators concluded that decitabine responsive patients may derive more benefit from a longer initial treatment exposure than from retreatment.31 Future studies will address extending initial decitabine treatment beyond six courses.
Study of Alternative Dosing Route and Schedule Kantarjian et al25 conducted a three-arm randomized study in higher-risk MDS in order to evaluate both a longer exposure course and subcutaneous route of administration. All patients received the same dose per course (100 mg/m2/course) but were randomized to decitabine: (1) 20 mg/m2 intravenously over 1 hour daily for 5 days; (2) 10 mg/m2 subcutaneously twice daily for 5 days; or (3) 10 mg/m2 intravenously over 1 hour daily for 10 days. The courses were delivered every 4 weeks regardless of the blood counts as long as there was persistent disease and no significant toxicities (myelosupression-associated complications). Delays to allow for recovery of counts were permitted every three courses. Evaluation of response occurred only after patients received at least three courses. Response criteria for CR and PR were as for AML (PR requiring also a decrease in blasts by ⬎50%). Clinical benefit referred to one of the following: (1) platelet increase by 50% and above 30 ⫻ 109/L; (2) granulocytes increase by 100% and to above 109/L; (3) hemoglobin increase by 2 g/dL or transfusion independence; (4) splenomegaly decrease by 50% or more; or (5) monocytes decrease by 50% or more. Preliminary results of 63 patients were presented in May 2005. Using the IPSS system, 30% had intermediate-1 disease, 35% had intermediate-2, 18% were high risk, and 17% had CMML. Cytogenetic abnormalities were present in 55% and secondary MDS was diagnosed in 22%. The overall response rate was 81% (CR 37%, PR 8%, clinical benefit ⫾ marrow CR 36%) following a median of one course (range, one to three). Half of the patients required two or more courses to achieve CR. The CR rates for each drug administration schedule were: 5 days intravenous (47%); 5 days subcutaneous (28%); and 10 days intravenous (24%).25 The 5-day intravenous schedule was shown to be superior to the other two. The final results of this study should help to define optimal dosing schedules.
Summary Decitabine is a promising new therapy for the treatment of MDS. It appears to be especially well tolerated in those MDS patients who are elderly, many of whom cannot tolerate the currently available treatment options. The availability of DNA methylation inhibitors could represent significant treatment advancement. Early interest was sparked when phase II studies reported a 50% response rate in advanced MDS independent of age, risk scores, and poor-prognosis cytogenetics. Similarly, the recent results of the North American phase III
trial have confirmed the significant clinical benefit of this agent in MDS patients. The Italian Society of Hematology has listed decitabine along with 5-azacytidine in their consensus practice guidelines for high-risk MDS patients who are not candidates for stem cell transplantation or AML-like therapy and are younger than 75 years of age. This represents the first treatment guideline to include demethylating agents. Currently, there are no head-to-head trials comparing these two cytidine analogs. A trial comparing the safety and efficacy of these agents may be warranted. Since DNA methylation and histone deacetylation act synergistically for silencing genes in cancer, the combination of demethylating agents with histone deacetylase inhibitors may be a logical next step for clinical evaluation of reactivating silenced genes.
References 1. Aguayo A, Kantarjian H, Manshouri T, et al: Angiogenesis in acute and chronic leukemias and myelodysplastic syndromes. Blood 96:22402245, 2000 2. Albitar M, Manshouri T, Shen Y, et al: Myelodysplastic syndrome is not merely “preleukemia”. Blood 100:791-798, 2002 3. Attadia V: Effects of 5-aza-2=-deoxycytidine on differentiation and oncogene expression in the human monoblastic leukemia cell line U-937. Leukemia 7:9-16, 1993 (suppl 1) 4. Aul C, Germing U, Gattermann N, et al: Increasing incidence of myelodysplastic syndromes: Real or fictitious? Leuk Res 22:93-100, 1998 5. Bellamy WT, Richter L, Sirjani D, et al: Vascular endothelial cell growth factor is an autocrine promoter of abnormal localized immature myeloid precursors and leukemia progenitor formation in myelodysplastic syndromes. Blood 97:1427-1434, 2001 6. Bennett JM, Catovsky D, Daniel MT, et al: Proposals for the classification of the myelodysplastic syndromes. Br J Haematol 51:189-199, 1982 7. Beran M, Estey E, O’Brien SM, et al: Results of topotecan single-agent therapy in patients with myelodysplastic syndromes and chronic myelomonocytic leukemia. Leuk Lymphoma 31:521-531, 1998 8. Bouchard J: Mechanism of action of 5-AZA-dC: induced DNA hypomethylation does not lead to aberrant gene expression in human leukemic CEM cells. Leuk Res 13:715-722, 1989 9. Cheson BD: Standard and low-dose chemotherapy for the treatment of myelodysplastic syndromes. Leuk Res 22:S17-21, 1998 (suppl 1) 10. Dansey R: Myelodysplasia. Curr Opin Oncol 12:13-21, 2000 11. Daskalakis M, Nguyen TT, Nguyen C, et al: Demethylation of a hypermethylated P15/INK4B gene in patients with myelodysplastic syndrome by 5-aza-2=-deoxycytidine (decitabine) treatment. Blood 100: 2957-2964, 2002 12. Dhodapkar M, Grill J, Lust JA: Abnormal regional hypermethylation of the calcitonin gene in myelodysplastic syndromes. Leuk Res 19:719726, 1995 13. Germing U, Gattermann N, Strupp C, et al: Validation of the WHO proposals for a new classification of primary myelodysplastic syndromes: A retrospective analysis of 1600 patients. Leuk Res 24:983992, 2000 14. Gonzalez-Zulueta M, Bender CM, Yang AS, et al: Methylation of the 5= CpG island of the p16/CDKN2 tumor suppressor gene in normal and transformed human tissues correlates with gene silencing. Cancer Res 55:4531-4535, 1995 15. Greenberg P, Cox C, LeBeau MM, et al: International scoring system for evaluating prognosis in myelodysplastic syndromes. Blood 89:20792088, 1997 16. Haase D, Fonatsch C, Freund M, et al: Cytogenetic findings in 179 patients with myelodysplastic syndromes. Ann Hematol 70:171-187, 1995 17. Harris NL, Jaffe ES, Diebold J, et al: The World Health Organization classification of neoplastic diseases of the hematopoietic and lymphoid
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p15(INK4b) gene in myelodysplastic syndromes is frequent and acquired during disease progression. Blood 91:2985-2990, 1998 Raza A, Gezer S, Mundle S, et al: Apoptosis in bone marrow biopsy samples involving stromal and hematopoietic cells in 50 patients with myelodysplastic syndromes. Blood 86:268-276, 1995 Rountree MR, Bachman KE, Baylin SB: DNMT1 binds HDAC2 and a new co-repressor, DMAP1, to form a complex at replication foci. Nat Genet 25:269-277, 2000 Saba H, Rosenfeld C, Issa JP, et al: First report of the Phase III North American trial of decitabine in advanced myelodysplastic syndrome (MDS). Blood 103:67, 2004 (abstr) Saba HI: Myelodysplastic syndromes in the elderly: the role of growth factors in management. Leuk Res 20:203-219, 1996 Saba HI: Myelodysplastic syndromes in the elderly. Cancer Control 8:79-102, 2001 Schmelz K, Sattler N, Wagner M, et al: Induction of gene expression by 5-aza-2=-deoxycytidine in acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS) but not epithelial cells by DNA-methylation-dependent and -independent mechanisms. Leukemia 19:103111, 2005 Serrano M, Hannon GJ, Beach D: A new regulatory motif in cell-cycle control causing specific inhibition of cyclin D/CDK4. Nature 366:704707, 1993 Shetty V, Hussaini S, Broady-Robinson L, et al: Intramedullary apoptosis of hematopoietic cells in myelodysplastic syndrome patients can be massive: Apoptotic cells recovered from high-density fraction of bone marrow aspirates. Blood 96:1388-1392, 2000 Silverman LR, Demakos EP, Peterson BL, et al: Randomized controlled trial of azacitidine in patients with the myelodysplastic syndrome: A study of the Cancer and Leukemia Group B. J Clin Oncol 20:24292440, 2002 Teofili L, Martini M, Di Mario A, et al: Expression of p15(ink4b) gene during megakaryocytic differentiation of normal and myelodysplastic hematopoietic progenitors. Blood 98:495-497, 2001 Tien HF, Tang JH, Tsay W, et al: Methylation of the p15(INK4B) gene in myelodysplastic syndrome: It can be detected early at diagnosis or during disease progression and is highly associated with leukaemic transformation. Br J Haematol 112:148-154, 2001 Tong H, Lin M, Jin J: Effect of 5-aza-2=-deoxycytidine in high-risk myelodysplasia cells in vitro. Blood 103:4707, 2004 (abstr) Uchida T, Kinoshita T, Nagai H, et al: Hypermethylation of the p15INK4B gene in myelodysplastic syndromes. Blood 90:1403-1409, 1997 van den Bosch J, Lubbert M, Verhoef G, et al: The effects of 5-aza-2=deoxycytidine (decitabine) on the platelet count in patients with intermediate and high-risk myelodysplastic syndromes. Leuk Res 28:785790, 2004 Verbeek W, Ganser A: Evolving treatment options of myelodysplastic syndromes. Ann Hematol 80:499-509, 2001 Wijermans P, Lubbert M, Verhoef G, et al: Low-dose 5-aza-2=-deoxycytidine, a DNA hypomethylating agent, for the treatment of high-risk myelodysplastic syndrome: A multicenter phase II study in elderly patients. J Clin Oncol 18:956-962, 2000 Wijermans P, Verhoef G, Luebbert M: Decitabine in elderly patients with high risk MDS: An update. Blood 100:355, 2002 (abstr) Wijermans PW, Krulder JW, Huijgens PC, et al: Continuous infusion of low-dose 5-aza-2=-deoxycytidine in elderly patients with high-risk myelodysplastic syndrome. Leukemia 11:1-5, 1997 Wilson VL, Jones PA, Momparler RL: Inhibition of DNA methylation in L1210 leukemic cells by 5-aza-2=-deoxycytidine as a possible mechanism of chemotherapeutic action. Cancer Res 43:3493-3496, 1983 Yoshiura K, Kanai Y, Ochiai A, et al: Silencing of the E-cadherin invasion-suppressor gene by CpG methylation in human carcinomas. Proc Natl Acad Sci U S A 92:7416-7419, 1995 Zagonel V, Lo Re G, Marotta G, et al: 5-Aza-2=-deoxycytidine (decitabine) induces trilineage response in unfavourable myelodysplastic syndromes. Leukemia 7:30-35, 1993 (suppl 1)
M
yelodysplastic syndromes (MDS) are a heterogenous spectrum of hematopoietic stem cell disorders affecting older adults, with a median age of 60 to 80 years at the time of diagnosis.28,43 The incidence of MDS is estimated to be between 10,000 and 20,000 cases per year in the United States.4 As the population ages, the incidence of MDS may be expected to increase.4 MDS is characterized by ineffective hematopoiesis; thus, cytopenias with dysplastic morphology of peripheral blood cells and bone marrow are hallmarks in most MDS cases. The clinical course can vary significantly among patients. MDS was originally thought to be synonymous with “preleukemia”; however, many patients die from complications of bone marrow failure (ie, infection, hemorrhage, or iron overload from frequent transfusions) rather than acute leukemia. Nonetheless, 20% of cases will still evolve into acute myeloid leukemia (AML). Clinical management is dependent on the patient’s age, MDS subtype, International Prognostic Scoring System (IPSS) score, and performance status.55 Currently, standard therapy includes sup-
aDepartment
of Internal Medicine, University of South Florida College of Medicine/James A. Haley Veterans Hospital / H. Lee Moffitt Cancer Center and Research Institute, Tampa, FL. bDepartment of Haematology, Leyenburg Hospital, The Hague, The Netherlands. Address correspondence to Hussain I. Saba, MD, PhD, Department of Internal Medicine, University of South Florida College of Medicine/James A. Haley Veterans Hospital / H. Lee Moffitt Cancer Center and Research Institute, Hematology/Oncology #111R, 13000 Bruce B. Downs Blvd, Tampa, FL 33612. E-mail: [email protected]
0037-1963/05/$-see front matter © 2005 Elsevier Inc. All rights reserved. doi:10.1053/j.seminhematol.2005.05.009
portive care, generally aimed at alleviating symptoms related to anemia, thrombocytopenia, or neutropenia, with no impact on disease progression or survival expected. The only curative treatment at this time is allogeneic stem cell transplantation with dose-intensive chemotherapy conditioning regimens, which is too toxic for the majority of elderly patients diagnosed with MDS. Low-dose chemotherapy may be used to treat intermediate-risk patients, but response rates are low and relapse rates are high.7,19,32 A review on low-dose cytarabine concluded that this was not an effective therapeutic approach,9 a conclusion supported by the fact that no survival improvement was observed in a phase III study.32 Based on these various treatment options, the current 5-year overall survival rate for MDS patients ranges from less than 10% to 60%.10 Therefore, identification of other pharmacologic interventions is warranted.
Classification and Prognostic Factors of MDS The classification of MDS is based on criteria from the French-American-British (FAB) group. These criteria became the framework for comparing all MDS studies. The FAB classification recognizes five distinct subgroups of MDS based on cell morphology and the percentage of blasts6 (Table 1). According to this classification, patients with less than 30% blasts in the bone marrow and peripheral blood along with evidence of ineffective hematopoiesis are considered to have MDS. On the other hand, when the blast percentage exceeds S23
H.I. Saba and P.W. Wijermans
S24 Table 1 MDS Classification: Comparison of FAB and WHO Classifications FAB Subtype6 RA RARS
RAEB CMML RAEB-T
WHO Subtypes17 RA RARS*, refractory cytopenias with multilineage dysplasia†, 5qⴚ syndrome RAEB MDS unclassifiable CMML <13,000 leukocytes/L AML
Blasts in Bone Marrow Peripheral Blood Blasts (%) (%) <5 <5 <5 <5 5–20 <1–20 <1–20 21–30
Monocytes Ringed >1,000/L in Sideroblasts Peripheral Blood >15% — — — — — — ⴙ ⴙ/ⴚ
<1 <1 <1 <1 <5 <5 <1–20
— ⴙ ⴙ/ⴚ ⴙ/ⴚ ⴙ/ⴚ ⴙ/ⴚ ⴙ/ⴚ ⴙ/ⴚ
Abbreviations: AML, acute myeloid leukemia; CMML, chronic myelomonocytic leukemia; RA, refractory anemia; RAEB, refractory anemia with excess of blasts; RAEB-T, refractory anemia with excess of blasts in transformation; RARS, refractory anemia with ringed sideroblasts; ⴙ, positive; ⴚ, negative; ⴙ/ⴚ, equivocal. *Only erythroid lineage. ††At least two lineages involved. Data from Verbeek et al.54
In order to develop a better prognostic system, the cytogenetic, morphologic, and clinical data from 816 patients with MDS were used to develop the IPSS (Table 2).15 This study determined that the most important prognostic variables were the percentage of blasts in the bone marrow and the number of cytopenias present. In this prognostic scoring system the upper limit of blast cell count used as a risk parameter is 30%. This information is used in order to determine the “IPSS score” for each patient. The IPSS scoring system subdivides MDS into four different risk groups for predicting survival and risk of transformation to AML (Table 2). This system appears to be the most practical and validated MDS classification system.
30%, patients are considered to have progressed to AML. The World Health Organization (WHO) recently modified this classification system to provide increased prognostic discrimination.18 This classification system was validated in a larger German patient cohort by Germing et al.13 The major changes in this classification included: (1) lowering the blast threshold for defining AML from 30% to 20%; (2) eliminating the categories of refractory anemia with excess blasts in transformation (RAEB-t) and chronic myelomonocytic leukemia (CMML); (3) subdividing refractory anemia with excess blasts (RAEB) into two categories based on the number of blasts in the bone marrow; (4) splitting refractory anemia (RA) into pure refractory anemia (PRA) and refractory cytopenia with multilineage dysplasia (RCMD); and (5) placing refractory anemia with ringed sideroblasts (RARS) in the pure sideroblastic anemia group with the exception of those with dysplastic features. Pure sideroblastic anemia with dysplastic features was placed into the RCMD category along with refractory anemias without ringed sideroblasts.28 The advantages and disadvantages of the WHO classification are still a matter of much debate.
Overview of MDS Pathophysiology The pathophysiology of MDS is multifactorial, leading to abnormal bone marrow morphology (myelodysplasia) and hypercellular bone marrow with decreased numbers of circu-
Table 2 International Prognostic Scoring System Score
Calculation of Prognostic Score
0
0.5
1.0
1.5
2.0
Bone marrow blasts % Cytogenetics* Cytopenias†
<5 Good 0/1
5–10 Intermediate 2/3
11–20 Poor
21–30
>30
Estimation of Prognosis Overall Score
IPSS Subgroup
Median Survival (yr)
0 0.5–1.0 1.5–2.0 >2.5
Low Intermediate-1 Intermediate-2 High
5.7 3.5 1.2 0.4
*Good risk [ⴚY, del(5q), NI]; intermediate risk (8ⴙ, other); poor risk (chromosome 7 abnormal, >3 abnormal). †Cytopenias: absolute neutrophil count <1.5, hemoglobin <10.0 g/dL, platelets <100,000. Data from Greenberg et al.15
Decitabine in myelodysplastic syndromes lating blood cells (ineffective hematopoiesis). The etiology of this ineffective hematopoiesis is probably primary, or secondary as a result of chemotherapy, radiation, or exposure to environmental toxins. Ineffective hematopoiesis has been attributed to an abnormal bone marrow microenvironment that results in premature apoptotic death of blood cell precursors. Apoptosis in bone marrow cells of patients with MDS has been established.2,26,40,47 Patients with high apoptotic activity in the bone marrow have been associated with poor response to therapy.2 In addition, clonal cytogenetic abnormalities can be present in up to 30% to 70% of patients, although a specific associated chromosomal abnormality has not yet been identified.16 The type (eg, chromosome 7 abnormalities) and number of chromosomal abnormalities may correlate with the risk of progression to AML.21,44 Some of the most frequent chromosomal abnormalities include: loss of chromosomes 5, 7, and 20; gain of chromosome 8; del(5q); monosomy 7; trisomy 8; del(20q); and loss of Y chromosome. Mutations in oncogenes such as Ras, p53, PDGF, and CSF-1 receptor, may also contribute to the development of MDS.1 In addition, there may also be an immune-mediated mechanism for this bone marrow failure as there is an association between autoimmune diseases and MDS.33 The expression and functional significance of VEGF in MDS has also been considered.5 Dysregulation of cytokines like tumor necrosis factor-␣ in the bone marrow has been linked to ineffective hematopoiesis. Finally, the role of DNA hypermethylation has also been identified in MDS. DNA hypermethylation is thought to contribute to the development and progression of cancer by inactivation of gene expression. The increased understanding of the pathophysiology of MDS has led to the development of new therapeutic interventions, including epigenetic therapies.
Genes Hypermethylated in MDS Aberrant DNA hypermethylation is thought to be involved in MDS. The silencing of numerous tumor-suppressor genes has been linked to the development of a growth advantage of malignant cells. Some of the most frequently evaluated genes are the cyclin-dependent kinase inhibitors, p15, p16, p21, and p57. Hypermethylation of the calcitonin gene has also been found in 65% of patients with MDS.12 The p15INK4B and P16INK4A genes encode the cyclin-dependent kinases 4 and 6 and control the progression of the cell cycle from G1 to the S phase.46 Inactivation of these genes has been detected in many cancers, leading to inappropriate cell cycle progression.24,37 DNA hypermethylation of CpG islands of the p15 promoter region has been reported in MDS and is associated with loss of p15 expression.11,39,52 There has also been a close association between the percentage of bone marrow blasts and p15 hypermethylation.11,39,52 Prognosis of MDS patients has been linked to p15INK4B. Patients with hypermethylation at the time of diagnosis were found to have significantly shorter survival than those patients with normal methylation.50 The investigators also assessed p15 methylation patterns in “low-risk” disease (RA and RARS) without excess blasts versus those seen in “high-risk” MDS (RAEB, RAEB-T,
S25 and CMML). p15 methylation was not detectable throughout the course of low-risk disease; however, in high-risk MDS, the incidence ranged from 23% at diagnosis to 30% at advanced states. In AML that previously evolved from MDS, p15 hypermethylation is as high as 60% to 75%.50 This suggests that p15 hypermethylation is a marker of leukemic transformation in MDS.
Rationale for Epigenetic Therapy Based on our knowledge that DNA hypermethylation occurs in bone marrow cells of patients with MDS, it would appear that pharmacologic reversal of this process may influence the course of the disease. DNA methyltransferase 1 (DNMT1) is considered to be an excellent target for intervention with pharmacologic agents, since it acts to induce DNA methylation and contains two domains that can recruit histone deacetylase 1 and 2.41 The use of demethylating agents, 5-azacytidine (Vidaza, Pharmion Corp, Boulder, CO) and 5-aza-2=-deoxycytidine (decitabine, Dacogen™, MGI Pharma, Inc, Bloomington, MN) can restore the normal demethylated state of several tumor suppressor genes, including p16, p15, E-cadherin, hMLH1, and VHL in vitro and in vivo.11,14,20,35,36,59 At low doses, these agents deplete the cell of DNA methylating activity, which subsequently results in hypomethylation after several rounds of DNA replication. Decitabine, at concentrations necessary for inhibiting DNA methylation, is 30 times more active than azacytidine.3 Following the first course of decitabine therapy in 21 high-risk MDS patients, reversal of p15INK4B hypermethylation with generation of partially demethylated p15 alleles and induction of p15 protein has been reported.11 This decrease in hypermethylation was correlated to clinical response. At this early time point, persistence of the abnormal karyotype was found, which is indicative of demethylation in clonal MDS cells. With continued treatment, however, there was emergence of fully demethylated p15 alleles and reversion to normal karyotype, indicating suppression of clonal MDS cells.11 Responses were also seen in patients lacking p15 hypermethylation, which suggests that there are mechanisms other than demethylation of this gene that are responsible for clinical responses. Issa et al22 did not find any correlation between clinical response and p16INK4b methylation status in patients given low doses of decitabine. It may be that demethylation of other genes is more critical for induction of a response or that technical limitations of methylation testing may provide explanations for the lack of effect. A recent report based on data obtained by microarray studies also indicates that there may be benefit of decitabine in MDS outside of its effects on methylation.45 Decitabine appears to preferentially alter gene expression in malignant myeloid cells; however, only 50% of the induced genes contained CpG islands in the 5= region and hypermethylation was only detectable in a small number of the inducible genes.45 In addition, in vivo results with decitabine illustrate an early and sometimes massive increase in platelet counts.53 Hypotheses for the observed increases in platelet counts include outgrowth of normal megakaryocytes, differentiation of the megakaryocytes that belong to the
H.I. Saba and P.W. Wijermans
S26 Table 3 Response Rates of Azacytidine in MDS Response Treatment
CR
PR
Overall
Aza C (n ⴝ 89) Observation before crossover* (n ⴝ 83)
5.6% 0%
10.1% 0%
15.7% 0%
Table 3 describes the clinical response of azacitidine based on information in the package insert. It was expected that clinical trials of decitabine in MDS patients would produce similar results.
Early Phase I/II Trials
Abbreviations: Aza C, azacitidine; CR, complete response; PR, partial response. *Patients in the observation group who crossed over to received azacitidine (47 patients) had a response rate of 12.8%. Data from azacitidine (Vidaza) Package insert. Boulder, CO: Pharmion Corporation, August 31, 2004.
pathologic clone, and stimulation of platelet production from the (ab)normal megakaryocytes or combinations of these possible explanations.53 In comparison, following treatment with azacytidine, MDS CD34⫹ cells only poorly differentiate into the megakaryocytic lineage.49 The mechanism of decitabine’s therapeutic effect is undergoing extensive current investigation. A report from December 2004 suggests that, in vitro, decitabine could significantly downregulate the expression of the gene DNMT3A, which encodes a de novo methyltransferase at the mRNA level in a dose-dependent manner.51 Interestingly, they reported that it had no effects on the DNMT3B gene or the DNMT1 gene, which encodes maintenance methyltransferase.51
Review of Clinical Experience of Decitabine in MDS Decitabine entered clinical trials over 20 years ago, before the unique pharmacology of this agent was completely understood. Since that time, our increased understanding of DNA methylation and the complexity of its pharmacology has allowed us to be able to capitalize on the potential benefits in patients with hematologic malignancies. Some of the most exciting data with demethylating agents is in the treatment of high-risk MDS patients. The interest for these patients was further strengthened by positive results of a phase III trial of a related compound, 5-azacitidine.48 This study compared azacitidine to supportive care and found that azacitidine treatment resulted in greater overall response, improved quality of life and reduced risk of leukemic transformation.48
Decitabine appears to display dual, dose-related, mechanisms. At high concentrations cytotoxicity has been reported and at low concentrations demethylation has been observed.3,8,23,27,34,38,49,58 Phase I and II trials established that decitabine has activity in patients with MDS.55-57,60 The first study, reported in 1993, included 10 patients affected by advanced MDS (two RAEB, eight RAEB-T) who were treated with a daily decitabine dose of 45 mg/m2 divided into three 4-hour infusions for 3 days (n ⫽ 6) or 50 mg/m2 given as a continuous infusion for 3 days (n ⫽ 4).60 More than 50% of patients enrolled showed increases in circulating neutrophils, platelets, and hemoglobin, accompanied by improvement in the bone marrow myeloid cells relative differentiation index and myeloid-to-erythroid cell ratio compared to pretreatment values. Complete hematologic response was reported in 40% of patients. A slow reduction of early leukemic progenitors was also observed. Most of the data on decitabine in MDS come from the Netherlands/Belgium/Germany based research group, who reported their first results in 199757 and a second phase II study in 200056 (Table 4). The response criteria used were defined by Cheson et al.9 Complete response (CR) criteria in these studies included recovery of hemoglobin greater than 11 g/dL, granulocytes greater than 1.0 ⫻ 109/L, platelets greater than 100 ⫻ 109/L, and blast percentage in bone marrow less than 5%. Partial response (PR) was defined by more than a 50% decrease in the number of bone marrow myeloblasts, and a trilineage response or at least an increase in hemoglobin by more than 2 g/dL, platelet count greater than 50 ⫻ 109/L, and a granulocyte count greater than 1.0 ⫻ 109/L. An improvement was defined as a decrease of at least 50% in the transfusion requirement together with improvement in one or two peripheral cell lineage counts by not significant enough increases to qualify for a PR. Stable disease was defined by the absence of CR, PR, or improvement but without disease progression. Progression was defined as a deterioration of blood counts leading to increased transfu-
Table 4 All Available Data of the Phase II Studies on Low-Dose Decitabine in MDS Patients Study No. N CR PR HI SD PD Toxic death Not evaluable
88-0160
91-0157
95-1155
97-06unpublished
97-19unpublished
Total (%)
10 4 1 1 3 1 — —
29 8 5 2 3 4 5 2
66 14 5 9 13 16 4 5
7 1 — 1 4 — 1 —
75 20 8 13 16 12 2 4
187 47 (25) 19 (10) 26 (14) 39 (16) 33 (18) 12 (6) 11 (6)
Abbreviations: CR, complete response; PR, partial response; HI, hematologic improvement; SD, stable disease; PD, progressive disease.
Decitabine in myelodysplastic syndromes
S27
Table 5 Low-Dose Decitabine Phase II Response Data IPSS Risk Groups
Overall Response n (%)56
IPSS Risk Groups
Major Cytogenetic Response n (%)30
Low risk Intermediate-1 Intermediate-2 High
— 4/16 (25%) 12/25 (48%) 16/25 (64%)
Low (NI, 5qⴚ, 20qⴚ, -Y) Intermediate (ⴙ8, other abnormality) — High (chromosome 7 abnormality, >3 abnormalities)
3/5 (60%) 6/30 (20%) — 10/26 (38%)
sion requirement or an increase in the number of myelobasts by more than 10%.55,57 A low-dose 72-hour continuous infusion schedule (120 – 225 mg/m2 total dose) was first evaluated in 29 elderly patients with high-risk MDS.57 The overall response rate was 52%, including eight patients with CR. The median survival from the start of therapy was 46 weeks. The majority of complications were related to myelosuppression. The same group also confirmed these results later in a multicenter trial in 66 patients.55 Patients received decitabine 45 mg/m2/d for 3 days every 6 weeks. Patients who achieved CR after two courses received two further courses as consolidation therapy. For others, a maximum of six cycles was administered. The overall response rate was 42% with a 64% response rate in patients classified as IPSS high-risk (Table 5). The median response duration was 31 weeks (95% confidence interval, 22.6 to 37.4 weeks) with a median survival time of 14 months in the high-risk patients. A significant effect on megakaryopoiesis was reported, with increases in platelet count occurring after one cycle of decitabine in the majority of patients. The most significant toxicity was myelosuppression with a 7% treatment-related mortality. Based on the results of these studies, decitabine has been found to be an effective therapeutic option for MDS patients, especially for those MDS patients with the worst prognosis. In 2002, this research group also presented an update of this study in elderly (median age, 70 years) MDS patients.56 This evaluation included 162 patients with IPSS score intermediate-1 (n ⫽ 45), intermediate-2 (n ⫽ 47), and high-risk (n ⫽ 70). The overall response rate was similar to that previously reported (49%). The response rate based on IPSS groups was as follows: intermediate-1, 44%; intermediate-2, 51%; and highrisk, 51%. Age was not found to be a determinant of response rate or survival. Like in the previous report, 63% of the patients who received at least two cycles of decitabine showed a significant increase in platelets. This platelet response was a strong predictor for overall survival.53 Median survival in this study was 15 months with a 2-year survival of 34%. Survival
was inferior in patients with a blast count greater than 20% and high-risk cytogenetic abnormalities (median survival, 11 months). Decitabine has been shown to result in hematologic and cytogenetic response in patients with MDS, but the mechanism of correction of neutropenia is not clearly understood. Patients who were enrolled in two of the European decitabine studies (in press) were evaluated to determine the ratio of clonal and nonclonal peripheral blood granulocytes.29 The conclusion was that restoration of nonclonal hematopoiesis may be the predominant effect in both early and late stages of decitabine treatment. This indicated that the effect of decitabine was not due to decreased apoptosis and/or differentiation of the malignant clone with the outgrowth of abnormal neutrophils.
Cytogenetic Responses It was previously shown that, clinically, decitabine ameliorates cytopenias, including an induction of trilineage responses in approximately 50% of patients. Lubbert et al30 sought: (1) to evaluate the ability of low-dose decitabine to suppress the abnormal cytogenetic clone in patients with high-risk MDS and chromosomal abnormalities; (2) to determine whether the type of cytogenetic abnormality had an effect on the cytogenetic response; and (3) to determine whether patients achieving major cytogenetic responses had better survival than those in whom the cytogenetic abnormality persisted despite treatment.30 A total of 124 patients from the three Netherlands/Belgium/Germany clinical trials were evaluated, and 115 were successfully karyotyped prior to treatment with follow up data available. An abnormal clone was defined by the presence of at least two cells with the same structural rearrangement or extra chromosome or at least three cells with the same missing chromosome. Cytogenetic responses were defined as follows: PR involved 1% to 35% abnormal metaphases; minor response was defined as the presence of 36% to 95% abnormal metaphases; and no re-
Table 6 Cytogenetic Response to Low-Dose Decitabine in MDS Patients Cytogenetic Classification Low risk Intermediate risk High risk Significance Data from Wijermans et al.56
N 91 40 38
Response Rate 54% 43% 47% P ⴝ .464
N 49 16 18
Response Duration, wk (range) 39 (35–43) 36 (18–54) 32 (22–42) P ⴝ .917
H.I. Saba and P.W. Wijermans
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Figure 1 Kaplan-Meier curve for time to AML progression or death in all patients42 (n ⫽ 170) showed early and clinically meaningful separation, consistent with clinical benefit in favor of decitabine in all MDS patients.
sponse, the presence of 96% to 100% abnormal metaphases. CRs and PRs were scored as major response. Of the 115 patients evaluated, 65 had abnormal metaphases and, in 61, the chromosomal abnormalities were clonal. Major cytogenetic responses were observed in 19 patients (31% of those with abnormal cytogenetics, 17% of all patients) after a median of three courses. The median duration of cytogenetic responses was 7.5 months. The analysis of response by IPSS cytogenetic risk groups of all 169 patients of whom cytogenetic data were available prior to therapy is described in Table 6. The relative risk of death in patients achieving a major cytogenetic response was 0.38 (95% confidence interval, 0.17– 0.88) compared to patients where the abnormal clone persisted. This study revealed that repeated doses of decitabine induces cytogenetic remissions in MDS patients with pre-existing chromosomal abnormalities.30
Low-Dose Phase I Trial A phase I, low-dose, prolonged exposure study was conducted in order to determine the optimal dose and duration of decitabine.22 Of the 60 patients enrolled, seven (14%) had MDS. Patient cohorts received decitabine at 5, 10, 15, or 20 mg/m2 intravenously over 1 hour daily, 5 days per week for 2 consecutive weeks. In addition, there were two groups that received 15 mg/m2 daily for 15 or 20 days. The overall response rate for all patients in the study was 32%; four of seven MDS patients had a response (two of seven CRs, two of seven PRs). Responses were observed at all dosing levels; however, it was determined that 15 mg/m2 for 10 days induced the most responses.22
Phase III Trials Two phase III trials have been done in MDS patients comparing decitabine with the current standard of care (growth factors, antibiotics, and/or transfusions). The results of the
North American trial were first reported in December 2004.43 This study randomized 170 patients (89 to decitabine [15 mg/m2 over 3 hours every 8 hours for 3 days every 6 weeks for up to 10 cycles] plus supportive care and 81 to supportive care alone). According to the IPSS scoring system criteria, 69% had intermediate-2 or high-risk MDS. Twenty-one percent of the patients had received prior therapy, and 14% had secondary MDS. Patients treated with decitabine had an overall (CR ⫹ PR) higher response rate (17% v 0%, P ⬍.001) based on International Working Group MDS criteria (Table 7). Responses were seen in patients of all IPSS risk groups. Kaplan-Meier curves for time to AML progression and death showed clinical benefit, especially for high-risk patients and the combined high-risk ⫹ intermediate-2 patients who received decitabine (Figs 1 through 3). The probability of progression to AML or death was 1.72 times greater in those patients who received supportive care. Red blood cell transfusion dependence was reduced from about 70% pretreatment to 35% after six cycles of decitabine, while patients in
Table 7 Phase III Study Results of Low-Dose Decitabine Versus Supportive Care in High-Risk MDS Patients42
N Responses (CR ⴙ PR) CR PR HI Response duration, d (range) Time to response, d (range)
Decitabine
Supportive Care
89 17% 9% 8% 13% 266 (131–346)
81 0% 0% 0% 7% —
89 (55–153)
—
Abbreviations: CR, complete response; PR, partial response; HI, hematologic improvement.
Decitabine in myelodysplastic syndromes
S29
Figure 2 Kaplan-Meier curve for time to AML progression or death in high-risk patients42 (n ⫽ 44) showed early and clinically meaningful separation, consistent with clinical benefit in favor of decitabine in all MDS patients.
the supportive care group did not show a reduction in transfusion requirements. All responders were transfusion-independent during the time of their response. They also had a longer median survival time than nonresponders (17.5 months v 9.8 months). As expected, grade 3 to 4 toxicity (febrile neutropenia and hematologic toxicity) occurred more frequently in the decitabine patients.42 The results of this study are the basis for the New Drug Application submission to the US Food and Drug Administration, currently under review. An ongoing European study is expected to enroll 220 elderly patients with MDS and compare low-dose decitabine to standard supportive care (www.clinicaltrials. gov).
Re-treatment in Previously Responsive Patients Even though there is a considerable body of evidence for the beneficial effects of decitabine in MDS, the optimal treatment duration and the utility in patients who have relapsed following an initial treatment response are still unknown. Luebbert et al31 evaluated 22 MDS patients who received decitabine initially and at relapse. Using the IPSS system, 23% were intermediate-1, 18% intermediate-2, and 59% were high risk. Patients had initially received six decitabine courses, which resulted in CR in 55%, PR in 27%, and HI in 18%. Re-treatment was initiated after the last course of the initial treatment for a median of 11 months
Figure 3 Kaplan-Meier curve for time to AML progression or death in high- plus intermediate-risk patients42 (n ⫽ 118) showed early and clinically meaningful separation, consistent with clinical benefit in favor of decitabine in all MDS patients.
H.I. Saba and P.W. Wijermans
S30 (range, 3 to 7). A median of three courses (range, one to six) was received during re-treatment with an overall response rate of 45% (one CR, two PR, and seven HI). The median time from second response to another relapse was 4 months (range, 1 to 16). Interestingly, more than half of the patients did not show a response to decitabine upon re-treatment. The investigators concluded that decitabine responsive patients may derive more benefit from a longer initial treatment exposure than from retreatment.31 Future studies will address extending initial decitabine treatment beyond six courses.
Study of Alternative Dosing Route and Schedule Kantarjian et al25 conducted a three-arm randomized study in higher-risk MDS in order to evaluate both a longer exposure course and subcutaneous route of administration. All patients received the same dose per course (100 mg/m2/course) but were randomized to decitabine: (1) 20 mg/m2 intravenously over 1 hour daily for 5 days; (2) 10 mg/m2 subcutaneously twice daily for 5 days; or (3) 10 mg/m2 intravenously over 1 hour daily for 10 days. The courses were delivered every 4 weeks regardless of the blood counts as long as there was persistent disease and no significant toxicities (myelosupression-associated complications). Delays to allow for recovery of counts were permitted every three courses. Evaluation of response occurred only after patients received at least three courses. Response criteria for CR and PR were as for AML (PR requiring also a decrease in blasts by ⬎50%). Clinical benefit referred to one of the following: (1) platelet increase by 50% and above 30 ⫻ 109/L; (2) granulocytes increase by 100% and to above 109/L; (3) hemoglobin increase by 2 g/dL or transfusion independence; (4) splenomegaly decrease by 50% or more; or (5) monocytes decrease by 50% or more. Preliminary results of 63 patients were presented in May 2005. Using the IPSS system, 30% had intermediate-1 disease, 35% had intermediate-2, 18% were high risk, and 17% had CMML. Cytogenetic abnormalities were present in 55% and secondary MDS was diagnosed in 22%. The overall response rate was 81% (CR 37%, PR 8%, clinical benefit ⫾ marrow CR 36%) following a median of one course (range, one to three). Half of the patients required two or more courses to achieve CR. The CR rates for each drug administration schedule were: 5 days intravenous (47%); 5 days subcutaneous (28%); and 10 days intravenous (24%).25 The 5-day intravenous schedule was shown to be superior to the other two. The final results of this study should help to define optimal dosing schedules.
Summary Decitabine is a promising new therapy for the treatment of MDS. It appears to be especially well tolerated in those MDS patients who are elderly, many of whom cannot tolerate the currently available treatment options. The availability of DNA methylation inhibitors could represent significant treatment advancement. Early interest was sparked when phase II studies reported a 50% response rate in advanced MDS independent of age, risk scores, and poor-prognosis cytogenetics. Similarly, the recent results of the North American phase III
trial have confirmed the significant clinical benefit of this agent in MDS patients. The Italian Society of Hematology has listed decitabine along with 5-azacytidine in their consensus practice guidelines for high-risk MDS patients who are not candidates for stem cell transplantation or AML-like therapy and are younger than 75 years of age. This represents the first treatment guideline to include demethylating agents. Currently, there are no head-to-head trials comparing these two cytidine analogs. A trial comparing the safety and efficacy of these agents may be warranted. Since DNA methylation and histone deacetylation act synergistically for silencing genes in cancer, the combination of demethylating agents with histone deacetylase inhibitors may be a logical next step for clinical evaluation of reactivating silenced genes.
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