Mitoxantrone, etoposide, and cytarabine with or without valspodar in patients with relapsed or refractory acute myeloid leukemia and high-risk myelodysplastic syndrome: a phase III trial (E2995)

Bone marrow cellularity at day 14 is the most important predictive factor for response in patients with AML who require double-induction chemotherapy: Analysis from a large, single institution experience

In patients with acute myeloid leukemia (AML), the presence of residual disease at day 14 after primary induction therapy warrants consideration of a second induction cycle. However, data to guide retreatment decisions in such patients are presently limited. Here, we retrospectively reviewed data from 176 patients with AML treated at our institution with a second induction chemotherapy regimen because of day 14 residual disease. Clinical variables and nadir bone marrow features were assessed for correlations with complete remission (CR) and overall survival (OS). In our patient group, 59% achieved CR after a second induction course. Median OS for the entire group was 12.40 months (95% CI, 9.90-14.90) but 19.07 months (95% CI, 13.13-25.01) for those who attained a CR. Nadir marrow hypocellularity (P < 0.001) at day 14, absolute blast reduction of >50% (P = 0.030), and de novo disease status (P = 0.018) were significantly correlated with CR achievement after re-induction. Marrow hypocellularity at day 14 was the most significant predictor of CR on multivariate analysis (P < 0.001). Nadir marrow features did not independently correlate with OS when accounting for CR status. Re-induction was successful in achieving CR in most patients. Study patients who did not achieve CR were more likely to have nonhypocellular marrows.

Clofarabine-based chemotherapy as a bridge to transplant in the setting of refractory or relapsed acute myeloid leukemia, after at least one previous unsuccessful salvage treatment containing fludarabine: a single institution experience

For refractory or relapsed acute myeloid leukemia patients, allogeneic hematopoietic stem cell transplantation is the only curative treatment option, but the disease must be in remission before this can be attempted. "Salvage" therapy regimens containing high-dose cytarabine plus fludarabine or cladribine with or without anthracyclines or plus mitoxantrone and etoposide fail in 30-50% of cases. We report the outcome of 14 patients treated with a clofarabine-based treatment administered after at least one failed fludarabine-based "salvage" attempt in a "real life" (outside a clinical trial) context. No death related to the clofarabine-based treatment was observed. Four of the 14 patients (29%) reached complete remission and one (7%) achieved a reduction of marrow blasts to fewer than 10%. Three of these five patients were successfully transplanted and have shown a long-term survival. The small number of this group of patients does not permit the identification of clinical features clearly related to a favorable outcome, but we note that all the three long-term survivals were FLT3 wild type. Clofarabine-based "salvage therapy" in patients with very poor expectancy is feasible even after a fludarabine-based salvage attempt, albeit with success only in a small percentage of cases (3/14 = 21%).

Disrupting P-glycoprotein function in clinical settings: what can we learn from the fundamental aspects of this transporter?

P-glycoprotein is one of the most well-studied drug transporters, significant for its role in cancer multiple drug resistance. However, using P-gp inhibitors with the aim of enhancing the therapeutic efficacy of anti-cancer drugs has led to disappointing outcomes. Furthermore, several lead compounds suggested by in vitro and pre-clinical studies have shown variable pharmacokinetics and therapeutic efficacies when applied in the clinical setting. This review will highlight the need to revisit a sound approach to better design and apply P-gp inhibitors in light of safety and efficacy. Challenges confronting the issue hinge upon myriad studies that do not necessarily represent the heterogeneous target population of this therapeutic approach. The application of P-gp modulators has also been complicated by the promiscuous substrate-binding behaviour of P-gp, as well as toxicities related to its intrinsic presence in healthy tissue. This review capitalizes on information spanning genetics, energetics, and pharmacology, bringing to light some fundamental aspects that ought to be reconsidered in order to improve upon and design the next generation of P-gp inhibitors.

[Efficacy and safety analysis of the combination of cladribine, cytarabine, granulocyte colonystimulating factor (CLAG) regime in patients with refractory or relapsed acute myeloid leukemia]

OBJECTIVE

To analyze efficacy and safety of CLAG regimen in patients with refractory or relapsed acute myeloid leukemia (AML).

METHODS

Efficacy and adverse events of patients with refractory or relapsed AML who were treated with one course of CLAG from April 1st, 2014 through December 9th, 2015 in our hospital were retrospectively reviewed.

RESULTS

Thirty- three patients (16 males and 17 females) with refractory or relapsed AML were treated with one course of CLAG with a median age of 49 (14-68) years. According to FAB subtype, there were 22 patients with M2, and 11 with other types. According to NCCN criteria, there were 6, 18 and 9 patients with favorable, intermediate and unfavorable risk respectively, including 5 with FLT3- ITD mutation. Of 16 refractory and 17 relapsed patients; the median previous chemotherapy courses were 2(1-36). After one course of CLAG, 78.8% (26/33) patients achieved hematological complete response (CR), with 93.8 %(15/16) in relapsed and 64.7 %(11/17) in refractory groups respectively. All five patients with FLT3- ITD mutation achieved CR. All patients had grade 4 neutropenia and thrombocytopenia and infection in different sites; three patients died early from infections. Five patients received allogeneic hematopoietic stem cell transplantation (allo- HSCT). Ten patients relapsed and thirteen patients died after the median follow-up 142(9-525) days. The median EFS and OS were 230 (9- 525) and 419(9- 525) days respectively, which in CR group (n=26) were significantly longer than those in NR one (n=7) [447 (165- 525) d vs 52 (9- 162) d,P <0.001].

CONCLUSIONS

CLAG regimen was effective and well tolerable in patients with refractory or relapsed AML, with the CR rate in relapsed patients higher than in refractory counterparts. Control of infections was imperative for treatment.

Relapsed Acute Myeloid Leukemia: Need for Innovative Treatment Strategies to Improve Outcome

Relapse continues to be a major hurdle in achieving cure in patients with acute myeloid leukemia (AML). The outcome after relapse is not uniform in all patients with AML and is dependent on several prognostic variables, including age, cytogenetics at initial diagnosis, duration of first complete remission, whether an allogeneic stem cell transplant was performed during first complete remission, and the presence of a number of molecular aberrations. Despite extensive research over the past several decades, there is no standard of care for treating patients with relapsed AML. This is possibly due to the accrual of patients with widely different disease profiles in most trials for relapsed AML. With increasing insights into the disease biology based on identification of pathogenic and aberrant molecular and cellular pathways, novel therapeutic strategies are emerging. Hopefully in the near future, we can improve the outcome of patients with relapsed AML with treatment strategies based on identification of specific targets and methods to overcome these aberrant processes.

Pharmacokinetics and tolerability of NSC23925b, a novel P-glycoprotein inhibitor: preclinical study in mice and rats

Overexpression of P-glycoprotein (Pgp) increases multidrug resistance (MDR) in cancer, which greatly impedes satisfactory clinical treatment and outcomes of cancer patients. Due to unknown pharmacokinetics, the use of Pgp inhibitors to overcome MDR in the clinical setting remains elusive despite promising in vitro results. The purpose of our current preclinical study is to investigate the pharmacokinetics and tolerability of NSC23925b, a novel and potent P-glycoprotein inhibitor, in rodents. Plasma pharmacokinetic studies of single-dose NSC23925b alone or in combination with paclitaxel or doxorubicin were conducted in male BALB/c mice and Sprague-Dawley rats. Additionally, inhibition of human cytochrome P450 (CYP450) by NSC23925b was examined in vitro. Finally, the maximum tolerated dose (MTD) of NSC23925b was determined. NSC23925b displayed favorable pharmacokinetic profiles after intraperitoneal/intravenous (I.P./I.V.) injection alone or combined with chemotherapeutic drugs. The plasma pharmacokinetic characteristics of the chemotherapy drugs were not affected when co-administered with NSC23925b. All the animals tolerated the I.P./I.V. administration of NSC23925b. Moreover, the enzymatic activity of human CYP450 was not inhibited by NSC23925b. Our results demonstrated that Pgp inhibitor NSC23925b exhibits encouraging preclinical pharmacokinetic characteristics and limited toxicity in vivo. NSC23925b has the potential to treat cancer patients with MDR in the future.

Vosaroxin plus cytarabine versus placebo plus cytarabine in patients with first relapsed or refractory acute myeloid leukaemia (VALOR): a randomised, controlled, double-blind, multinational, phase 3 study

BACKGROUND

Safe and effective treatments are urgently needed for patients with relapsed or refractory acute myeloid leukaemia. We investigated the efficacy and safety of vosaroxin, a first-in-class anticancer quinolone derivative, plus cytarabine in patients with relapsed or refractory acute myeloid leukaemia.

METHODS

This phase 3, double-blind, placebo-controlled trial was undertaken at 101 international sites. Eligible patients with acute myeloid leukaemia were aged 18 years of age or older and had refractory disease or were in first relapse after one or two cycles of previous induction chemotherapy, including at least one cycle of anthracycline (or anthracenedione) plus cytarabine. Patients were randomly assigned 1:1 to vosaroxin (90 mg/m(2) intravenously on days 1 and 4 in a first cycle; 70 mg/m(2) in subsequent cycles) plus cytarabine (1 g/m(2) intravenously on days 1-5) or placebo plus cytarabine through a central interactive voice system with a permuted block procedure stratified by disease status, age, and geographical location. All participants were masked to treatment assignment. The primary efficacy endpoint was overall survival and the primary safety endpoint was 30-day and 60-day all-cause mortality. Efficacy analyses were done by intention to treat; safety analyses included all treated patients. This study is registered with ClinicalTrials.gov, number NCT01191801.

FINDINGS

Between Dec 17, 2010, and Sept 25, 2013, 711 patients were randomly assigned to vosaroxin plus cytarabine (n=356) or placebo plus cytarabine (n=355). At the final analysis, median overall survival was 7·5 months (95% CI 6·4-8·5) in the vosaroxin plus cytarabine group and 6·1 months (5·2-7·1) in the placebo plus cytarabine group (hazard ratio 0·87, 95% CI 0·73-1·02; unstratified log-rank p=0·061; stratified p=0·024). A higher proportion of patients achieved complete remission in the vosaroxin plus cytarabine group than in the placebo plus cytarabine group (107 [30%] of 356 patients vs 58 [16%] of 355 patients, p<0·0001). Early mortality was similar between treatment groups (30-day: 28 [8%] of 355 patients in the vosaroxin plus cytarabine group vs 23 [7%] of 350 in the placebo plus cytarabine group; 60-day: 70 [20%] vs 68 [19%]). Treatment-related deaths occurred at any time in 20 (6%) of 355 patients given vosaroxin plus cytarabine and in eight (2%) of 350 patients given placebo plus cytarabine. Treatment-related serious adverse events occurred in 116 (33%) and 58 (17%) patients in each group, respectively. Grade 3 or worse adverse events that were more frequent in the vosaroxin plus cytarabine group than in the placebo plus cytarabine group included febrile neutropenia (167 [47%] vs 117 [33%]), neutropenia (66 [19%] vs 49 [14%]), stomatitis (54 [15%] vs 10 [3%]), hypokalaemia (52 [15%] vs 21 [6%]), bacteraemia (43 [12%] vs 16 [5%]), sepsis (42 [12%] vs 18 [5%]), and pneumonia (39 [11%] vs 26 [7%]).

INTERPRETATION

Although there was no significant difference in the primary endpoint between groups, the prespecified secondary analysis stratified by randomisation factors suggests that the addition of vosaroxin to cytarabine might be of clinical benefit to some patients with relapsed or refractory acute myeloid leukaemia.

FUNDING

Sunesis Pharmaceuticals.

Nsc23925 prevents the development of paclitaxel resistance by inhibiting the introduction of P-glycoprotein and enhancing apoptosis

Strategies to prevent the emergence of drug resistance will increase the effectiveness of chemotherapy treatment and prolong survival of women with ovarian cancer. The aim of our study is to determine the effects of NSC23925 on preventing the development of paclitaxel resistance in ovarian cancer both in cultured cells in vitro and in mouse xenograft models in vivo, and to further elucidate these underlying mechanisms. We first developed a paclitaxel-resistant ovarian cancer cell line, and demonstrated that NSC23925 could prevent the introduction of paclitaxel resistance by specifically inhibiting the overexpression of P-glycoprotein (Pgp) in vitro. The paclitaxel-resistant ovarian cancer cells were then established in a mouse model by continuous paclitaxel treatment in combination with or without NSC23925 administration in the mice. The majority of mice continuously treated with paclitaxel alone eventually developed paclitaxel resistance with overexpression of Pgp and antiapoptotic proteins, whereas mice remained sensitivity to paclitaxel and displayed lower expression levels of Pgp and antiapoptotic proteins after administered continuously with combination of paclitaxel-NSC23925. Paclitaxel-NSC23925-treated mice experienced significantly longer overall survival time than paclitaxel-treated mice. Furthermore, the combination of paclitaxel and NSC23925 therapy did not induce obvious toxicity as measured by mice body weight changes, blood cell counts and histology of internal organs. Collectively, our observations provide evidence that NSC23925 in combination with paclitaxel may prevent the onset of Pgp or antiapoptotic-mediated paclitaxel resistance, and improve the long-term clinical outcome in patients with ovarian cancer.

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.

A novel nanoparticle formulation overcomes multiple types of membrane efflux pumps in human breast cancer cells

Multidrug resistance (MDR) in cancer cells can involve overexpression of different types of membrane drug efflux pumps and other drug resistance mechanisms. Hence, inhibition of one resistance mechanism may not be therapeutically effective. Previously we demonstrated a new polymer lipid hybrid nanoparticle (PLN) system was able to circumvent drug resistance of P-glycoprotein (P-gp) overexpressing breast cancer cells. The objectives of the present study were 2-fold: (1) to evaluate the ability of the PLN system to overcome two other membrane efflux pumps-multidrug resistance protein 1 (MRP1+) and breast cancer resistance protein (BCRP+) overexpressed on human breast cancer cell lines MCF7 VP (MRP1+) and MCF7 MX (BCRP+); and (2) to evaluate possible synergistic effects of doxorubicin (Dox)-mitomycin C (MMC) in these cell lines. These objectives were accomplished by measuring in vitro cellular uptake, intracellular trafficking, and cytotoxicity (using a clonogenic assay and median effect analysis), of Dox, MMC, or Dox-MMC co-loaded PLN. Treatment of MDR cells with PLN encapsulating single anticancer agents significantly enhanced cell kill compared to free Dox or MMC solutions. Dox-MMC co-loaded PLN were 20-30-folds more effective in killing MDR cells than free drugs. Co-encapsulated Dox-MMC was more effective in killing MDR cells than single agent-encapsulated PLN. Microscopic images showed perinuclear localization of fluorescently labelled PLN in all cell lines. These results are consistent with our previous results for P-gp overexpressing breast cancer cells suggesting the PLN system can overcome multiple types of membrane efflux pumps increasing the cytotoxicity of Dox-MMC at significantly lower doses than free drugs.

Is targeted therapy feasible in acute myelogenous leukemia?

The prognosis for patients with acute myeloid leukemia (AML) is determined to a large degree by the biology of the leukemic cell. In recent years, the identification and characterization of genetic aberrations has vastly improved our understanding of the pathogenesis of AML. In contrast, however, there has been a lack of clinically meaningful therapeutic advances. The same chemotherapeutic strategies have been applied to AML for several decades now, and while these regimens are effective in inducing remission, most patients relapse within months after initial treatment. Hence, there is an urgent need for novel therapies. We review herein a number of lines of laboratory and clinical trial data supporting the clinical value of targeted treatment approaches that will likely result in improved outcomes for patients with AML.

A tamoxifen derivative, N,N-diethyl-2-[4-(phenylmethyl) phenoxy] ethanamine, selectively targets P-glycoprotein-positive multidrug resistant Chinese hamster cells

DPPE, a tamoxifen derivative with antihistamine activity, was previously shown to potentiate the toxicity of chemotherapeutic drugs. Recently, a Phase III clinical study using doxorubicin with DPPE demonstrated significant increase in the overall survival of breast cancer patients. In this study we examined the effects of DPPE alone on the growth of drug sensitive and P-gp positive CHO cell line. Our results demonstrate DPPE is selectively toxic to P-gp positive cells and the sensitivity to DPPE alone correlated with the levels of P-gp expression. Moreover, in MDR cells, DPPE-induced apoptosis was significantly reduced with Bcl2 overexpression and in the presence of P-gp ATPase inhibitor, PSC833. Furthermore, knockdown of P-gp expression in MDR cells with P-gp-siRNA reversed DPPE sensitivity and increased their sensitivity to doxorubicin and taxol but not to cisplatin. The addition of DPPE to membrane fractions led to dose-dependent increase in P-gp ATPase that was inhibited with PSC833. Moreover, incubation of P-gp positive cells with DPPE led to a significant increase in superoxide levels and a drop in cellular ATP and GSH pools that were reversible with inhibitors of P-gp ATPase. The combined presence of DPPE and the mitochondria electron transport complex III inhibitor, antimycin A, synergized in their effects on the growth of MDR cells but had no effect on the growth of parental drug sensitive cells. Collectively, the results of this study provide a possible mechanism that may be relevant to the clinical results of DPPE in breast cancer trial and demonstrates DPPE as P-gp collateral sensitivity drug.

Reversal of ATP-binding cassette drug transporter activity to modulate chemoresistance: why has it failed to provide clinical benefit?

Enhanced drug extrusion from cells due to the overexpression of the ATP-binding cassette (ABC) drug transporters inhibits the cytotoxic effects of structurally diverse and mechanistically unrelated anticancer agents and is a major cause of multidrug resistance (MDR) of human malignancies. Multiple compounds can suppress the activity of these efflux transporters and sensitize resistant tumor cells, but despite promising preclinical and early clinical data, they have yet to find a role in oncologic practice. Based on the knowledge of the structure, function, and distribution of MDR-related ABC transporters and the results of their preclinical and clinical evaluation, we discuss probable reasons why these inhibitors have not improved the outcome of therapy for cancer patients. We also outline new MDR-reversing strategies that directly target ABC transporters or circumvent relevant signaling pathways.

Tivozanib reverses multidrug resistance mediated by ABCB1 (P-glycoprotein) and ABCG2 (BCRP)

AIM

This study aimed to investigate the mechanism of reversal of multidrug resistance mediated by ABC transporters with tivozanib (AV-951 and KRN-951). Tivozanib is a potent inhibitor of VEGF-1, -2 and -3 receptors.

MATERIALS & METHODS

ABCB1- and ABCG2-overexpressing cell lines were treated with respective substrate antineoplastic agents in the presence or absence of tivozanib.

RESULTS

The results indicate that tivozanib can significantly reverse ABCB1-mediated resistance to paclitaxel, vinblastine and colchicine, as well as ABCG2-mediated resistance to mitoxantrone, SN-38 and doxorubicin. Drug efflux assays showed that tivozanib increased the intracellular accumulation of substrates by inhibiting the ABCB1 and ABCG2 efflux activity. Furthermore, at a higher concentration, tivozanib inhibited the ATPase activity of both ABCB1 and ABCG2 and inhibited the photolabeling of ABCB1 or ABCG2.

CONCLUSION

We conclude that tivozanib at noncytotoxic concentrations has the previously unknown activity of reversing multidrug resistance mediated by ABCB1 and ABCG2 transporters.

Diagnosis and treatment of primary myelodysplastic syndromes in adults: recommendations from the European LeukemiaNet

Within the myelodysplastic syndrome (MDS) work package of the European LeukemiaNet, an Expert Panel was selected according to the framework elements of the National Institutes of Health Consensus Development Program. A systematic review of the literature was performed that included indexed original papers, indexed reviews and educational papers, and abstracts of conference proceedings. Guidelines were developed on the basis of a list of patient- and therapy-oriented questions, and recommendations were formulated and ranked according to the supporting level of evidence. MDSs should be classified according to the 2008 World Health Organization criteria. An accurate risk assessment requires the evaluation of not only disease-related factors but also of those related to extrahematologic comorbidity. The assessment of individual risk enables the identification of fit patients with a poor prognosis who are candidates for up-front intensive treatments, primarily allogeneic stem cell transplantation. A high proportion of MDS patients are not eligible for potentially curative treatment because of advanced age and/or clinically relevant comorbidities and poor performance status. In these patients, the therapeutic intervention is aimed at preventing cytopenia-related morbidity and preserving quality of life. A number of new agents are being developed for which the available evidence is not sufficient to recommend routine use. The inclusion of patients into prospective clinical trials is strongly recommended.

The FLT3 inhibitor quizartinib inhibits ABCG2 at pharmacologically relevant concentrations, with implications for both chemosensitization and adverse drug interactions

The oral second-generation bis-aryl urea fms-like tyrosine kinase 3 (FLT3) inhibitor quizartinib (AC220) has favorable kinase selectivity and pharmacokinetics. It inhibits mutant and wild-type FLT3 in vivo at 0.1 and 0.5 µM, respectively, and has shown favorable activity and tolerability in phase I and II trials in acute myeloid leukemia, with QT prolongation as the dose-limiting toxicity. Co-administration with chemotherapy is planned. We characterized interactions of quizartinib with the ATP-binding cassette (ABC) proteins ABCB1 (P-glycoprotein) and ABCG2 (breast cancer resistance protein). Its effects on uptake of fluorescent substrates and apoptosis were measured by flow cytometry, binding to ABCB1 and ABCG2 drug-binding sites by effects on [¹²⁵I]iodoarylazidoprazosin ([¹²⁵I]-IAAP) photolabeling and ATPase activity, and cell viability by the WST-1 colorimetric assay. Quizartinib inhibited transport of fluorescent ABCG2 and ABCB1 substrates in ABCG2- and ABCB1-overexpressing cells in a concentration-dependent manner, from 0.1 to 5 µM and from 0.5 to 10 µM, respectively, and inhibited [¹²⁵I]-IAAP photolabeling of ABCG2 and ABCB1 with IC₅₀ values of 0.07 and 3.3 µM, respectively. Quizartinib at higher concentrations decreased ABCG2, but not ABCB1, ATPase activity. Co-incubation with quizartinib at 0.1 to 1 µM sensitized ABCG2-overexpressing K562/ABCG2 and 8226/MR20 cells to ABCG2 substrate chemotherapy drugs in a concentration-dependent manner in cell viability and apoptosis assays. Additionally, quizartinib increased cellular uptake of the ABCG2 substrate fluoroquinolone antibiotic ciprofloxacin, which also prolongs the QT interval, in a concentration-dependent manner, predicting altered ciprofloxacin pharmacokinetics and pharmacodynamics when co-administered with quizartinib. Thus quizartinib inhibits ABCG2 at pharmacologically relevant concentrations, with implications for both chemosensitization and adverse drug interactions. These interactions should be considered in the design of treatment regimens combining quizartinib and chemotherapy drugs and in choice of concomitant medications to be administered with quizartinib.

Myelodysplastic syndromes: clinical practice guidelines in oncology

The myelodysplastic syndromes (MDS) represent a heterogeneous group of clonal hematopoietic disorders characterized by cytopenias, dysplasia in one or more myeloid lineages, and the potential for development of acute myeloid leukemia. These disorders primarily affect older adults. The NCCN Clinical Practice Guidelines in Oncology for MDS provide recommendations on the diagnostic evaluation and classification of MDS, risk evaluation according to established prognostic assessment tools (including the new revised International Prognostic Scoring System), treatment options according to risk categories, and management of related anemia.

The Pim kinase inhibitor SGI-1776 decreases cell surface expression of P-glycoprotein (ABCB1) and breast cancer resistance protein (ABCG2) and drug transport by Pim-1-dependent and -independent mechanisms

Overexpression of the ATP-binding cassette (ABC) drug efflux proteins P-glycoprotein (ABCB1) and breast cancer resistance protein (ABCG2) on malignant cells is associated with inferior chemotherapy outcomes. Both, ABCB1 and ABCG2, are substrates of the serine/threonine kinase Pim-1; Pim-1 knockdown decreases their cell surface expression, but SGI-1776, the first clinically tested Pim inhibitor, was shown to reverse drug resistance by directly inhibiting ABCB1-mediated transport. We sought to characterize Pim-1-dependent and -independent effects of SGI-1776 on drug resistance. SGI-1776 at the Pim-1-inhibitory and non-cytotoxic concentration of 1 μM decreased the IC(50)s of the ABCG2 and ABCB1 substrate drugs in cytotoxicity assays in resistant cells, with no effect on the IC(50) of non-substrate drug, nor in parental cells. SGI-1776 also increased apoptosis of cells overexpressing ABCG2 or ABCB1 exposed to substrate chemotherapy drugs and decreased their colony formation in the presence of substrate, but not non-substrate, drugs, with no effect on parental cells. SGI-1776 decreased ABCB1 and ABCG2 surface expression on K562/ABCB1 and K562/ABCG2 cells, respectively, with Pim-1 overexpression, but not HL60/VCR and 8226/MR20 cells, with lower-level Pim-1 expression. Finally, SGI-1776 inhibited uptake of ABCG2 and ABCB1 substrates in a concentration-dependent manner irrespective of Pim-1 expression, inhibited ABCB1 and ABCG2 photoaffinity labeling with the transport substrate [(125)I]iodoarylazidoprazosin ([(125)I]IAAP) and stimulated ABCB1 and ABCG2 ATPase activity. Thus SGI-1776 decreases cell surface expression of ABCB1 and ABCG2 and inhibits drug transport by Pim-1-dependent and -independent mechanisms, respectively. Decrease in ABCB1 and ABCG2 cell surface expression mediated by Pim-1 inhibition represents a novel mechanism of chemosensitization.

Acute myeloid leukaemia in adults

The outlook for patients with acute myeloid leukaemia has improved in the past 30 years. Unlike other cancers, much of this progress is attributable to refinement of supportive treatment, rather than the introduction of new drugs. New antibacterial and antifungal agents, antiemetics, and improved transfusion support have decreased the rate of early death, and morbidity and mortality from allogeneic stem cell transplantation has been substantially reduced. However, more than half of young adult patients and about 90% of older patients still die from their disease. Refractoriness to initial induction treatment and, more frequently, relapse after complete remission, are still the main obstacles to cure. Accordingly, new treatment approaches with mechanisms of action different from those of conventional chemotherapy are needed. Our knowledge of the various chromosomal and molecular abnormalities implicated in the pathogenesis of the many subtypes of the disease has greatly expanded; as a result, clinical research is moving towards the investigation of new non-cytotoxic agents in combination with chemotherapy. The goal is to target the molecular abnormalities identified at diagnosis; however, several aberrations can coexist in subclones of acute myeloid leukaemia, making the disease less likely to be inhibited by a single agent.

Fludarabine, cytarabine, granulocyte-colony stimulating factor and amsacrine: an effective salvage therapy option for acute myeloid leukemia at first relapse

Improved therapeutic options for relapsing patients with acute myeloid leukemia (AML) are urgently needed. Poor outcomes following salvage therapy have been reported in those with short initial remission duration, adverse risk karyotype, prior allograft, older age, FLT3-internal tandem duplication (ITD) AML and prior high-dose cytarabine (HiDAC) induction therapy. We present a cohort of 58 patients (aged 18-70) treated with fludarabine, cytarabine, granulocyte-colony stimulating factor (G-CSF) and amsacrine (FLAG-amsacrine) as salvage chemotherapy for AML at first relapse. 83% had received prior HiDAC-based therapy. The overall complete remission (CR/CR with incomplete blood count recovery [CRi]) rate was 59%, with median event-free survival (EFS) and overall survival (OS) of 6.9 and 10.6 months, respectively. FLAG-amsacrine was an effective bridge to allogeneic transplant with 38% successfully transplanted with excellent outcomes (median OS not reached). FLAG-amsacrine was also effective in elderly patients (≥ 60 years), with 61% achieving second remission. The regimen was well tolerated, with 30- and 42-day treatment-related mortality of 3.4% and 13.8%, respectively. Outcomes remained poor in those with short initial remission duration (<6 months). We conclude that FLAG-amsacrine is a useful salvage option for AML at first relapse.

Amonafide: a future in treatment of resistant and secondary acute myeloid leukemia?

Development of the novel topoisomerase II inhibitor, amonafide, began almost 40 years ago. The drug was selected for further investigation owing to evidence of marked antineoplastic efficacy in preclinical models of cancer. When its usefulness in the treatment of various solid malignancies proved limited, focus was shifted to establishing its use as an antileukemic agent, specifically against secondary and treatment-associated acute myeloid leukemia (AML). While Phase I and II studies gave rise to hopes that amonafide might hold the key to treating older patients, including those with multidrug resistant, cytogenetically unfavorable secondary and treatment-associated AML, when used in combination with cytarabine, it failed to demonstrate a survival advantage over standard-of-care therapy in randomized studies. This article will outline the development of amonafide from the laboratory to the bedside and discuss the potential place that this agent has in the current management of AML.

High TOP2B/TOP2A expression ratio at diagnosis correlates with favourable outcome for standard chemotherapy in acute myeloid leukaemia

Background:

Cytosine arabinoside-based chemotherapy coupled with anthracycline is currently the first-line treatment for acute myeloid leukaemia (AML), but diverse responses to the regimen constitute obstacles to successful treatment. Therefore, outcome prediction to chemotherapy at diagnosis is believed to be a critical consideration.

Methods:

The mRNA expression of 12 genes closely involved in the actions of cytosine arabinoside and anthracycline was evaluated by real-time reverse transcriptase PCR (RT–PCR), in 54 diagnostic bone marrow specimens of M2-subtype AML.

Results:

Low expression levels of ribonucleotide reductase M2 (RRM2) and high expression levels of topoisomerase 2 beta (TOP2B) were correlated with longer survival in a univariate analysis. Another interesting finding is that high ratios of TOP2B/RRM2 and TOP2B/TOP2 alpha (TOP2A) in a combined analysis were also shown to have a prognostic impact for longer survival with improved accuracy. Among the four markers, when adjusted for the influence of other clinical factors in multivariate analysis, the TOP2B/TOP2A ratio was significantly correlated with treatment outcomes; patients with high ratios trended toward longer disease-free survival (HR, 0.24; P=0.002) and overall survival (HR, 0.29; P=0.005).

Conclusion:

Genes with distinct expression profiles such as TOP2B/TOP2A expression ratio at diagnosis can be employed for outcome prediction after the treatment with standard regimens in AML patients with M2 subtype.

Clofarabine plus cytarabine compared with cytarabine alone in older patients with relapsed or refractory acute myelogenous leukemia: results from the CLASSIC I Trial

PURPOSE

To compare the receipt of clofarabine plus cytarabine (Clo+Ara-C arm) with cytarabine (Ara-C arm) in patients ≥ 55 years old with refractory or relapsed acute myelogenous leukemia (AML).

PATIENTS AND METHODS

Patients were randomly assigned to receive either clofarabine (Clo) 40 mg/m(2) or a placebo followed by Ara-C 1 g/m(2) for five consecutive days. The primary end point was overall survival (OS). Secondary end points included event-free survival (EFS), 4-month EFS, overall remission rate (ORR; complete remission [CR] plus CR with incomplete peripheral blood count recovery), disease-free survival (DFS), duration of remission (DOR), and safety.

RESULTS

Among 320 patients with confirmed AML (median age, 67 years), the median OS was 6.6 months in the Clo+Ara-C arm and 6.3 months in the Ara-C arm (hazard ratio [HR], 1.00; 95% CI, 0.78 to 1.28; P = 1.00). The ORR was 46.9% in the Clo+Ara-C arm (35.2% CR) versus 22.9% in the Ara-C arm (17.8% CR; P < .01). EFS (HR: 0.63; 95% CI, 0.49 to 0.80; P < .01) and 4-month EFS (37.7% v 16.6%; P < .01) favored the Clo+Ara-C arm compared with Ara-C arm, respectively. DFS and DOR were similar in both arms. Overall 30-day mortality was 16% and 5% for CLO+Ara-C and Ara-C arms, respectively. In the Clo+Ara-C and Ara-C arms, the most common grade 3 to 4 toxicities were febrile neutropenia (47% v 35%, respectively), hypokalemia (18% v 11%, respectively), thrombocytopenia (16% v 17%, respectively), pneumonia (14% v 10%, respectively), anemia (13% v 0%, respectively), neutropenia (11% v 9%, respectively), increased AST (11% v 2%, respectively), and increased ALT (10% v 3%, respectively).

CONCLUSION

Although the primary end point of OS did not differ between arms, Clo+Ara-C significantly improved response rates and EFS. Study follow-up continues, and the role of clofarabine in the treatment of adult patients with AML continues to be investigated.

Flow cytometry-based assessment of mitoxantrone efflux from leukemic blasts varies with response to induction chemotherapy in acute myeloid leukemia

BACKGROUND

Accurate prediction of chemotherapy drug resistance would aid treatment decisions in acute myeloid leukemia (AML). The aim of this study was to determine if mitoxantrone efflux from AML blasts would correlate with response to induction chemotherapy.

METHODS

Flow cytometry was used to measure the median fluorescence intensity (MFI) for AML blasts incubated with mitoxantrone [an ATP-binding cassette (ABC) transporter substrate] with or without coincubation with cyclosporine A (a broad-spectrum inhibitor of ABC transporters) and a ratio (MFIR) between the inhibited and uninhibited MFI was calculated.

RESULTS

Among 174 AML patient blast samples, the mean MFIR for complete remission (CR) patients was lower than that obtained for induction failure (IF) patients (mean MFIR ± SD 1.62 ± 0.53 for CR after one cycle of chemotherapy vs. 2.22 ± 1.29 for CR after two cycles and 2.59 ± 0.98 for IF, P < 0.001). Logistic regression analysis determined 2.45 as the MFIR threshold above which 29% of patients achieved CR vs. a CR rate of 84% when the MFIR was ≤ 2.45 (P < 0.0001). In AML patients with normal karyotype (n = 80), CR was obtained for 33% of patients with an MFIR > 2.45 vs. 89% of those with MFIR ≤ 2.45 (P < 0.0001). In patients > age 60 (n = 77), 30% vs. 87% of those with MFIR > vs. ≤ 2.45 achieved CR (P < 0.0001).

CONCLUSIONS

This assay of ABC transporter function can potentially predict response to induction chemotherapy in AML.

Drug resistance: still a daunting challenge to the successful treatment of AML

Resistance to chemotherapy remains a challenging issue for patients and their physicians. P-glycoprotein (Pgp, MDR1, ABCB1), as well as a family of structurally and functionally related proteins, are plasma membrane transporters able to efflux a variety of substrates from the cell cytoplasm, including chemotherapeutic agents. The discovery of ABCB1 made available a potential target for pharmacologic down-regulation of efflux-mediated chemotherapy resistance. In patients with acute myeloid leukemia (AML), a neoplasm characterized by proliferation of poorly differentiated myeloid progenitor cells, leukemic cells often express ABCB1 at high levels, which may lead to the development of resistance to chemotherapy. Thus, AML seemed to be a likely cancer for which the addition of drug efflux inhibitors to the chemotherapeutic regimen would improve outcomes in patients. Despite this rational hypothesis, the majority of clinical trials evaluating this strategy have failed to reach a positive endpoint, most recently the Eastern Cooperative Oncology Group E3999 trial. Here we review data suggesting the importance of ABCB1 in AML, address the failure of clinical trials to support a therapeutic strategy aimed at modulating ABCB1-mediated resistance, and consider the type of research that should be conducted in this field going forward.

A phase 1/2 study of chemosensitization with the CXCR4 antagonist plerixafor in relapsed or refractory acute myeloid leukemia

The interaction of acute myeloid leukemia (AML) blasts with the leukemic microenvironment is postulated to be an important mediator of resistance to chemotherapy and disease relapse. We hypothesized that inhibition of the CXCR4/CXCL12 axis by the small molecule inhibitor, plerixafor, would disrupt the interaction of leukemic blasts with the environment and increase the sensitivity of AML blasts to chemotherapy. In this phase 1/2 study, 52 patients with relapsed or refractory AML were treated with plerixafor in combination with mitoxantrone, etoposide, and cytarabine. In phase 1, plerixafor was escalated to a maximum of 0.24 mg/kg/d without any dose-limiting toxicities. In phase 2, 46 patients were treated with plerixafor 0.24 mg/kg/d in combination with chemotherapy with an overall complete remission and complete remission with incomplete blood count recovery rate (CR + CRi) of 46%. Correlative studies demonstrated a 2-fold mobilization in leukemic blasts into the peripheral circulation. No evidence of symptomatic hyperleukocytosis or delayed count recovery was observed with the addition of plerixafor. We conclude that the addition of plerixafor to cytotoxic chemotherapy is feasible in AML, and results in encouraging rates of remission with correlative studies demonstrating in vivo evidence of disruption of the CXCR4/CXCL12 axis.

The controversial role of ABC transporters in clinical oncology

The phenomenon of multidrug resistance in cancer is often associated with the overexpression of the ABC (ATP-binding cassette) transporters Pgp (P-glycoprotein) (ABCB1), MRP1 (multidrug resistance-associated protein 1) (ABCC1) and ABCG2 [BCRP (breast cancer resistance protein)]. Since the discovery of Pgp over 35 years ago, studies have convincingly linked ABC transporter expression to poor outcome in several cancer types, leading to the development of transporter inhibitors. Three generations of inhibitors later, we are still no closer to validating the 'Pgp hypothesis', the idea that increased chemotherapy efficacy can be achieved by inhibition of transporter-mediated efflux. In this chapter, we highlight the difficulties and past failures encountered in the development of clinical inhibitors of ABC transporters. We discuss the challenges that remain in our effort to exploit decades of work on ABC transporters in oncology. In learning from past mistakes, it is hoped that ABC transporters can be developed as targets for clinical intervention.

Analysis of the interaction of induction regimens with p-glycoprotein expression in patients with acute myeloid leukaemia: results from the MRC AML15 trial

Retrospective analyses in non-randomised cohorts suggest that regimens containing fludarabine/Ara C and/or idarubicin/ara C may be more effective than daunorubicin/AraC (DA)-containing regimens in cases of acute myeloid leukaemia (AML) overexpressing p-glycoprotein (Pgp). We prospectively measured Pgp protein and function by flow cytometry in CD45-gated blasts from 434 AML15 trial patients randomised to remission induction therapy with two courses of FLAG-Ida or DA±etoposide (DA/ADE). In all, 34% were positive for Pgp protein and 38% for function. Pgp protein-positive cases had a higher incidence of resistant disease (14% vs 5%), adjusted odds ratio 2.67 (1.14–6.24). There was a trend towards a higher cumulative incidence of relapse at 5 years for Pgp-positive cases (46% vs 55%), adjusted hazard ratio 1.42 (0.98–2.07) (P=0.06). For patients treated with FLAG-Ida, the complete remission (CR) rate was 86% for both Pgp-positive and Pgp-negative patients. In patients treated with DA/ADE, 78% of Pgp-positive and 90% of Pgp-negative cases achieved CR (P=0.06). In analyses of overall survival, there was no interaction between treatment received and Pgp expression. Data for Pgp function followed similar trends. Our data suggest that FLAG-Ida may improve the remission rate for Pgp-positive AML, but the malignant clone is reduced rather than eradicated such that the relapse rate remains high in Pgp-positive patients.

P-glycoprotein and breast cancer resistance protein in acute myeloid leukaemia cells treated with the aurora-B kinase inhibitor barasertib-hQPA

BACKGROUND

Aurora kinases play an essential role in orchestrating chromosome alignment, segregation and cytokinesis during mitotic progression, with both aurora-A and B frequently over-expressed in a variety of human malignancies. Over-expression of the ABC drug transporter proteins P-glycoprotein (Pgp) and Breast cancer resistance protein (BCRP) is a major obstacle for chemotherapy in many tumour types with Pgp conferring particularly poor prognosis in acute myeloid leukaemia (AML). Barasertib-hQPA is a highly selective inhibitor of aurora-B kinase that has shown tumouricidal activity against a range tumour cell lines including those of leukaemic AML origin.

METHODS

Effect of barasertib-hQPA on the pHH3 biomarker and cell viability was measured in a panel of leukaemic cell lines and 37 primary AML samples by flow cytometry. Pgp status was determined by flow cytometry and BCRP status by flow cytometry and real-time PCR.

RESULTS

In this study we report the creation of the cell line OCI-AML3DNR, which over-expresses Pgp but not BCRP or multidrug resistance-associated protein (MRP), through prolonged treatment of OCI-AML3 cells with daunorubicin. We demonstrate that Pgp (OCI-AML3DNR and KG-1a) and BCRP (OCI-AML6.2) expressing AML cell lines are less sensitive to barasertib-hQPA induced pHH3 inhibition and subsequent loss of viability compared to transporter negative cell lines. We also show that barasertib-hQPA resistance in these cell lines can be reversed using known Pgp and BCRP inhibitors. We report that barasertib-hQPA is not an inhibitor of Pgp or BCRP, but by using 14[C]-barasertib-hQPA that it is effluxed by these transporters. Using phosphoHistone H3 (pHH3) as a biomarker of barasertib-hQPA responsiveness in primary AML blasts we determined that Pgp and BCRP positive primary samples were less sensitive to barasertib-hQPA induced pHH3 inhibition (p = <0.001) than samples without these transporters. However, we demonstrate that IC50 inhibition of pHH3 by barasertib-hQPA was achieved in 94.6% of these samples after 1 hour drug treatment, in contrast to the resistance of the cell lines.

CONCLUSION

We conclude that Pgp and BCRP status and pHH3 down-regulation in patients treated with barasertib should be monitored in order to establish whether transporter-mediated efflux is sufficient to adversely impact on the efficacy of the agent.

ATP Binding Cassette transporters associated with chemoresistance: transcriptional profiling in extreme cohorts and their prognostic impact in a cohort of 281 acute myeloid leukemia patients

BACKGROUND

A major issue in the treatment of acute myeloid leukemia is resistance to chemotherapeutic drugs. An increasing number of ATP-Binding-Cassette transporters have been demonstrated to cause resistance to cancer drugs. The aim of this study was to highlight the putative role of other ATP-Binding-Cassette transporters in primary chemoresistant acute myeloid leukemia.

DESIGN AND METHODS

In the first part of this study, using taqman custom arrays, we analyzed the relative expression levels of 49 ATP-Binding-Cassette genes in 51 patients divided into two extreme cohorts, one very sensitive and one very resistant to chemotherapy. In the second part of this study, we evaluated the prognostic impact, in a cohort of 281 patients, of ATP-Binding-Cassette genes selected in the first part of the study.

RESULTS

In the first part of the study, six genes (ATP-Binding-CassetteA2, ATP-Binding-CassetteB1, ATP-Binding-CassetteB6, ATP-Binding-CassettC13, ATP-Binding-CassetteG1, and ATP-Binding-CassetteG2) were significantly over-expressed in the resistant group compared with the sensitive group. In the second cohort, overexpression of 5 of these 6 ATP-Binding-Cassette genes was correlated with outcome in univariate analysis, and only the well-known ATP-Binding-CassetteB1 and G2, and the new ATP-Binding-CassetteG1 in multivariate analysis. Prognosis decreased remarkably with the number of these over-expressed ABC genes. Complete remission was achieved in 71%, 59%, 54%, and 0%, (P=0.0011) and resistance disease in 21%, 37%, 43%, and 100% (P<0.0001) of patients over-expressing 0, 1, 2, or 3, ABC genes, respectively. The number of ATP-Binding-Cassette genes expressed, among ATP-Binding-CassetteB1, G1, and G2, was the strongest prognostic factor correlated, in multivariate analysis, with achievement of complete remission (P=0.01), resistant disease (P=0.01), and overall survival (P=0.02).

CONCLUSIONS

Using expression profiling, we have emphasized the diversity of ATP-Binding-Cassette transporters that cooperate to promote chemoresistance rather than overexpression of single transporters and the putative role of new ATP-Binding-Cassette tranporters, such as ATP-Binding-CassetteG1. Modulation of these multiple transporters might be required to eradicate leukemic cells.

Amonafide: a potential role in treating acute myeloid leukemia

INTRODUCTION

Amonafide is a novel topoisomerase II (Topo II) inhibitor and DNA intercalator that induces apoptotic signaling by blocking the binding of Topo II to DNA. Amonafide retains cytotoxic activity even in the presence of P-glycoprotein (Pgp)-mediated multi-drug resistance (MDR), a major contributor to clinical treatment failure.

AREAS COVERED

In vitro, Pgp-mediated transport (efflux) of amonafide from myeloblasts obtained from patients with secondary acute myeloid leukemia (sAML) was significantly less than efflux of daunorubicin. Amonafide has shown efficacy in patients with sAML, as well as in patients with poor prognostic characteristics such as older age and unfavorable cytogenetics, all associated with MDR. Improved antileukemic activity is observed when amonafide is given together with cytarabine, rather than as monotherapy, with a complete remission rate of ∼ 40% in a recent Phase II trial in sAML. The efficacy of amonafide was maintained among poor-risk subsets of patients, including older patients and patients who had previous myelodysplastic syndrome or previous leukemogenic therapy. The safety profile was acceptable and manageable.

EXPERT OPINION

Amonafide plus cytarabine may have clinical utility in patients with sAML and in other poor-risk subgroups of acute myeloid leukemia (AML). Ongoing trials will help define the role for amonafide in the treatment of poor-risk AML.

Cancer stem cells and side population cells in breast cancer and metastasis

In breast cancer it is never the primary tumour that is fatal; instead it is the development of metastatic disease which is the major cause of cancer related mortality. There is accumulating evidence that suggests that Cancer Stem Cells (CSC) may play a role in breast cancer development and progression. Breast cancer stem cell populations, including side population cells (SP), have been shown to be primitive stem cell-like populations, being long-lived, self-renewing and highly proliferative. SP cells are identified using dual wavelength flow cytometry combined with Hoechst 33342 dye efflux, this ability is due to expression of one or more members of the ABC transporter family. They have increased resistance to chemotherapeutic agents and apoptotic stimuli and have increased migratory potential above that of the bulk tumour cells making them strong candidates for the metastatic spread of breast cancer. Treatment of nearly all cancers usually involves one first-line agent known to be a substrate of an ABC transporter thereby increasing the risk of developing drug resistant tumours. At present there is no marker available to identify SP cells using immunohistochemistry on breast cancer patient samples. If SP cells do play a role in breast cancer progression/Metastatic Breast Cancer (MBC), combining chemotherapy with ABC inhibitors may be able to destroy both the cells making up the bulk tumour and the cancer stem cell population thus preventing the risk of drug resistant disease, recurrence or metastasis.

NCCN Clinical Practice Guidelines in Oncology: myelodysplastic syndromes

These suggested practice guidelines are based on extensive evaluation of the reviewed risk-based data and indicate useful current approaches for managing patients with MDS. Four drugs have recently been approved by the FDA for treating specific subtypes of MDS: lenalidomide for MDS patients with del(5q) cytogenetic abnormalities; azacytidine and decitabine for treating patients with higher-risk or nonresponsive MDS; and deferasirox for iron chelation of iron overloaded patients with MDS. However, because a substantial proportion of patient subsets with MDS lack effective treatment for their cytopenias or for altering disease natural history, clinical trials with these and other novel therapeutic agents along with supportive care remain the hallmark of management for this disease. The role of thrombopoietic cytokines for management of thrombocytopenia in MDS needs further evaluation. In addition, further determination of the effects of these therapeutic interventions on the patient's quality of life is important.(116,119,120,128,129) Progress toward improving management of MDS has occurred over the past few years, and more advances are anticipated using these guidelines as a framework for coordination of comparative clinical trials.