A Phase 2 study of combination therapy with arsenic trioxide and gemtuzumab ozogamicin in patients with myelodysplastic syndromes or secondary acute myeloid leukemia

Has Drug Repurposing Fulfilled its Promise in Acute Myeloid Leukaemia?

Drug repurposing is a method of drug discovery that consists of finding a new therapeutic context for an old drug. Compound identification arises from screening of large libraries of active compounds, through interrogating databases of cell line gene expression response upon treatment or by merging several types of information concerning disease-drug relationships. Although, there is a general consensus on the potential and advantages of this drug discovery modality, at the practical level to-date no non-anti-cancer repurposed compounds have been introduced into standard acute myeloid leukaemia (AML) management, albeit that preclinical validation yielded several candidates. The review presents the state-of-the-art drug repurposing approach in AML and poses the question of what has to be done in order to take a full advantage of it, both at the stage of screening design and later when progressing from the preclinical to the clinical phases of drug development. We argue that improvements are needed to model and read-out systems as well as to screening technologies, but also to more funding and trust in drug repurposing strategies.

Secondary Acute Myeloid Leukemia: A Primary Challenge of Diagnosis and Treatment

Secondary acute myeloid leukemia (sAML) is a complex diagnosis that includes AML caused by either an antecedent hematologic disease (AML-AHD) or from previous treatment with chemotherapy or radiation. This disease carries a poor prognosis and is historically chemorefractory; additionally, often patients are ineligible for standard chemotherapy because of advanced age and other comorbidities. The advances of molecular diagnostics and reclassification of World Health Organization criteria have aided in the categorization of this disease. This article describes the etiology and pathophysiology of sAML, and delves into past successful treatments as well as promising new treatments.

Overview of Current Targeted Anti-Cancer Drugs for Therapy in Onco-Hematology

The upgraded knowledge of tumor biology and microenviroment provides information on differences in neoplastic and normal cells. Thus, the need to target these differences led to the development of novel molecules (targeted therapy) active against the neoplastic cells' inner workings. There are several types of targeted agents, including Small Molecules Inhibitors (SMIs), monoclonal antibodies (mAbs), interfering RNA (iRNA) molecules and microRNA. In the clinical practice, these new medicines generate a multilayered step in pharmacokinetics (PK), which encompasses a broad individual PK variability, and unpredictable outcomes according to the pharmacogenetics (PG) profile of the patient (e.g., cytochrome P450 enzyme), and to patient characteristics such as adherence to treatment and environmental factors. This review focuses on the use of targeted agents in-human phase I/II/III clinical trials in cancer-hematology. Thus, it outlines the up-to-date anticancer drugs suitable for targeted therapies and the most recent finding in pharmacogenomics related to drug response. Besides, a summary assessment of the genotyping costs has been discussed. Targeted therapy seems to be an effective and less toxic therapeutic approach in onco-hematology. The identification of individual PG profile should be a new resource for oncologists to make treatment decisions for the patients to minimize the toxicity and or inefficacy of therapy. This could allow the clinicians to evaluate benefits and restrictions, regarding costs and applicability, of the most suitable pharmacological approach for performing a tailor-made therapy.

An update on treatment of higher risk myelodysplastic syndromes

INTRODUCTION

Myelodysplastic syndromes (MDS) are clonal stem cell disorders mostly affecting the elderly. They are classified into lower and higher risk MDS according to prognostic scoring systems. In higher risk patients, treatments should aim to modify the disease course by avoiding progression to acute myeloid leukemia and, therefore, to improve survival. Areas covered: Stem cell transplantation remains the only curative treatment when feasible, but this concerns a small minority of patients. Treatment is principally based on hypomethylating agents (HMAs). Our understanding of MDS biology has led to the development of drugs targeting key cellular processes such as apoptosis or posttranslational protein changes, microenvironment-like immunotherapy, and gene mutations. Currently, new drugs are mainly being tested in combination with HMAs in several clinical trials. Expert commentary: Significant advances have been made in the field of MDS, especially in molecular typing, which are improving our ability to offer patients risk-adapted therapies. The current challenge in the management of higher risk MDS is to improve outcome by combining classical HMAs with novel drugs.

Immunosuppressive therapy in myelodysplastic syndromes: a borrowed therapy in search of the right place

INTRODUCTION

Myelodysplastic syndromes (MDS) encompass a heterogenous collection of clonal hematopoietic stem cell disorders defined by dysregulated hematopoiesis, peripheral cytopenias, and a risk of leukemic progression. Increasing data support the role of innate and adaptive immune pathways in the pathogenesis and disease course of MDS. The role of immunosuppressive therapy has an established role in the treatment of other hematologic diseases, such as aplastic anemia whose pathogenesis is postulated to reflect that of MDS with regards to many aspects of immune activation. Areas covered: This paper discusses the current understanding of immune dysregulation as it pertains to MDS, the clinical experience with immunosuppressive therapy in the management of MDS, as well as future prospects which will likely improve therapeutic options and outcomes for patients with MDS. Expert commentary: Though limited by paucity of high quality data, immunomodulatory and immunosuppressive therapies for the treatment of MDS have shown meaningful clinical activity in selected patients. Continued clarification of the immune pathways that are dysregulated in MDS and establishing predictors for clinical benefit of immunosuppressive therapy are vital to improve the use and outcomes with these therapies.

Incidence, Diagnosis, and Management of QT Prolongation Induced by Cancer Therapies: A Systematic Review

Background

The cardiovascular complications of cancer therapeutics are the focus of the burgeoning field of cardio‐oncology. A common challenge in this field is the impact of cancer drugs on cardiac repolarization (ie, QT prolongation) and the potential risk for the life‐threatening arrhythmia torsades de pointes. Although QT prolongation is not a perfect marker of arrhythmia risk, this has become a primary safety metric among oncologists. Cardiologists caring for patients receiving cancer treatment should become familiar with the drugs associated with QT prolongation, its incidence, and appropriate management strategies to provide meaningful consultation in this complex clinical scenario.

Methods and Results

In this article, we performed a systematic review (using Preferred Reporting Items of Systematic Reviews and Meta‐Analyses (PRISMA) guidelines) of commonly used cancer drugs to determine the incidence of QT prolongation and clinically relevant arrhythmias. We calculated summary estimates of the incidence of all and clinically relevant QT prolongation as well as arrhythmias and sudden cardiac death. We then describe strategies to prevent, identify, and manage QT prolongation in patients receiving cancer therapy. We identified a total of 173 relevant publications. The weighted incidence of any corrected QT (QTc) prolongation in our systematic review in patients treated with conventional therapies (eg, anthracyclines) ranged from 0% to 22%, although QTc >500 ms, arrhythmias, or sudden cardiac death was extremely rare. The risk of QTc prolongation with targeted therapies (eg, small molecular tyrosine kinase inhibitors) ranged between 0% and 22.7% with severe prolongation (QTc >500 ms) reported in 0% to 5.2% of the patients. Arrhythmias and sudden cardiac death were rare.

Conclusions

Our systematic review demonstrates that there is variability in the incidence of QTc prolongation of various cancer drugs; however, the clinical consequence, as defined by arrhythmias or sudden cardiac death, remains rare.

Drug Repurposing for the Treatment of Acute Myeloid Leukemia

Acute myeloid leukemia (AML) is a heterogeneous disease characterized by the accumulation of immature myeloid progenitor cells in the bone marrow, compromising of normal blood cell production and ultimately resulting in bone marrow failure. With a 20% overall survival rate at 5 years and 50% in the 18- to 65-year-old age group, new medicines are needed. It is proposed that development of repurposed drugs may be a part of the new therapy needed. AML is subdivided into recurrent molecular entities based on molecular genetics increasingly accessible for precision medicine. Novel therapy developments form a basis for novel multimodality therapy and include liposomal daunorubicin/cytarabine, broad or FLT3-specific tyrosine kinase inhibitors, Bcl-2 family inhibitors, selective inhibitors of nuclear export, metabolic inhibitors, and demethylating agents. The use of non-transplant immunotherapy is in early development in AML with the exceptional re-approval of a toxin-conjugated anti-CD33. However, the full potential of small molecule inhibitors and modalities like immunological checkpoint inhibitors, immunostimulatory small molecules, and CAR-T cell therapy is unknown. Some novel therapeutics will certainly benefit AML patient subgroups; however, due to high cost, more affordable alternatives are needed globally. Also the heterogeneity of AML will likely demand a broader repertoire of therapeutic molecules. Drug repurposing or repositioning represent a source for potential therapeutics with well-known toxicity profiles and reasonable prices. This implies that biomarkers of response need to accompany the development of antileukemic therapies for sharply defined patient subgroups. We will illustrate repurposing in AML with selected examples and discuss some experimental and regulatory limitations that may obstruct this development.

Arsenic trioxide targets MTHFD1 and SUMO-dependent nuclear de novo thymidylate biosynthesis

Arsenic exposure increases risk for cancers and is teratogenic in animal models. Here we demonstrate that small ubiquitin-like modifier (SUMO)- and folate-dependent nuclear de novo thymidylate (dTMP) biosynthesis is a sensitive target of arsenic trioxide (As2O3), leading to uracil misincorporation into DNA and genome instability. Methylenetetrahydrofolate dehydrogenase 1 (MTHFD1) and serine hydroxymethyltransferase (SHMT) generate 5,10-methylenetetrahydrofolate for de novo dTMP biosynthesis and translocate to the nucleus during S-phase, where they form a multienzyme complex with thymidylate synthase (TYMS) and dihydrofolate reductase (DHFR), as well as the components of the DNA replication machinery. As2O3 exposure increased MTHFD1 SUMOylation in cultured cells and in in vitro SUMOylation reactions, and increased MTHFD1 ubiquitination and MTHFD1 and SHMT1 degradation. As2O3 inhibited de novo dTMP biosynthesis in a dose-dependent manner, increased uracil levels in nuclear DNA, and increased genome instability. These results demonstrate that MTHFD1 and SHMT1, which are key enzymes providing one-carbon units for dTMP biosynthesis in the form of 5,10-methylenetetrahydrofolate, are direct targets of As2O3-induced proteolytic degradation, providing a mechanism for arsenic in the etiology of cancer and developmental anomalies.

Arsenic trioxide and triptolide synergistically induce apoptosis in the SKM‑1 human myelodysplastic syndrome cell line

Although certain combination therapies comprising arsenic trioxide (As₂O₃) with other agents exist for the treatment of several types of human cancer, few As₂O₃ combination therapies are clinically effective for myelodysplastic syndromes (MDS). Triptolide (TL) may be an effective therapeutic agent for the treatment of MDS. However, to date, there is no combination therapy for MDS with As₂O₃ and TL. Therefore, the aim of the present study was to investigate this combination therapy on the apoptosis of MDS SKM-1 cells. The MDS SKM-1 cells were treated with As₂O₃, TL or the two in combination at various concentrations, or were mock-treated. Cell viability, cell apoptosis, levels of reactive oxygen species (ROS) and the expression of the cell apoptosis-associated genes, B cell lymphoma-2 (Bcl-2), Bcl-2-associated X protein (Bax) and caspase-3, were determined using an MTT assay, flow cytometric analysis of annexin V-fluorescein isothiocyanate/propidium iodide double-stained cells, flow cytometic analysis of intracellular 2′,7′-dichlorodihydrofluorescein diacetate fluorescence and reverse transcription-quantitative polymerase chain reaction analysis, respectively. Combination index (CI) analysis was performed to determine whether effects were synergistic (CI<1). The combination treatment was found to synergistically inhibit MDS SKM-1 cell growth, induce cell apoptosis, increase ROS levels, upregulate the expression levels of Bax and caspase-3, and downregulate the mRNA expression of Bcl-2. In conclusion, the combination treatment of As₂O₃ and TL synergistically induced apoptosis in the MDS SKM-1 cells.

Molecular and Cellular Mechanisms of Myelodysplastic Syndrome: Implications on Targeted Therapy

Myelodysplastic syndrome (MDS) is a group of heterogeneous clonal hematopoietic stem cell disorders characterized by cytopenia, ineffective hematopoiesis, and progression to secondary acute myeloid leukemia in high-risk cases. Conventional prognostication relies on clinicopathological parameters supplemented by cytogenetic information. However, recent studies have shown that genetic aberrations also have critical impacts on treatment outcome. Moreover, these genetic alterations may themselves be a target for treatment. The mutation landscape in MDS is shaped by gene aberrations involved in DNA methylation (TET2, DNMT3A, IDH1/2), histone modification (ASXL1, EZH2), the RNA splicing machinery (SF3B1, SRSF2, ZRSR2, U2AF1/2), transcription (RUNX1, TP53, BCOR, PHF6, NCOR, CEBPA, GATA2), tyrosine kinase receptor signaling (JAK2, MPL, FLT3, GNAS, KIT), RAS pathways (KRAS, NRAS, CBL, NF1, PTPN11), DNA repair (ATM, BRCC3, DLRE1C, FANCL), and cohesion complexes (STAG2, CTCF, SMC1A, RAD21). A detailed understanding of the pathogenetic mechanisms leading to transformation is critical for designing single-agent or combinatorial approaches in target therapy of MDS.

The Synergistic Effects of Decitabine Combined with Arsenic Trioxide (ATO) in the Human Myelodysplastic Syndrome Cell Line SKM-1

Despite recent advances in the treatment of myelodysplastic syndrome (MDS), single-agent clinical effects remain unsatisfactory, and decitabine monotherapy is also associated with a relatively low rate of complete remission. To study the combined effects and mechanism of decitabine (DAC) and arsenic trioxide (ATO) on the human myelodysplastic cell line SKM-1,we used the MTS assay and CalcuSyn software to determine the cytotoxicity and potential synergistic effects, respectively. Furthermore, we determined apoptosis and measured the mRNA expression level of two genes that are considered main regulators of the apoptosis process. The results showed that DAC and/or ATO can inhibit the proliferation of SKM-1 cells and demonstrated significant synergy between the two agents (CI < 1). Additionally, combination of 2.5 μmol/L DAC and 5 μmol/L ATO led to a significantly higher apoptosis rate and more significantly decreased the Bcl2/Bax ratio than either compound alone (P < 0.001). Based on the observations of this study, we suggest that combined administration of these two drugs might be considered a novel therapeutic regimen for treating MDS.

The evolution of arsenic in the treatment of acute promyelocytic leukemia and other myeloid neoplasms: Moving toward an effective oral, outpatient therapy

The therapeutic potential of arsenic derivatives has long been recognized and was recently rediscovered in modern literature. Early studies demonstrated impressive activity of this compound in patients with relapsed acute promyelocytic leukemia (APL). Over the last 2 decades, intravenous arsenic trioxide has been used successfully, both alone and in combination with other agents, for the treatment of APL and, with some success, of other myeloid neoplasms. Arsenic trioxide is currently part the standard of care for patients with APL. More recently, oral formulations of this compound have been developed and are entering clinical practice. In this review, the authors discuss the evolution of arsenic in the treatment of APL and other myeloid neoplasms.

Clinical activity and safety of the dual pathway inhibitor rigosertib for higher risk myelodysplastic syndromes following DNA methyltransferase inhibitor therapy

Rigosertib (ON 01910.Na) is an inhibitor of the phosphoinositide 3-kinase and polo-like kinase pathways that induces mitotic arrest and apoptosis in neoplastic cells, while sparing normal cells. Our purpose is to summarize the clinical activity and safety of intravenous (IV) rigosertib delivered by an external ambulatory infusion pump in patients with refractory anemia with excess blasts-1, -2, or, -t myelodysplastic syndromes (MDS) following prior treatment with DNA methyltransferase (DNMT) inhibitors. A total of 39 patients with MDS who fulfilled these criteria were enrolled in four phase 1-2 clinical trials of IV rigosertib. Thirty five (88%) had higher risk disease according to the Revised International Prognostic Scoring System. Median overall survival for this group of 39 patients was 35 weeks. Of 30 evaluable patients with follow-up bone marrow biopsies, 12 (40%) achieved complete (n = 5) or partial (n = 7) bone marrow blast responses. In addition, 15 patients achieved stabilization of bone marrow blasts. One patient with a complete bone marrow response also achieved a complete cytogenetic response. A second patient with stable bone marrow blasts achieved a partial cytogenetic response. Two of the responding patients and three patients with stable disease had hematological improvements. Rigosertib-induced bone marrow blast decreases and stability appeared to be predictive of prolonged survival. IV rigosertib had a favorable safety profile without significant myelosuppression. Most common drug-related toxicities included fatigue, diarrhea, nausea, dysuria, and hematuria. In summary, IV rigosertib is well tolerated and has clinical activity in patients with higher risk MDS following DNMT inhibitor treatment. A multinational pivotal phase 3 randomized clinical trial of rigosertib versus best supportive care for patients with MDS with excess blasts following prior treatment with DNMT inhibitors (ONTIME: ON 01910.Na Trial In Myelodysplastic SyndromE) has recently completed enrollment.

A phase II study of arsenic trioxide in patients with relapsed or refractory malignant lymphoma

Limited data have been reported regarding the use of arsenic trioxide (ATO) in the treatment of patients with relapsed or refractory malignant lymphoma; therefore, the present phase II study evaluated the efficacy and toxicity of ATO in such patients. A total of 35 patients were treated with ATO (0.25 mg/kg) infused for 1 h daily, 5 days a week, for a 6-week cycle. Patients were evaluated for the efficacy and toxicity of this regimen. The primary outcome evaluated was the overall response rate (ORR), including the complete and partial response rates. The secondary outcomes evaluated were the overall survival (OS), progression-free survival (PFS), and toxicity. Tumor response data were obtained from all 35 enrolled patients. The ORR was 43%, including complete responses in four patients (11%) and partial responses in 11 patients (31%). The median duration of response was 16 weeks (range 11-23 weeks). The median OS was 79 weeks (range 14-171 weeks), and the median PFS was 55 weeks (range 14-135 weeks). Grade I or II hematological toxicities were the most commonly reported adverse events. The results of this study appear promising for the treatment of relapsed or refractory malignant lymphoma, with well-tolerated ATO toxicity.

More is better: combination therapies for myelodysplastic syndromes

The myelodysplastic syndromes (MDS) are a heterogenous collection of clonal hematopoietic malignancies that exist as a subgroup of the myeloid neoplasms as classified by the World Health Organization (WHO). They are characterized by ineffective hematopoiesis, subsequent cytopenias, transformation to acute myeloid leukemia (AML), and poor overall survival. There are currently three FDA-approved medications for MDS; lenalidomide, azacitidine, and decitabine. The role of these agents is to diminish the clinical impact of MDS and delay its progression to AML. However, despite known results with these monotherapies, recent clinical trials with a variety of combinations for MDS have demonstrated promising results. These trials include combinations of hypomethylating agents, histone deacetylase inhibitors, growth factors, and chemotherapy among others. In this paper we review the current literature on combination therapies in MDS, analyze on-going and concluded trials, and suggest future possibilities for combination strategies in MDS.

Retinoic acid synergizes ATO-mediated cytotoxicity by precluding Nrf2 activity in AML cells

Background:

Standard therapy for acute promyelocytic leukaemia (APL) includes retinoic acid (all-trans retinoic acid (ATRA)), which promotes differentiation of promyelocytic blasts. Although co-administration of arsenic trioxide (ATO) with ATRA has emerged as an effective option to treat APL, the molecular basis of this effect remains unclear.

Methods:

Four leukaemia cancer human models (HL60, THP-1, NBR4 and NBR4-R2 cells) were treated either with ATO alone or ATO plus ATRA. Cancer cell survival was monitored by trypan blue exclusion and DEVDase activity assays. Gene and protein expression changes were assessed by RT-PCR and western blot.

Results:

ATO induced an antioxidant response characterised by Nrf2 nuclear translocation and enhanced transcription of downstream target genes (that is, HO-1, NQO1, GCLM, ferritin). In cells exposed to ATO plus ATRA, the Nrf2 nuclear translocation was prevented and cytotoxicity was enhanced. HO-1 overexpression reversed partially the cytotoxicity by ATRA-ATO in HL60 cells. The inhibitory effects of ATRA on ATO-mediated responses were not observed in either the ATRA-resistant NB4-R2 cells or in NB4 cells pre-incubated with the RARα antagonist Ro-41-52-53.

Conclusions:

The augmented cytotoxicity observed in leukaemia cells following combined ATO-ATRA treatment is likely due to inhibition of Nrf2 activity, thus explaining the efficacy of combined ATO-ATRA treatment in the APL therapy.

Myelodysplastic syndromes

Myelodysplastic syndromes are clonal marrow stem-cell disorders, characterised by ineffective haemopoiesis leading to blood cytopenias, and by progression to acute myeloid leukaemia in a third of patients. 15% of cases occur after chemotherapy or radiotherapy for a previous cancer; the syndromes are most common in elderly people. The pathophysiology involves cytogenetic changes with or without gene mutations and widespread gene hypermethylation at advanced stages. Clinical manifestations result from cytopenias (anaemia, infection, and bleeding). Diagnosis is based on examination of blood and bone marrow showing blood cytopenias and hypercellular marrow with dysplasia, with or without excess of blasts. Prognosis depends largely on the marrow blast percentage, number and extent of cytopenias, and cytogenetic abnormalities. Treatment of patients with lower-risk myelodysplastic syndromes, especially for anaemia, includes growth factors, lenalidomide, and transfusions. Treatment of higher-risk patients is with hypomethylating agents and, whenever possible, allogeneic stem-cell transplantation.

Hypomethylating agents and chemotherapy in MDS

Until recently, the treatment of higher risk myelodysplastic syndrome was based on [1] Intensive chemotherapy using anthracycline-AraC combinations, leading to a lower complete remission rates and a shorter CR duration compared with de novo AML [2], low dose chemotherapy with limited CR rate mainly restricted to patients with normal karyotype. Azacitidine was the first drug to significantly improve survival in higher risk MDS, although it is not curative. Thus, the survival improvement obtained with azacitidine must be the starting point for combination studies, and for utilization of this drug in other situations (before allo SCT, or after chemotherapy or allo SCT as maintenance treatment).

Novel therapeutic strategies: hypomethylating agents and beyond

The treatment of symptomatic and high-risk myelodysplastic syndrome (MDS) spans several therapeutic goals and options. Key to the successful therapy of these heterogeneous diseases is careful characterization and diagnosis, including clinical, cytogenetic, biological, and molecular evaluation of individual patients. Any novel management strategy in MDS must be based on accepted and validated prognostic scoring systems, such as the International Prognostic Scoring System (IPSS), and should take into account predictive parameters of response to the available therapeutic agents and individual comorbidities. For IPSS lower-risk MDS patients, several first-line options are available, including erythropoietic stimulating agents, lenalidomide, and immunosuppressive drugs. Sequential therapy is advisable whenever response is lost, and the activity of azacitidine and decitabine in first- or second-line therapy is relevant, especially in patients with symptomatic cytopenias and anemia. Hypomethylating agents have a central role in therapy of IPSS higher-risk MDS patients. These agents include azacitidine and decitabine, which allow treatment of very elderly and frail patients, resulting in hematological improvement and transfusion independency in roughly half, and for azacitidine a demonstrated significant prolongation of survival. Because hypomethylating agents are not curative, they are not satisfactory for younger MDS patients, for whom a transplantation strategy should be planned. Although hypomethylating agent therapy is used extensively, a growing number of MDS patients fail to respond or progress. The future challenge is not only to find treatment regimens that target the dysplastic clone(s) so that durable remissions are achieved (particularly in high-risk patients with short survival and/or increased leukemic transformation rates), but also to also identify active salvage regimens.

A phase 2 trial of combination therapy with thalidomide, arsenic trioxide, dexamethasone, and ascorbic acid (TADA) in patients with overlap myelodysplastic/myeloproliferative neoplasms (MDS/MPN) or primary myelofibrosis (PMF)

BACKGROUND

Primary myelofibrosis (PMF) and overlap myelodysplastic/myeloproliferative neoplasms (MDS/MPN) are clonal hematopoietic disorders that share similar clinical features and molecular abnormalities, such as the Janus kinase 2 (JAK2) valine to phenylalanine mutation at codon 617 (V617F) and the tet methylcytosine dioxygenase 2 (TET2) mutation. There are limited therapeutic options available for these diseases, and single agents have only modest efficacy. In this phase 2 study, the authors combined multiple active agents (thalidomide, arsenic trioxide, dexamethasone, and ascorbic acid [TADA]) to treat patients with these disorders.

METHODS

This multicenter trial was conducted from January 2005 to July 2007. The primary endpoint was to evaluate the efficacy of TADA therapy. Patients received the combination for one 12-week cycle followed by maintenance thalidomide for an additional 3 months. Response was assessed using International Working Group criteria.

RESULTS

Among 28 enrolled patients, the median age was 66.5 years; 15 patients had MDS/MPN-unclassifiable, 8 patients had chronic myelomonocytic leukemia type 1, and 5 patients had PMF. Approximately 60% of the patients had normal cytogenetics. The JAK2V617F mutation was detected in 5 of 14 tested patients, and TET2 mutations were detected in 2 of 8 tested patients. Almost half of the patients had splenomegaly. With a median on-study follow-up of 5.7 months, 21 patients (75%) completed the entire 12-week course of therapy, and 6 patients (29%) responded to TADA. With a median extended follow-up of 24.1 months for 15 evaluable patients, the median progression-free survival was 14.4 months, and the median overall survival was 21.4 months.

CONCLUSIONS

The TADA regimen yielded clinical responses in patients with PMF and MDS/MPN. To the authors' knowledge, this study represents the first trial targeting this patient population. The results indicated that it is reasonable to incorporate multiple novel agents in the treatment of these rare diseases.

Combination strategies in myelodysplastic syndromes

The myelodysplastic syndromes (MDS) consist of an array of clonal hematological malignancies resulting from disorders of pluripotent hematopoietic stem cells. MDS is associated with a poor overall prognosis and patients are categorized as higher risk and lower risk on the basis of the International Prognostic Scoring System. Currently, lenalidomide, azacitidine, and decitabine are the only three FDA-approved drugs for MDS. Traditional therapies for MDS involve the administration of single agents providing either supportive measures or disease-modifying effects directed to slowing progression to acute myeloid leukemia (AML) and improving survival. Recently, however, there has been increasing evidence suggesting that the combination of drugs with different mechanisms of action offers substantial benefit in the form of diminished side effects, improved overall survival, and delayed progression to AML. Multiple studies indicate that when compared with traditional monotherapies, combining various medications with non-overlapping mechanisms of action and toxicities may result in significant benefit for patients with MDS. A variety of combination therapies with growth factors, DNA methytransferase inhibitors, histone deacetylase inhibitors, and immunosuppressant treatments provide encouraging data indicating that the successful future of MDS treatment rests in the combination of multiple treatments modalities to achieve improved clinical outcomes.

Synergism between arsenite and proteasome inhibitor MG132 over cell death in myeloid leukaemic cells U937 and the induction of low levels of intracellular superoxide anion

Increased oxygen species production has often been cited as a mechanism determining synergism on cell death and growth inhibition effects of arsenic-combined drugs. However the net effect of drug combination may not be easily anticipated solely from available knowledge of drug-induced death mechanisms. We evaluated the combined effect of sodium arsenite with the proteasome inhibitor MG132, and the anti-leukaemic agent CAPE, on growth-inhibition and cell death effect in acute myeloid leukaemic cells U937 and Burkitt's lymphoma-derived Raji cells, by the Chou-Talalay method. In addition we explored the association of cytotoxic effect of drugs with changes in intracellular superoxide anion (O₂⁻) levels. Our results showed that combined arsenite+MG132 produced low levels of O₂⁻ at 6h and 24h after exposure and were synergic on cell death induction in U937 cells over the whole dose range, although the combination was antagonistic on growth inhibition effect. Exposure to a constant non-cytotoxic dose of 80μM hydrogen peroxide together with arsenite+MG132 changed synergism on cell death to antagonism at all effect levels while increasing O₂⁻ levels. Arsenite+hydrogen peroxide also resulted in antagonism with increased O₂⁻ levels in U937 cells. In Raji cells, arsenite+MG132 also produced low levels of O₂⁻ at 6h and 24h but resulted in antagonism on cell death and growth inhibition. By contrast, the combination arsenite+CAPE showed high levels of O₂⁻ production at 6h and 24 h post exposure but resulted in antagonism over cell death and growth inhibition effects in U937 and Raji cells. We conclude that synergism between arsenite and MG132 in U937 cells is negatively associated to O₂⁻ levels at early time points after exposure.

Gemtuzumab ozogamicin in non-acute promyelocytic acute myeloid leukemia

INTRODUCTION

Gemtuzumab ozogamicin (GO) has been used in relapsed, refractory and newly diagnosed acute myeloid leukemia (AML) as a single agent and in combination with intensive chemotherapy. Results of recent Phase III trials have led to its withdrawal in the USA although a beneficial effect of GO in genetically defined AML subgroups was evident.

AREAS COVERED

This review examines the use of GO as a single agent or in combination with intensive chemotherapy in non-acute promyelocytic AML. The literature search was based on publications on GO indexed in the PubMed electronic database and selected meeting abstracts. GO has shown moderate activity as a single agent but promising activity in combination with intensive chemotherapy in refractory or relapsed AML. Relapsed AML defined molecularly by mutant nucleophosmin-1 without concurrent fms-related tyrosine kinase 3 (FLT3) internal tandem duplication seems to benefit most from GO. In newly diagnosed AML two up-front randomized Phase III trials evaluating GO in induction therapy failed to demonstrate an improvement in response and survival. Again, genetically defined subgroups may benefit.

EXPERT OPINION

Future challenges of personalized therapy in AML will be to integrate the signals from current subgroup analyses underlining the role of GO in genetically defined AML entities.