Phase IIb multicenter trial of vorinostat in patients with persistent, progressive, or treatment refractory cutaneous T-cell lymphoma

Optimizing chemotherapeutic strategies for peripheral T-cell lymphomas

Peripheral T-cell lymphomas are a heterogenous mix of histology, as well as clinical presentation, and outcome and remain a challenging group of diseases to treat. Because of difficulty and variability in diagnosis, improvements in diagnostic technology, and changing classification systems over time, the interpretation of studies is complicated. In addition, the response to current treatments and long-term outcome is generally poor. This review outlines these problems and discusses the current status of treatment strategies, including the disappointing results with standard anthracycline-based therapy as well as experience with modifications to CHOP (cyclophosphamide/doxorubicin/vincristine/prednisone); increasing dose intensity; antimetabolites; and T-cell-targeted therapies. We conclude with a description of a new agent, pralatrexate, including the preclinical and early clinical experience as well as a description of a large phase II prospective trial. Because of the relative rarity of this group of diseases, large-scale prospective clinical trials are difficult to implement. New treatment strategies are needed if we hope to improve patient outcomes.

Pathobiology of mature T-cell lymphomas

Mature T- and natural killer (NK)-cell neoplasms are relatively rare forms of leukemia/lymphoma. The diagnosis of these entities is often difficult, necessitating extensive immunophenotypic, molecular, and genetic testing. Despite the accumulating information on the pathobiology of these neoplasms, in many cases the prognosis remains poor. This article presents an updated view of the morphologic, immunophenotypic, genetic, and molecular characteristics of the mature T- and NK-cell neoplasms. For a better understanding of this complex topic, the development of normal T and NK cells is briefly discussed. The presentation of the characteristic features of the neoplasms in the 2008 World Health Organization classification of hematopoietic neoplasms includes advances in the understanding of the pathobiology of each diagnostic category.

The DNA repair proteins BRCA1 and ERCC1 as predictive markers in sporadic ovarian cancer

This study compares Breast Cancer 1 (BRCA1) and excision repair cross complementation group 1 (ERCC1) expression as predictive markers and evaluates the in vitro enhancement of platinum sensitivity using targeted agents in sporadic ovarian cancer (OC). A retrospective study was performed of advanced stage OC patients receiving platinum-based chemotherapy. BRCA1 and ERCC1 mRNA expression was determined from frozen tissue of 51 patients. Median overall survival (OS) was longer for patients with lower BRCA1 vs. higher BRCA1 (46 vs.33 months, p = 0.03). High BRCA1 was predictive of poorer OS specifically in patients with residual disease (RD) <2 cm (p = 0.03). There was a non-significant association for patients with lower ERCC1 and RD <2 cm in favor of improved OS and time to progression. Patients who expressed higher levels of both BRCA1 and ERCC1 mRNA had a shorter OS compared to patients with lower levels of either or both transcript (33 vs.46 months, p = 0.04). When Cox proportional modeling was used by representing BRCA1 and ERCC1 mRNA expression as a continuous variable, both emerge as potential predictors of survival. OC cell lines were exposed to chemotherapy in combination with DNA repair pathway inhibitors and cell viability was assessed. In vitro histone deacetylase (HDAC) inhibition increased the sensitivity of A2780s/cp cells to cisplatin and carboplatin but not to taxol, coincident with a significant decrease in BRCA1 and ERCC1 expression, suggesting that this compound directly targets DNA repair. In summary, this study shows that low BRCA1 and ERCC1 expression correlate with improved survival in advanced OC and HDAC inhibition induces synergistic cytotoxicity with platinum in vitro.

Prognostic significance of the therapeutic targets histone deacetylase 1, 2, 6 and acetylated histone H4 in cutaneous T-cell lymphoma

AIMS

Aberrant histone acetylation has been associated with malignancy and histone deacetylase (HDAC) inhibitors are currently being investigated in numerous clinical trials. So far, the malignancy most sensitive to HDAC inhibitors has been cutaneous T-cell lymphoma (CTCL). The reason for this sensitivity is unclear and studies on HDAC expression and histone acetylation in CTCL are lacking. The aim of this study was to address this issue.

METHODS AND RESULTS

The immunohistochemical expression of HDAC1, HDAC2, HDAC6, and acetylated H4 was examined in 73 CTCLs and the results related to histological subtypes and overall survival. HDAC1 was most abundantly expressed (P < 0.0001), followed by HDAC2; HDAC6 and H4 acetylation were equally expressed. HDAC2 (P = 0.001) and H4 acetylation (P = 0.03) were significantly more common in aggressive than indolent CTCL subtypes. In contrast, no differences were observed for HDAC1 and HDAC6. In a Cox analysis, elevated HDAC6 was the only parameter showing significant influence on survival (P = 0.04).

CONCLUSIONS

High expression of HDAC2 and acetylated H4 is more common in aggressive than indolent CTCL. HDAC6 expression is associated with a favorable outcome independent of the subtype.

Epigenetic therapy of leukemia: An update

Carcinogenesis is classically thought to result from genetic alterations in DNA sequence such as deletions, mutations, or chromosomal translocations. These in turn may lead to the activation of oncogenes, inactivation of tumor suppressor genes or formation of chimeric oncoproteins. Epigenetics, in contrast, refers to a number of biochemical modifications of chromatin, either to DNA directly or to its associated protein complexes that affect gene expression without altering the primary sequence of DNA [Robertson KD, Wolffe AP. DNA methylation in health and disease. Nat Rev Genet 2000;1:11-9; Jones PA, Baylin SB. The epigenomics of cancer. Cell. 2007;128:683-92]. A fundamental difference between genetic and epigenetic alterations is the irreversible nature of genetic lesions whereas epigenetic ones are potentially reversible, allowing for therapeutic intervention. In the last decade, it has become apparent that epigenetic changes play an important role in cancer, particularly in leukemia. Significant advances have been made in the elucidation of these processes as well as in translating this knowledge to the clinic, as in the development of new prognostic biomarkers or targeted therapies. In this review, we will focus on recent advances in epigenetic therapy in leukemia.

Lack of therapeutic effect of the histone deacetylase inhibitor vorinostat in patients with metastatic radioiodine-refractory thyroid carcinoma

CONTEXT

Aberrant histone deacetylase activity is seen in a variety of malignancies, and histone deacetylase inhibitors such as vorinostat have been shown to induce cell death and sensitize cells to cytotoxic chemotherapy in thyroid cancer cell lines. This phase II study was undertaken to assess objective response to vorinostat in patients with advanced thyroid cancer.

EXPERIMENTAL DESIGN

A total of 19 patients with differentiated thyroid cancer (n = 16) and medullary thyroid cancer (n = 3) were enrolled in the study. Patients received oral vorinostat at a starting dose of 200 mg twice daily, with dose adjustments allowed as necessary for toxicity. Patients were treated for 2 wk, followed by 1 wk off therapy (3-wk cycle) until disease progression or study withdrawal. Responses were measured by Response Evaluation Criteria in Solid Tumors criteria and correlated with tumor markers.

RESULTS

No patient achieved a partial or complete response. Median duration of therapy in patients with differentiated thyroid cancer was 17 wk, whereas in medullary thyroid cancer patients it was 25 wk. Reasons for termination included progression of disease by RECIST criteria (n = 7), clinical progression (n = 3), and adverse events (AEs) (n = 9). AEs were primarily grade 1-3; no clinical grade 4 or grade 5 events were observed. Clinical grade 3 AEs consisted of fatigue, dehydration, ataxia, pneumonia, bruises, and deep vein thrombosis. Severe thrombocytopenia was seen in seven patients (grade 3, n = 5; grade 4, n = 2) and was associated with minor bleeding or bruises.

CONCLUSIONS

Vorinostat at this dose and schedule is not an effective treatment for advanced thyroid cancer.

[Skin cancer: what's new in clinical research?]

Every year skin cancer is the subject of many publications. In this review of the recent literature, we selected epidemiological, clinical, and therapeutic data published between October 2006 and September 2007. Some of the studies presented in conferences in 2007 are also mentioned. New epidemiological data have been provided regarding the incidence of different types of skin cancers, the effect of certain risk factors or drug or food protective factors, the overall improvement of survival in melanoma, the epidemiological, clinical, and/or therapeutic particularities of rapidely growing melanomas and thick melanomas, and the relations between sun exposure, skin cancers, and other solid tumors. New prognostic studies in melanoma have improved the evaluation of prognosis in specific situations such as thin melanoma, acrolentiginous melanoma, and melanoma with positive sentinel lymph nodes (depending on the type of positivity) or negative sentinel lymph nodes. Important results on adjuvant interferon in melanoma have been presented. Clinical trials evaluating new therapeutic approaches in stage III and IV melanoma are going on. Several studies confirmed the clinical benefit of adjuvant irradiation on the tumor site in Merkel cell carcinoma. New treatments are being studied or have been approved in refractory forms of cutaneous T-cell lymphoma and in inoperable forms of squamous cell carcinoma and dermatofibrosarcoma protuberans.

Cotreatment with BCL-2 antagonist sensitizes cutaneous T-cell lymphoma to lethal action of HDAC7-Nur77-based mechanism

Pan-histone deacetylase inhibitors, for example, vorinostat and panobinostat (LBH589; Novartis Pharmaceuticals, East Hanover, NJ), have shown clinical efficacy against advanced cutaneous T-cell lymphoma (CTCL). However, the molecular basis of this activity remains unclear. HDAC7, a class IIA histone deacetylase (HDAC), is overexpressed in thymocytes, where it represses expression of the proapoptotic nuclear orphan receptor Nur77. Here, we demonstrate that treatment with panobinostat rapidly inhibits the in vitro and intracellular activity, as well as the mRNA and protein levels of HDAC7, and induces expression and translocation of Nur77 to the mitochondria. There, Nur77 converts death resistance protein Bcl-2 into a killer protein, promoting cell death of cultured and patient-derived human CTCL cells. Treatment with panobinostat improved survival of athymic nude mice implanted with human CTCL cells. Ectopic expression of Nur77 induced apoptosis and sensitized HH cells to panobinostat, whereas combined knockdown of Nur77 and its family member Nor1 was necessary to inhibit panobinostat-induced apoptosis of CTCL cells. Cotreatment with the Bcl-2/Bcl-x(L) antagonist ABT-737 decreased resistance and synergistically induced apoptosis of human CTCL cells. These findings mechanistically implicate HDAC7 and Nur77 in sensitizing human CTCL cells to panobinostat as well as suggest that cotreatment with an anti-Bcl-2 agent would augment the anti-CTCL activity of panobinostat.

Chromatin, cancer and drug therapies

The structure and organization of chromatin have attracted a great deal of attention recently because of their implications for the field of epigenetics. DNA methylation and the post-translational modifications that occur on histones can specify transcriptional competency. During cancer development, tumor suppressor genes become silenced by DNA hypermethylation and chromatin modifiers no longer perform in their usual manner. Current epigenetic therapy has been able to take advantage of the reversibility of these epimutations. Progress has been made in the treatment of hematological malignancies and some solid tumors. As the knowledge of how chromatin regulates gene expression is enhanced, improvements in the treatment of cancer can be made.

Histone deacetylase inhibitors in cancer therapy

PURPOSE OF REVIEW

The purpose of this review is to provide an overview of recent advances in the development of histone deacetylase inhibitors (HDACi) for the treatment of cancer.

RECENT FINDINGS

Recently, there has been a dramatic expansion of HDACi clinical investigation. There are now 11 HDACi in clinical trial, including inhibitors with a broad spectrum of HDAC isoform inhibitory activity as well as drugs with isoform selectivity. Over 70 combination therapy trials are in progress. Major areas of progress covered include the entry of new HDAC inhibitors into clinical development, recent progress in understanding of molecular mechanisms of HDACi anticancer activity, and a preclinical and clinical update on HDACi in combination.

SUMMARY

In the period under review there have been advances in understanding of HDACi mechanisms of action, identification of rational combinations that address increased efficacy and overcoming resistance, and greatly expanded clinical development of pan-HDAC-inhibitory and isoform-selective inhibitors in monotherapy and combination therapy protocols.

Chemical targeting of the innate antiviral response by histone deacetylase inhibitors renders refractory cancers sensitive to viral oncolysis

Intratumoral innate immunity can play a significant role in blocking the effective therapeutic spread of a number of oncolytic viruses (OVs). Histone deacetylase inhibitors (HDIs) are known to influence epigenetic modifications of chromatin and can blunt the cellular antiviral response. We reasoned that pretreatment of tumors with HDIs could enhance the replication and spread of OVs within malignancies. Here, we show that HDIs markedly enhance the spread of vesicular stomatitis virus (VSV) in a variety of cancer cells in vitro, in primary tumor tissue explants and in multiple animal models. This increased oncolytic activity correlated with a dampening of cellular IFN responses and augmentation of virus-induced apoptosis. These results illustrate the general utility of HDIs as chemical switches to regulate cellular innate antiviral responses and to provide controlled growth of therapeutic viruses within malignancies. HDIs could have a profoundly positive impact on the clinical implementation of OV therapeutics.

Promising antitumor activity with MGCD0103, a novel isotype-selective histone deacetylase inhibitor

BACKGROUND

Histone deacetylases (HDACs), which target histones as well as non-histone proteins as substrates, have the potential to regulate aberrant gene expression and restore normal growth control in malignancies.

OBJECTIVE

This review provides an updated summary of preclinical and clinical experience with the oral isotype-selective HDAC inhibitor MGCD0103 in cancer.

METHODS

Data presented in abstract form from international conferences or journal articles found within a PubMed search of article up to May 2008 are described in this review.

RESULTS/CONCLUSIONS

MGCD0103 appears tolerable and exhibits favorable pharmacokinetic and pharmacodynamic profiles with evidence of target inhibition in surrogate tissues. Clinical and pharmacodynamic data support a three-times-weekly administration at a 90-mg fixed dose. MGCD0103 displays promising antitumor activity in hematological and lymphoproliferative diseases.

Prognostic significance of the therapeutic targets histone deacetylase 1, 2, 6 and acetylated histone H4 in cutaneous T-cell lymphoma

AIMS

Aberrant histone acetylation has been associated with malignancy and histone deacetylase (HDAC) inhibitors are currently being investigated in numerous clinical trials. So far, the malignancy most sensitive to HDAC inhibitors has been cutaneous T-cell lymphoma (CTCL). The reason for this sensitivity is unclear and studies on HDAC expression and histone acetylation in CTCL are lacking. The aim of this study was to address this issue.

METHODS AND RESULTS

The immunohistochemical expression of HDAC1, HDAC2, HDAC6, and acetylated H4 was examined in 73 CTCLs and the results related to histological subtypes and overall survival. HDAC1 was most abundantly expressed (P < 0.0001), followed by HDAC2; HDAC6 and H4 acetylation were equally expressed. HDAC2 (P = 0.001) and H4 acetylation (P = 0.03) were significantly more common in aggressive than indolent CTCL subtypes. In contrast, no differences were observed for HDAC1 and HDAC6. In a Cox analysis, elevated HDAC6 was the only parameter showing significant influence on survival (P = 0.04).

CONCLUSIONS

High expression of HDAC2 and acetylated H4 is more common in aggressive than indolent CTCL. HDAC6 expression is associated with a favorable outcome independent of the subtype.

Emerging drugs in cutaneous T cell lymphoma

BACKGROUND

Mycosis fungoides (MF) represents the most common type of primary cutaneous T cell-lymphomas (CTCL), which are characterized by a clonally proliferation of malignant CD4+ lymphocytes in the skin.

OBJECTIVE

Skin-directed treatment regimens, like phototherapy and corticosteroids, are commonly used in early stages; systemic treatments and chemotherapies are used in advanced stages. Because conventional treatments usually end in a transient remission without curative results, there is a high need for new therapeutic strategies with acceptable side effects.

METHODS

Literature and reference research was done by using the data bank PubMed, and updates of ongoing studies were taken out of ASCO and ASH annual meeting abstracts.

RESULTS/CONCLUSIONS

This article gives an overview of the various medications in current use, with emphasis on emerging drugs with novel therapeutic targets.

Constitutive activation of signal transducers and activators of transcription predicts vorinostat resistance in cutaneous T-cell lymphoma

Vorinostat is a histone deacetylase inhibitor that induces differentiation, growth arrest, and/or apoptosis of malignant cells both in vitro and in vivo and has shown clinical responses in approximately 30% of patients with advanced mycosis fungoides and Sézary syndrome cutaneous T-cell lymphoma (CTCL). The purpose of this study was to identify biomarkers predictive of vorinostat response in CTCL using preclinical model systems and to assess these biomarkers in clinical samples. The signal transducer and activator of transcription (STAT) signaling pathway was evaluated. The data indicate that persistent activation of STAT1, STAT3, and STAT5 correlate with resistance to vorinostat in lymphoma cell lines. Simultaneous treatment with a pan-Janus-activated kinase inhibitor resulted in synergistic antiproliferative effect and down-regulation of the expression of several antiapoptotic genes. Immunohistochemical analysis of STAT1 and phosphorylated tyrosine STAT3 (pSTAT3) in skin biopsies obtained from CTCL patients enrolled in the vorinostat phase IIb trial showed that nuclear accumulation of STAT1 and high levels of nuclear pSTAT3 in malignant T cells correlate with a lack of clinical response. These results suggest that deregulation of STAT activity plays a role in vorinostat resistance in CTCL, and strategies that block this pathway may improve vorinostat response. Furthermore, these findings may be of prognostic value in predicting the response of CTCL patients to vorinostat.

Avicin D selectively induces apoptosis and downregulates p-STAT-3, bcl-2, and survivin in cutaneous T-cell lymphoma cells

Avicin D, a natural triterpenoid saponin, inhibits cell growth and induces apoptosis in transformed tumor cell lines in vitro and mouse skin carcinogenesis models in vivo. To investigate the anti-tumor effects of avicin D in cutaneous T-cell lymphomas (CTCL), we compared three CTCL cell lines and Sézary cells from three Sézary syndrome (SS) patients with normal CD4+ and activated CD4+ T cells from three healthy donors. Avicin D at 0.5-5 mug ml(-1) induced apoptosis in a time- and dose-dependent manner in three cell lines: MJ (-0.2 to 13% and 0.6-37%), Hut78 (2-39% and 3-53%), and HH (13-83% and 44-89%) at 24 and 48 hours, respectively. Avicin D at 0.5-5 microg ml(-1) for 48 hours caused more apoptosis in patients' Sézary cells than in healthy donors' CD4+ T cells and activated CD4+ T cells. The general caspase inhibitor Z-VAD-FMK and caspase-3 inhibitor Z-DEVD-FMK decreased avicin D-induced apoptosis in CTCL cells. Caspase-3 was activated and poly (ADP-ribose) polymerase was cleaved after avicin D treatment. Avicin D did not change the expression of signal transducer and activator of transcription-3 (STAT-3) but decreased phospho-signal transducer and activator of transcription-3 (p-STAT-3) protein levels in all three cell lines and two patients' Sézary cells. Avicin D also decreased expression of the inhibitor of apoptosis protein survivin, the anti-apoptotic protein bcl-2, but not the pro-apoptotic protein bax in these CTCL cells. In summary, avicin D selectively induced apoptosis, inhibited STAT-3 activation, and decreased apoptosis inhibitors (bcl-2 and survivin) in CTCL cell lines and SS patients' Sézary cells. Our findings underlie the therapeutic potential of avicin D in patients with SS.

Phase I study of MGCD0103 given as a three-times-per-week oral dose in patients with advanced solid tumors

PURPOSE

MGCD0103 is a novel isotype-selective inhibitor of human histone deaceylases (HDACs) with the potential to regulate aberrant gene expression and restore normal growth control in malignancies.

PATIENTS AND METHODS

A phase I trial of MGCD0103, given as a three-times-per-week oral dose for 2 of every 3 weeks, was performed in patients with advanced solid tumors. Primary end points were safety, tolerability, pharmacokinetics (PK), pharmacodynamic (PD) assessments of HDAC activity, and histone acetylation status in peripheral WBCs.

RESULTS

Six dose levels ranging from 12.5 to 56 mg/m(2)/d were evaluated in 38 patients over 99 cycles (median, 2; range, 1 to 11). The recommended phase II dose was 45 mg/m(2)/d. Dose-limiting toxicities consisting of fatigue, nausea, vomiting, anorexia, and dehydration were observed in three (27%) of 11 and two (67%) of three patients treated at the 45 and 56 mg/m(2)/d dose levels, respectively. Disease stabilization for four or more cycles was observed in five (16%) of 32 patients assessable for efficacy. PK analyses demonstrated interpatient variability which was improved by coadministration with low pH beverages. Elimination half-life ranged from 6.7 to 12.2 hours, and no accumulation was observed with repeated dosing. PD evaluations confirmed inhibition of HDAC activity and induction of acetylation of H3 histones in peripheral WBCs from patients by MGCD0103.

CONCLUSION

At doses evaluated, MGCD0103 appears tolerable and exhibits favorable PK and PD profiles with evidence of target inhibition in surrogate tissues.

Early phase II trial of oral vorinostat in relapsed or refractory breast, colorectal, or non-small cell lung cancer

Vorinostat (Zolinza) is a histone deacetylase inhibitor that has demonstrated activity in patients with advanced solid tumors in phase I trials. A multicenter, open-label phase II trial of oral vorinostat 200, 300 or 400 mg bid for 14 days followed by a 7-day rest until disease progression or intolerable toxicity was conducted. Patients with measurable, relapsed or refractory breast or non-small cell lung cancer who had received > or = 1 prior therapy or colorectal cancer who had received > or = 2 prior therapies were eligible. The response rate, safety and tolerability were evaluated. Sixteen patients (median age, 62 years; median 5.5 prior therapies) were enrolled. Six patients received 400 mg bid, six received 300 mg bid and four received 200 mg bid (14 days/3 weeks). Dose-limiting toxicities (DLTs) at the 400 or 300 mg bid levels were anorexia, asthenia, nausea, thrombocytopenia, vomiting, and weight loss. No DLTs were observed at the 200 mg bid level. Disease stabilization was observed in eight patients, but there were no confirmed responses. The median TTP was 33.5 days. Eleven patients discontinued due to clinical adverse experiences (AEs). The most common drug-related AEs were anorexia (81%), fatigue (62%), nausea (62%), diarrhea (56%), vomiting (56%), thrombocytopenia (50%) and weight loss (50%). Drug-related AEs > or = grade 3 included thrombocytopenia (50%), anemia (12%), asthenia (12%) and nausea (12%). Vorinostat in a daily oral schedule for 14 days/3 weeks was tolerable at 200 mg bid only, and no responses were observed in this study. Most patients, however, had limited drug exposure which did not allow a reliable efficacy analysis.

The potential role of histone deacetylase inhibitors in the treatment of non-small-cell lung cancer

Non-small-cell lung cancer (NSCLC) arises from a complex series of genetic and epigenetic changes leading to uncontrolled cell growth and metastases. The exponential growth in the level of research about the histone deacetylase (HDAC) enzymes, responsible for deacetylating core nucleosomal histones and other proteins, has been driven by the ability of HDAC inhibitors to modulate transcriptional activity. As a result, this therapeutic class is able to block angiogenesis and cell cycling, and promote apoptosis and differentiation. The mechanisms resulting in the antiproliferative biologic effects of these agents are not yet known. Clinical experience indicates these agents generally well tolerated, and active in several haematological and solid tumours. HDAC inhibitors, under clinical evaluation in the treatment of NSCLC patients, are pivanex, CI-994, vorinostat, and LBH589. Here, we discuss about the potential role of HDAC inhibitors focusing on their activity, tolerability, efficacy and future development, in the treatment of NSCLC.

Emerging drugs for rarer chronic lymphoid leukemias

BACKGROUND

Rarer indolent lymphoid leukemias include well defined mature B-cell and T-cell neoplasm with widely varying natural history and specific morphological, immunophenotypic and molecular characteristics. Among these are prolymphocytic leukemia (PLL), hairy cell leukemia (HCL) and its variants, large granular lymphocyte leukemia (LGLL) and adult T-cell leukemia/lymphoma (ATLL).

OBJECTIVE

To present current therapies and emerging drugs potentially useful in the treatment of rarer chronic lymphoid leukemias.

METHODS

After searching MEDLINE, PubMed and the Current Contents database, and conference proceedings from the previous 3 years of the American Society of Hematology (ASH), the European Society of Hematology (EHA) and the American Society of Clinical Oncology (ASCO) were searched manually; articles written in English and additional relevant publications were then selected.

RESULTS/CONCLUSION

New drugs including monoclonal antibodies (mAbs), new purine analogs, small molecules targeting specific molecular targets and other agents are included. Future research should focus on the novel therapeutic strategies based on the molecular pathogenic mechanisms and the development of new targeted therapies for each distinct chronic lymphoid leukemia.

Phase II trial of oral vorinostat (suberoylanilide hydroxamic acid) in relapsed diffuse large-B-cell lymphoma

BACKGROUND

Vorinostat has demonstrated activity in refractory cutaneous T-cell lymphoma. In a phase I trial, an encouraging activity in diffuse large-B-cell lymphoma (DLBCL) was noted.

PATIENTS AND METHODS

We carried out a phase II trial (NCT00097929) of oral vorinostat 300 mg b.i.d. (14 days/3 weeks or 3 days/week) in patients with measurable, relapsed DLBCL who had received two or more systemic therapies. Response rate and duration (DOR), time to progression (TTP) and safety were assessed.

RESULTS

Eighteen patients were enrolled (median age: 66 years; median prior therapies: 2). Seven received 300 mg b.i.d. 14 days/3 weeks, but four had grade 3 or 4 toxicity (dose-limiting toxicity, DLT). The schedule was amended to 300 mg b.i.d. 3 days/week), and none had DLT. One achieved a complete response (TtR = 85 days; DOR =or >468 days) and one had stable disease (301 days). Sixteen discontinued for progressive disease; median TTP was 44 days. Median number of cycles was 2 (1 to >19). Common drug-related adverse experiences (AEs; mostly grade 1/2) were diarrhea, fatigue, nausea, anemia and vomiting. Three patients had dose reduction; none discontinued for drug-related AEs. Drug-related AE >or=grade 3 included thrombocytopenia (16.7%) and asthenia (11.1%).

CONCLUSION

Vorinostat was well tolerated at 300 mg b.i.d. 3 days/week or 200 mg b.i.d. 14 days/3 weeks but had limited activity against relapsed DLBCL.

Determination of the class and isoform selectivity of small-molecule histone deacetylase inhibitors

The human HDAC (histone deacetylase) family, a well-validated anticancer target, plays a key role in the control of gene expression through regulation of transcription. While HDACs can be subdivided into three main classes, the class I, class II and class III HDACs (sirtuins), it is presently unclear whether inhibiting multiple HDACs using pan-HDAC inhibitors, or targeting specific isoforms that show aberrant levels in tumours, will prove more effective as an anticancer strategy in the clinic. To address the above issues, we have tested a number of clinically relevant HDACis (HDAC inhibitors) against a panel of rhHDAC (recombinant human HDAC) isoforms. Eight rhHDACs were expressed using a baculoviral system, and a Fluor de Lystrade mark (Biomol International) HDAC assay was optimized for each purified isoform. The potency and selectivity of ten HDACs on class I isoforms (rhHDAC1, rhHDAC2, rhHDAC3 and rhHDAC8) and class II HDAC isoforms (rhHDAC4, rhHDAC6, rhHDAC7 and rhHDAC9) was determined. MS-275 was HDAC1-selective, MGCD0103 was HDAC1- and HDAC2-selective, apicidin was HDAC2- and HDAC3-selective and valproic acid was a specific inhibitor of class I HDACs. The hydroxamic acid-derived compounds (trichostatin A, NVP-LAQ824, panobinostat, ITF2357, vorinostat and belinostat) were potent pan-HDAC inhibitors. The growth-inhibitory effect of the HDACis on HeLa cells showed that both pan-HDAC and class-I-specific inhibitors inhibited cell growth. The results also showed that both pan-HDAC and class-I-specific inhibitor treatment resulted in increased acetylation of histones, but only pan-HDAC inhibitor treatment resulted in increased tubulin acetylation, which is in agreement with their activity towards the HDAC6 isoform.

Novel Therapies and Role of Transplant in the Treatment of Peripheral T-Cell Lymphomas

Peripheral T-cell lymphomas (PTCL) are an uncommon, heterogeneous group of non-Hodgkin lymphomas that carry a much poorer prognosis than their more common B-cell counterparts. The most commonly used treatment is CHOP or its variations. However, while the results with CHOP are inadequate, there is little compelling data to suggest a preferred alternate strategy. Many of these alternate strategies have been assembled from retrospective data, small case series, subset analyses, phase II studies and individual experience. The greatest experience with alternative treatments has been with the use of high-dose therapy as consolidation. These approaches are promising, but most of the studies are retrospective and include patients with diverse prognoses, making interpretation difficult. Preliminary results of prospective trials in PTCL are only recently being reported. Perhaps more exciting have been the increasing numbers of new therapies being studied for patients with PTCL. The activities of new drugs are being described in studies specifically for PTCL, and attempts at novel combinations are beginning.

FDA approval summary: vorinostat for treatment of advanced primary cutaneous T-cell lymphoma

On October 6, 2006, the U.S. Food and Drug Administration granted regular approval to vorinostat (Zolinza(R); Merck & Co., Inc., Whitehouse Station, NJ), a histone deacetylase inhibitor, for the treatment of cutaneous manifestations of cutaneous T-cell lymphoma (CTCL) in patients with progressive, persistent, or recurrent disease on or following two systemic therapies. The pivotal study supporting approval was a single-arm open-label phase II trial that enrolled 74 patients with stage IB and higher CTCL who had failed two systemic therapies (one of which must have contained bexarotene). Patients received vorinostat at a dose of 400 mg orally once daily, which could be reduced for toxicity to 300 mg daily or 300 mg 5 days a week. The median age of patients was 61 years. Sixty-one patients (82%) had stage IIB or higher CTCL and 30 patients (41%) had Sézary syndrome. The median duration of protocol treatment was 118 days. The primary efficacy endpoint was objective response assessed by the Severity-Weighted Assessment Tool. The objective response rate was 30% (95% confidence interval [CI], 19.7%-41.5%), the estimated median response duration was 168 days, and the median time to tumor progression was 202 days. An additional single-center study enrolled 33 patients with similar baseline and demographic features as the pivotal trial. Thirteen of the 33 received vorinostat (400 mg/day). The response rate in these 13 patients was 31% (95% CI, 9.1%-61.4%). The most common clinical adverse events (AEs) of any grade were diarrhea (52%), fatigue (52%), nausea (41%), and anorexia (24%). Grade 3 or 4 clinical AEs included fatigue (4%) and pulmonary embolism (5%). Hematologic laboratory abnormalities included thrombocytopenia (26%) and anemia (14%). Chemistry laboratory abnormalities included increased creatinine (16%), increased serum glucose (69%), and proteinuria (51%). Most abnormalities were National Cancer Institute Common Terminology Criteria for Adverse Events grade 1 or 2. Grade 3 or greater chemistry abnormalities included hyperglycemia, hypertriglyceridemia, and hyperuricemia, hypoglycemia, hypokalemia, hyponatremia, hyperkalemia, hypercholesterolemia, hypophosphatemia, and increased creatinine.

A functional genetic screen identifies retinoic acid signaling as a target of histone deacetylase inhibitors

Understanding the pathways that are targeted by cancer drugs is instrumental for their rational use in a clinical setting. Inhibitors of histone deacetylases (HDACI) selectively inhibit proliferation of malignant cells and are used for the treatment of cancer, but their cancer selectivity is understood poorly. We conducted a functional genetic screen to address the mechanism(s) of action of HDACI. We report here that ectopic expression of two genes that act on retinoic acid (RA) signaling can cause resistance to growth arrest and apoptosis induced by HDACI of different chemical classes: the retinoic acid receptor alpha (RARalpha) and preferentially expressed antigen of melanoma (PRAME), a repressor of RA signaling. Treatment of cells with HDACI induced RA signaling, which was inhibited by RARalpha or PRAME expression. Conversely, RAR-deficient cells and PRAME-knockdown cells show enhanced sensitivity to HDACI in vitro and in mouse xenograft models. Finally, a combination of RA and HDACI acted synergistically to activate RA signaling and inhibit tumor growth. These experiments identify the RA pathway as a rate-limiting target of HDACI and suggest strategies to enhance the therapeutic efficacy of HDACI.

Phase 1 study of the histone deacetylase inhibitor vorinostat (suberoylanilide hydroxamic acid [SAHA]) in patients with advanced leukemias and myelodysplastic syndromes

Vorinostat (suberoylanilide hydroxamic acid, SAHA) is a histone deacetylase inhibitor active clinically in cutaneous T-cell lymphoma and preclinically in leukemia. A phase 1 study was conducted to evaluate the safety and activity of oral vorinostat 100 to 300 mg twice or thrice daily for 14 days followed by 1-week rest. Patients with relapsed or refractory leukemias or myelodysplastic syndromes (MDS) and untreated patients who were not candidates for chemotherapy were eligible. Of 41 patients, 31 had acute myeloid leukemia (AML), 4 chronic lymphocytic leukemia, 3 MDS, 2 acute lymphoblastic leukemia, and 1 chronic myelocytic leukemia. The maximum tolerated dose (MTD) was 200 mg twice daily or 250 mg thrice daily. Dose-limiting toxicities were fatigue, nausea, vomiting, and diarrhea. Common drug-related adverse experiences were diarrhea, nausea, fatigue, and anorexia and were mild/moderate in severity. Grade 3/4 drug-related adverse experiences included fatigue (27%), thrombocytopenia (12%), and diarrhea (10%). There were no drug-related deaths; 7 patients had hematologic improvement response, including 2 complete responses and 2 complete responses with incomplete blood count recovery (all with AML treated at/below MTD). Increased histone acetylation was observed at all doses. Antioxidant gene expression may confer vorinostat resistance. Further evaluation of vorinostat in AML/MDS is warranted.