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Steven D Gore

Publications and source records attributed to Steven D Gore.

At least 19 recordsLinked to original sources
PubMed2007

Phase 1 and pharmacologic study of MS-275, a histone deacetylase inhibitor, in adults with refractory and relapsed acute leukemias.

MS-275 is a benzamide derivative with potent histone deacetylase (HDAC) inhibitory and antitumor activity in preclinical models. We conducted a phase 1 trial of orally administered MS-275 in 38 adults with advanced acute leukemias. Cohorts of patients were treated with MS-275 initially once weekly x 2, repeated every 4 weeks from 4 to 8 mg/m2, and after 13 patients were treated, once weekly x 4, repeated every 6 weeks from 8 to 10 mg/m2. The maximum-tolerated dose was 8 mg/m2 weekly for 4 weeks every 6 weeks. Dose-limiting toxicities (DLTs) included infections and neurologic toxicity manifesting as unsteady gait and somnolence. Other frequent non-DLTs were fatigue, anorexia, nausea, vomiting, hypoalbuminemia, and hypocalcemia. Treatment with MS-275 induced increase in protein and histone H3/H4 acetylation, p21 expression, and caspase-3 activation in bone marrow mononuclear cells. No responses by classical criteria were seen. Our results show that MS-275 effectively inhibits HDAC in vivo in patients with advanced myeloid leukemias and should be further tested, preferably in patients with less-advanced disease.

Acetylation↗
PubMed2006

Flavopiridol synergizes TRAIL cytotoxicity by downregulation of FLIPL.

PURPOSE: Flavopiridol is known to modulate the transcription of genes. We investigated the effect of flavopiridol pretreatment on TRAIL cytotoxicity and on the expression of FLIP(L) in different TRAIL-resistant cell lines, because FLIP expression is known to confer TRAIL-resistance. METHODS: Apoptosis was assessed by PI staining and protein expression by Western blotting. RT-PCR was used for mRNA quantitation. siRNA gene silencing was used to knock down FLIP(L). RESULTS: Flavopiridol pretreatment synergized TRAIL-induced apoptosis in human myeloma and breast cancer cells. Flavopiridol treatment repressed the transcription of FLIP(L) and downregulated its expression in both myeloma and breast cancer cells. Silencing of FLIP(L) gene by siRNA sensitized myeloma cells to TRAIL. Flavopiridol treatment downregulated the expression of the proapoptotic members of the Bcl-2 family proteins (Bak, Bax and PUMA-alpha). The expression of the antiapoptotic Bcl-2 members (Bcl-2 and Bcl-X(L)) was not altered by flavopiridol treatment in myeloma cells. CONCLUSION: Our data indicate that flavopiridol synergizes TRAIL cytotoxicity by downregulation of FLIP(L) and this synergistic effect is Bcl-2 family independent.

Antineoplastic Agents↗
PubMed2006

Combined DNA methyltransferase and histone deacetylase inhibition in the treatment of myeloid neoplasms.

Optimal reexpression of most genes silenced through promoter methylation requires the sequential application of DNA methyltransferase inhibitors followed by histone deacetylase inhibitors in tumor cell cultures. Patients with myelodysplastic syndrome or acute myeloid leukemia (AML) were treated with the methyltransferase inhibitor 5-azacitidine (aza-CR) followed by the histone deacetylase inhibitor sodium phenylbutyrate. Major responses associated with cytogenetic complete response developed in patients receiving prolonged dosing schedules of aza-CR. Bisulfite sequencing of the p15 promoter in marrow DNA during the first cycle of treatment showed heterogeneous allelic demethylation in three responding patients, suggesting ongoing demethylation within the tumor clone, but no demethylation in two nonresponders. Six of six responding patients with pretreatment methylation of p15 or CDH-1 promoters reversed methylation during the first cycle of therapy (methylation-specific PCR), whereas none of six nonresponders showed any demethylation. Gene demethylation correlated with the area under the aza-CR plasma concentration-time curve. Administration of both drugs was associated with induction of acetylation of histones H3 and H4. This study provides the first demonstration that molecular mechanisms responsible for responses to DNA methyltransferase/histone deacetylase inhibitor combinations may include reversal of aberrant epigenetic gene silencing. The promising percentage of major hematologic responses justifies the testing of such combinations in prospective randomized trials.

Acetylation↗
PubMed2006

Clinical application and proposal for modification of the International Working Group (IWG) response criteria in myelodysplasia.

The myelodysplastic syndromes (MDSs) are heterogeneous with respect to clinical characteristics, pathologic features, and cytogenetic abnormalities. This heterogeneity is a challenge for evaluating response to treatment. Therapeutic trials in MDS have used various criteria to assess results, making cross-study comparisons problematic. In 2000, an International Working Group (IWG) proposed standardized response criteria for evaluating clinically significant responses in MDS. These criteria included measures of alteration in the natural history of disease, hematologic improvement, cytogenetic response, and improvement in health-related quality of life. The relevance of the response criteria has now been validated prospectively in MDS clinical trials, and they have gained acceptance in research studies and in clinical practice. Because limitations of the IWG criteria have surfaced, based on practical and reported experience, some modifications were warranted. In this report, we present recommendations for revisions of some of the initial criteria.

Humans↗
PubMed2006

Decitabine.

Explore the source record for details and available documents.

Antimetabolites, Antineoplastic↗
PubMed2006

Six (or more) drugs in search of a mechanism: DNA methyltransferase and histone deacetylase inhibitors in the treatment of myelodysplastic syndromes.

The clinical activity of the DNA methyltransferase inhibitors 5-azacitidine and 2'-deoxy-5-azacytidine in myelodysplastic syndromes (MDS) suggests that epigenetic modulation of gene transcription may play an important pathogenetic role in the development and expression of these diseases. Approximately 50% of patients treated with these compounds experience hematologic improvement, making these the most active single agents for unselected patients with MDS. Responses include complete and partial hematologic responses. Two randomized trials have shown that the use of these drugs significantly alters the natural history of MDS compared with supportive care. Histone deacetylase inhibitors, which may also impact the expression of genes through epigenetic mechanisms, seem to have measurable activity in MDS in preliminary studies. Histone deacetylase inhibitors are most likely used in combination with other agents, including DNA methyltransferase inhibitors. Despite the clinical activity of these classes of drugs, there is no conclusive evidence that their clinical activity is attributable to their impact on the epigenome. Such information will be critical in the development of more effective congeners and drug combinations in ongoing attempts to improve the outcome of patients with MDS.

Antimetabolites, Antineoplastic↗
PubMed2005

Phase I and pharmacokinetic study of flavopiridol followed by 1-beta-D-arabinofuranosylcytosine and mitoxantrone in relapsed and refractory adult acute leukemias.

PURPOSE: The serine/threonine kinase inhibitor flavopiridol targets multiple cyclin-dependent kinases, induces checkpoint arrest, and interrupts transcriptional elongation. We designed a phase I clinical trial using a timed sequential therapy approach where flavopiridol was given for the dual purpose of initial cytoreduction and enhancing cell cycle progression of the remaining leukemia cell cohort followed by cycle-dependent drugs 1-beta-D-arabinofuranosylcytosine (ara-C) and mitoxantrone. EXPERIMENTAL DESIGN: Flavopiridol was given by 1-hour infusion daily for 3 days beginning day 1 followed by 2 g/m2/72 h ara-C beginning day 6 and 40 mg/m2 mitoxantrone beginning day 9. In vivo correlates included pharmacokinetics, modulation of blast cycle regulators, and serum and marrow supernatant vascular endothelial growth factor levels. RESULTS: Of 34 adults receiving induction therapy, 16 (47%) evinced direct leukemia cytotoxicity with > or =50% drop in peripheral blast counts and tumor lysis in 9 (26%). Four (12%) died during therapy (two fungal infections and two sudden death). Dose-limiting toxicity occurred at 60 mg/m2/d with profound neutropenia >40 days duration, and maximal tolerated dose was 50 mg/m2/d. Overall response rate was 31% in 26 acute myelogenous leukemia and 12.5% in acute lymphoblastic leukemia. Pharmacokinetics showed that a linear two-compartment model with first-order elimination provided the best fit of the observed concentration versus time data. Flavopiridol down-regulated one or more target proteins in marrow blasts in vivo. Vascular endothelial growth factor was detected in sera and marrow supernatant pretreatment, and sera obtained on day 3 inhibited bovine aortic endothelial cell proliferation by a mean of 32% (range, 10-80%). CONCLUSIONS: Our data suggest that flavopiridol is cytotoxic to leukemic cells and, when followed by ara-C and mitoxantrone, exerts biological and clinical effects in patients with relapsed and refractory acute leukemias. These findings warrant continuing development of flavopiridol at 50 mg/m2/d x 3 days in combination with cytotoxic and biological agents for acute leukemias.

Adult↗
PubMed2005

Alkyl-substituted polyaminohydroxamic acids: a novel class of targeted histone deacetylase inhibitors.

The reversible acetylation of histones is critical for regulation of eukaryotic gene expression. The histone deacetylase inhibitors trichostatin (TSA, 1), MS-275 (2) and suberoylanilide hydroxamic acid (SAHA, 3) arrest growth in transformed cells and in human tumor xenografts. However, 1-3 suffer from lack of specificity among the various HDAC isoforms, prompting us to design and synthesize polyaminohydroxamic acid (PAHA) derivatives 6-21. We felt that PAHAs would be selectively directed to chromatin and associated histones by the positively charged polyamine side chain. At 1 microM, compounds 12, 15 and 20 inhibited HDAC by 74.86, 59.99 and 73.85%, respectively. Although 20 was a less potent HDAC inhibitor than 1, it was more potent than 2, more effective as an initiator of histone hyperacetylation, and significantly more effective than 2 at re-expressing p21Waf1 in ML-1 leukemia cells. On the basis of these results, PAHAs 6-21 represent an important new chemical class of HDAC inhibitors.

Acetylation↗
PubMed2005

Pharmacokinetics of 5-azacitidine administered with phenylbutyrate in patients with refractory solid tumors or hematologic malignancies.

PURPOSE: To characterize the pharmacokinetic behavior of 5-azacitidine (5-AC), a cytidine nucleoside analog, when given with phenylbutyrate, a histone deaceytlase inhibitor. PATIENTS AND METHODS: Pharmacokinetic data were obtained from two trials involving patients with solid tumor and hematologic malignancies. 5-AC at doses ranging from 10 to 75 mg/m2/d was administered once daily as a subcutaneous injection for 5 to 21 days in combination with phenylbutyrate administered as a continuous intravenous infusion for varying dose and duration every 28 or 35 days. Serial plasma samples were collected up to 24 hours after 5-AC administration. 5-AC was quantitated using a validated liquid chromatograph/tandem mass spectrometry method. RESULTS: 5-AC was rapidly absorbed with the mean T(max) occurring at 0.47 hour. Average maximum concentration (C(max)) and area under the curve (AUC(0-infinity)) values increased in a dose-proportionate manner with increasing dose from 10 to 75 mg/m2/d; the mean +/- SD C(max) and AUC(0-infinity) at 10 mg/m2/d were 776 +/- 459 nM and 1,355 +/- 1,125 h*nM, respectively, and at 75 mg/m2/d were 4,871 +/- 1,398 nM and 6,582 +/- 2,560 h*nM, respectively. Despite a short terminal half-life of 1.5 +/- 2.3 hours, inhibition of DNA methyl transferase activity in tumors of patients receiving 5-AC has been documented. CONCLUSION: 5-AC is rapidly absorbed and eliminated when administered subcutaneously. Sufficient 5-AC exposure is achieved to produce pharmacodynamic effects in tumors.

Antimetabolites, Antineoplastic↗
PubMed2005

Durable molecular remissions with a single cycle of timed sequential consolidation chemotherapy in acute promyelocytic leukemia.

In a pilot study to reduce the duration of treatment and potential long-term toxicities, 39 patients with acute promyelocytic leukemia in remission received a single cycle of intensive consolidation therapy, followed by intermittent ATRA maintenance. Consolidation therapy required prolonged hospitalization and was associated with a high incidence of mucositis (43% grade II or greater) and documented infection (45%). No deaths occurred during consolidation. Seven patients have relapsed; all other patients are in molecular remission (median follow-up, 2.75 years). Kaplan-Meier estimate of 3 year disease-free survival is 73% (95% confidence interval 55-91%). The relapse rate (0.06 relapses/patient-year of follow-up) is well within the range of larger published series that administer more prolonged consolidation. One patient has developed secondary myelodysplastic syndrome. These pilot data suggest that decreasing the total duration of consolidation chemotherapy did not compromise disease-free survival for APL patients induced with ATRA/anthracycline and given intermittent ATRA maintenance. However, the toxicity of the consolidation module and the development of secondary myelodysplasia despite decreased total therapy emphasize the need to further improve and refine curative therapy for APL.

Adult↗
PubMed2005

Combination therapy with DNA methyltransferase inhibitors in hematologic malignancies.

A variety of epigenetic changes contribute to transcriptional dysregulation in myelodysplastic syndromes (MDSs) and acute myeloid leukemia (AML). DNA methyltransferase (DNMT) inhibitors--azacitidine and decitabine--have significant activity in the treatment of MDS. Despite marked activity in myeloid malignancy, monotherapy with DNMT inhibitors is limited by low complete and partial response rates (7-20%) and median response durations of 15 months. As with classical cytotoxic therapy, the targeting of biologic pathways and mechanisms may best be accomplished using a combination of agents offering complementary mechanisms and synergistic pharmacodynamic interactions. The goal of this approach is to improve response rates, quality, and duration, and to minimize adverse events. There are a number of new therapies under development for the management of MDS and AML. This review article touches on some of the more promising combination regimens in various phases of investigation. The treatment of MDS and AML is undergoing rapid evolution. Cytogenetic complete remission and prolonged survival represent important goals. Incremental improvements in disease state and quality-of-life issues are also important for patients. Given the overall failure of cytotoxic chemotherapy in the achievement of cures in MDS and MDS-related AML, the application of less toxic, biologically directed agents may represent a more promising approach to treatment. Combination therapies with DNMT inhibitors using optimal dosing regimens to focus on methylation reversal with lower doses over longer periods of time, rather than direct cytotoxic effects, are beginning to suggest promising results in MDS and AML.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed2005

Future directions for the use of hypomethylating agents.

Epigenetics refers to heritable changes in DNA and chromatin that impact gene expression without a change in DNA sequence. Two major steps involved in epigenetic regulation of gene expression include methylation of the promoter region of the gene and deacetylation of specific lysine residues on promoter-associated histones leading to changes in chromatin structure. Promoter hypermethylation is the most extensively studied epigenetic process. Our expanding knowledge of this process has led to its application in the diagnosis, prognosis, and treatment of various hematologic and neoplastic diseases. Several agents, which reverse promoter methylation or inhibit histone deacetylases, are under development for use alone or in combination for a variety of neoplastic diseases. This review discusses the potential use of methylation reversing agents in the treatment of solid tumors and in benign hematologic disorders along with the rationale for combination therapies using hypomethylating agents.

DNA Modification Methylases↗
PubMed2005

Clinical translation of epigenetics in cancer: eN-CORe--a report on the second workshop.

Recent advances in understanding the role that epigenetics plays in cancer pathogenesis and understanding the mechanisms through which these processes regulate gene expression have stimulated considerable interest in developing clinically viable antineoplastic agents that target enzymatic components of transcriptional regulatory complexes responsible for the establishment of pathologic epigenetic modifications that lead to deregulated gene expression in cancer. In January 2003, a workshop was held in Baltimore to discuss the therapeutic potential of several agents that can modify chromatin structure. A follow-up meeting on "Clinical Translation of Epigenetics in Cancer" was held in Charleston, SC, in January 2005. The aim of this workshop was to assess the progress that has been made over the past 2 years in bringing effective therapeutic protocols that use agents capable of reverting pathologic epigenetic changes into the clinic. The meeting was attended by approximately 70 investigators and included formal presentations, panel group discussions, and two break-out sessions that addressed targeted therapies in hematologic and solid tumors. The aim of this article is to summarize topics discussed at this workshop and highlight conclusions as to the immediate and long-term future of epigenetic therapy in cancer.

Animals↗
PubMed2005

Emerging drugs for the treatment of myelodysplastic syndrome.

Myelodysplastic syndromes (MDS) are a heterogeneous group of clonal haematopoietic stem cell disorders characterised by ineffective haematopoiesis and an increased risk of developing acute myeloid leukaemia. At present, the only curative option is allogeneic stem cell transplantation. However, the majority of patients are not eligible for this therapy, due to excessive treatment-related morbidity and mortality or lack of a suitable donor. As a result, the need for alternative therapies is great. Our improved understanding of the molecular pathogenesis of MDS has resulted in several new promising therapeutic agents. This review will consider the rational development of new agents based on the molecular biology of MDS.

Clinical Trials as Topic↗
PubMed2004

State of the translational science: summary of Baltimore workshop on gene re-expression as a therapeutic target in cancer January 2003.

A workshop was held in Baltimore, Maryland in January 2003 to discuss translational aspects of cancer therapies targeted at impacting aberrant gene transcription due to epigenetic changes. The mission of the meeting was the development of strategies for scientifically sound, clinically feasible applications targeting epigenetics in cancer therapy. Sessions included preclinical discussions of DNA methylation, the histone code, chromatin remodeling, and transcriptional control. Data on the histone deacetylase and DNA methyltransferase inhibitors under preclinical and clinical investigation were presented and discussed. The optimal correlative laboratory studies for monitoring clinical trials with these agents remain controversial. DNA methyltransferase and histone deacetylase inhibitors will be combined with each other to maximally re-express genes silenced through promoter methylation. Other classes of agents that may be rationally combined with these classes of drugs include retinoids, steroid hormones, and cytotoxic drugs.

Acetylation↗
PubMed2004

Inhibitors of signaling in myelodysplastic syndrome.

Treatment of myelodysplastic syndrome (MDS) has been hampered by the lack of understanding of the molecular and biological abnormalities associated with this disease. Biological abnormalities may lead to typical phenotypic changes in more differentiated cells. Recent developments in the natural history and underlying molecular mechanisms of MDS and acute myeloid leukemia (AML) have identified new molecular therapeutic targets. Several new classes of drugs have shown promise in early clinical trials and may alter the standard of care of these patients. Among these new drugs are farnesyltransferase inhibitors, receptor tyrosine kinase inhibitors, protein kinase C inhibitors, and VEGF inhibitors. These agents have been tested in patients with solid tumors and hematological malignancies such as AML and MDS. Most of the studies in MDS are in early stages of development, where doses are being determined based on the experience in refractory or relapsed AML or solid tumors. Future therapies in MDS will attempt to resolve cytopenias, eliminate malignant clones and allow differentiation by attacking specific mechanisms of the disease.

Alkyl and Aryl Transferases↗
PubMed2004

Oral valacyclovir as prophylaxis against herpes simplex virus reactivation during high dose chemotherapy for leukemia.

Reactivation of herpes simplex virus is a common event in patients undergoing dose-intensive remission induction or consolidation chemotherapy of acute leukemia, for which either intravenous or oral acyclovir provides effective prophylaxis. This drug's short serum half-life and low oral bioavailability make frequent dosing necessary, however, and we therefore sought to determine if the pro-drug valacyclovir, which has improved bioavailability, could be successfully substituted for this indication. Eighty-one patients with leukemia were randomized to receive either 500 mg or 1,000 mg of valacyclovir orally every 8 h and followed clinically, as well as with serial surveillance cultures. Over a total of 1,979 days on study between the groups, and 380 throat cultures, no documented episodes of herpes simplex reactivation were noted. Valacyclovir was tolerated well with no evident drug-related toxicities. We conclude that valacyclovir at either of the two doses studied can be safely substituted for oral or intravenous acyclovir, and that it provides effective prophylaxis against reactivation of herpes simplex virus in this patient population.

Acyclovir↗