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

G-CSF priming, clofarabine, and high dose cytarabine (GCLAC) for upfront treatment of acute myeloid leukemia, advanced myelodysplastic syndrome or advanced myeloproliferative neoplasm

Prior study of the combination of clofarabine and high dose cytarabine with granulocyte colony-stimulating factor (G-CSF) priming (GCLAC) in relapsed or refractory acute myeloid leukemia resulted in a 46% rate of complete remission despite unfavorable risk cytogenetics. A multivariate analysis demonstrated that the remission rate and survival with GCLAC were superior to FLAG (fludarabine, cytarabine, G-CSF) in the relapsed setting. We therefore initiated a study of the GCLAC regimen in the upfront setting in a multicenter trial. The objectives were to evaluate the rates of complete remission (CR), overall and relapse-free survival (OS and RFS), and toxicity of GCLAC. Clofarabine was administered at 30 mg m(-2) day(-1) × 5 and cytarabine at 2 g m(-2) day(-1) × 5 after G-CSF priming in 50 newly-diagnosed patients ages 18-64 with AML or advanced myelodysplastic syndrome (MDS) or advanced myeloproliferative neoplasm (MPN). Responses were assessed in the different cytogenetic risk groups and in patients with antecedent hematologic disorder. The overall CR rate was 76% (95% confidence interval [CI] 64-88%) and the CR + CRp (CR with incomplete platelet count recovery) was 82% (95% CI 71-93%). The CR rate was 100% for patients with favorable, 84% for those with intermediate, and 62% for those with unfavorable risk cytogenetics. For patients with an antecedent hematologic disorder (AHD), the CR rate was 65%, compared to 85% for those without an AHD. The 60 day mortality was 2%. Thus, front line GCLAC is a well-tolerated, effective induction regimen for AML and advanced myelodysplastic or myeloproliferative disorders.

Final results of a phase 2 trial of clofarabine and low-dose cytarabine alternating with decitabine in older patients with newly diagnosed acute myeloid leukemia

BACKGROUND

The treatment of older adults with acute myeloid leukemia (AML) using standard intensive chemotherapy has been associated with poor outcomes. Effective, less toxic therapies are needed to achieve and maintain durable remissions.

METHODS

One hundred eighteen patients with newly diagnosed AML (median age, 68 years; range, 60-81 years) were treated with a regimen of clofarabine and low-dose cytarabine (LDAC) alternating with decitabine (DAC). The induction consisted of intravenous clofarabine at 20 mg/m(2) on days 1 to 5 combined with subcutaneous LDAC at 20 mg twice daily on days 1 to 10. Responding patients were then treated with a prolonged consolidation/maintenance regimen consisting of cycles of clofarabine plus LDAC alternating with cycles of DAC.

RESULTS

The overall response rate was 68%. The complete remission (CR) rate was 60% overall, 71% for patients with a diploid karyotype, and 50% for patients with an adverse karyotype. The median overall survival (OS) was 11.1 months for all patients and 18.5 months for those achieving a CR/complete remission with incomplete platelet recovery (CRp). The median relapse-free survival for patients achieving a CR/CRp was 14.1 months. According to a multivariate analysis, only adverse cytogenetics and a white blood cell count ≥ 10 × 10(9)/L predicted worse OS. The regimen was well tolerated with 4- and 8-week mortality rates of 3% and 7%, respectively. The most common nonhematologic adverse events were nausea, elevated liver enzymes, and rash.

CONCLUSIONS

The lower intensity, prolonged-therapy program of clofarabine and LDAC alternating with DAC is well tolerated and highly effective in older patients with AML.

Treatment of relapse of acute myeloid leukemia after allogeneic hematopoietic stem cell transplantation

Disease relapse remains a major cause of mortality for patients with acute myeloid leukemia (AML) undergoing allogeneic hematopoietic stem cell transplantation (HSCT). Historically, patients who experience disease relapse after HSCT have a dismal prognosis with very few long-term survivors. There is no standard treatment for patients in this situation given the variability in patient characteristics, disease biology, complications such as graft-vs.-host disease (GVHD) and infections, donor availability, and patient choice. Here, we discuss the current options for treatment of relapsed AML after HSCT including conventional chemotherapy, novel agents, donor leukocyte infusion, second allogeneic HSCT, and emerging therapies.

Low efficacy and high mortality associated with clofarabine treatment of relapsed/refractory acute myeloid leukemia and myelodysplastic syndromes

Clofarabine, a second-generation nucleoside analog, has clinical activity in relapsed or refractory acute myelogenous leukemia (AML) and higher-risk myelodysplastic syndromes (MDS). However, there are few data evaluating performance of clofarabine in populations of patients not enrolled in clinical trials. We reviewed outcomes for 84 patients treated with clofarabine for relapsed or refractory AML or MDS, either with clofarabine as monotherapy (n=19) or in combination with cytarabine (n=65). Using International Working Group (IWG) response criteria, the overall response rate (ORR) of all treated patients was 21%, with a complete response rate with either complete or incomplete hematopoietic recovery (CRR=CR+CRi) of 14%. For combination therapy, ORR was 22% with CRR of 18%, and monotherapy patients had an ORR of 21% with CRR of 11%. Although limited by small numbers, subgroup analysis did not reveal variation in response rates when comparing different risk factors. The 30-day mortality was 21% and median survival was 3 months; a subset of 12 patients who were able to go to transplant had an 18-month median survival. Clofarabine's efficacy in a "real-world" setting appears to be less than has been reported in clinical trials, and treatment is associated with a high early mortality rate.

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).

The role of Clofarabine in the treatment of adults with acute myeloid leukemia

The therapeutic scenario available for adult patients with acute myeloid leukemia (AML) has shown only partial progresses over the last few years. This is especially true for refractory and relapsed AML whose outcome is still extremely disappointing. In this context Clofarabine has offered new promising perspectives within first and second line protocols. This review will firstly describe the initial development in monotherapy, considering then the different potential combination strategies which include both polichemotherapeutic regimens and less conventional approaches with new generation drugs. The potential use of Clofarabine as induction treatment for patients candidate to stem cell transplantation and within conditioning regimens will be finally evaluated.

Inching toward cure of acute myeloid leukemia: a summary of the progress made in the last 50 years

Despite some claims to the contrary, I believe substantial progress has been made in the last half century toward cure of acute myeloid leukemia in children and adults. The tried and true mechanism for this progress has been clinical trial and error. This method has been supplemented with an ever-increasing amount of work at the clinical laboratory interface that is beginning to allow us to develop specific therapy for afflicted individuals. This review details where we stand today and how we got here.

Phase I/II study of clofarabine, etoposide, and mitoxantrone in patients with refractory or relapsed acute leukemia

BACKGROUND

Clofarabine, a second-generation nucleoside analogue, was studied in combination with etoposide and mitoxantrone in acute leukemia.

PATIENTS AND METHODS

In the phase I portion of this study clofarabine was given 20 or 25 mg/m(2) daily for 5 days (Days 2-6) with etoposide 100 mg/m(2) from day 1 to 5 and mitoxantrone 8 mg/m(2) from day 1 to 3. The dose-limiting toxicity was myelosuppression, and dose level 1, with clofarabine 20 mg/m(2) daily for 5 days was identified as the phase 2 dose. In total, 22 patients with relapsed or refractory acute myeloid leukemia (n = 18) and acute lymphocytic leukemia (n = 4) were treated.

RESULTS

Five of 22 patients (23%) achieved complete response (CR), and 3 (13%) achieved CR with incomplete platelet recovery; an overall response rate of 36%. Median overall survival was 167 days (range, 22-1327 days). For 2 patients this regimen represented an effective bridge to allogeneic stem cell transplantation.

CONCLUSION

Clofarabine in combination with etoposide and mitoxantrone is tolerable and shows significant activity in relapsed and refractory acute leukemia in adults.

AAML0523: a report from the Children's Oncology Group on the efficacy of clofarabine in combination with cytarabine in pediatric patients with recurrent acute myeloid leukemia

BACKGROUND

The discovery of new, effective non-anthracycline-based reinduction regimens for children with recurrent acute myeloid leukemia (AML) is critical. In this phase 1/2 study, the tolerability and overall response rate of clofarabine in combination with cytarabine was investigated in children with recurrent/refractory AML.

METHODS

AAML0523 enrolled 49 children with AML in first recurrence or who were refractory to induction therapy. The study consisted of a dose-finding phase (9 patients) and an efficacy phase (40 patients). Two children received clofarabine at a dose of 40 mg/m(2)/day and 47 children at a dose of 52 mg/m(2)/day.

RESULTS

Toxicities typical for intensive chemotherapy regimens were observed at all doses of clofarabine. The recommended pediatric phase 2 dose of clofarabine in combination with cytarabine was 52 mg/m(2)/day for 5 days. Of 48 evaluable patients, the overall response rate (complete remission plus complete remission with partial platelet recovery) was 48%. Four patients met conventional criteria for complete remission with incomplete count recovery. Twenty-one of 23 responders subsequently underwent hematopoietic stem cell transplantation. The overall survival rate at 3 years was 46% for responders compared with 16% for nonresponders (P < .001). Patients found to have no minimal residual disease at the end of the first cycle by flow cytometric analysis had superior overall survival after 1 year (100% vs 38%; P = .01).

CONCLUSIONS

The combination of clofarabine and cytarabine yielded an acceptable response rate without excess toxicity in children with recurrent AML. The nearly 50% survival rate reported in responders is highly encouraging in these high-risk patients and suggests that this combination is an effective bridge to hematopoietic stem cell transplantation.

Efficacy and feasibility of cyclophosphamide combined with intermediate- dose or high-dose cytarabine for relapsed and refractory acute myeloid leukemia (AML)

BACKGROUND

Approximately, 70 % of adult patients with de novo acute myeloid leukemia (AML) achieve a complete remission (CR) while 10-20 % of AML are refractory to induction chemotherapy. Furthermore, a significant proportion of AML patients in CR will relapse during or after consolidation treatment. There is no evidence for a standard salvage regimen and most centers use a combination of an anthracycline and cytarabine (AraC). The aim of this study was to investigate the impact of two age-adjusted regimens containing AraC and cyclophosphamide applied for the treatment of relapsed or refractory AML.

PATIENTS AND METHODS

We retrospectively analyzed 60 patients (24 male, 36 female; median age 56 years) with relapsed or refractory AML who were treated with a combination of AraC and cyclophosphamide monocentrically between October 2000 and January 2013. Two different protocols containing either high-dose (hAC) or intermediate-dose cytarabin (iAC) have been applied dependent on age and performance status.

RESULTS

We demonstrate an overall response rate (CR + PR) induced by hAC and iAC of 56.7 %. Importantly, a complete remission rate (CR + CRp) of 52.2 % was found in patients who received the hAC regimen while only 8.8 % of patients achieved a CR following the iAC protocol (p < 0.001). The rate of refractory disease was 26.1 and 47.1 %, respectively. High-risk cytogenetics, i.e., a complex aberrant or monosomal karyotype had no effect on achievement of CR after hAC. In addition, there was no impact of activating FLT3 mutations on response to treatment according to the hAC regimen. In the cohort of patients treated with the iAC protocol, treatment-related mortality of 11.8 % within 60 days was observed but none of the patients who received the hAC regimen died within the first 2 months following chemotherapy. The toxicity profile was acceptable at both cytarabine dose levels. Importantly, 19 patients (82.6 %) of the hAC cohort underwent allogeneic hematopoietic stem cell transplantation (HSCT) as consecutive treatment.

CONCLUSION

The hAC regimen represents a promising therapeutic approach to induce a second CR in younger patients with relapsed or refractory AML prior to HSCT without using anthracyclines.

Effectiveness of primary anti-Aspergillus prophylaxis during remission induction chemotherapy of acute myeloid leukemia

Although antifungal prophylaxis is frequently administered to patients with acute myeloid leukemia (AML) during remission-induction chemotherapy (RIC), its impact on reducing invasive fungal infections (IFIs) outside clinical trials is rarely reported. We performed a retrospective observational study to identify risk factors for development of IFIs (definite or probable, using revised European Organization for Research and Treatment of Cancer [EORTC] criteria) and all-cause mortality in a cohort of 152 AML patients receiving RIC (2009 to 2011). We also compared rates of IFI and mortality in patients who received echinocandin versus anti-Aspergillus azole (voriconazole or posaconazole) prophylaxis during the first 120 days of RIC. In multivariate analysis, clofarabine-based RIC (hazard ratio [HR], 3.5; 95% confidence interval [CI], 1.5 to 8.3; P = 0.004) and echinocandin prophylaxis (HR, 4.6; 95% CI, 1.8 to 11.9; P = 0.002) were independently associated with higher rates of IFI rates during RIC. Subsequent analysis failed to identify any malignancy- or chemotherapy-related covariates linked to echinocandin prophylaxis that accounted for the higher rates of breakthrough IFI. Although the possibility of other confounding variables cannot be excluded, our findings suggest that echinocandin-based prophylaxis during RIC for AML may be associated with a higher risk of breakthrough IFI.

Prospective, multicenter, phase II study on reducing the dosage of idarubicin and FLAG for patients younger than 65 years with resistant acute myeloid leukemia: a comparison with a higher dosage trial

We previously assessed continuous infusion (CI) of fludarabine and cytarabine plus idarubicin (CI-FLAG1) for patients under 65 years of age with resistant acute myeloid leukemia. Induction chemotherapy consisted of idarubicin (IDA) plus fludarabine and cytarabine (ARAC) as a 24-hour CI. In response to induction, 31.6% of patients achieved complete remission (CR) and in 68.4% the treatment failed. We concluded that CI-FLAG1 carried a high risk of toxicity and reduced CI-FLAG doses were recommended. Therefore, we revised the protocol (CI-FLAG2) by reducing the dose of IDA and ARAC. In total, 38 and 68 patients were enrolled into CI-FLAG1 and CI-FLAG2, respectively. When comparing outcomes between CI-FLAG1 and CI-FLAG2, there were no differences in terms of the CR rate (p = 0.306) and the overall response rate (ORR; p = 0.206). The treatment failure patterns were different between CI-FLAG1 and CI-FLAG2. The median overall survival showed only a trend towards longer survival in CI-FLAG2 (p = 0.074). Among intermediate-risk patients, there were high response rates favoring CI-FLAG2 in terms of the CR rate (p = 0.108), the ORR (p = 0.031), and overall survival (p = 0.033). This represented a relatively improved response rate compared to our previous study. There was decreased aplasia with dose reductions at the expense of increased resistance. A reduced dose of CI-FLAG might be most beneficial for intermediate-risk groups.

The combination of fludarabine, cytarabine and etoposide is an active and well-tolerated regimen in relapsed/refractory acute myeloid leukemia

We retrospectively reviewed the outcome of 20 consecutive subjects with refractory/relapsed acute myeloid leukemia (AML; 9 refractory and 11 relapsed) treated at our institution with a fludarabine, cytarabine and etoposide (FCE) salvage regimen. Of 20 patients with refractory/relapsed AML, 15 (75%) achieved complete remission (CR)/CR with incomplete peripheral blood count recovery (CRi), including 14 CR and 1 CRi. The 4- and 8-week treatment-related mortality (TRM) for all patients during reinduction was 0 and 5%, respectively. Eight of 15 patients (53%) who successfully achieved CR were able to undergo allogeneic hematopoietic stem cell transplantation with a 0% non-relapse mortality rate. FCE is a new, well-tolerated, anthracycline-free regimen, which has a promising activity in relapsed/refractory AML and is associated with low TRM in this high-risk population.

Developmental therapeutics in acute myelogenous leukemia: are there any new effective cytotoxic chemotherapeutic agents out there?

Therapies for AML have remained mostly unchanged since the introduction of anthracyline- and cytarabine-based regimens in the 1970s. Though some changes have been made in the dosing of anthracylines, in the choice of consolidation regimens versus allogeneic stem cell transplant, and in supportive care, clinical outcomes remain poor for most patients. As we continue to strive for better treatment options to improve upon outcomes, different agents, both chemotherapeutic and targeted therapies, are being studied. Here we discuss new chemotherapeutic agents that show promise in recent clinical trials and attempt to answer the question if there are any new effective cytotoxic chemotherapy agents out there.

New agents: great expectations not realized

A number of new agents in acute myeloid leukemia (AML) have held much promise in recent years, but most have failed to change the therapeutic landscape. Indeed, with the exception of gemtuzumab ozogamicin (which was subsequently voluntarily withdrawn from the commercial market), no new agent has been approved for acute myeloid leukemia (AML) beyond the 7 + 3 regimen, which was has been in use for over 40 years. This review touches upon the potential reasons for these failures and explores the newer therapeutic approaches being pursued in AML.

Relapsed acute myeloid leukemia: why is there no standard of care?

Relapse after achieving a prior response remains one of the most important obstacles to improving the outcome of patients with acute myeloid leukemia (AML). Although overall, the majority of patients with disease relapse do poorly, this is by no means uniform and a number of predictors of outcome have been identified. Previously, most trials of investigational agents in the setting of disease relapse in AML have accrued a wide range of patients with widely different patient and disease characteristics. With increased understanding of the biology of the neoplastic change in AML, and better identification of disease subsets based on their molecular characterization, target-specific novel agents are being developed that will hopefully lead to better strategies, not only for treating relapsed disease, but also for the initial induction treatment.

Outcome of older patients with acute myeloid leukemia in first relapse

To provide data for future drug evaluation, we analyzed the outcome of 393 patients aged 50 years or older (median, 64 years) with AML in first relapse after treatment in recent ALFA trials. Salvage options were retrospectively classified as follows: best supportive care (BSC), low-dose cytarabine (LDAC), gemtuzumab ozogamicin (GO), intensive chemotherapy (ICT), or ICT combined with GO. Second complete remission (CR2) rate was 31% and median post-relapse survival was 6.8 months (0, 17, 42.5, 53, and 80% and 3.2, 5.6, 8.9, 9, and 19.8 months in BSC, LDAC, GO, ICT, and ICT + GO subsets, respectively). Age, performance status, WBC, CR1 duration, and favorable AML karyotype, but not other cytogenetic or molecular features, influenced post-relapse outcome. Multivariate adjustment and propensity score matching showed that intensive salvage (ICT/ICT+GO/GO versus LDAC/BSC) was associated with longer post-relapse survival, at least in patients with CR1 duration ≥12 months (P = 0.001 and 0.0005, respectively). Of interest, GO appeared to be as effective as standard ICT, and ICT + GO combination more effective than standard ICT. In conclusion, older patients with CR1 duration ≥12 months appeared to benefit from intensive salvage and results observed with GO-containing salvage suggest that GO combination studies should be actively pursued in this setting.

Acute myeloid leukemia in the elderly: do we know who should be treated and how?

Abstract Acute myeloid leukemia (AML) in the elderly is associated with several distinctive biological and clinical features compared to younger patients. Despite the advances in supportive care and the introduction of less intensive chemotherapy regimens, the overall outcome for this population remains poor. More importantly, the decision making process for choosing the appropriate treatment for individual patients, based on their comorbidities and the biological features of their disease, continues to be challenging for treating physicians. Currently, a significant number of elderly patients with AML do not receive treatment above and beyond supportive care; several studies have suggested that patients who receive any therapy have a better outcome than patients who receive palliation alone. Furthermore, the development of novel, targeted and less intensive therapies is providing new options suitable for older patients with multiple comorbidities and with high risk disease features. In this review, we highlight the challenges that face treating physicians when encountering elderly patients with AML and describe some of the potential strategies under development for treating older patients with AML and the available data from recent clinical trials.

Phase II trial of clofarabine and daunorubicin as induction therapy for acute myeloid leukemia patients greater than or equal to 60 years of age

We designed a phase II study evaluating the upfront combination of clofarabine and daunorubicin in acute myeloid leukemia (AML) patients≥60 years old. The median age of the 21 patients was 69 (range 60-85) years. Fourteen patients (67%) had unfavorable risk features. The principal toxicities were grade ≥3 infections and prolonged myelosuppression. Three (14%) deaths occurred from infectious complications. Six (28.6%) patients achieved complete remission including three (21.4%) of 14 patients with unfavorable AML. The median disease-free survival was 6.8 months and the median overall survival was 11.2 months.

Update on optimal management of acute myeloid leukemia

Acute myeloid leukemia (AML) represents a malignant accumulation of immature myeloid cells in the marrow, presenting with impaired hematopoiesis and its attendant complications, including bleeding, infection, and organ infiltration. Chromosomal abnormalities remain the most powerful predictors of AML prognosis and help to identify a subgroup with favorable prognosis. However, the majority of AML patients who are not in the favorable category succumb to the disease. Therefore, better efforts to identify those patients who may benefit from more aggressive and investigational therapeutic approaches are needed. Newer molecular markers aim at better characterizing the large group of intermediate-risk patients and to identify newer targets for therapy. A group that has seen little improvement over the years is the older AML group, usually defined as age ≥ 60. Efforts to develop less intensive but equally efficacious therapy for this vulnerable population are underway.

The combination of valproic acid, all-trans retinoic acid and low-dose cytarabine as disease-stabilizing treatment in acute myeloid leukemia

Background

A large proportion of patients with acute myeloid leukemia (AML) are not fit for intensive and potentially curative therapy due to advanced age or comorbidity. Previous studies have demonstrated that a subset of these patients can benefit from disease-stabilizing therapy based on all-trans retinoic acid (ATRA) and valproic acid. Even though complete hematological remission is only achieved for exceptional patients, a relatively large subset of patients respond to this treatment with stabilization of normal peripheral blood cell counts.

Methods

In this clinical study we investigated the efficiency and safety of combining (i) continuous administration of valproic acid with (ii) intermittent oral ATRA treatment (21.5 mg/m² twice daily) for 14 days and low-dose cytarabine (10 mg/m² daily) for 10 days administered subcutaneously. If cytarabine could not control hyperleukocytosis it was replaced by hydroxyurea or 6-mercaptopurin to keep the peripheral blood blast count below 50 × 10⁹/L.

Results

The study included 36 AML patients (median age 77 years, range 48 to 90 years) unfit for conventional intensive chemotherapy; 11 patients responded to the treatment according to the myelodysplastic syndrome (MDS) response criteria and two of these responders achieved complete hematological remission. The most common response to treatment was increased and stabilized platelet counts. The responder patients had a median survival of 171 days (range 102 to > 574 days) and they could spend most of this time outside hospital, whereas the nonresponders had a median survival of 33 days (range 8 to 149 days). The valproic acid serum levels did not differ between responder and nonresponder patients and the treatment was associated with a decrease in the level of circulating regulatory T cells.

Conclusion

Treatment with continuous valproic acid and intermittent ATRA plus low-dose cytarabine has a low frequency of side effects and complete hematological remission is seen for a small minority of patients. However, disease stabilization is seen for a subset of AML patients unfit for conventional intensive chemotherapy.

Elacytarabine (CP-4055) in the treatment of acute myeloid leukemia

Elacytarabine (formerly CP-4055) is a lipid-conjugated derivative of the nucleoside analog cytarabine. Elacytarabine was rationally designed to circumvent cytarabine resistance related to decreased cellular uptake, due to the ability of the lipophilic drug moiety to enter the cell without the requirement of specialized nuclear transport proteins, including the hENT1. In preclinical and clinical studies, elacytarabine has demonstrated both safety and efficacy in acute myeloid leukemia (AML), with noteworthy activity among the cytarabine-refractory AML population. Elacytarabine was granted orphan drug designation status from the European Commission in 2007 and from the US FDA in 2008, with a fast-track approval designation from the FDA in 2010. Results of a recent randomized Phase III clinical trial, however, failed to show superiority of elacytarabine over the investigator's choice of therapy for relapsed or refractory AML.

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.

Phase I/II trial of clofarabine and cytarabine in children with relapsed/refractory acute lymphoblastic leukemia (AAML0523): a report from the Children's Oncology Group

BACKGROUND

The discovery of effective re-induction regimens for children with more than one relapse of acute lymphoblastic leukemia (ALL) remains elusive. The novel nucleoside analog clofarabine exhibits modest single agent efficacy in relapsed ALL, though optimal combinations of this agent with other active chemotherapy drugs have not yet been defined. Herein we report the response rates of relapsed ALL patients treated on Children's Oncology Group study AAML0523, a Phase I/II study of the combination of clofarabine and cytarabine.

PROCEDURE

AAML0523 enrolled 21 children with ALL in second or third relapse, or those refractory to re-induction therapy. The study consisted of two phases: a dose finding phase and an efficacy phase. The dose finding portion consisted of a single dose escalation/de-escalation of clofarabine for 5 days in combination with a fixed dose of cytarabine (1 g/m(2)/day for 5 days). Eight patients received clofarabine at 40 mg/m(2)/day and 13 patients at 52 mg/m(2)/day.

RESULTS

Toxicities observed at all doses of clofarabine were typical of intensive chemotherapy regimens for leukemia, with infection being the most common. We did not observe significant hepatotoxicity as reported in other clofarabine combination regimens. The recommended pediatric Phase II dose of clofarabine in combination with cytarabine for the efficacy portion of AAML0523 was 52 mg/m(2). Of 21 patients with ALL, 3 (14%) achieved a complete response (CR). Based on the two-stage design definition of first-stage inactivity, the therapy was deemed ineffective.

CONCLUSION

The combination of clofarabine and cytarabine in relapsed/refractory childhood ALL does not warrant further clinical investigation.

A novel clofarabine bridge strategy facilitates allogeneic transplantation in patients with relapsed/refractory leukemia and high-risk myelodysplastic syndromes

Patients with relapsed/refractory leukemias or advanced myelodysplastic syndrome (MDS) fare poorly following allogeneic hematopoietic cell transplant (HCT). We report prospective phase II study results of 29 patients given clofarabine 30 mg/m(2)/day i.v. × 5 days followed immediately by HCT conditioning while at the cytopenic nadir. A total of 15/29 patients (52%) were cytoreduced according to pre-defined criteria (cellularity <20% and blasts <10%). Marrow cellularity (P<0.0001) and blast% (P=0.03) were reduced. Toxicities were acceptable, with transient hyperbilirubinemia (48%) and gr3-4 infections (10%). In all, 28/29 proceeded to transplant; 27 received ATG or alemtuzumab. Post HCT, 180 day non-relapse mortality (NRM) was 7% (95% confidence interval (CI): 1-21), relapse was 29% (95% CI: 13-46) and OS was 71% (95% CI: 51-85), comparing favorably to published data for high-risk patients. Two-year graft vs host disease incidence was 40% (95% CI: 21-58) and 2 year OS was 31% (95% CI: 14-48). Disease at the nadir correlated with inferior OS after HCT (HR=1.22 for each 10% marrow blasts, 95% CI: 1.02-1.46). For AML/MDS patients, there was a suggestion that successful cytoreduction increased PFS (330 vs 171 days, P=0.3) and OS (375 vs 195 days, P=0.31). Clofarabine used as a bridge to HCT reduces disease burden, is well tolerated, and permits high-risk patients to undergo HCT with acceptable NRM. Late relapses are common; thus, additional strategies should be pursued. NCT-00724009.

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.

Older and new purine nucleoside analogs for patients with acute leukemias

Purine nucleoside analogs (PNAs) compose a class of cytotoxic drugs that have played an important role in the treatment of hematological neoplasms, especially lymphoid and myeloid malignancies. All PNA drugs have a chemical structure similar to adenosine or guanosine, and they have similar mechanisms of action. They have many intracellular targets: they act as antimetabolites, competing with natural nucleosides during DNA or RNA synthesis, and as inhibitors of key cell enzymes. In contrast to other antineoplastic drugs, PNAs act cytotoxically, both in the mitotic and quiescent cell cycle phases. In the last few years, three PNAs have been approved for the treatment of lymphoid malignancies and other hematological disorders: 2-chlorodeoxyadenosine (2-CdA), fludarabine and pentostatin. 2-CdA and fludarabine are also active in the treatment of acute myeloid leukemia (AML). These drugs, in combination with cytarabine and other agents, are commonly used as salvage regimens in relapsed or refractory AML. Moreover, the addition of 2-CdA to the standard induction regimen is associated with an increased rate of complete remission and improved survival of adult patients with AML. More recently three novel PNAs have been synthesized and introduced into clinical trials: clofarabine, nelarabine and forodesine. Clofarabine is the most promising PNA in current clinical trials in pediatric and adult patients with acute leukemias. Nelarabine is more cytotoxic in T-lineage than in B-lineage leukemias. Clofarabine and nelarabine have been approved for the treatment of refractory patients with acute lymphoblastic leukemia (ALL) and lymphoblastic lymphoma. Clofarabine is also an active drug in AML treatment when administered either alone or in combination regimens as front-line treatment and in relapsed or refractory patients. Unlike other PNA, forodesine is not incorporated into DNA but displays a highly selective purine nucleoside phosphorylase inhibitory action. Forodesine is undergoing clinical trials for the treatment of T-cell malignancies, including T-cell ALL. This article summarizes recent achievements in the mechanism of action, pharmacological properties and clinical activity and toxicity of PNAs, as well as their emerging role in lymphoid and myeloid acute leukemias.

Acute myeloid leukemia: 2013 update on risk-stratification and management

DISEASE OVERVIEW

Acute myeloid leukemia (AML) results from accumulation of abnormal blasts in the marrow. These cells interfere with normal hematopoiesis, can escape into the peripheral blood, and infiltrate CSF and lung. It is likely that many different mutations, epigenetic aberrations, or abnormalities in micro RNA expression can produce the same morphologic disease with these differences responsible for the very variable response to therapy, which is AMLs principal feature.

DIAGNOSIS

This rests on demonstration that the marrow or blood has > 20% blasts of myeloid lineage. Blast lineage is assessed by multiparameter flow cytometry, with CD33 and CD13 being surface markers typically expressed by myeloid blasts. It should be realized that clinical/prognostic considerations, not the blast % per se, should be the main factor determining how a patient is treated.

RISK STRATIFICATION

Two features determine risk: the probability of treatment-related mortality (TRM) and, more important, even in patients aged >75 with Zubrod performance status 1, the probability of resistance to standard therapy despite not incurring TRM. The chief predictor of resistance is cytogenetics, with a monosomal karyotype (MK) denoting the disease is essentially incurable with standard therapy even if followed by a standard allogeneic transplant (HCT). The most common cytogentic finding is a normal karyotype(NK) and those of such patients with an NPM1 mutation but no FLT3 internal tandem duplication (ITD), or with a CEBPA mutation, have a prognosis similar to that of patients with the most favorable cytogenetics (inv 16 or t[8;21]) (60-70% cure rate). In contrast, NK patients with a FLT3 ITD have only a 30-40% chance of cure even after HCT. Accordingly analyses of NPM1, FLT3, and CEBPA should be part of routine evaluation, much as is cytogenetics. Risk is best assessed considering several variables simultaneously rather than, for example, only age. Increasing evidence indicates that other mutations and abnormalities in microRNA (miRNA) expression also affect resistance as do post treatment factors, in particular the presence of minimal residual disease. These newer mutations and MRD are discussed in this update.

RISK-ADAPTED THERAPY

Patients with inv (16) or t(8;21) or who are NPM1+/FLT3ITD-can receive standard therapy (daunorubicin + cytarabine) and should not receive HCT in first CR. It seems likely that use of a daily daunorubicin dose of 90 mg/m(2) will further improve outcome in these patients. There appears no reason to use doses of cytarabine > 1 g/m(2) (for example bid X 6 days), as opposed to the more commonly used 3 g/m(2) . Patients with an unfavorable karyotype (particularly MK) are unlikely to benefit from standard therapy (even with dose escalation) and are thus prime candidates for clinical trials of new drugs or new approaches to HCT; the latter should be done in first CR. Patients with intermediate prognoses (for example NK and NPM and FLT3ITD negative) should also receive HCT in first CR and can plausibly receive either investigational or standard induction therapy, with the same prognostic information about standard therapy leading one patient to choose the standard and another an investigational option. This update discusses results with newer agents: quizartinib and crenolanib, gemtuzumab ozogamicin, clofarabine and cladribine, azacitidine and decitabine, volasertib, and means to prevent relapse after allogeneic transplant. The diagnosis of AML essentially is made as it was in 2012. Thus this review will emphasize new developments in risk stratification and treatment using as references many papers published in 2012.

The role of clofarabine in acute myeloid leukemia

Clofarabine is a second-generation purine nucleoside analog that has been synthesized to overcome the limitations and incorporate the best qualities of fludarabine and cladribine. Clofarabine acts by inhibiting ribonucleotide reductase and DNA polymerase, thereby depleting the amount of intracellular deoxynucleoside triphosphates available for DNA replication. Compared to its precursors, clofarabine has an increased resistance to deamination and phosphorolysis, and hence better stability as well as higher affinity to deoxycytidine kinase (dCyd), the rate-limiting step in nucleoside phosphorylation. Since the initiation of the first phase I study of clofarabine in 1993 in patients with hematologic and solid malignancies, clofarabine has demonstrated single-agent antitumor activity in adult acute leukemia, including acute myeloid leukemia (AML). Due to its unique properties of biochemical modulation when used in combination with other chemotherapy drugs, mainly cytarabine, combination regimens containing clofarabine have been evaluated. A review of the English literature was performed that included original articles and related reviews from the MEDLINE (PubMed) database and from abstracts based on the publication of meeting materials. This review describes the development, pharmacology and clinical activity of clofarabine, as well as its emerging role in the treatment of adult patients with AML and myelodysplastic syndrome.

Conventional chemotherapy or hypomethylating agents for older patients with acute myeloid leukaemia?

Acute myeloid leukaemia (AML) is the second more frequent hematologic malignancy in developed countries and primarily affects older adults with a median age at diagnosis of 69 years. Given the progressive ageing of the general population, the incidence of the disease in elderly people is expected to further increase in the years to come. Along with cytogenetics at diagnosis, age represents the most relevant prognostic factor in AML, in that the outcome steadily declines with increasing age. Reasons for poor prognosis include more frequent unfavourable karyotype and other adverse biologic characteristics, such as high rates of expression of genes drug resistance related and high prevalence of secondary AML. Noticeably, as compared with young adults, poorer results in elderly patients have been reported within any cytogenetic and molecular prognostic subgroup, because of frequent comorbid diseases, which render many patients ineligible to intensive chemotherapy. Therefore, predictive models have been developed with the aim of achieving best therapeutic results avoiding unnecessary toxicity. Following conventional induction therapy, older AML patients have complete remission rates in the range of 45-65%, and fewer than 10% of them survive for a minimum of 5 years. On the other hand, hypomethylating agents, such as azacytidine and decitabine offer the possibility of long-term disease control without necessarily achieving complete remission and can represent a reasonable alternative to intensive chemotherapy. Either intensive chemotherapy or hypomethylating agents have lights and shadows, and the therapeutic selection is often influenced by physician's and patient's attitude rather than definite criteria. Research is progress in order to assess predictive biologic factors, which would help clinicians in the selection of patients who can take actual benefit from different therapeutic options.

High-risk acute myelogenous leukemia: treatment today ... and tomorrow

High-risk acute myelogenous leukemia (AML) constitutes a distinct subset of disease based on clinical and biological characteristics and comprises a significant percentage of all cases of adult AML. Biologic features such as distinct clonal cytogenetic and molecular abnormalities identify a subgroup of AML patients characterized by poor response to induction chemotherapy and poor long-term survival after treatment with consolidation chemotherapy. Clinical variables that predict for poor response include AML relapsed after less than 1 year of remission and AML characterized by resistance to conventional agents. We review here our understanding of the defining biologic subtypes of AML and discuss how adequate initial evaluation can be used to inform the choice of treatment. By defining high-risk biologic and clinical variables, a strong case can be made for treating patients with investigational agents, with treatment directed at distinct cytogenetic or molecular abnormalities. Allogeneic transplantation is the only form of therapy available outside of the setting of a clinical trial that may offer a chance for long-term survival for patients with high-risk AML.

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.

Acute myeloid leukemia: focus on novel therapeutic strategies

Acute myeloid leukemia (AML) is a heterogeneous disease with variable clinical outcomes. Cytogenetic analysis reveals which patients may have favorable risk disease, but 5-year survival in this category is only approximately 60%, with intermediate and poor risk groups faring far worse. Advances in our understanding of the biology of leukemia pathogenesis and prognosis have not been matched with clinical improvements. Unsatisfactory outcomes persist for the majority of patients with AML, particularly the elderly. Novel agents and treatment approaches are needed in the induction, post-remission and relapsed settings. The additions of clofarabine for relapsed or refractory disease and the hypomethylating agents represent recent advances. Clinical trials of FLT3 inhibitors have yielded disappointing results to date, with ongoing collaborations attempting to identify the optimal role for these agents. Potential leukemia stem cell targeted therapies and treatments in the setting of minimal residual disease are also under investigation. In this review, we will discuss recent advances in AML treatment and novel therapeutic strategies.