Clofarabine and cytarabine combination as induction therapy for acute myeloid leukemia (AML) in patients 50 years of age or older

Chemotherapy-induced acute kidney injury: epidemiology, pathophysiology, and therapeutic approaches

Despite significant advancements in oncology, conventional chemotherapy remains the primary treatment for diverse malignancies. Acute kidney injury (AKI) stands out as one of the most prevalent and severe adverse effects associated with these cytotoxic agents. While platinum compounds are well-known for their nephrotoxic potential, other drugs including antimetabolites, alkylating agents, and antitumor antibiotics are also associated. The onset of AKI poses substantial risks, including heightened morbidity and mortality rates, prolonged hospital stays, treatment interruptions, and the need for renal replacement therapy, all of which impede optimal patient care. Various proactive measures, such as aggressive hydration and diuresis, have been identified as potential strategies to mitigate AKI; however, preventing its occurrence during chemotherapy remains challenging. Additionally, several factors, including intravascular volume depletion, sepsis, exposure to other nephrotoxic agents, tumor lysis syndrome, and direct damage from cancer's pathophysiology, frequently contribute to or exacerbate kidney injury. This article aims to comprehensively review the epidemiology, mechanisms of injury, diagnosis, treatment options, and prevention strategies for AKI induced by conventional chemotherapy.

Nucleoside-based anticancer drugs: Mechanism of action and drug resistance

Nucleoside-based drugs, recognized as purine or pyrimidine analogs, have been potent therapeutic agents since their introduction in 1950, deployed widely in the treatment of diverse diseases such as cancers, myelodysplastic syndromes, multiple sclerosis, and viral infections. These antimetabolites establish complex interactions with cellular molecular constituents, primarily via activation of phosphorylation cascades leading to consequential interactions with nucleic acids. However, the therapeutic efficacy of these agents is frequently compromised by the development of drug resistance, a continually emerging challenge in their clinical application. This comprehensive review explores the mechanisms of resistance to nucleoside-based drugs, encompassing a wide spectrum of phenomena from alterations in membrane transporters and activating kinases to changes in drug elimination strategies and DNA damage repair mechanisms. The critical analysis in this review underlines complex interactions of drug and cell and also guides towards novel therapeutic strategies to counteract resistance. The development of targeted therapies, novel nucleoside analogs, and synergistic drug combinations are promising approaches to restore tumor sensitivity and improve patient outcomes.

Acute Myeloid Leukemia Treatment in the Elderly: A Comprehensive Review of the Present and Future

BACKGROUND

Acute myeloid leukemia (AML) is a disease of the hematopoietic system that remains a therapeutic challenge despite advances in our understanding of the underlying cancer biology in the past decade. It is also an affliction of the elderly that predominantly affects patients over 60 years of age. Standard therapy involves intensive chemotherapy that is often difficult to tolerate in older populations. Fortunately, recent developments in molecular targeting have shown promising results in treating leukemia, paving the way for novel treatment strategies that are easier to tolerate.

SUMMARY

Venetoclax, a BCL-2 inhibitor, when combined with a hypomethylating agent, has proven to be a highly effective and well-tolerated drug and established itself as a new standard for treating AML in patients who are unfit for standard intensive therapy. Other targeted therapies include clinically proven and FDA-approved agents, such as IDH1/2 inhibitors, FLT3 inhibitors, and Gemtuzumab, as well as newer and more experimental drugs such as magrolimab, PI-kinase inhibitors, and T-cell engaging therapy. Some of the novel agents such as magrolimab and menin inhibitors are particularly promising, providing therapeutic options to a wider population of patients than ever before. Determining who will benefit from intense or novel low-intense therapy remains a challenge, and it requires careful assessment of individual patient's fitness and disease characteristics.

KEY MESSAGES

This article reviews past and current treatment strategies that harness various mechanisms of leukemia-targeting agents and introduces novel therapies on the horizon aimed at exploring therapeutic options for the elderly and unfit patient population. It also provides a strategy to select the best available therapy for elderly patients with both newly diagnosed and relapsed/refractory AML.

Solute Carrier Nucleoside Transporters in Hematopoiesis and Hematological Drug Toxicities: A Perspective

Simple Summary

Anticancer nucleoside analogs are promising treatments that often result in damaging toxicities and therefore ineffective treatment. Mechanisms of this are not well-researched, but cellular nucleoside transport research in mice might provide additional insight given transport’s role in mammalian hematopoiesis. Cellular nucleoside transport is a notable component of mammalian hematopoiesis due to how mutations within it relate to hematological abnormities. This review encompasses nucleoside transporters, focusing on their inherent properties, hematopoietic role, and their interplay in nucleoside drug treatment side effects. We then propose potential mechanisms to explain nucleoside transport involvement in blood disorders. Finally, we point out and advocate for future research areas that would improve therapeutic outcomes for patients taking nucleoside analog therapies.

Abstract

Anticancer nucleoside analogs produce adverse, and at times, dose-limiting hematological toxicities that can compromise treatment efficacy, yet the mechanisms of such toxicities are poorly understood. Recently, cellular nucleoside transport has been implicated in normal blood cell formation with studies from nucleoside transporter-deficient mice providing additional insights into the regulation of mammalian hematopoiesis. Furthermore, several idiopathic human genetic disorders have revealed nucleoside transport as an important component of mammalian hematopoiesis because mutations in individual nucleoside transporter genes are linked to various hematological abnormalities, including anemia. Here, we review recent developments in nucleoside transporters, including their transport characteristics, their role in the regulation of hematopoiesis, and their potential involvement in the occurrence of adverse hematological side effects due to nucleoside drug treatment. Furthermore, we discuss the putative mechanisms by which aberrant nucleoside transport may contribute to hematological abnormalities and identify the knowledge gaps where future research may positively impact treatment outcomes for patients undergoing various nucleoside analog therapies.

Anti-Relapse effects of donor natural killer cells and IL-2 gene modification on allogeneic hematopoietic stem cell transplantation in acute leukemia

BACKGROUND

Patients with acute leukemia (AL) refractory to induction or reinduction chemotherapy show poor prognoses if they do not undergo allogeneic hematopoietic stem-cell transplantation (AHSCT). The present study aims to investigate whether donor natural killer (NK) cells and interleukin-2 (IL-2) gene modification exert anti-relapse effects on AHSCT after establishing a mouse model of AL.

METHODS

C57BL/6 (H-2b) mice were selected as donor mice to obtain NK cells and hematopoietic stem cells, while BALB/c (H-2d) mice were selected as the recipient mice for AHSCT. The AHSCT-treated mice were then injected with the donor NK cells, recombinant adenovirus expressing IL-2 (AdIL-2), or the NK cells infected by AdIL-2. Flow cytometry was performed to detect the cell transplantation rate, immune cell number, and cell immunogenicity. Enzyme-linked immunosorbent assay (ELISA) was employed to quantify the secretion of IL-2 in spleen cells, and the level of peripheral blood factors, including interferon-γ (IFN-γ), tumor necrosis factor-α (TNF-α), IL-35, transforming growth factor β (TGF-β), and IL-10.

RESULTS

In our experiments, promotional effects of NK cells and AdIL-2 were found on cell transplantation rate, immune reconstitution ability, cell immunogenicity, IL-2 secretion, as well as increased peripheral blood factor levels in the recipient mice treated with AHSCT, with improved pathological changes observed. Moreover, the aforementioned changes were further promoted in the AHSCT-treated recipient mice injected with the AdIL-2-infected NK cells.

CONCLUSIONS

These results uncover that the donor NK cells and IL-2 gene modification could inhibit the relapse of AL mice underwent AHSCT, hereby providing a new target for leukemia treatment.

Clofarabine, cytarabine, and mitoxantrone in refractory/relapsed acute myeloid leukemia: High response rates and effective bridge to allogeneic hematopoietic stem cell transplantation

Clofarabine is active in refractory/relapsed acute myeloid leukemia (AML). In this phase 2 study, we treated 18‐ to 65‐year‐old AML patients refractory to first‐line 3 + 7 daunorubicin/cytarabine induction or relapsing after 3 + 7 induction and high‐dose cytarabine consolidation, with clofarabine (30 mg/m²/d, Days 1‐5), cytarabine (750 mg/m²/d, Days 1‐5), and mitoxantrone (12 mg/m²/d, Days 3‐5) (CLAM). Patients achieving remission received up to two consolidation cycles of 50% CLAM, with eligible cases bridged to allogeneic hematopoietic stem cell transplantation (allo‐HSCT). The mutational profile of a 69‐gene panel was evaluated. Twenty‐six men and 26 women at a median age of 46 (22‐65) years were treated. The overall response rate after the first cycle of CLAM was 90.4% (complete remission, CR: 69.2%; CR with incomplete hematologic recovery, CRi: 21.2%). Twenty‐two CR/CRi patients underwent allo‐HSCT. The 2‐year overall survival (OS), relapse‐free survival (RFS), and event‐free survival (EFS) were 65.8%, 45.7%, and 40.2%, respectively. Multivariate analyses showed that superior OS was associated with CR after CLAM (P = .005) and allo‐HSCT (P = .005), and superior RFS and EFS were associated with allo‐HSCT (P < .001). Remarkably, CR after CLAM and allo‐HSCT resulted in 2‐year OS of 84.3% and 90%, respectively. Karyotypic aberrations and genetic mutations did not influence responses or survivals. Grade 3/4 neutropenia/thrombocytopenia and grade 3 febrile neutropenia occurred in all cases. Other nonhematologic toxicities were mild and uncommon. There was no treatment‐related mortality and the performance of allo‐HSCT was not compromised. Clofarabine, cytarabine, and mitoxantrone was highly effective and safe in refractory/relapsed AML. This study was registered at ClinicalTrials.gov (NCT02686593).

Cancer Therapy-Related Cardiac Dysfunction of Nonanthracycline Chemotherapeutics: What Is the Evidence?

Cancer therapy–related cardiac dysfunction (CTRCD) is one of the most concerning cardiovascular side effects of cancer treatment. Important reviews within the field of cardio-oncology have described various agents to be associated with a high risk of CTRCD, including mitomycin C, ifosfamide, vincristine, cyclophosphamide, and clofarabine. The aim of this study was to provide insight into the data on which these incidence rates are based. We observed that the reported cardiotoxicity of mitomycin C and ifosfamide is based on studies in which most patients received anthracyclines, complicating the interpretation of their association with CTRCD. The high incidence of vincristine-induced cardiotoxicity is based on an incorrect interpretation of a single study. Incidence rates of clofarabine remain uncertain due to a lack of cardiac screening in clinical trials. The administration of high-dose cyclophosphamide (>1.5 g/m²/day) is associated with a high incidence of CTRCD. Based on our findings, a critical re-evaluation of the cardiotoxicity of these agents is warranted.

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CTRCD is one of the most concerning cardiovascular side effects of anticancer treatment.

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Mitomycin C, ifosfamide, cyclophosphamide, clofarabine, and vincristine are frequently recognized as being highly cardiotoxic, causing CTRCD in ≥10% of patients.

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This primer provides insight into the data upon which the CTRCD incidence rates of these agents have been based.

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A critical re-evaluation of CTRCD rates is necessary because these numbers have been based on data in which most patients received prior or concurrent treatment with other cardiotoxic drugs, including anthracyclines.

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Systematic reviews, meta-analyses, consistent and detailed reporting of cardiovascular toxicity, and international registries are of pivotal importance to establish the cardiotoxicity profile of these chemotherapeutics.

Sorafenib Population Pharmacokinetics and Skin Toxicities in Children and Adolescents with Refractory/Relapsed Leukemia or Solid Tumor Malignancies

PURPOSE

To determine the pharmacokinetics and skin toxicity profile of sorafenib in children with refractory/relapsed malignancies.

PATIENTS AND METHODS

Sorafenib was administered concurrently or sequentially with clofarabine and cytarabine to patients with leukemia or with bevacizumab and cyclophosphamide to patients with solid tumor malignancies. The population pharmacokinetics (PPK) of sorafenib and its metabolites and skin toxicities were evaluated.

RESULTS

In PPK analysis, older age, bevacizumab and cyclophosphamide regimen, and higher creatinine were associated with decreased sorafenib apparent clearance (CL/f; P < 0.0001 for all), and concurrent clofarabine and cytarabine administration was associated with decreased sorafenib N-oxide CL/f (P = 7e-4). Higher bilirubin was associated with decreased sorafenib N-oxide and glucuronide CL/f (P = 1e-4). Concurrent use of organic anion-transporting polypeptide 1B1 inhibitors was associated with increased sorafenib and decreased sorafenib glucuronide CL/f (P < 0.003). In exposure-toxicity analysis, a shorter time to development of grade 2-3 hand-foot skin reaction (HFSR) was associated with concurrent (P = 0.0015) but not with sequential (P = 0.59) clofarabine and cytarabine administration, compared with bevacizumab and cyclophosphamide, and with higher steady-state concentrations of sorafenib (P = 0.0004) and sorafenib N-oxide (P = 0.0275). In the Bayes information criterion model selection, concurrent clofarabine and cytarabine administration, higher sorafenib steady-state concentrations, larger body surface area, and previous occurrence of rash appeared in the four best two-predictor models of HFSR. Pharmacokinetic simulations showed that once-daily and every-other-day sorafenib schedules would minimize exposure to sorafenib steady-state concentrations associated with HFSR.

CONCLUSIONS

Sorafenib skin toxicities can be affected by concurrent medications and sorafenib steady-state concentrations. The described PPK model can be used to refine exposure-response relations for alternative dosing strategies to minimize skin toxicity.

Analysis of Efficacy and Prognostic Factors of CLAG Treatment in Chinese Patients with Refractory or Relapsed Acute Myeloid Leukemia

BACKGROUND/AIMS

The aim of this work was to investigate the efficacy and predictive factors of CLAG treatment in refractory or relapsed (R/R) acute myeloid leukemia (AML) patients.

METHODS

Sixty-seven R/R AML patients were enrolled in this prospective cohort study and treated by a CLAG regimen: 5 mg/m2/day cladribine (days 1-5), 2 g/m2/day cytarabine (days 1-5), and 300 μg/day filgrastim (days 0-5). The median follow-up duration was 10 months.

RESULTS

A total of 57 out of 67 patients were evaluable for remission after CLAG therapy, of whom 57.9% achieved a complete remission (CR) and the overall remission rate was 77.2%. The median overall survival (OS) was 10.0 months, with a 1-year OS of 40.3 ± 6.0% and 3-year OS of 16.7 ± 5.7%. CR at first induction after the initial diagnosis was associated with a favorable CR. Age above 60 years, high risk stratification, second or higher salvage therapy, and bone marrow (BM) blasts ≥42.1% were correlated with an unfavorable CR. Secondary disease, age ≥60 years, high risk stratification, and second or higher salvage therapy were associated with worse OS. Patients developed thrombocytopenia (41, 61%), febrile neutropenia (37, 55%), leukopenia (33, 49%), neutropenia (18, 27%), and anemia (9, 13%).

CONCLUSION

CLAG was effective and well tolerated for R/R AML. BM blasts ≥42.1%, age ≥60 years, high risk stratification, and second or higher salvage therapy were independent factors for a poor prognosis.

Clofarabine, high-dose cytarabine and liposomal daunorubicin in pediatric relapsed/refractory acute myeloid leukemia: a phase IB study

Survival in children with relapsed/refractory acute myeloid leukemia is unsatisfactory. Treatment consists of one course of fludarabine, cytarabine and liposomal daunorubicin, followed by fludarabine and cytarabine and stem-cell transplantation. Study ITCC 020/I-BFM 2009-02 aimed to identify the recommended phase II dose of clofarabine replacing fludarabine in the abovementioned combination regimen (3+3 design). Escalating dose levels of clofarabine (20-40 mg/m²/day × 5 days) and liposomal daunorubicin (40-80 mg/m²/day) were administered with cytarabine (2 g/m²/day × 5 days). Liposomal DNR was given on day 1, 3 and 5 only. The cohort at the recommended phase II dose was expanded to make a preliminary assessment of anti-leukemic activity. Thirty-four children were enrolled: refractory 1^st (n=11), early 1st (n=15), ≥2^nd relapse (n=8). Dose level 3 (30 mg/m²clofarabine; 60 mg/m²liposomal daunorubicin) appeared to be safe only in patients without subclinical fungal infections. Infectious complications were dose-limiting. The recommended phase II dose was 40 mg/m² clofarabine with 60 mg/m² liposomal daunorubicin. Side-effects mainly consisted of infections. The overall response rate was 68% in 31 response evaluable patients, and 80% at the recommended phase II dose (n=10); 22 patients proceeded to stem cell transplantation. The 2-year probability of event-free survival (pEFS) was 26.5±7.6 and probability of survival (pOS) 32.4±8.0%. In the 21 responding patients, the 2-year pEFS was 42.9±10.8 and pOS 47.6±10.9%. Clofarabine exposure in plasma was not significantly different from that in single-agent studies. In conclusion, clofarabine was well tolerated and showed high response rates in relapsed/refractory pediatric acute myeloid leukemia. Patients with (sub) clinical fungal infections should be treated with caution. Clofarabine has been taken forward in the Berlin-Frankfurt-Münster study for newly diagnosed acute myeloid leukemia. The Study ITCC-020 was registered as EUDRA-CT 2009-009457-13; Dutch Trial Registry number 1880.

A real-world study of clofarabine and cytarabine combination therapy for patients with acute myeloid leukemia

Clofarabine and cytarabine (Clo + Ara-C) combinations have efficacy in treatment of acute myeloid leukemia (AML). We retrospectively analyzed clinical outcomes of 71 AML patients receiving Clo + Ara-C regimens at the University of Minnesota from 2011 to 2016: 44 patients (62%) had newly diagnosed AML and 27 patients (38%) had relapsed/refractory AML. The median age of patients was 69 years (interquartile range [IQR], 63-75 years). Nearly 60% of the patients had secondary AML, and about half of patients had adverse risk cytogenetics. Objective response rate (ORR) was 42% in all patients with complete remission (CR) rate of 20%. Progression-free survival (PFS) at 2 years was 16% (95% CI 8-27%) and overall survival (OS) at 2 years was 21% (95% CI 11-33%) for all patients. The 30-day mortality rate was 18%. Clo + Ara-C- containing regimens are an acceptable upfront therapy option for patients who are not candidates for "7 + 3" induction, but do not induce durable remissions.

Outcomes of previously untreated elderly patients with AML: a propensity score-matched comparison of clofarabine vs. FLAG

The 5-year overall survival (OS) in patients ≥ 60 years old with acute myeloid leukemia (AML) remains < 10%. Clofarabine-based induction (CLO) provides an alternative to low-intensity therapy (LIT) and palliative care for this population, but supporting data are conflicted. Recently, our institution adopted the FLAG regimen (fludarabine, cytarabine, and granulocyte colony-stimulating factor) based on data reporting similar outcomes to CLO in elderly patients with AML unable to tolerate anthracycline-based induction. We retrospectively analyzed the efficacy and safety of patients ≥ 60 years old with AML treated with FLAG or CLO over the past 10 years. We performed a propensity score match that provided 32 patients in each group. Patients treated with FLAG had a higher CR/CRi rate (65.6 vs. 37.5%, P = 0.045) and OS (7.9 vs. 2.8 months, P = 0.085) compared to CLO. Furthermore, FLAG was better tolerated with significantly less grade 3/4 toxicities and a shorter duration of neutropenia (18.5 vs. 30 days, P = 0.002). Finally, we performed a cost analysis that estimated savings to be $30,000-45,000 per induction with FLAG. Our study supports the use of FLAG both financially and as an effective, well-tolerated high-dose treatment regimen for elderly patients with AML. No cases of cerebellar neurotoxicity occurred.

A Comparison of Clofarabine-based (GCLAC) and Cladribine-based (CLAG) Salvage Chemotherapy for Relapsed/Refractory AML

BACKGROUND

Salvage regimens for patients with relapsed/refractory acute myeloid leukemia (rrAML) lack comparative data for superiority. Thus, we conducted a retrospective analysis of clofarabine-based (GCLAC; granulocyte colony-stimulating factor [filgrastim], clofarabine, high-dose cytarabine) versus cladribine-based (CLAG; cladribine, cytarabine, granulocyte colony-stimulating factor [filgrastim]) regimens in rrAML.

PATIENTS AND METHODS

We identified 41 consecutive patients with rrAML who had received either GCLAC or CLAG from 2011 to 2014. The primary outcome measure was the complete remission (CR) rate defined according to the International Working Group criteria. The secondary outcomes included the proportion of patients who underwent allogenic stem cell transplantation and the rate of relapse-free survival and overall survival.

RESULTS

We found no significant differences in the baseline characteristics of the patients treated with GCLAC (n = 22) or CLAG (n = 19). The outcomes with these 2 regimens were not significantly different. Patients treated with GCLAC had a CR/CR with incomplete blood count recovery rate of 64% compared with 47% for the patients treated with CLAG (P = .36). Of the GCLAC patients, 45% underwent allogeneic stem cell transplantation compared with 26% of the CLAG patients (P = .32). The median relapse-free survival after GCLAC and CLAG was 1.59 years and 1.03 years, respectively (P = .75). The median overall survival after GCLAG and CLAG was 1.03 years and 0.70 years, respectively (P = .08). The drug costs were significantly different for GCLAC versus CLAG. Using an average wholesale price, the cost per patient per cycle was $60,821.60 for GCLAC and $4910.60 for CLAG.

CONCLUSION

A single-institutional retrospective analysis found no significant differences in the outcomes between GCLAC and CLAG for rrAML patients, although formal comparisons should be performed in a randomized clinical trial. The cost of GCLAC was greater than that of CLAG, which should be considered when evaluating the choice for the salvage chemotherapy options.

Randomized Phase II Study of Clofarabine-Based Consolidation for Younger Adults With Acute Myeloid Leukemia in First Remission

Purpose To evaluate the efficacy and safety of a clofarabine-based combination (CLARA) versus conventional high-dose cytarabine (HDAC) as postremission chemotherapy in younger patients with acute myeloid leukemia (AML). Patients and Methods Patients age 18 to 59 years old with intermediate- or unfavorable-risk AML in first remission and no identified donor for allogeneic stem-cell transplantation (SCT) were eligible. Two hundred twenty-one patients were randomly assigned to receive three CLARA or three HDAC consolidation cycles. The primary end point was relapse-free survival (RFS). To handle the confounding effect of SCT that could occur in patients with late donor identification, hazard ratios (HRs) of events were adjusted on the time-dependent treatment × SCT interaction term. Results At 2 years, RFS was 58.5% (95% CI, 49% to 67%) in the CLARA arm and 46.5% (95% CI, 37% to 55%) in the HDAC arm. Overall, 110 patients (55 in each arm) received SCT in first remission. On the basis of a multivariable Cox-adjusted treatment × SCT interaction, the HR of CLARA over HDAC before or in absence of SCT was 0.65 (95% CI, 0.43 to 0.98; P = .041). In a sensitivity analysis, when patients who received SCT in first remission were censored at SCT time, 2-year RFS was 53.3% (95% CI, 39% to 66%) in the CLARA arm and 31.0% (95% CI, 19% to 43%) in the HDAC arm (HR, 0.63; 95% CI, 0.41 to 0.98; P = .043). Gain in RFS could be related to the lower cumulative incidence of relapse observed in the CLARA arm versus the HDAC arm (33.9% v 46.4% at 2 years, respectively; cause-specific HR, 0.61; 95% CI, 0.40 to 0.94; P = .025). CLARA cycles were associated with higher hematologic and nonhematologic toxicity than HDAC cycles. Conclusion These results suggest that CLARA might be considered as a new chemotherapy option in younger patients with AML in first remission.

Clofarabine for the treatment of adult acute lymphoid leukemia: the Group for Research on Adult Acute Lymphoblastic Leukemia intergroup

Clofarabine, a second-generation purine analog displaying potent inhibition of DNA synthesis and favorable pharmacologic profile, is approved for the treatment of acute lymphoblastic leukemia (ALL) after failure of at least two previous regimens in patients up to 21 years of age at diagnosis. Good neurologic tolerance, synergy with alkylating agents, management guidelines defined through pediatric ALL and adult acute myeloid leukemia, have also prompted its administration in more than 100 adults with Philadelphia chromosome-positive and negative B lineage and T lineage ALL, as single agent (40 mg/m(2)/ day for 5 days), or in combination. In a Group for Research on Adult Acute Lympho- blastic Leukemia (GRAALL) retrospective study of two regimens (clofarabine ± cyclophosphamide + / - etoposide (ENDEVOL) ± mitoxantrone ± asparaginase ± dexamethasone (VANDEVOL)), remission was achieved in 50% of 55 relapsed/refractory patients, and 17-35% could proceed to allogeneic stem cell. Clofarabine warrants further exploration in advanced ALL treatment and bridge-to-transplant.

An update of current treatments for adult acute myeloid leukemia

Recent advances in acute myeloid leukemia (AML) biology and its genetic landscape should ultimately lead to more subset-specific AML therapies, ideally tailored to each patient's disease. Although a growing number of distinct AML subsets have been increasingly characterized, patient management has remained disappointingly uniform. If one excludes acute promyelocytic leukemia, current AML management still relies largely on intensive chemotherapy and allogeneic hematopoietic stem cell transplantation (HSCT), at least in younger patients who can tolerate such intensive treatments. Nevertheless, progress has been made, notably in terms of standard drug dose intensification and safer allogeneic HSCT procedures, allowing a larger proportion of patients to achieve durable remission. In addition, improved identification of patients at relatively low risk of relapse should limit their undue exposure to the risks of HSCT in first remission. The role of new effective agents, such as purine analogs or gemtuzumab ozogamicin, is still under investigation, whereas promising new targeted agents are under clinical development. In contrast, minimal advances have been made for patients unable to tolerate intensive treatment, mostly representing older patients. The availability of hypomethylating agents likely represents an encouraging first step for this latter population, and it is hoped will allow for more efficient combinations with novel agents.

Clofarabine and Cytarabine Regimen for Acute Myeloid Leukemia

The complexity of cancer chemotherapy requires pharmacists be familiar with the complicated regimens and highly toxic agents used. This column reviews various issues related to preparation, dispensing, and administration of antineoplastic therapy, and the agents, both commercially available and investigational, used to treat malignant diseases. Questions or suggestions for topics should be addressed to Dominic A. Solimando, Jr, President, Oncology Pharmacy Services, Inc., 4201 Wilson Blvd #110-545, Arlington, VA 22203, e-mail: OncRxSvc@comcast.net; or J. Aubrey Waddell, Professor, University of Tennessee College of Pharmacy; Oncology Pharmacist, Pharmacy Department, Blount Memorial Hospital, 907 E. Lamar Alexander Parkway, Maryville, TN 37804, e-mail: waddfour@charter.net.

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 elderly patients with acute myeloid leukemia with azacitidine results in fewer hospitalization days and infective complications but similar survival compared with intensive chemotherapy

AIMS

Azacitidine has been shown to prolong overall survival (OS) compared with best supportive care in elderly patients with acute myeloid leukemia (AML) with low blast counts but it is unknown if azacitidine has a similar efficacy in patients with blast counts of >30%. It is also unknown if azacitidine is comparable to intensive chemotherapy in terms of survival and morbidity.

METHODS

Differences between the outcomes of elderly AML patients who received intensive chemotherapy, azacitidine-based therapy or best supportive care are studied in this retrospective review. Patients 60 years or older diagnosed with AML between January 2009 and June 2011 were included. Those who passed away within less than 2 weeks of diagnosis were excluded.

RESULTS

At a median follow-up of 7.2 months (range: 0.5-26.4 months), estimated median OS for patients who received azacitidine-based therapy was 9.8 months (range: 2.4-22.5 months) compared with 8.9 months (range: 0.9-26.4 months) for patients who received intensive chemotherapy (P=0.89). Compared with azacitidine-based therapy, intensive chemotherapy is associated with more inpatient days and episodes of febrile illness requiring inpatient stay or intravenous antibiotics.

CONCLUSIONS

Compared with intensive chemotherapy in elderly patients with AML, azacitidine-based therapy is associated with similar median survival but lower number of hospitalization days and infective episodes.

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.

Clofarabine in the treatment of elderly patients with acute myeloid leukemia

BACKGROUND

Elderly patients with acute myeloid leukemia (AML) have a poor outcome because of co- morbidities, poor tolerance to intensive chemotherapy and inherently more resistant disease. Clofarabine is a second generation nucleoside analogue which has shown promising activity in elderly patients with AML. This study was conducted to review the outcome of treatment with clofarabine in a group of such patients.

METHODS

The records of 5 elderly patients who were diagnosed to have AML and treated with clofarabine over a 12 month period were reviewed retrospectively.

RESULTS

There were 2 female and 3 male patients with a median age of 68 years (range 65-82). At the time of treatment, 2 patients had newly diagnosed AML not considered suitable for intensive therapy, while 3 patients had partial or no response to conventional chemotherapy. The overall response rate was 100%, all patients achieving a complete remission. Induction and consolidation were well tolerated. All patients developed neutropenia with a median duration of 20 days (range 17-42). One patient developed hand and foot syndrome and a generalized rash but recovered. There was no mortality and all patients remained in remission after a median follow-up of 5.2 months (Range 3-10).

CONCLUSION

Clofarabine (alone or in combination) is active in elderly AML patients with an acceptable safety profile and should be considered a potential option in this group.

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.

Phase I study of oral clofarabine consolidation in adults aged 60 and older with acute myeloid leukemia

Clofarabine has shown activity and tolerability in older patients with acute myeloid leukemia (AML). We investigated the safety and tolerability of an oral formulation of clofarabine for consolidation therapy of patients aged 60 and older with AML. In this phase I study, twenty-two patients older than 60 years with AML in first complete remission were treated once daily with oral clofarabine for 14 or 21 days of a 28-day cycle, for up to five cycles. Dose escalation from 1 mg to 6 mg daily using a 3 + 3 design was used to determine dose-limiting toxicities (DLT), the maximum tolerated dose (MTD), and tolerability of oral clofarabine. No DLTs or Grade 3-4 nonhematologic toxicities were observed. The primary toxicities were hematologic, including uncomplicated grade 3-4 neutropenia (50%) and thrombocytopenia (50%). Given that myelosuppression necessitating dose delays/reductions was observed more commonly at higher doses, the recommended phase II dose is 2 mg daily for 21 of 28 days. At doses equal to or greater than 2 mg, the median relapse-free survival was 28.35 months. Oral clofarabine was well-tolerated with encouraging activity in patients older than 60 years. Further investigation of oral clofarabine as a consolidation and/or maintenance therapy in AML for older individuals is warranted. (ClinicalTrials.gov:NCT00727766).

Relapsed and refractory pediatric acute myeloid leukemia: current and emerging treatments

Survival rates for children with acute myeloid leukemia (AML) exceed 60 % when modern, intensified chemotherapeutic regimens and enhanced supportive care measures are employed. Despite well-recognized improvements in outcomes, primary refractory or relapsed pediatric AML yields significant morbidity and mortality, and improved understanding of this obstinate population along with refined treatment protocols are urgently needed. Although a significant number of patients with refractory or relapsed disease will achieve remission, long-term survival rates remain poor, and efforts to identify therapies which will improve OS are under continuous investigation. The current fundamental goal of such investigation is the achievement of as complete a remission as possible without dose-limiting toxicities, and the progression to hematopoietic stem cell transplantation thereafter. In this review the scope of the problem of relapsed and refractory AML as well as current and emerging chemotherapy options will be discussed.

Clofarabine in combination with a standard remission induction regimen (cytosine arabinoside and idarubicin) in patients with previously untreated intermediate and bad-risk acute myelogenous leukemia (AML) or high-risk myelodysplastic syndrome (HR-MDS): phase I results of an ongoing phase I/II study of the leukemia groups of EORTC and GIMEMA (EORTC GIMEMA 06061/AML-14A trial)

This study aims to determine the maximum tolerated dose (MTD) of clofarabine combined with the EORTC-GIMEMA 3 + 10 induction regimen (idarubicin + cytosine arabinoside) in adults with untreated acute myelogenous leukemia or high-risk myelodysplastic syndrome. In this phase I trial, 25 patients (median age 56 years) received 5 days of clofarabine as 1-h infusion (arm A) or push injection (arm B) at the dose level of 5 × 10 or 5 × 15 mg/m(2)/day in an algorithmic dose escalation 3 + 3 design. A consolidation course (intermediate dose cytosine arabinoside, idarubicin) was planned for patients in complete remission (CR). Primary endpoint was safety and tolerance as measured by dose limiting toxicity (DLT); secondary endpoints were response rate, other grade III/IV toxicities, and hematological recovery after induction and consolidation. Five DLTs were observed (in arm A: one DLT at 10 mg/m(2)/day, three at 15 mg/m(2)/day; in arm B: one DLT at 15 mg/m(2)/day). Three patients receiving 15 mg/m(2)/day were withdrawn due to adverse events not classified as DLT. Prolonged hypoplasia was observed in five patients. CR + complete remission with incomplete recovery were achieved in 21 patients (11/12 (92 %) receiving clofarabine 10 mg/m(2)/day; 10/13 (77 %) receiving clofarabine 15 mg/m(2)/day). Clofarabine, 5 × 10 mg/m(2)/day, resulted in one DLT and no early treatment withdrawals. MTD of clofarabine combined with cytosine arabinoside and idarubicin is 5 × 10 mg/m(2)/day.

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.

Treatment of acute myeloid leukemia in older patients

Acute myeloid leukemia carries a dismal prognosis in patients over 60 years of age and, despite many clinical trials of both novel and conventional agents, there has been no significant improvement in overall survival during the last 30 years. Combinations of anthracyclines and cytarabine remain the cornerstone of therapy and produce complete remission in 45-55% of older patients, with a median survival of only 8-12 months. These statistics become even worse in patients over 70 years and those with unfavorable cytogenetics and/or poor performance status. Deciding which older acute myeloid leukemia patients would benefit from intensive chemotherapy is difficult and efforts are underway to improve existing risk-assessment tools. Many new agents are under development, including signal transduction inhibitors, farnesyl transferase inhibitors, antibodies and novel chemotherapeutics. To date, small-molecule inhibitors and targeted therapies have had limited single-agent efficacy and have required combination with chemotherapy. The role of hematopoietic stem cell transplantation in older patients is under investigation. All patients over 60 years of age with acute myeloid leukemia should be encouraged to participate in a clinical trial if possible.

Clofarabine-induced kidney toxicity

Clofarabine is a purine nucleoside analog indicated for treatment of relapsed or refractory acute lymphoblastic leukaemia in children. The drug is also increasingly used, outside of its FDA approved indication, for treatment of relapsed or refractory acute myeloid leukemia in adults. It acts by inhibiting DNA synthesis, the enzyme ribonucleotide reductase and repair and activation of mitochondrial repair processes. We describe a case of a 48-year-old male with refractory acute myeloid leukemia with acute kidney injury associated with clofarabine treatment. We conducted a review of the literature and utilized the Food and Drug Administration Adverse Event Reporting System to identify spontaneous reporting of renal adverse events with this drug in 29 other cases. Since clofarabine inhibits ribonucleotide reductase, we postulate by extrapolation from the animal studies that collapsing glomerulopathy or severe tubular injury or a combination of both may be the mechanism of acute kidney injury observed with this agent. This would be consistent with the observed severe acute kidney injury and proteinuria in humans.

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.

Feasibility of clofarabine cytoreduction followed by haploidentical hematopoietic stem cell transplantation in patients with relapsed or refractory advanced acute leukemia

Clofarabine is a novel purine nucleoside analogue with immunosuppressive and anti-leukemic activity in acute lymphoblastic and myeloid leukemia (AML, ALL). This retrospective study was performed to evaluate the feasibility and anti-leukemic activity of a sequential therapy using clofarabine for cytoreduction followed by conditioning for haploidentical hematopoietic stem cell transplantation (HSCT) in patients with non-remission acute leukemia. Patients received clofarabine (5 × 30 mg/m² IV) followed by a T cell replete haploidentical transplantation for AML (n = 15) or ALL (n = 3). Conditioning consisted of fludarabine, cyclophosphamide plus either melphalan, total body irradiation or treosulfan/etoposide. High-dose cyclophosphamide was administered for post-grafting immunosuppression. Neutrophil engraftment was achieved in 83 % and complete remission in 78% at day +30. The rate of acute graft versus host disease (GvHD) grade II-IV was 22%, while chronic GvHD occured in five patients (28%). Non-relapse mortality (NRM) after 1 year was 23%. At a median follow-up of 19 months, estimated overall survival and relapse-free survival at 1 year from haploidentical HSCT were 56 and 39%, respectively. Non-hematological regimen-related grade III-IV toxicity was observed in ten patients (56%) and included most commonly transient elevation of liver enzymes (44%), mucositis (40%), and skin reactions including hand-foot syndrome (17%), creatinine elevation (17%), and nausea/vomiting (17%). The concept of a sequential therapy using clofarabine for cytoreduction followed by haploidentical HSCT proved to be feasible and allows successful engraftment, while providing an acceptable toxicity profile and anti-leukemic efficacy in patients with advanced acute leukemia. NRM and rate of GvHD were comparable to results after HSCT from HLA-matched donors.

Effect of NPM1 and FLT3 mutations on the outcomes of elderly patients with acute myeloid leukemia receiving standard chemotherapy

BACKGROUND

The effect of prognostically important gene mutations (MUTs), nucleophosmin (nucleolar phosphoprotein B23, numatrin) (NPM1) and fms-related tyrosine kinase 3 (FLT3), in elderly patients with acute myeloid leukemia (AML) is not well defined.

PATIENTS AND METHODS

We analyzed 557 patients, 65 years of age or older with newly diagnosed AML, treated at our institution between 2000 and 2010 with cytotoxic chemotherapy. NPM1 and FLT3 analysis were available in 146 patients (26%) and 388 patients (70%), respectively.

RESULTS

NPM1 and FLT3 MUTs occurred in 16% and 12% of patients, respectively. No difference in median overall survival was observed between FLT3-MUT and NPM1-MUT patients who received cytotoxic chemotherapy. Outcome was significantly better among patients with NPM1-MUT/FLT3-wild type (WT) genotype (n = 14) compared with patients carrying FLT3/NPM1 genotypes other than NPM1-MUT/FLT3-WT (n = 125). The complete remission rates were 71% and 49%, respectively (P = .11). The median survival was 21.5 months vs. 9.0 months and estimated 2-year survival rates were 51% vs. 38%, respectively (P = .003). NPM1 and FLT3 MUTs appear to occur less frequently in elderly AML patients. The prognostic effect of isolated NPM1- or isolated FLT3-MUT is minimal.

CONCLUSION

Elderly AML patients with NPM1-MUT/FLT3-WT genotype have significantly improved outcomes compared with patients with other NPM1/FLT3 genotypes when treated with cytotoxic chemotherapy.

Clofarabine in the treatment of acute myeloid leukemia in older adults

OBJECTIVE

To review the literature evaluating the efficacy and tolerability of clofarabine as a single agent and in combination therapy for older patients with acute myeloid leukemia (AML).

METHOD

A literature search of the PubMed database (1996-April 2012) using the search terms clofarabine and acute myeloid leukemia was performed. All relevant English language articles were reviewed. Clinical trials with patients aged 50 years or older diagnosed with AML were included.

RESULTS

Two studies evaluating clofarabine as monotherapy and five studies evaluating clofarabine in combination with cytarabine were reviewed. Clofarabine demonstrated activity in older adults with AML. Response rates and median overall survival (OS) for patients receiving clofarabine were similar to those for patients receiving conventional induction chemotherapy. The induction mortality rate with clofarabine was lower than that seen with intensive chemotherapy. However, clofarabine was associated with a significant risk of severe complications including myelosuppression and sepsis.

CONCLUSION

Clofarabine is an active agent for the treatment of older patients with AML as a single agent or in combination therapy. Based on published data and side-effect profiles, clofarabine may be an appropriate alternative to intensive chemotherapy for older patients with AML, offering similar response rates to traditional 7+3 chemotherapy with potentially decreased induction mortality. The use of clofarabine in combination with newer agents including DNA methyltransferase inhibitors like decitabine is a promising approach for older patients who are not eligible for intensive chemotherapy. Additional randomized controlled trials are needed to directly compare the efficacy of clofarabine as a single agent and in combination therapy compared with intensive chemotherapy regimens.

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.

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.

Lenalidomide as a novel treatment of acute myeloid leukemia

INTRODUCTION

Lenalidomide is an oral immunomodulatory drug derived from thalidomide. This drug has been approved by the Food and Drug Administration for transfusion-dependent anemia due to low-risk myelodysplastic syndromes (MDS) associated with deletion 5q abnormality with or without additional cytogenetic abnormalities and multiple myeloma in combination with dexamethasone. Trials have been conducted for its use in higher-risk MDS and acute myeloid leukemia (AML).

AREAS COVERED

The pharmacokinetic and mechanism of action are discussed and clinical studies of lenalidomide in AML are reported herein in detail. An overview of safety and tolerability is also presented.

EXPERT OPINION

Lenalidomide has clinical activity in AML with manageable toxicity. The population that would benefit from lenalidomide and optimal dose needs to be better defined. Recent trials have focused on combining lenalidomide with other agents active in MDS and AML and promising data are emerging.

A phase Ib GOELAMS study of the mTOR inhibitor RAD001 in association with chemotherapy for AML patients in first relapse

The mTORC1 signaling pathway is constitutively activated in almost all acute myelogenous leukemia (AML) patients. We conducted a phase Ib trial combining RAD001 (everolimus), an allosteric inhibitor of mTORC1, and conventional chemotherapy, in AML patients under 65 years of age at first relapse (clinical trial NCT 01074086). Increasing doses of RAD001 from 10-70 mg were administrated orally on days 1 and 7 (d1 and d7) of a 3+7 daunorubicin+cytarabine conventional induction chemotherapy regimen. Twenty-eight patients were enrolled in this trial. The treatment was well tolerated with <10% toxicity, mainly involving the gastrointestinal tract and lungs. In this phase Ib trial, the RAD001 maximum tolerated dose was not reached at 70 mg. Sixty-eight percent of patients achieved CR, of which 14 received a double induction. Eight subsequently were intensified with allogeneic-stem cell transplant. Strong plasma inhibition of P-p70S6K was observed after RAD001 administration, still detectable at d7 (d7)at the 70 mg dosage. CR rates in patients with RAD001 areas under or above the curve median were 53% versus 85%. A 70 mg dose of RAD001 at d1 and d7 of an induction chemotherapy regimen for AML has acceptable toxicity and may improve treatment.

Valproic acid synergistically enhances the cytotoxicity of clofarabine in pediatric acute myeloid leukemia cells

BACKGROUND

Acute myeloid leukemia (AML) remains a major therapeutic challenge in pediatric oncology even with intensified cytarabine (ara-C)-based chemotherapy. Therefore, new therapies are urgently needed to improve treatment outcome of this deadly disease. In this study, we evaluated antileukemic interactions between clofarabine (a second-generation purine nucleoside analog) and valproic acid (VPA, a FDA-approved agent for treating epilepsy in both children and adult and a histone deacetylase inhibitor), in pediatric AML.

METHODOLOGY

In vitro clofarabine and VPA cytotoxicities of the pediatric AML cell lines and diagnostic blasts were measured by using MTT assays. The effects of clofarabine and VPA on apoptosis and DNA double strand breaks (DSBs) were determined by flow cytometry analysis and Western blotting, respectively. Active form of Bax was measured by Western blotting post-immunoprecipitation.

RESULTS

We demonstrated synergistic antileukemic activities between clofarabine and VPA in both pediatric AML cell lines and diagnostic blasts sensitive to VPA. In contrast, antagonism between the two agents could be detected in AML cells resistant to VPA. Clofarabine and VPA cooperate in inducing DNA DSBs, accompanied by Bax activation and apoptosis in pediatric AML cells.

CONCLUSION

Our results document synergistic antileukemic activities of combined VPA and clofarabine in pediatric AML and suggest that this combination could be an alternative treatment option for the disease.

Cytarabine and clofarabine after high-dose cytarabine in relapsed or refractory AML patients

Clofarabine has been shown to be effective in AML patients, either as single agent or, mainly, in association with intermediate dose cytarabine. Based on these reports, we conducted a preliminary study combining clofarabine and intermediate dose cytarabine in AML patients who relapsed or failed to respond to at least two induction therapies. We treated 47 patients affected by relapsed/refractory AML with a regimen including clofarabine at 22.5 mg/m(2) daily on days 1-5, followed after 3 hr by cytarabine at 1 g/m(2) daily on days 1-5. Ten patients received a further consolidation cycle with clofarabine at 22.5 mg/m(2) and cytarabine at 1 g/m(2) day 1-4. Among the 47 patients, 24/47 (51%) achieved a complete remission, 5/47 (10.5%) a partial response, 10/47 (21%) had a resistant disease, and 6/47 (13%) died of complications during the aplastic phase. The most frequent nonhematologic adverse events were vomiting, diarrhea, transient liver toxicity, febrile neutropenia, and infections microbiologically documented. Among the 24 patients who obtained a CR 13 underwent allogeneic bone marrow transplantation. In 14 patients, complete remission duration was shorter than 12 months, whereas 10 patients experienced longer complete remission duration. These very preliminary results suggest that clofarabine-cytarabine regimen is effective in this particularly poor prognosis category of patients, representing a potential "bridge" toward bone marrow transplant procedures. Safety data were consistent with previously reported salvage therapies. Further studies and a longer follow up are warranted.

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.

Epigenetic therapy is associated with similar survival compared with intensive chemotherapy in older patients with newly diagnosed acute myeloid leukemia

We reviewed the outcome of 671 patients 65 years of age or older with newly diagnosed acute myeloid leukemia (AML) treated at our institution between 2000 and 2010 with intensive chemotherapy (n = 557) or azacitidine- or decitabine-based therapy (n = 114). Both groups were balanced according to cytogenetics and performance status. The complete response rates with chemotherapy and epigenetic therapy were 42% and 28%, respectively (P = .001), and the 8-week mortality 18% and 11%, respectively (P = .075). Two-year relapse-free survival rates (28% vs 39%, P = .843) and median survival (6.7 vs 6.5 months, P = .413) were similar in the 2 groups. Multivariate analysis identified older age, adverse cytogenetics, poor performance status, elevated creatinine, peripheral blood and BM blasts, and hemoglobin, but not type of AML therapy, as independent prognostic factors for survival. No outcome differences were observed according to cytogenetics, FLT3 mutational status, age, or performance status by therapy type. Decitabine was associated with improved median overall survival compared with azacitidine (5.5 vs 8.8 months, respectively, P = .03). Survival after failure of intensive chemotherapy, azacitidine, or decitabine was more favorable in patients who had previously received decitabine (1.1 vs 0.9 vs 3.1 months, respectively, P = .109). The results of the present study show that epigenetic therapy is associated with similar survival rates as intensive chemotherapy in older patients with newly diagnosed AML. The studies reviewed are registered at www.clinicaltrials.gov as 2009-0172 (NCT00926731) and 2009-0217 (NCT00952588).

Clofarabine in pediatric acute leukemia: current findings and issues

Clofarabine is a second-generation purine nucleoside analog and has significant anti-leukemic activity as a single agent. It is approved by the United States Food and Drug Administration (FDA) for the treatment of relapsed or refractory acute lymphoblastic leukemia (ALL) in children. Combinations of clofarabine with purine nucleoside analogs or DNA-damaging agents have been investigated utilizing synergistic effects and now tested in a number of studies including a frontline study. In this article, we review the development of clofarabine, rationale and history of combination regimens, and their potential roles and toxicities in the treatment of pediatric ALL that are important to treating clinicians.