Phase I trial and pharmacokinetic study of high-dose clofarabine and busulfan and allogeneic stem cell transplantation in adults with high-risk and refractory acute leukemia. Leukemia. 2011;25:599-605. [PMID: 21252987 DOI: 10.1038/leu.2010.319]

Clofarabine and Busulfan Myeloablative Conditioning in Allogeneic Hematopoietic Cell Transplantation for Patients With Active Myeloid Malignancies

Patients with refractory or relapsed and refractory myeloid malignancies have a poor prognosis. Allogeneic hematopoietic cell transplantation (HCT) with myeloablative conditioning (MAC) in patients with active, chemotherapy-refractory myeloid disease is historically associated with high rates of relapse and nonrelapse mortality (NRM). A MAC regimen combining clofarabine with busulfan (Clo/Bu4) has been reported to exhibit antileukemic activity with acceptable toxicity in patients age ≤70 years. Here we describe the clinical outcomes of a real-world population of patients with active myeloid malignancies undergoing allogeneic HCT with Clo/Bu4 MAC. In a single-center retrospective descriptive analysis, we identified patients who underwent HCT for myeloid malignancies not in remission using Clo/Bu4 MAC between 2012 and 2020. We report event-free survival (EFS) and overall survival (OS), cumulative incidences of relapse and NRM, and the incidence and severity of acute and chronic graft-versus-host disease (GVHD). We identified 69 patients with a median age of 60 years (range, 22 to 70 years). Most patients had relapsed/refractory or primary refractory acute myelogenous leukemia (AML; n = 55) or refractory myelodysplastic syndrome (MDS; n = 12); 1 patient had chronic myelogenous leukemia, and 1 patient had a blastic plasmacytoid dendritic cell neoplasm. Fifty patients (72.5%) had complete remission at day 100 post-transplantation. Two-year EFS and OS were 30% (95% confidence interval [CI], 20% to 44%) and 40% (95% CI, 29% to 54%), respectively. Patients with AML had a 2-year EFS and OS of 28% (95% CI, 18% to 44%) and 38% (95% CI, 27% to 54%), respectively; those with MDS had a 2-year EFS and OS of 47% (95% CI, 25% to 88%) and 56% (95% CI, 33% to 94%), respectively. The cumulative incidence of relapse at 2 years was 39% (95% CI, 27% to 51%) for all patients, including 45% (95% CI, 31% to 58%) in the patients with AML and 18% (95% CI, 2% to 45%) in those with MDS. NRM at 2 years was 31% (95% CI, 20% to 42%), including 27% (95% CI, 15% to 39%) in patients with AML and 35% (95% CI, 10% to 63%) in those with MDS. The total incidence of acute GVHD (aGVHD) of any severity was 80%, and the incidence of grade III-IV aGVHD was 22%. In patients who achieved remission, those who required systemic immunosuppression for aGVHD (58%) had poorer 2-year EFS (29% versus 54%; P = .05) and 2-year OS (39% versus 70%; P = .04) compared to those who did not. The 2-year cumulative incidence of chronic GVHD was 44% (95% CI, 28% to 58%). Clo/Bu4 MAC followed by allogeneic HCT for patients with active myeloid malignancies is an effective transplantation strategy for patients up to age 70, particularly those with advanced MDS. The high incidence of and poor outcomes associated with aGVHD highlight the importance of optimizing preventative strategies.

Minimal residual disease monitoring and preemptive immunotherapies for frequent 11q23 rearranged acute leukemia after allogeneic hematopoietic stem cell transplantation

The prognosis of 11q23/KMT2A-rearranged (KMT2A-r) acute leukemia (AL) after allogeneic hematopoietic stem cell transplantation (allo-HSCT) is poor. Minimal residual disease (MRD) is an important prognostic factor for relapse. Thus, we aimed to identify the evolution of KMT2A before and after allo-HSCT and the efficacy of preemptive immunotherapies for KMT2A-r AL patients receiving allo-HSCT. KMT2A expression was determined through TaqMan-based RQ-PCR technology. Preemptive immunotherapies included interferon-α and donor lymphocyte infusion. We collected 1751 bone marrow samples from 177 consecutive KMT2A-r AL patients. Pre-HSCT KMT2A positivity was correlated with post-HSCT KMT2A positivity (correlation coefficient=0.371, P<0.001). The rates of achieving KMT2A negativity after allo-HSCT were 96.6%, 92.9%, and 68.8% in the pre-HSCT low-level group (>0, <0.1%), intermediate-level group (≥ 0.1%, <1%), and high-level group (≥1%), respectively. The rates of regaining KMT2A positivity after allo-HSCT were 7.7%, 35.7%, 38.5%, and 45.5% for the pre-HSCT KMT2A-negative, low-level, intermediate-level, and high-level groups, respectively (P<0.001). The 4-year cumulative incidence of relapse after allo-HSCT was as high as 53.7% in the pre-HSCT KMT2A expression ≥ 0.1% group, which was compared to the KMT2A-negative group (15.1%) and KMT2A <0.1% group (31.2%). The clinical outcomes of patients with post-HSCT KMT2A positivity were poorer than those of patients with persistent KMT2A negativity. Although post-HSCT preemptive immunotherapies might help to achieve KMT2A negativity, the long-term efficacy was unsatisfactory. Thus, pre-HSCT KMT2A positivity was significantly associated with post-HSCT KMT2A positivity. The clinical outcomes of patients with post-HSCT KMT2A positivity were poor, which might not be overcome by commonly used immunotherapies.

Phase I/II multisite trial of optimally dosed clofarabine and low-dose TBI for hematopoietic cell transplantation in acute myeloid leukemia

Clofarabine is an immunosuppressive purine nucleoside analog that may have better anti-leukemic activity than fludarabine. We performed a prospective phase I/II multisite trial of clofarabine with 2 Gy total body irradiation as non-myeloablative conditioning for allogeneic hematopoietic cell transplantation in adults with acute myeloid leukemia who were unfit for more intense regimens. Our main objective was to improve the 6-month relapse rate following non-myeloablative conditioning, while maintaining historic rates of non-relapse mortality (NRM) and engraftment. Forty-four patients, 53 to 74 (median: 69) years, were treated with clofarabine at 150 to 250 mg/m² , of whom 36 were treated at the maximum protocol-specified dose. One patient developed multifactorial acute kidney injury and another developed multiorgan failure, but no other grade 3 to 5 non-hematologic toxicities were observed. All patients fully engrafted. The 6-month relapse rate was 16% (95% CI, 5%-27%) among all patients and 14% (95% CI, 3%-26%) among high-risk patients treated at the maximum dose, meeting the pre-specified primary efficacy endpoint. Overall survival was 55% (95% CI, 40%-70%) and leukemia-free survival was 52% (95% CI, 37%-67%) at 2 years. Compared to a historical high-risk cohort treated with the combination of fludarabine at 90 mg/m² and 2 Gy TBI, protocol patients treated with the clofarabine-TBI regimen had lower rates of overall mortality (HR of 0.50, 95% CI, 0.28-0.91), disease progression or death (HR 0.48, 95% CI, 0.27-0.85), and morphologic relapse (HR 0.30, 95% CI, 0.13-0.69), and comparable NRM (HR 0.85, 95% CI 0.36-2.00). The combination of clofarabine with TBI warrants further investigation in patients with high-risk AML.

Haploidentical Donor Transplantation Using a Novel Clofarabine-containing Conditioning Regimen for Very High-risk Hematologic Malignant Neoplasms

Recurrent/refractory hematologic malignancies have a poor prognosis, and there is a need for novel treatment regimens that can be tolerated by this heavily pretreated patient group. Clofarabine has antileukemic activity with an acceptable toxicity profile. In a phase I clinical trial (NCT00824135), we substituted clofarabine for fludarabine in a well-established reduced-intensity conditioning regimen for a T cell-depleted, mismatched-related (haploidentical) donor transplant backbone and explored the maximum tolerated dose of clofarabine in this combination in 15 patients undergoing hematopoietic cell transplantation for recurrent/refractory or secondary leukemia. Clofarabine was well tolerated at a dose of 50 mg/m/d for 5 days in this regimen, with minimal treatment-related mortality in a heavily pretreated group of high-risk patients. All patients exhibited quick hematopoietic recovery, with median times to neutrophil and platelet engraftment being 11 and 16 days, respectively. Transient elevation of transaminases was the most common toxicity-observed in 13 patients (86.7%), with 6 (40%) grade III or above. Three patients (20%) developed hepatic veno-occlusive disease. Eleven patients (73.3%) died, with the most common cause of death being disease relapse (in 9 patients [60%]), followed by treatment-related mortality (in 2 patients [13.3%]). Four (26.6%) of the patients are long-term survivors.

Clofarabine-based reduced intensity conditioning regimen with peripheral blood stem cell graft and post-transplant cyclophosphamide in adults with myeloid malignancies

BACKGROUND

The Baltimore reduced-intensity conditioning (RIC) regimen using high-dose post-transplant cyclophosphamide (PTCY) is considered as a standard of care for haploidentical allogeneic stem cell transplantation (allo-SCT). However, it is associated with relatively low survivals and high incidence of relapse, especially when considering myeloid malignancies.

RESULTS

This retrospective study included 36 adults (males n = 18; median age: 60.5 years old; haplodonors n = 27; matched donors n = 8) with myeloid malignancies transplanted between March 2014 and March 2017 at the University Hospital of Nantes. Very encouraging results were observed with a 18-month overall survival (OS), disease-free survival (DFS) and relapse incidence (RI) of 72% ± 7.5%, 63.8 ± 8%, and 25 ± 6% respectively, and a GVHD relapse-free survival (GRFS) of 52.6 ± 8%. In univariate analysis, there were no differences regarding 18-month survivals between patients allografted: i) for acute myeloid leukemia vs myelodysplastic syndrome (OS 70 ± 11% vs 69.2 ± 13%, p = 0.3; DFS 64.7 ± 11% vs 61.5 ± 13%, p = 0.65), or ii) with haplo-identical vs other donors (OS: 66.2 ± 9% vs 88.8 ± 10.4%, p = 0.16; DFS 59 ± 9.5% vs 77.8%, p = 0.6).

CONCLUSION

The "Clo-Baltimore regimen" is safe and feasible and provides good survivals for patients with myeloid malignancies and haplo-donors.

METHODS

Here, we report a variant of the Baltimore regimen, where 1) fludarabine was replaced by clofarabine, 2) bone marrow was replaced by peripheral blood stem cells, and 3) tacrolimus was replaced by cyclosporine, in a "Clo-Baltimore regimen".

Clinical pharmacology and clinical trials of ribonucleotide reductase inhibitors: is it a viable cancer therapy?

PURPOSE

Ribonucleotide reductase (RR) enzymes (RR1 and RR2) play an important role in the reduction of ribonucleotides to deoxyribonucleotides which is involved in DNA replication and repair. Augmented RR activity has been ascribed to uncontrolled cell growth and tumorigenic transformation.

METHODS

This review mainly focuses on several biological and chemical RR inhibitors (e.g., siRNA, GTI-2040, GTI-2501, triapine, gemcitabine, and clofarabine) that have been evaluated in clinical trials with promising anticancer activity from 1960's till 2016. A summary on whether their monotherapy or combination is still effective for further use is discussed.

RESULTS

Among the RR2 inhibitors evaluated, GTI-2040, siRNA, gallium nitrate and didox were more efficacious as a monotherapy, whereas triapine was found to be more efficacious as combination agent. Hydroxyurea is currently used more in combination therapy, even though it is efficacious as a monotherapy. Gallium nitrate showed mixed results in combination therapy, while the combination activity of didox is yet to be evaluated. RR1 inhibitors that have long been used in chemotherapy such as gemcitabine, cladribine, fludarabine and clofarabine are currently used mostly as a combination therapy, but are equally efficacious as a monotherapy, except tezacitabine which did not progress beyond phase I trials.

CONCLUSIONS

Based on the results of clinical trials, we conclude that RR inhibitors are viable treatment options, either as a monotherapy or as a combination in cancer chemotherapy. With the recent advances made in cancer biology, further development of RR inhibitors with improved efficacy and reduced toxicity is possible for treatment of variety of cancers.

Impact of pharmacokinetics on the toxicity and efficacy of clofarabine in patients with relapsed or refractory acute myeloid leukemia

Common side effects of clofarabine (CFB) are liver toxicity, particularly a transient elevation of transaminases and skin toxicity. We studied the correlation of pharmacokinetic (PK) parameters with these toxicities and the efficacy of CFB in patients with relapsed or refractory acute myeloid leukemia. Clofarabine PK parameters showed large inter-individual variability. A higher CFB area under the curve was significantly associated with higher transaminase levels (p = .011 for aspartate aminotransferase (AST), adjusted for age, sex, cumulated CFB dosage, baseline AST, and glomerular filtration rate (GFR)). No significant association could be found between maximum concentration and the liver toxicity parameters. The occurrence of skin toxicity and the response to re-induction chemotherapy evaluated at day 15 were also not associated with PK. In conclusion, a higher individual CFB exposure is associated with increased liver toxicity reflected by elevated liver enzymes, without having an impact on anti-leukemic efficacy.

A multicenter trial of myeloablative clofarabine and busulfan conditioning for relapsed or primary induction failure AML not in remission at the time of allogeneic hematopoietic stem cell transplantation

Allogeneic hematopoietic cell transplantation (HCT) may produce long-term survival in AML after relapse or primary induction failure (PIF). However, outcomes of HCT performed for AML not in remission are historically poor given high relapse rates and transplant-related mortality. Preliminary studies suggest conditioning with clofarabine and myeloablative busulfan (CloBu4) may exert significant anti-leukemic effects without excessive toxicity in refractory hematologic malignancies. A prospective multicenter phase II trial was conducted to determine the efficacy of CloBu4 for patients proceeding directly to HCT with AML not in remission. Seventy-one patients (median age: 56 years) received CloBu4. At day 30 after HCT, 90% achieved morphologic remission. The incidence of non-relapse mortality and relapse at 2 years was 25% and 55%, respectively. The 2-year overall survival (OS) and event-free survival (EFS) were 26% and 20%, respectively. Patients entering HCT in PIF had significantly greater EFS than those in relapse (34% vs 8%; P<0.01). Multivariate analysis comparing CloBu4 with a contemporaneous cohort (Center for International Blood and Marrow Transplantation Research) of AML not in remission receiving other myeloablative conditioning (n=105) demonstrated similar OS (HR: 1.33, 95% confidence interval: 0.92-1.92; P=0.12). HCT with myeloablative CloBu4 is associated with high early response rates and may produce durable remissions in select patients with AML not in remission.

Phase II Trial of Reduced-Intensity Busulfan/Clofarabine Conditioning with Allogeneic Hematopoietic Stem Cell Transplantation for Patients with Acute Myeloid Leukemia, Myelodysplastic Syndromes, and Acute Lymphoid Leukemia

Clofarabine has potent antileukemia activity and its inclusion in reduced-intensity conditioning (RIC) allogeneic hematopoietic stem cell transplantation (HSCT) for acute leukemia could potentially improve outcomes. We conducted a phase II study of busulfan (.8 mg/kg i.v. twice daily on days -5, -4, -3, and -2) with clofarabine (40 mg/m(2) i.v. daily on days -5, -4, -3, and -2) conditioning before allogeneic 8/8 HLA-matched related or unrelated HSCT. The primary endpoint was donor neutrophil engraftment by day +40. Secondary endpoints included nonrelapse mortality (NRM), acute and chronic graft-versus-host disease (GVHD), progression-free survival (PFS), and overall survival (OS). Thirty-four patients (acute myeloid leukemia [AML], n = 25; myelodysplastic syndromes, n = 5; and acute lymphoid leukemia, n = 4) were enrolled. Day 40+ engraftment with donor chimerism was achieved in 33 of 34 patients with 1 patient dying before count recovery. Day 100 and 1-year NRM were 5.9% (95% confidence interval [CI], 1.0 to 17.4) and 24% (95% CI, 11 to 39), respectively. The 2-year relapse rate was 26% (95% CI, 13 to 42). Cumulative incidences of acute and chronic GVHD were 21% and 44%, respectively. The 2-year PFS was 50% (95% CI, 32 to 65) and OS was 56% (95% CI, 38 to 71). For patients with AML in first complete remission, 2-year PFS and OS were both 82% (95% CI, 55 to 94). RIC with busulfan and clofarabine leads to successful engraftment with acceptable rates of NRM and GVHD.

Comparison of the cytotoxicity of cladribine and clofarabine when combined with fludarabine and busulfan in AML cells: Enhancement of cytotoxicity with epigenetic modulators

Clofarabine (Clo), fludarabine (Flu), and busulfan (Bu) combinations are efficacious in hematopoietic stem cell transplantation for myeloid leukemia. We sought to determine whether the more affordable drug cladribine (Clad) can provide a viable alternative to Clo, with or without panobinostat (Pano) and 5-aza-2'-deoxycytidine (DAC). Both Clad+Flu+Bu and Clo+Flu+Bu combinations showed synergistic cytotoxicity in KBM3/Bu250(6), HL60, and OCI-AML3 cell lines. Cell exposure to these drug combinations resulted in 60%-80% inhibition of proliferation; activation of the ATM pathway; increase in histone modifications; decrease in HDAC3, HDAC4, HDAC5 and SirT7 proteins; decrease in mitochondrial membrane potential; activation of apoptosis and stress signaling pathways; and downregulation of the AKT pathway. These drug combinations activated DNA-damage response and apoptosis in primary cell samples from AML patients. At lower concentrations of Clad/Clo, Flu, and Bu, inclusion of Pano and DAC enhanced cell killing, increased histone modifications and DNA demethylation, and increased the levels of P16/INK4a, P15/INK4b and P21/Waf1/Cip1 proteins. The observed DNA demethylating activity of Clad and Clo may complement DAC activity; increase demethylation of the gene promoters for SFRP1, DKK3, and WIF1; and cause degradation of β-catenin in cells exposed to Clad/Clo+Flu+Bu+DAC+Pano. The overlapping activities of Clad/Clo+Flu+Bu, Pano, and DAC in DNA-damage formation and repair, histone modifications, DNA demethylation, and apoptosis may underlie their synergism. Our results provide a basis for supplanting Clo with Clad and for including epigenetic modifiers in the pre-hematopoietic stem cell transplantation conditioning regimen for myeloid leukemia patients.

New drug toxicities in the onco-nephrology world

New anticancer medications are rapidly entering the clinical arena offering patients with previously resistant cancers the promise of more effective therapies capable of extending their lives. However, adverse renal consequences develop in treated patients with underlying risk factors, requiring the nephrology community to be familiar with the nephrotoxic effects. The most common clinical nephrotoxic manifestations of these drugs include acute kidney injury, varying levels of proteinuria, hypertension, electrolyte disturbances, and at times chronic kidney disease. Thus, to practice competently in the 'onco-nephrology' arena, nephrologists will garner benefit from an update on older drugs with newly recognized nephrotoxic potential as well as newer agents, which may be associated with kidney injury. With that in mind, this brief update is meant to provide clinicians with the currently available evidence on the nephrotoxicity of a group of anticancer medications.

Four-component reaction leading to highly functionalized sulfoalkoxy carbonyl compounds

Four components together: a new paradigm of four component reaction brings α-bromo-β-sulfoalkoxyl carbonyl compounds with good stereocontrol in moderate to excellent yields.

Allogeneic hematopoietic cell transplantation for acute myeloid leukemia in older adults

Acute myeloid leukemia (AML) is primarily a disease of the elderly and the numbers of these patients are increasing. Patients ≥60 years of age continue to have poor prognosis. Preliminary results suggest benefit from reduced-intensity allogeneic hematopoietic cell transplantation (HCT) in selected patients 60-80 years of age. However, although patients in this age range comprise >50% of those with AML, they currently constitute only 17% of those offered HCT. In the absence of prospective randomized studies comparing HCT and chemotherapy, the decision to recommend HCT rests on retrospective analyses of the risks of relapse and nonrelapse mortality after each approach. There is strong evidence that pre-HCT comorbidities can predict HCT-related morbidity and mortality. Age alone does not appear predictive and, particularly if the risk of relapse with chemotherapy is high, should not be the sole basis for deciding against HCT. Use of geriatric assessment tools, inflammatory biomarkers, and genetic polymorphism data may further aid in predicting nonrelapse mortality after HCT. Disease status and pretreatment cytogenetics with FLT3-TID, NPM-1, and CEBP-α status are the main factors predicting relapse and these are likely to be supplemented by incorporation of other molecular markers and the level of minimal residual disease after chemotherapy. HLA-matched related and unrelated donor grafts seem preferable to those from other donor sources. Donor age is of no clear significance. Models combining comorbidities with AML risk factors are useful in risk assessment before HCT. In this chapter, we integrated information on AML-specific, HCT-specific, and patient-specific risk factors into a risk-adapted approach to guide decisions about HCT versus no HCT.

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.

Clofarabine-associated acute kidney injury in patients undergoing hematopoietic stem cell transplant

Abstract We examined clofarabine pharmacokinetics and association with renal toxicity in 62 patients participating in a phase I-II study of clofarabine-melphalan-alemtuzumab conditioning for hematopoietic stem cell transplant (HSCT). Pharmacokinetic parameters, including clofarabine area under the concentration-time curve (AUC), maximum concentration and clearance, were measured, and patients were monitored for renal injury. All patients had normal pretreatment creatinine values, but over half (55%) experienced acute kidney injury (AKI) after clofarabine administration. Age was the strongest predictor of AKI, with older patients at greater risk (p = 0.002). Clofarabine AUC was higher in patients who developed AKI, and patients with the highest dose-normalized AUCs experienced the most severe grades of AKI (p = 0.01). Lower baseline renal function, even when normal, was associated with lower clofarabine clearance (p = 0.008). These data suggest that renal-adjustment of clofarabine dosing should be considered for older and at-risk patients even when renal function is ostensibly normal.

Allogeneic hematopoietic cell transplant for acute myeloid leukemia: Current state in 2013 and future directions

Acute myeloid leukemia (AML) represents a heterogeneous group of high-grade myeloid neoplasms of the elderly with variable outcomes. Though remission-induction is an important first step in the management of AML, additional treatment strategies are essential to ensure long-term disease-free survival. Recent pivotal advances in understanding the genetics and molecular biology of AML have allowed for a risk-adapted approach in its management based on relapse-risk. Allogeneic hematopoietic cell transplantation (allo-HCT) represents an effective therapeutic strategy in AML providing the possibility of cure with potent graft-versus-leukemia reactions, with a demonstrable survival advantage in younger patients with intermediate- or poor-risk cytogenetics. Herein we review the published data regarding the role of allo-HCT in adults with AML. We searched MEDLINE/PubMed and EMBASE/Ovid. In addition, we searched reference lists of relevant articles, conference proceedings and ongoing trial databases. We discuss the role of allo-HCT in AML patients stratified by cytogenetic- and molecular-risk in first complete remission, as well as allo-HCT as an option in relapsed/refractory AML. Besides the conventional sibling and unrelated donor allografts, we review the available data and recent advances for alternative donor sources such as haploidentical grafts and umbilical cord blood. We also discuss conditioning regimens, including reduced intensity conditioning which has broadened the applicability of allo-HCT. Finally we explore recent advances and future possibilities and directions of allo-HCT in AML. Practical therapeutic recommendations have been made where possible based on available data and expert opinion.

Indications for allogeneic hematopoietic cell transplantation for acute myeloid leukemia in the genomic era

Few choices in medical oncology are as stark as the decision of whether or not to proceed with allogeneic hematopoietic cell transplantation (HCT) in the treatment of acute myeloid leukemia (AML). Recent advances provide more information to inform the decision, including molecular studies of leukemia that predict tumor responsiveness, assays of minimal residual disease that measure early treatment outcome, and comorbidity indices that predict nonrelapse mortality. Although large prospective studies incorporating all of these factors are lacking, literature reviews and consensus statements exist that can help the clinician in this difficult choice. Allogeneic HCT should be considered for all patients younger than age 65, with an available donor, an acceptable comorbidity index, and whose had initial induction therapy has failed. Similarly, allogeneic HCT is appropriate therapy for all patients with AML in second remission younger than age 75, with an appropriate donor, and a comorbidity index of 5 or less. For patients younger than age 60 with AML in first complete remission (CR), there is little evidence that HCT benefits those with favorable-risk disease who achieve CR with one cycle of induction and have no evidence of minimal residual disease. Allogeneic HCT is indicated for essentially all other categories of patients. For those age 60 and older, few prospective studies are available on which to base recommendations, but, as in younger patients, the benefit of allogeneic HCT is questionable for patients with favorable-risk AML. For patients with higher-risk disease, allogeneic HCT is a reasonable option with the caution that the risk of HCT increases dramatically in those with a comorbidity index of 3 or higher.

Risk assessment before allogeneic hematopoietic cell transplantation for older adults with acute myeloid leukemia

Acute myeloid leukemia (AML) most commonly affects patients older than 60 years. Outcomes of treatment of older AML patients have been poor. The advent of reduced-intensity conditioning (RIC) regimens made allogeneic hematopoietic cell transplantation (HCT) an available treatment option with curative intent for older AML patients. Because older patients are often excluded from clinical trials, little is known about the stratification of their risks before allogeneic HCT. While recent studies of RIC and allogeneic HCT have shown little impact of age on outcomes, other variables such as the recipient health status and the AML disease status and chromosomal aberrations have proven to be of prognostic significance. Here, the authors review recent studies of allogeneic HCT for older patients with AML with detailed evaluation of risk factors for relapse as well as non-relapse mortality. The authors have integrated the currently available information on transplant risks into a five-category risk-benefit system that could aid in the decision-making in this patient population.

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.

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.

High-dose etoposide in allogeneic stem cell transplantation

The anti-leukemic effect of etoposide is well documented. High-dose etoposide 60 mg/kg in combination with fractionated total body irradiation (TBI), usually single fractions of 1.2 Gy up to a total of 13.2 Gy, is used as conditioning therapy for allogeneic stem cell transplantation. Most studies of this conditioning regimen have included patients with acute leukemia receiving bone marrow or mobilized stem cell grafts derived from family or matched unrelated donors, and the treatment is then effective even in patients with high-risk disease. The most common adverse effects are fever with hypotension and rash, nausea and vomiting, sialoadenitis, neuropathy and metabolic acidosis. A small minority of patients develop severe allergic reactions. Etoposide has also been tested in a wide range of combination regimens, but for many of these combinations, relatively few patients are included, and some combinations have only been tested in patients who have undergone autologous transplants. However, the general conclusion is that many of these combinations are effective in patients with high-risk malignancies and the toxicity often seems acceptable. Thus, etoposide-based conditioning therapy should be further evaluated in patients having allogeneic transplants, but randomized trials are needed and the design of future trials should be based on the well-characterized TBI + high-dose etoposide regimen.

Clofarabine-containing conditioning regimen for allo-SCT in AML/ALL patients: a survey from the Acute Leukemia Working Party of EBMT

Clofarabine (CLO), a second-generation purine analogue, has demonstrated an efficient anti-leukemia activity while showing a favorable toxicity profile. This retrospective multicenter report assessed the outcome of 90 patients who received a CLO-containing conditioning regimen before allo-SCT for AML (n = 69) or ALL (n = 21). Median age was 42 yr at transplant. The majority of cases (n = 66) presented with an active disease at transplant while 38 patients had received previous transplantation(s). A total of 88 and two patients received a reduced-intensity conditioning or a myeloablative regimen, respectively. Engraftment was achieved in 97% of evaluable patients. With a median follow-up of 14 months (range, 1-45), the 2-year OS, LFS, relapse, and NRM rates were 28 ± 5%, 23 ± 5%, 41 ± 6%, and 35 ± 5%, respectively. When comparing AML and ALL patients, OS and LFS were significantly higher for AML (OS, 35 ± 6% vs. 0%, P < 0.0001); LFS: 30 ± 6% vs. 0%, P < 0.0001). In a Cox multivariate analysis, an AML diagnosis was the only factor associated with a better LFS (HR = 0.37; 95%CI, 0.21-0.66; P = 0.001). We conclude that a CLO-containing conditioning regimen prior to allo-SCT might be an effective treatment. Prospective studies are needed to evaluate the potential role of CLO as part of conditioning regimens in acute leukemias.

Targeting of polo-like kinases and their cross talk with Aurora kinases--possible therapeutic strategies in human acute myeloid leukemia?

INTRODUCTION

Five human polo-like kinases (PLKs) have been identified, and PLK1 - 4 seem to interact with Aurora kinases and act as cell cycle regulators in both normal and malignant human cells.

AREAS COVERED

The present review describes i) experimental evidence for a role for PLKs and Aurora kinases in human leukemogenesis and ii) the results from clinical studies of PLK and Aurora kinase inhibitors in the treatment of human acute myeloid leukemia (AML). The review was based on searches in the PubMed and the ClinicalTrials.gov databases. These inhibitors have antiproliferative and proapoptotic effects in AML cells. Hematological and gastrointestinal toxicities are frequently dose limiting, and this may limit the use of these agents in combination with conventional AML therapy. Aurora kinase inhibitors seem to be most effective for patients with high expression of the target kinases, and the same may be true for PLK inhibitors.

EXPERT OPINION

PLK inhibition is a promising strategy for the treatment of AML. Future clinical studies have to clarify i) whether this strategy is most effective for certain subsets of patients; ii) whether multikinase inhibitors targeting several cell cycle regulators should be preferred; and iii) how this therapeutic strategy eventually should be combined with conventional antileukemic chemotherapy.

Synergistic cytotoxicity of the DNA alkylating agent busulfan, nucleoside analogs and suberoylanilide hydroxamic acid in lymphoma cell lines

Hematopoietic stem cell transplant (HSCT) is a promising treatment for lymphomas. Its success depends on effective pre-transplant conditioning regimens. We previously reported on the efficacy of DNA alkylating agent-nucleoside analog (NA) combinations for conditioning in acute myeloid leukemia (AML). We hypothesized that a similar combinatory approach can be used for lymphomas. A combination of busulfan (Bu) with two NAs - clofarabine (Clo), fludarabine (Flu) or gemcitabine (Gem) - resulted in synergistic cytotoxicity in lymphoma cell lines. We demonstrated that the [2 NAs + Bu] combination activates a DNA damage response through the ATM-CHK2 and ATM-CHK1 pathways, leading to cell cycle checkpoint activation and apoptosis. Histone modifications and KAP1 phosphorylation are indicative of chromatin relaxation mediated by the nucleoside analogs, which sequentially increase Bu alkylation. Addition of suberoylanilide hydroxamic acid (SAHA) enhanced chromatin relaxation through increased histone acetylation and further augmented the cytotoxicity of [2 NAs + Bu]. Our results provide a preclinical basis for a clinical trial on using [2 NAs + Bu ± SAHA] combinations as conditioning therapy for patients with chemotherapy-refractory lymphoma undergoing HSCT.

Phase I-II study of clofarabine-melphalan-alemtuzumab conditioning for allogeneic hematopoietic cell transplantation

We conducted a phase I-II study of transplantation conditioning with clofarabine-melphalan-alemtuzumab for patients with advanced hematologic malignancies. Ten patients were accrued to the phase I portion, which utilized an accelerated titration design. No dose-limiting toxicity was observed, and clofarabine 40 mg/m(2) × 5, melphalan 140 mg/m(2) × 1, and alemtuzumab 20 mg × 5 was adopted for the phase II study, which accrued 72 patients. Median age was 54 years. There were 44 patients with acute myelogenous leukemia or myelodysplastic syndromes, 27 with non-Hodgkin lymphoma, and nine patients with other hematologic malignancies. The largest subgroup of 35 patients had American Society for Blood and Marrow Transplantation high-risk, active disease. All evaluable patients engrafted with a median time to neutrophil and platelet recovery of 10 and 18 days, respectively. The cumulative incidence of treatment-related mortality was 26% at 1 year. Cumulative incidence of relapse was 29% at 1 year. Overall survival was 80% (95% confidence interval [CI], 71-89) at 100 days and 59% (95% CI, 47-71) at 1 year. Progression-free-survival was 45% (95% CI, 33-67) at 1 year. Rapid-onset renal failure was the main toxicity in the phase II study and more frequent in older patients and those with baseline decrease in glomerular filtration rate. Grade 3-5 renal toxicity was observed in 16 of 74 patients (21%) treated at the phase II doses. Clofarabine-melphalan-alemtuzumab conditioning yields promising response and duration of response, but renal toxicity poses a considerable risk particularly in older patients.

Clofarabine and busulfan conditioning facilitates engraftment and provides significant antitumor activity in nonremission hematologic malignancies

Patients with hematologic malignancies not in remission before allogeneic hematopoietic stem cell transplantation (HSCT) have a poor prognosis. To improve the antitumor activity of conditioning, we combined clofarabine with myeloablative doses of busulfan in a phase 1/2 study in nonremission hematologic malignancies. Forty-six patients were enrolled, including 31 patients with nonremission acute myelogenous leukemia (AML). Patients had a median age of 53 years, with a median comorbidity index of 3. Donors were unrelated, HLA mismatched, or both in 59% of patients. Common grade III to IV nonhematologic toxicities included transient transaminitis (50%), mucositis (24%), hand-foot syndrome (13%), transient hypoxia (13%), nausea/vomiting (9%), and diarrhea (9%). All patients engrafted. Complete remission was achieved in 80% of all patients by day +30 and in 100% of AML patients without prior hematopoietic stem cell transplantation. Two-year nonrelapse mortality for all patients was 31%, and overall survival was 28%. In AML, the overall survival was 48% at 1 year and 35% at 2 years. These data suggest that clofarabine combined with myeloablative doses of busulfan is well tolerated, secures engraftment, and possesses significant antitumor activity, particularly in nonremission AML. This study is registered at www.ClinicalTrials.gov under identifier NCT00556452.

Comparison of reduced-intensity hematopoietic cell transplantation with chemotherapy in patients age 60-70 years with acute myelogenous leukemia in first remission

We compared the outcomes of patients age 60-70 years with acute myelogenous leukemia receiving reduced-intensity allogeneic hematopoietic cell transplantation (HCT) in first remission (CR1) reported to the Center for International Blood and Marrow Research (n = 94) with the outcomes in patients treated with induction and postremission chemotherapy on Cancer and Leukemia Group B protocols (n = 96). All patients included had been in CR1 for at least 4 months. The HCT recipients were slightly younger than the chemotherapy patients (median age, 63 years vs 65 years; P < .001), but there were no significant between-group differences in the proportion with therapy-related leukemia or in different cytogenetic risk groups. Time from diagnosis to CR1 was longer for the HCT recipients (median, 44 days vs 38 days; P = .031). Allogeneic HCT was associated with significantly lower risk of relapse (32% vs 81% at 3 years; P < .001), higher nonrelapse mortality (36% vs 4% at 3 years; P < .001), and longer leukemia-free survival (32% vs 15% at 3 years; P = .001). Although overall survival was longer for HCT recipients, the difference was not statistically significant (37% vs 25% at 3 years; P = .08). Our findings suggest that reduced-intensity conditioning allogeneic HCT in patients age 60-70 with acute myelogenous leukemia in CR1 reduces relapse and improves leukemia-free survival. Strategies that reduce nonrelapse mortality may yield significant improvements in overall survival.