A phase Ib study of vosaroxin, an anticancer quinolone derivative, in patients with relapsed or refractory acute leukemia

Monitoring clonal burden as an alternative to blast count for myelodysplastic neoplasm treatment response

Accurate assessment of therapy response in myelodysplastic neoplasm (MDS) has been challenging. Directly monitoring mutational disease burden may be useful, but is not currently included in MDS response criteria, and the correlation of mutational burden and traditional response endpoints is not completely understood. Here, we used genome-wide and targeted next-generation sequencing (NGS) to monitor clonal and subclonal molecular disease burden in 452 samples from 32 patients prospectively treated in a clinical trial. Molecular responses were compared with International Working Group (IWG) 2006-defined response assessments. We found that myeloblast percentage consistently underestimates MDS molecular disease burden and that mutational clearance patterns for marrow complete remission (mCR), which depends on myeloblast assessment, was not different than stable disease or bone marrow aplasia, underscoring a major limitation of using mCR. In contrast, achieving a complete remission (CR) was associated with the highest level of mutation clearance and lowest residual mutational burden in higher-risk MDS patients. A targeted gene panel approach was inferior to genome-wide sequencing in defining subclones and their molecular responses but may be adequate for monitoring molecular disease burden when a targeted gene is present in the founding clone. Our work supports incorporating serial NGS-based monitoring into prospective MDS clinical trials.

In Silico Evaluation of Some Computer-Designed Fluoroquinolone-Glutamic Acid Hybrids as Potential Topoisomerase II Inhibitors with Anti-Cancer Effect

Background/Objectives: Fluoroquinolones (FQs) are topoisomerase II inhibitors with antibacterial activity, repositioned recently as anti-cancer agents. Glutamic acid (GLA) is an amino acid that affects human metabolism. Since an anti-cancer mechanism of FQs is human topoisomerase II inhibition, it is expected that FQ-GLA hybrids can act similarly. Methods: We designed 27 hypothetical hybrids of 6 FQs and GLA through amide bonds at the 3- and 7-position groups of FQs or via ethylenediamine/ethanolamine linkers at the carboxyl group of the FQ. Hydroxamic acid derivatives were also theoretically formulated. Computational methods were used to predict their physicochemical, pharmacokinetic, or toxicological properties and their anti-cancer activity. For comparison, etoposide was used as an anti-cancer agent inhibiting topoisomerase II. Molecular docking assessed whether the hybrids could interact with the human topoisomerase II beta in the same binding site and interaction sites as etoposide. Results: All the hybrids acted as potential topoisomerase II inhibitors, demonstrating possible anti-cancer activity on several cancer cell lines. Among all the proposed hybrids, MF-7-GLA would be the ideal candidate as a lead compound. The hybrid OF-3-EDA-GLA and the hydroxamic acid derivatives also stood out. Conclusions: Both FQs and GLA have advantageous structures for obtaining hybrids with favourable properties. Improvements in the hybrids' structure could lead to promising results.

NHC-BIAN-Cu(I)-Catalyzed Friedländer-Type Annulation of 2-Amino-3-(per)fluoroacetylpyridines with Alkynes on Water

The direct catalytic alkynylation/dehydrative cyclization of 2-amino-3-trifluoroacetyl-pyridines on water was developed for the efficient synthesis of a broad range of fluorinated 1,8-naphthyridines from terminal alkynes. A novel N-heterocyclic carbene (NHC) ligand system that combines a π-extended acenaphthylene backbone with sterically bulky pentiptycene pendant groups was successfully utilized in a copper- or silver-mediated cyclization. Computational analysis of the reaction pathway supports our explanation of the different experimental conversions and yields for the set of copper and silver catalysts. The impact of steric hindrance at the metal center and the flexibility of substituents on the imidazole ring of the NHC on catalytic performance are also discussed.

Topoisomerase II inhibitors in AML: past, present, and future

Introduction: Topoisomerase II inhibitors have long been used in the frontline and as salvage therapy for AML, with daunorubicin and idarubicin being prototypical agents in this therapeutic class, classically in combination with nucleoside analogs, e.g. cytarabine. Most recently, several other compounds from this drug class have or are being investigated. Areas covered: The current paper reviews older and newer topoisomerase II inhibitors in clinical development for the treatment of AML. The authors discuss the clinical use of these agents, current trials involving them as well as their safety profile. Important side effects of these medications including therapy-related AML (t-AML) are also covered. Expert opinion: Topoisomerase II inhibitors have helped improve outcomes in AML. Recently, the FDA approved several agents including CPX-351 for the treatment of secondary and t-AML. CPX-351 may have applicability in other high-risk myeloid diseases. Future directions include a combination of these agents with other targeted therapies. Finally, the authors believe that small molecule inhibitors, such as venetoclax and possibly immunotherapy options could also be incorporated to our treatment paradigm in selected patients.

Establishing a Preclinical Multidisciplinary Board for Brain Tumors

Purpose: Curing all children with brain tumors will require an understanding of how each subtype responds to conventional treatments and how best to combine existing and novel therapies. It is extremely challenging to acquire this knowledge in the clinic alone, especially among patients with rare tumors. Therefore, we developed a preclinical brain tumor platform to test combinations of conventional and novel therapies in a manner that closely recapitulates clinic trials.Experimental Design: A multidisciplinary team was established to design and conduct neurosurgical, fractionated radiotherapy and chemotherapy studies, alone or in combination, in accurate mouse models of supratentorial ependymoma (SEP) subtypes and choroid plexus carcinoma (CPC). Extensive drug repurposing screens, pharmacokinetic, pharmacodynamic, and efficacy studies were used to triage active compounds for combination preclinical trials with "standard-of-care" surgery and radiotherapy.Results: Mouse models displayed distinct patterns of response to surgery, irradiation, and chemotherapy that varied with tumor subtype. Repurposing screens identified 3-hour infusions of gemcitabine as a relatively nontoxic and efficacious treatment of SEP and CPC. Combination neurosurgery, fractionated irradiation, and gemcitabine proved significantly more effective than surgery and irradiation alone, curing one half of all animals with aggressive forms of SEP.Conclusions: We report a comprehensive preclinical trial platform to assess the therapeutic activity of conventional and novel treatments among rare brain tumor subtypes. It also enables the development of complex, combination treatment regimens that should deliver optimal trial designs for clinical testing. Postirradiation gemcitabine infusion should be tested as new treatments of SEP and CPC. Clin Cancer Res; 24(7); 1654-66. ©2018 AACR.

Enhancement of radiosensitivity by the novel anticancer quinolone derivative vosaroxin in preclinical glioblastoma models

Purpose

Glioblastoma multiforme (GBM) is the most aggressive brain tumor. The activity of vosaroxin, a first-in-class anticancer quinolone derivative that intercalates DNA and inhibits topoisomerase II, was investigated in GBM preclinical models as a single agent and combined with radiotherapy (RT).

Results

Vosaroxin showed antitumor activity in clonogenic survival assays, with IC₅₀ of 10−100 nM, and demonstrated radiosensitization. Combined treatments exhibited significantly higher γH2Ax levels compared with controls. In xenograft models, vosaroxin reduced tumor growth and showed enhanced activity with RT; vosaroxin/RT combined was more effective than temozolomide/RT. Vosaroxin/RT triggered rapid and massive cell death with characteristics of necrosis. A minor proportion of treated cells underwent caspase-dependent apoptosis, in agreement with in vitro results. Vosaroxin/RT inhibited RT-induced autophagy, increasing necrosis. This was associated with increased recruitment of granulocytes, monocytes, and undifferentiated bone marrow–derived lymphoid cells. Pharmacokinetic analyses revealed adequate blood-brain penetration of vosaroxin. Vosaroxin/RT increased disease-free survival (DFS) and overall survival (OS) significantly compared with RT, vosaroxin alone, temozolomide, and temozolomide/RT in the U251-luciferase orthotopic model.

Materials and Methods

Cellular, molecular, and antiproliferative effects of vosaroxin alone or combined with RT were evaluated in 13 GBM cell lines. Tumor growth delay was determined in U87MG, U251, and T98G xenograft mouse models. (DFS) and (OS) were assessed in orthotopic intrabrain models using luciferase-transfected U251 cells by bioluminescence and magnetic resonance imaging.

Conclusions

Vosaroxin demonstrated significant activity in vitro and in vivo in GBM models, and showed additive/synergistic activity when combined with RT in O6-methylguanine methyltransferase-negative and -positive cell lines.

Therapies for acute myeloid leukemia: vosaroxin

Vosaroxin, a quinolone-derivative chemotherapeutic agent, was considered a promising drug for the treatment of acute myeloid leukemia (AML). Early-stage clinical trials with this agent led to a large randomized double-blind placebo-controlled study of vosaroxin in combination with intermediate-dose cytarabine for the treatment of relapsed or refractory AML. The study demonstrated better complete remission rates with vosaroxin, but there was no statistically significant overall survival benefit in the whole cohort. A subset analysis censoring patients who had undergone allogeneic stem cell transplantation, however, revealed a modest but statistically significant improvement in overall survival particularly among older patients. This article reviews the data available on vosaroxin including clinical trials in AML and offers an analysis of findings of these studies as well as the current status of vosaroxin.

Molecular and Pharmacologic Properties of the Anticancer Quinolone Derivative Vosaroxin: A New Therapeutic Agent for Acute Myeloid Leukemia

Vosaroxin is a first-in-class anticancer quinolone derivative that targets topoisomerase II and induces site-selective double-strand breaks in DNA, leading to tumor cell apoptosis. Vosaroxin has chemical and pharmacologic characteristics distinct from other topoisomerase II inhibitors due to its quinolone scaffold. The efficacy and safety of vosaroxin in combination with cytarabine were evaluated in patients with relapsed/refractory acute myeloid leukemia (AML) in a phase III, randomized, multicenter, double-blind, placebo-controlled study (VALOR). In this study, the addition of vosaroxin produced a 1.4-month improvement in median overall survival (OS; 7.5 months with vosaroxin/cytarabine vs. 6.1 months with placebo/cytarabine; hazard ratio [HR] 0.87, 95 % confidence interval [CI] 0.73−1.02; unstratified log-rank p\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$=$$\end{document}= 0.061; stratified log-rank p\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$=$$\end{document}=0.024), with the greatest OS benefit observed in patients ≥60 years of age (7.1 vs. 5.0 months; HR 0.75, 95 % CI 0.62−0.92; p\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$=$$\end{document}=0.003) and patients with early relapse (6.7 vs. 5.2 months; HR 0.77, 95 % CI 0.59−1.00; p\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$=$$\end{document}= 0.039), two AML patient groups that typically have poor prognosis. Here we review the chemical and pharmacologic properties of vosaroxin, how these properties are distinct from those of currently available topoisomerase II inhibitors, how they may contribute to the efficacy and safety profile observed in the VALOR trial, and the status of clinical development of vosaroxin for treatment of AML.

The preclinical discovery of vosaroxin for the treatment of acute myeloid leukemia

INTRODUCTION

Acute myeloid leukemia (AML) represents a disease with a very poor outcome and remains an area of significant unmet need necessitating novel therapeutic strategies. Among novel therapeutic agents, vosaroxin is a first-in-class anticancer quinolone derivative that targets topoisomerase II and induces site-selective double-strand breaks in DNA, leading to tumor cell apoptosis. Areas covered: Herein, the authors provide a comprehensive review of the preclinical development of vosaroxin. This includes coverage of vosaroxin's mechanism of action in addition to its pharmacology and of the main studies reported over the past few years with vosaroxin when used to treat adult AML. Expert opinion: Given that vosaroxin is associated with fewer potential side effects, it may be of benefit to elderly patients with relapsed/refractory AML and to those with additional comorbidities who have previously received an anthracycline and cytarabine combination. Furthermore, vosaroxin also was seen to be active in multidrug-resistant preclinical models. However, further studies have to be performed to better evaluate its place in the armamentarium against AML.

Emerging therapies for acute myeloid leukemia

Acute myeloid leukemia (AML) is characterized by clinical and biological heterogeneity. Despite the advances in our understanding of its pathobiology, the chemotherapy-directed management has remained largely unchanged in the past 40 years. However, various novel agents have demonstrated clinical activity, either as single agents (e.g., isocitrate dehydrogenase (IDH) inhibitors, vadastuximab) or in combination with standard induction/consolidation at diagnosis and with salvage regimens at relapse. The classes of agents described in this review include novel cytotoxic chemotherapies (CPX-351 and vosaroxin), epigenetic modifiers (guadecitabine, IDH inhibitors, histone deacetylase (HDAC) inhibitors, bromodomain and extraterminal (BET) inhibitors), FMS-like tyrosine kinase receptor 3 (FLT3) inhibitors, and antibody-drug conjugates (vadastuximab), as well as cell cycle inhibitors (volasertib), B-cell lymphoma 2 (BCL-2) inhibitors, and aminopeptidase inhibitors. These agents are actively undergoing clinical investigation alone or in combination with available chemotherapy.

Metabolism and disposition of the anticancer quinolone derivative vosaroxin, a novel inhibitor of topoisomerase II

Background Vosaroxin is a first-in-class anticancer quinolone derivative that is being investigated for patients with relapsed or refractory acute myeloid leukemia (AML). The primary objective of this study was to quantitatively determine the pharmacokinetics of vosaroxin and its metabolites in patients with advanced solid tumors. Methods This mass balance study investigated the pharmacokinetics (distribution, metabolism, and excretion) of vosaroxin in cancer patients after a single dose of 60 mg/m^{2 14}C-vosaroxin, administered as short intravenous injection. Blood, urine and feces were collected over 168 h after injection or until recovered radioactivity over 24 h was less than 1% of the administered dose (whichever was earlier). Total radioactivity (TRA), vosaroxin and metabolites were studied in all matrices. Results Unchanged vosaroxin was the major species identified in plasma, urine, and feces. N-desmethylvosaroxin was the only circulating metabolite detected in plasma, accounting for <3% of the administered dose. However, in plasma, the combined vosaroxin + N-desmethylvosaroxin AUC_0-∞ was 21% lower than the TRA AUC_0-∞ , suggesting the possible formation of protein bound metabolites after 48 h when the concentration-time profiles diverged. The mean recovery of TRA in excreta was 81.3% of the total administered dose; 53.1% was excreted through feces and 28.2% through urine. Conclusions Unchanged vosaroxin was the major compound found in the excreta, although 10 minor metabolites were detected. The biotransformation reactions were demethylation, hydrogenation, decarboxylation and phase II conjugation including glucuronidation.

Targeting acute myeloid leukemia with TP53-independent vosaroxin

Vosaroxin is a quinolone compound that intercalates DNA and induces TP53-independent apoptosis, demonstrating activity against acute myeloid leukemia (AML) in Phase I-III trials. Here, we examine vosaroxin's mechanism of action and pharmacology, and we review its use in AML to date, focusing on details of individual clinical trials. Most recently, when combined with cytarabine in a randomized Phase III trial (VALOR), vosaroxin improved outcomes versus cytarabine alone for relapsed/refractory AML in patients older than 60 years and for patients in early relapse. We consider its continued role in the context of a multifaceted strategy against AML, including its current use in clinical trials. Prospective use will define its role in the evolving landscape of AML therapy.

Considerations and challenges for patients with refractory and relapsed acute myeloid leukaemia

Despite advances in understanding the complexities of acute myeloid leukaemia (AML), the treatment of refractory or relapsed AML (rrAML) remains a daunting clinical challenge. Numerous clinical trials have failed to identify new treatments or combinations of existing therapies that substantially improve outcomes and survival. This may be due, at least in part, to heterogeneity among study patients with respect to multiple inter-related factors that have been shown to affect treatment outcomes for patients with rrAML; such factors include age, cytogenetics, immunophenotypic changes, and (in the case of relapsed AML) duration of first complete remission, or if the patient has had a previous blood and marrow transplant (BMT). A clear understanding of disease characteristics and patient-related factors that influence treatment response, as well as expected outcomes with existing and emerging therapies, can aid clinicians in helping their patients navigate through this complex disease state.

Quantification of vosaroxin and its metabolites N-desmethylvosaroxin and O-desmethylvosaroxin in human plasma and urine using high-performance liquid chromatography-tandem mass spectrometry

Vosaroxin is a first-in-class anticancer quinolone derivative topoisomerase II inhibitor that is currently in development in combination with cytarabine for the treatment of acute myeloid leukemia (AML). To investigate vosaroxin pharmacokinetics (PK) in patients, liquid chromatography tandem mass spectrometry (LC-MS/MS) assays to quantify vosaroxin and the two metabolites N-desmethylvosaroxin and O-desmethylvosaroxin in human plasma and urine were developed and validated. Immediately after collection the samples were stored at -80°C. Prior to analysis, the plasma samples were subjected to protein precipitation and the urine samples were diluted. For both assays the reconstituted extracts were injected on a Symmetry Shield RP8 column and gradient elution was applied using 0.1% formic acid in water and acetonitrile-methanol (50:50, v/v). Analyses were performed with a triple quadruple mass spectrometer in positive-ion mode. A deuterated isotope of vosaroxin was used as internal standard for the quantification. The validated assays quantify vosaroxin and N-desmethylvosaroxin in the concentration range of 2-500ng/mL in plasma and urine. For O-desmethylvosaroxin the concentration range of 4-500ng/mL in plasma and urine was validated. Dilution integrity experiments show that samples can be diluted 25 fold in control matrix prior to analysis. The expanded concentration range for plasma and urine for vosaroxin and N-desmethylvosaroxin is therefore from 2 to 15,000ng/mL and in plasma for O-desmethylvosaroxin from 4 to 15,000ng/mL.

New drugs in acute myeloid leukemia

The standard therapy for acute myeloid leukemia (AML) has not changed meaningfully for the past four decades. Improvements in supportive care and modifications to the dose and schedule of existing agents have led to steady improvements in outcomes. However, developing new therapies for AML has been challenging. Although there have been advances in understanding the biology of AML, translating this knowledge to viable treatments has been slow. Active research is currently ongoing to address this important need and several promising drug candidates are currently in the pipeline. Here, we review some of the most advanced and promising compounds that are currently in clinical trials and may have the potential to be part of our future armamentarium. These drug candidates range from cytotoxic chemotherapies, targeted small-molecule inhibitors, and monoclonal antibodies.

The safety of treatment options for elderly people with acute myeloid leukemia

INTRODUCTION

Life expectancy in elderly patients with acute myeloid leukemia (AML) is a function of age, disability, and co-morbidity, combined with leukemia characteristics. There is currently no consensus regarding the optimal therapeutic strategy for older adults with AML. Although selected older adults with AML can benefit from intensive therapies, recent evidence supports the use of lower-intensity therapies in most patients and emphasizes the importance of tolerability and quality of life.

AREAS COVERED

Results of the current clinical trials and safety data are reviewed.

EXPERT OPINION

Treatment recommendations for elderly patients with AML need to be individualized. In order to avoid toxicities, hematologists should collaborate more with geriatricians to identify clues of vulnerability in elderly patients through the study of functional physical, physiological, cognitive, social, and psychological parameters.

Management of Relapsed/Refractory Acute Myeloid Leukemia in the Elderly: Current Strategies and Developments

Elderly patients with acute myeloid leukemia (AML) who are refractory to or relapse following frontline treatment constitute a poor-risk group with a poor long-term outcome. Host-related factors and unfavorable disease-related features contribute to early treatment failures following frontline therapy, thus making attainment of remission and long-term survival with salvage therapy particularly challenging for elderly patients. Currently, no optimal salvage strategy exists for responding patients, and allogeneic hematopoietic stem cell transplant is the only curative option in this setting; however, the vast majority of elderly patients are not candidates for this procedure due to poor functional status secondary to age and age-related comorbidities. Furthermore, the lack of effective salvage programs available for elderly patients with recurrent AML underscores the need for therapies that consistently yield durable remissions or durable control of their disease. The purpose of this review was to highlight the currently available strategies, as well as future strategies under development, for treating older patients with recurrent AML.

Iron(III)-binding of the anticancer agents doxorubicin and vosaroxin

The Fe(iii)-binding constant of vosaroxin, an anticancer quinolone derivative, has been determined spectrophotometrically and compared with the analogous Fe(iii) complex formed with doxorubicin. The in vivo metabolic stability and iron coordination properties of the quinolones compared to the anthracylines may provide significant benefit to cardiovascular safety. The mechanism of action of both molecules target the topoisomerase II enzyme. Both doxorubicin (Hdox, log βFeL3 = 33.41, pM = 17.0) and vosaroxin (Hvox, log βFeL3 = 33.80(3), pM = 15.9) bind iron(iii) with comparable strength; at physiological pH however, [Fe(vox)3] is the predominant species in contrast to a mixture of species observed for the Fe:dox system. Iron(iii) nitrate and gallium(iii) nitrate at a 1 : 3 ratio with vosaroxin formed stable tris(vosaroxacino)-iron(iii) and tris(vosaroxino)gallium(iii) complexes that were isolated and characterized. Their redox behavior was studied by CV, and their stereochemistry was further explored in temperature dependent (1)H NMR studies. The molecular pharmacology of their interaction with iron(iii) may be one possible differentiation in the safety profile of quinolones compared to anthracyclines in relation to cardiotoxicity.

Vosaroxin is a novel topoisomerase-II inhibitor with efficacy in relapsed and refractory acute myeloid leukaemia

INTRODUCTION

Vosaroxin is a first-in-class anti-cancer quinolone that inhibits topoisomerase-II leading to cell cycle arrest and apoptosis. It has shown efficacy in a range of solid organ and haematopoietic tumours in vitro, and several clinical trials are underway or completed in the field of Acute Myeloid Leukaemia (AML). The treatment of relapsed and refractory AML is a clinical challenge, where long-term survival is rare without allogeneic haematopoietic stem cell transplantation.

AREAS COVERED

We review the data from the published clinical trials of vosaroxin, including the recently presented Phase III VALOR study. In combination with intermediate dose cytarabine, vosaroxin almost doubled complete response (CR) rates in relapsed and refractory AML compared with cytarabine alone, and prolonged median survival by 1.4 months.

EXPERT OPINION

Vosaroxin is a promising new agent in the treatment of AML, with the potential to improve CR rates in a high-risk group of patients with relapsed and refractory AML. However, higher CR rates have been associated with higher rates of treatment-related morbidity and mortality, especially in elderly/unfit patients. Maximising the potential of vosaroxin will therefore require the identification of patients most likely to benefit from vosaroxin-containing combination regimens.

Current Approaches in the Treatment of Relapsed and Refractory Acute Myeloid Leukemia

The limited sensitivity of the historical treatment response criteria for acute myeloid leukemia (AML) has resulted in a different paradigm for treatment compared with most other cancers presenting with widely disseminated disease. Initial cytotoxic induction chemotherapy is often able to reduce tumor burden to a level sufficient to meet the current criteria for "complete" remission. Nevertheless, most AML patients ultimately die from their disease, most commonly as clinically evident relapsed AML. Despite a variety of available salvage therapy options, prognosis in patients with relapsed or refractory AML is generally poor. In this review, we outline the commonly utilized salvage cytotoxic therapy interventions and then highlight novel investigational efforts currently in clinical trials using both pathway-targeted agents and immunotherapy based approaches. We conclude that there is no current standard of care for adult relapsed or refractory AML other than offering referral to an appropriate clinical trial.

Vosaroxin and vosaroxin plus low-dose Ara-C (LDAC) vs low-dose Ara-C alone in older patients with acute myeloid leukemia

The development of new treatments for older patients with acute myeloid leukemia is an active area, but has met with limited success. Vosaroxin, a quinolone-derived intercalating agent has several properties that could prove beneficial. Initial clinical studies showed it to be well-tolerated in older patients with relapsed/refractory disease. In vitro data suggested synergy with cytarabine (Ara-C). To evaluate vosaroxin, we performed 2 randomized comparisons within the "Pick a Winner" program. A total of 104 patients were randomized to vosaroxin vs low-dose Ara-C (LDAC) and 104 to vosaroxin + LDAC vs LDAC. When comparing vosaroxin with LDAC, neither response rate (complete recovery [CR]/complete recovery with incomplete count recovery [CRi], 26% vs 30%; odds ratio [OR], 1.16 (0.49-2.72); P = .7) nor 12-month survival (12% vs 31%; hazard ratio [HR], 1.94 [1.26-3.00]; P = .003) showed benefit for vosaroxin. Likewise, in the vosaroxin + LDAC vs LDAC comparison, neither response rate (CR/CRi, 38% vs 34%; OR, 0.83 [0.37-1.84]; P = .6) nor survival (33% vs 37%; HR, 1.30 [0.81-2.07]; P = .3) was improved. A major reason for this lack of benefit was excess early mortality in the vosaroxin + LDAC arm, most obviously in the second month following randomization. At its first interim analysis, the Data Monitoring and Ethics Committee recommended closure of the vosaroxin-containing trial arms because a clinically relevant benefit was unlikely.

REVEAL-1, a phase 2 dose regimen optimization study of vosaroxin in older poor-risk patients with previously untreated acute myeloid leukaemia

This phase 2 study (N = 116) evaluated single-agent vosaroxin, a first-in-class anticancer quinolone derivative, in patients ≥60 years of age with previously untreated unfavourable prognosis acute myeloid leukaemia. Dose regimen optimization was explored in sequential cohorts (A: 72 mg/m² d 1, 8, 15; B: 72 mg/m² d 1, 8; C: 72 mg/m² or 90 mg/m² d 1, 4). The primary endpoint was combined complete remission rate (complete remission [CR] plus CR with incomplete platelet recovery [CRp]). Common (>20%) grade ≥3 adverse events were thrombocytopenia, febrile neutropenia, anaemia, neutropenia, sepsis, pneumonia, stomatitis and hypokalaemia. Overall CR and CR/CRp rates were 29% and 32%; median overall survival (OS) was 7·0 months; 1-year OS was 34%. Schedule C (72 mg/m²) had the most favourable safety and efficacy profile, with faster haematological recovery (median 27 d) and lowest incidence of aggregate sepsis (24%) and 30-d (7%) and 60-d (17%) all-cause mortality; at this dose and schedule, CR and CR/CRp rates were 31% and 35%, median OS was 7·7 months and 1-year OS was 38%. Overall, vosaroxin resulted in low early mortality and an encouraging response rate; vosaroxin 72 mg/m² d 1, 4 is recommended for further study in this population. Registered at www.clinicaltrials.gov: #NCT00607997.

A phase 1b/2 study of vosaroxin in combination with cytarabine in patients with relapsed or refractory acute myeloid leukemia

Vosaroxin is a first-in-class anticancer quinolone derivative that intercalates DNA and inhibits topoisomerase II. This study assessed the safety and tolerability of vosaroxin plus cytarabine in patients with relapsed/refractory acute myeloid leukemia. Escalating vosaroxin doses (10-minute infusion; 10-90 mg/m(2); days 1, 4) were given in combination with cytarabine on one of two schedules: schedule A (24-hour continuous intravenous infusion, 400 mg/m(2)/day, days 1-5) or schedule B (2-hour intravenous infusion, 1 g/m(2)/day, days 1-5). Following dose escalation, enrollment was expanded at the maximum tolerated dose. Of 110 patients enrolled, 108 received treatment. The maximum tolerated dose of vosaroxin was 80 mg/m(2) for schedule A (dose-limiting toxicities: grade 3 bowel obstruction and stomatitis) and was not reached for schedule B (recommended phase 2 dose: 90 mg/m(2)). In the efficacy population (all patients in first relapse or with primary refractory disease treated with vosaroxin 80-90 mg/m(2); n=69), the complete remission rate was 25% and the complete remission/complete remission with incomplete blood count recovery rate was 28%. The 30-day all-cause mortality rate was 2.5% among all patients treated at a dose of 80-90 mg/m(2). Based upon these results, a phase 3 trial of vosaroxin plus cytarabine was initiated in patients with relapsed/refractory acute myeloid leukemia. (Clinicaltrials.gov identifier: NCT00541866).

Novel drugs for older patients with acute myeloid leukemia

Acute myeloid leukemia (AML) is the second most common form of leukemia and the most frequent cause of leukemia-related deaths in the United States. The incidence of AML increases with advancing age and the prognosis for patients with AML worsens substantially with increasing age. Many older patients are ineligible for intensive treatment and require other therapeutic approaches to optimize clinical outcome. To address this treatment gap, novel agents with varying mechanisms of action targeting different cellular processes are currently in development. Hypomethylating agents (azacitidine, decitabine, SGI-110), histone deacetylase inhibitors (vorinostat, pracinostat, panobinostat), FMS-like tyrosine kinase receptor-3 inhibitors (quizartinib, sorafenib, midostaurin, crenolanib), cytotoxic agents (clofarabine, sapacitabine, vosaroxin), cell cycle inhibitors (barasertib, volasertib, rigosertib) and monoclonal antibodies (gentuzumab ozogamicin, lintuzumab-Ac225) represent some of these promising new treatments. This review provides an overview of novel agents that have either completed or are currently in ongoing phase III trials in patients with previously untreated AML for whom intensive treatment is not an option. Other potential drugs in earlier stages of development will also be addressed in this review.

The thorny issue of relapsed acute myeloid leukemia

PURPOSE OF REVIEW

Acute myeloid leukemia (AML) is a devastating disease, in which the majority of afflicted patients eventually experience relapse and die from their disease.

RECENT FINDINGS

Clinical and molecular characterization of the disease have greatly aided in prognostication in both primary and relapsed settings, which may broadly guide therapy, but truly effective standards of care for relapsed AML remain lacking. Traditional chemotherapeutic drugs have modest but limited efficacy in relapsed AML, whereas more novel and potent cytotoxic chemotherapeutic agents hold promise and are entering the advanced phases of testing. Targeted therapies for AML have demonstrated activity, often as single agents, generating enthusiasm for further development in subgroups of patients with appropriate molecular anomalies. Finally, allogeneic stem cell transplantation continues to evolve as an effective and potentially curative therapy for limited numbers of patients with relapsed AML.

SUMMARY

The complexity of relapsed AML will dictate the need for continued development of novel chemotherapeutic and targeted therapies that suit the molecular and clinical profiling of individual patients.

Vosaroxin: a new valuable tool with the potential to replace anthracyclines in the treatment of AML?

INTRODUCTION

Despite significant advances in diagnosis and supportive care, the majority of patients diagnosed with acute myeloid leukemia (AML) ultimately die of their disease. Standard intensive induction treatment continues to comprise cytarabine and a topoisomerase II (topo II) poison, usually an anthracycline. Vosaroxin , a novel first-in-class quinolone derivative has been developed for use in the treatment of AML as a new-generation topo II inhibitor. It has shown promising activity as a monotherapy and also in combination with intermediate dose cytarabine (IDAC) in relapsed and refractory patient cohorts with minimal toxicity and good tolerability.

AREAS COVERED

The authors discuss the mechanism of action of vosaroxin, the pharmacokinetics, safety and tolerability, preclinical and clinical trial results available as well as areas of ongoing research.

EXPERT OPINION

Vosaroxin has shown efficacy as a novel cytotoxic agent, and despite a similar mechanism of action has significant advantages over anthracyclines. It evades common resistance pathways of p53 and P-glycoprotein (P- gp) and does not appear to generate significant reactive oxygen species (ROS) associated with these agents. Should future investigation confirm its efficacy and advantageous safety profile, vosaroxin could potentially replace older generation topoisomerase poisons in the treatment of AML and other malignant conditions.

Current treatment of acute myeloid leukemia

PURPOSE OF REVIEW

The objectives of this review are to discuss standard and investigational nontransplant treatment strategies for acute myeloid leukemia (AML), excluding acute promyelocytic leukemia.

RECENT FINDINGS

Most adults with AML die from their disease. The standard treatment paradigm for AML is remission induction chemotherapy with an anthracycline/cytarabine combination, followed by either consolidation chemotherapy or allogeneic stem cell transplantation, depending on the patient's ability to tolerate intensive treatment and the likelihood of cure with chemotherapy alone. Although this approach has changed little in the last three decades, increased understanding of the pathogenesis of AML and improvements in molecular genomic technologies are leading to novel drug targets and the development of personalized, risk-adapted treatment strategies. Recent findings related to prognostically relevant and potentially 'druggable' molecular targets are reviewed.

SUMMARY

At the present time, AML remains a devastating and mostly incurable disease, but the combination of optimized chemotherapeutics and molecularly targeted agents holds significant promise for the future.

γH2AX as a marker of DNA double strand breaks and genomic instability in human population studies

DNA double strand breaks (DSB) are the gravest form of DNA damage in eukaryotic cells. Failure to detect DSB and activate appropriate DNA damage responses can cause genomic instability, leading to tumorigenesis and possibly accelerated aging. Phosphorylated histone H2AX (γH2AX) is used as a biomarker of cellular response to DSB and its potential for monitoring DNA damage and repair in human populations has been explored in this review. A systematic search was conducted in PubMed for articles, in English, on human studies reporting γH2AX as a biomarker of either DNA repair or DNA damage. A total of 68 publications were identified. Thirty-four studies (50.0%) evaluated the effect of medical procedures or treatments on γH2AX levels; 20 (29.4%) monitored γH2AX in specific pathological conditions with a case/control or case/case design; 5 studies (7.4%) evaluated the effect of environmental genotoxic exposures, and 9 (13.2%) were descriptive studies on cancer and aging. Peripheral blood lymphocytes (44.6%) or biopsies/tissue specimens (24.3%) were the most commonly used samples. γH2AX was scored by optical microscopy as immunostained foci (78%), or by flow cytometry (16%). Critical features affecting the reliability of the assay, including protocols heterogeneity, specimen, cell cycle, kinetics, study design, and statistical analysis, are hereby discussed. Because of its sensitivity, efficiency and mechanistic relevance, the γH2AX assay has great potential as a DNA damage biomarker; however, the technical and epidemiological heterogeneity highlighted in this review infer a necessity for experimental standardization of the assay.

Novel and emerging drugs for acute myeloid leukemia

Acute myeloid leukemia (AML) is a challenging disease to treat with the majority of patients dying from their illness. While overall survival has been markedly prolonged in acute promyelocytic leukemia (APL), survival in younger adults with other subtypes of AML has only modestly improved over the last twenty years. Physicians who treat AML eagerly await drugs like Imatinib for chronic myeloid leukemia, Cladribine for hairy cell leukemia, and Rituximab for non-Hodgkin Lymphoma which have had an important impact on improving outcome. Recent research efforts have focused on refining traditional chemotherapeutic agents to make them more active in AML, targeting specific genetic mutations in myeloid leukemia cells, and utilizing novel agents such as Lenalidomide that have shown activity in other hematologic malignancies. Here, we focus on reviewing the recent literature on agents that may assume a role in clinical practice for patients with AML over the next five years.

Vosaroxin : a novel antineoplastic quinolone

INTRODUCTION

The antineoplastic quinolone derivative vosaroxin (SNS-595, Sunesis, South San Francisco, CA, USA) was first described in 2002. It represents a novel class of anticancer drugs and is currently in a Phase III clinical trial for relapsed and refractory acute myeloid leukemia (AML). AML is the most common form of acute leukemia in adults and is increasing in incidence due to the aging of the American population. Despite advances in diagnosis, prognostic prediction, and treatment in younger age groups, there has been little improvement in survival among patients over 60 years of age, who make up the majority of those affected.

AREAS COVERED

The development of vosaroxin, its mechanism of action, pharmacology, and metabolism, and the preclinical and clinical data to date will be covered.

EXPERT OPINION

Despite its structural dissimilarity, vosaroxin has mechanisms of action similar to the anthracyclines and anthracenediones already in use for the treatment of AML. However, unlike these agents, vosaroxin is not a P-gp substrate, appears to be unaffected by overexpression of P-gp or TP53 mutations, and may be useful in the treatment of AML, especially in the elderly.

Induction and postremission strategies in acute myeloid leukemia: state of the art and future directions

Although the past decade has brought improvements in the treatment of AML, particularly for younger individuals, most patients succumb to the disease. With current induction therapy, most patients achieve remission, but the optimal strategy for post-remission therapy is unclear. Refinements to risk classification systems that incorporate additional molecular markers may better guide physicians in recommendations for postremission therapy. The prognosis for older patients with AML remains uniformly poor, because only a minority can benefit from intensive chemotherapy and novel HCT strategies. Despite active investigation, no standard of care has emerged for patients who are not suitable candidates for standard induction therapy. The development of less toxic, more effective therapies for this population is sorely needed. Advances in molecular genetics, immunology, and the biology of normal and malignant hematopoiesis pathogenesis have led to an improved understanding of the pathogenesis of AML and to the discovery of potential therapeutic targets. Until a greater proportion of individuals with AML attain long-term survival, patients should routinely be referred to cancer centers and enrolled in investigational studies.