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ABT199/venetoclax, an inhibitor of the pro-survival BCL-2 protein, has improved AML treatment. Its efficacy in hematopoietic stem cell transplantation (HSCT), when combined with other chemotherapeutic drugs, has not been thoroughly investigated. The present study demonstrates the synergistic cytotoxicity of ABT199/venetoclax with the DNA alkylator thiotepa (Thio) in AML cells. Cleavage of Caspase 3, PARP1 and HSP90, as well as increased Annexin V positivity, suggest potent activation of apoptosis by this two-drug combination; increased levels of γ-H2AX, P-CHK1 (S317), P-CHK2 (S19) and P-SMC1 (S957) indicate an enhanced DNA damage response. Likewise, the increased level of P-SAPK/JNK (T183/Y185) and decreased P-PI3Kp85 (Y458) suggest enhanced activation of stress signaling pathways. These molecular readouts were synergistically enhanced when ABT199/venetoclax and Thio were combined with fludarabine, cladribine and busulfan. The five-drug combination decreased the levels of BCL-2, BCL-xL and MCL-1, suggesting its potential clinical relevance in overcoming ABT199/venetoclax resistance. Moreover, this combination is active against P53-negative and FLT3-ITD-positive cell lines. Enhanced activation of apoptosis was observed in leukemia patient-derived cell samples exposed to the five-drug combination, suggesting a clinical relevance. The results provide a rationale for clinical trials using these two- and five-drug combinations as part of a conditioning regimen for AML patients undergoing HSCT.

Pretransplant conditioning with Fludarabine (Flu)-Busulfan (Bu) is safe, but clofarabine (Clo) has improved antileukemic activity. Hypothesis: Flu+Clo-Bu (FCB) yields superior progression-free survival (PFS) after allogeneic transplantation. We randomized 250 AML/MDS patients aged 3-70, Karnofsky Score ≥80, with matched donors, to FCB (n = 120) or Flu-Bu (n = 130), stratifying complete remission (CR) vs. No CR, (NCR). HCT-CI scores varied, from 0 to 10. All evaluable patients engrafted. Median follow-up was 66 months (interquartile range: 58-80). Three-year relapse incidence (RI), 25% with FCB, vs. 39% with Flu-Bu (p = 0.018), offset by higher non-relapse mortality, 22.6% (95%CI: 16-30.2%) vs. 12.3% (95%CI: 6.5-19%). Three-year PFS was 52% (95%CI: 44-62%) (FCB), vs. 48% (95%CI: 41-58%) (Flu-Bu). FCB benefited CR patients less, NCR patients age ≤ 60 had 3-year 34% RI (95%CI: 19-49%) (FCB) vs. 56% (95%CI: 38-70%) after Flu-Bu (p = 0.037). NCR patients >60 years had 3-year RI 10.0% (FCB), vs. 56.0%, after Flu-Bu (p = 0.003). Bayesian regression analysis including treatment-covariate interactions showed FCB superiority in NCR patients with low HCT-CI (0-2). Serious adverse event profiles were similar for the regimens. Conditioning with FCB did not improve PFS overall, but improved disease control in NCR patients, mandating confirmatory trials. Remission status and HCT-CI should be considered when using FCB., (© 2022. The Author(s).)

Bisantrene (Bis), a topoisomerase-II inhibitor, is less cardiotoxic than the current anthracyclines. Its synergistic cytotoxicity with newly developed antineoplastic drugs has not been reported. We demonstrated the synergism of [Bis + ABT199/venetoclax] in combination with panobinostat (Pano), decitabine (DAC), or olaparib (Ola), known inhibitors of BCL2, histone deacetylase, DNA methyltransferase, and poly(ADP-ribose) polymerase, respectively, in AML cells. [Bis + ABT199] with Pano, DAC, or Ola synergistically inhibited cell proliferation with combination indices of 0.25-0.6, 0.2-0.35, and 0.2-0.4 (at 50% inhibition of proliferation), respectively. Increased γ-H2AX suggests enhanced DNA damage; cleavages of Caspase 3 and PARP1, DNA fragmentation, increased ROS, and decreased MMP indicate potent apoptosis activation. Similar results were observed using mononuclear cells from leukemia patients but not from healthy donors. The SAPK/JNK signaling pathway was strongly activated by the combination treatments, whereas the PI3K/mTOR and Wnt/β-catenin pro-survival pathways were inhibited. These drug combinations may be used in cytoreductive clinical trials for AML patients.

The antineoplastic activity of pre-transplant regimens in hematopoietic stem cell transplantation (HSCT) is a critical factor for acute myeloid leukemia (AML) patients. There is an urgent need to identify novel approaches without jeopardizing patient safety. We hypothesized that combination of drugs with different mechanisms of action would provide better cytotoxicity. We, therefore, determined the synergistic cytotoxicity of various combinations of the alkylating agents busulfan (Bu) and 4-hydroperoxycyclophosphamide (4HC), the nucleoside analog fludarabine (Flu) and the BCL2 inhibitor ABT199/venetoclax in AML cells. [Bu+4HC] and [Bu+Flu] inhibited cell proliferation and activated apoptosis; addition of ABT199 to either combinations significantly increased these effects with combination indexes < 1. Apoptosis is suggested by cleavages of PARP1 and CASPASE 3, DNA fragmentation, increased reactive oxygen species, decreased mitochondrial membrane potential, and increased pro-apoptotic proteins in the cytoplasm. A similar enhancement of apoptosis was observed in patient-derived cell samples. ABT199/venetocalx upregulated anti-apoptotic MCL1 as a compensatory mechanism but addition of [Bu+4HC] or [Bu+Flu] negated this effect by CASPASE 3-mediated cleavage of MEK1/2 and its substrate MCL1. CASPASE 3 caused cleavage of pro-survival β-CATENIN, which likely contributed to the activation of stress signaling pathways involving SAPK/JNK and AMPK. The observed synergistic cytotoxicity was associated with an inhibition of pro-survival pathways involving STAT1, STAT5 and PI3K. These findings will be useful in designing clinical trials using these drug combinations as pre-transplant conditioning regimens for AML patients., Competing Interests: CONFLICTS OF INTEREST Authors have no conflict of interest to declare., (Copyright: © 2022 Valdez et al.)

Relapse is the major cause of mortality in patients with acute myeloid leukemia (AML) after allogeneic hematopoietic stem cell transplantation (allo-HSCT). Effective preventive intervention in high-risk AML may be crucial. In this study, we investigated the clinical efficacy and safety of low dose decitabine (DAC) as part of a modified Busulfan-Cyclophosphamide (Bu-Cy) regimen for high-risk AML patients undergoing allo-HSCT to reduce relapse rate. Fifty-nine patients received DAC (20 mg/m 2 /d, i.v.) for 5 days, followed by modified Bu-Cy (DAC group). A matched-pair control (CON) group of 177 patients (matched 1:3) received modified Bu-Cy only. The differences were more substantial among patients with active disease: 2-year OS, 80.7% (DAC) versus 43.5% (CON), P = 0.011 and 2-year LFS, 64.9% (DAC) versus 39.2% (CON), P = 0.024. Median time to relapse was 8 months (DAC) versus 5 months (CON) for the entire groups and 6.5 months (DAC) versus 3.5 months (CON) for patients with active disease. In summary, our data indicated that the conditioning regimen containing low dose DAC may confer a survival advantage in high-risk AML patients with active disease undergoing allo-HSCT, and a prospective randomized trial is warranted to confirm these observations.

Background: A myeloablative conditioning regimen can be safely given to older patients and those with comorbidities without increasing nonrelapse mortality (NRM) by fractionating the dose of intravenous busulfan. How this approach compares in efficacy with traditional, nonfractionated, lower dose regimens is unknown., Methods: Outcomes were compared in patients with acute myeloid leukemia (AML) or myelodysplastic syndrome who received either myeloablative, fractionated busulfan (f-Bu) dosed to achieve an area under the curve of 20,000 μmol per minute (f-Bu20K) over 2 weeks (n = 84) or a standard, nonfractionated, lower busulfan dose regimen of 16,000 μmol per minute (Bu16K) over 4 days (n = 78). Both groups also received fludarabine 40 mg/m 2 intravenously for 4 days. Graft-versus-host disease prophylaxis was tacrolimus and methotrexate. Patients in the Bu16K group who had unrelated donors also received antithymocyte globulin. The primary endpoint was progression-free survival., Results: Roughly one-half of the patients were aged >65 years, approximately 40% had poor-risk cytogenetics, approximately 40% of those with AML were not in complete remission, and approximately 40% had a comorbidity index >3. At 2 years, progression-free survival was significantly improved in the f-Bu20K group compared with the Bu16K group (45% vs 24%, respectively; hazard ratio [HR], 0.6; 95% CI, 0.4-0.8; P = .004). This was because of a significant reduction in progression (34% vs 59%, respectively; HR, 0.5; 95% CI, 0.3-0.8; P = .003) without any increase in NRM (21% vs 15%, respectively; HR, 1.4; 95% CI, 0.7-3; P = .3), which resulted in improved overall survival (51% vs 31%, respectively; HR, 0.6; 95% CI, 0.3-0.9; P = .01)., Conclusions: A myeloablative, fractionated busulfan regimen reduces relapse and improves survival without increasing NRM in older patients with AML and myelodysplastic syndrome., (© 2021 American Cancer Society.)

Acute myeloid leukemia (AML) patients not in remission and beyond first or second complete remission are considered allogeneic stem cell transplant (SCT) candidates. We present 361 patients who underwent SCT from matched related or unrelated donors between 2005 and 2013. The purpose was to identify a subgroup of patients with active disease at the time of transplant that benefit. Cox proportional hazards regression analysis was used for univariate and multivariate analyses to predict overall survival (OS). Variables considered were age, sex, SWOG cytogenetic risk group, bone marrow (BM) and peripheral blood (PB) blast percentage, regimen intensity, and type of AML. At a median of 26 months after transplantation, OS, progression-free survival (PFS), non-relapse mortality, and relapse rates were 26, 24, 23, and 48%, respectively. In a univariate analysis, risk cytogenetics (p < 0.001) and BM blasts >4% (p = 0.006) or any blasts in PB (p < 0.001) indicated worse OS. In a multivariate analysis, patients with <5% BM blasts or absence of circulating blasts and good or intermediate risk cytogenetics had significantly superior OS (46%), PFS (44%), and disease progression at 3 years. Based on these findings, patients not in remission with good or intermediate risk cytogenetics and low blast counts should be considered for SCT., (© 2020 S. Karger AG, Basel.)

Optimal conditioning regimens for older patients with myelofibrosis undergoing allogeneic hematopoietic cell transplant are not known. Likewise, the role of dose intensity is not clear. We conducted a nonrandomized, prospective, phase II trial using low-dose, later escalated to high-dose (myeloablative conditioning), busulfan with fludarabine (Bu-Flu) in myelofibrosis patients up to age 74 years. The first 15 patients received i.v. busulfan 130 mg/m 2 /day on days -3 and -2 ("low dose"); 31 patients received high-dose conditioning, either 100 mg/m 2 /day (days -5 to -2; n = 4) or pharmacokinetic-guided area under the curve of 4000 μmol/min (days -5 to -2; n = 27). The primary endpoint was day 100 nonrelapse mortality (NRM). Median age was 58 years (interquartile range [IQR], 53-63). Dynamic international prognostic scoring system-plus was intermediate (n = 28) or high (n = 18). Donors were related (n = 19) or unrelated (n = 27). Cumulative incidence of NRM was 9.7% (95% confidence interval [CI], 0-20.3) at day 100 and at 3 years in the high-dose group and 0% in the low-dose group at day 100, which increased to 20% (95% CI, 0-41.9) at 3 years. With a median follow-up of 5.1 years (IQR, 3.8-6), 3-year relapse was 32.3% (95% CI, 15.4-49.1) in high dose versus 53.3% (95% CI, 26.6-80.1) in low dose. Event-free survival was 58% (95% CI, 43-78) versus 27% (95% CI, 12-62), and overall survival was 74% (95% CI, 60-91) versus 60% (95% CI, 40-91). In multivariate analysis, high-dose busulfan had a trend toward lower relapse (hazard ratio, .44; 95% CI, .18-1.07; P = .07), with no impact on NRM. Intensifying the Bu-Flu regimen using pharmacokinetic-monitoring appears to be promising in reducing relapse without increasing NRM., (Copyright © 2020 American Society for Transplantation and Cellular Therapy. Published by Elsevier Inc. All rights reserved.)

Conditioning regimens contribute significantly to outcomes following allogeneic stem cell transplantation (allo-SCT). Reduced-intensity conditioning (RIC) regimens provide lower toxicity at the cost of reduced efficacy compared with myeloablative conditioning (MAC) regimens. However, because pre-transplant prognostic variables often determine the conditioning regimen, studies of RIC vs. MAC have been inconclusive. We present a retrospective analysis of 242 acute myeloid leukemia (AML) or myelodysplastic syndrome (MDS) patients, 112 of whom were in 56 pairs matched using propensity scores, to account for variation that may confound clinical outcomes. The uniform conditioning regimens consisted of fludarabine with pharmacokinetic (PK)-guided intravenous busulfan (Bu). The RIC and MAC regimens were dosed at the average daily area under the concentration-vs-time curve (AUC) of 4000 µMol min and 5000-6000 µMol min, or total course AUC of 16,000 µMol min and 20,000-24,000 µMol min, respectively; PK-guided dosing removes overlap in systemic Bu exposure. When patients' data were propensity-matched, there was a trend toward significantly increased full donor chimerism and decreased chronic graft vs. host disease in RIC, and no significant differences in progression free survival and overall survival between RIC and MAC. Our results also elucidate the efficacy of PK-guided-dosing in the setting of allo-SCT for AML and MDS.

Outcomes after allogeneic stem-cell transplantation (AHSCT) are influenced by both disease- and patient-related factors. Here, we developed a novel prognostic model, hematopoietic cell transplant-composite risk (HCT-CR), by combining the refined disease risk index (DRI-R) and hematopoietic stem-cell transplant comorbidity/age index (HCT-CI/Age) to predict post-transplant survival for patients with acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS). The analysis included 942 AML/MDS patients treated with AHSCT. Patients were stratified into 4 HCT-CR risk groups: Low-risk-patients with low/intermediate DRI-R and HCT-CI/Age ≤3 (N = 272); Intermediate-risk-patients with low/intermediate DRI-R and HCT-CI/Age >3 (N = 168); High-risk-patients with high/very high DRI-R and HCT-CI/Age ≤3 (N = 284); and Very high-risk-patients with high/very high DRI-R and HCT-CI/Age >3 (N = 184). Compared with the low-risk group, intermediate, high, and very high-risk groups had a significantly increased risk of death [adjusted HR of 1.37 (P < 0.04), 2.08 (P < 0.001), and 2.92 (P < 0.001), respectively]. The concordance test showed that the HCT-CR model provided better discriminative capacity for OS prediction compared with all prior models independently, including cytogenetic risk group, DRI-R, and HCT-CI/Age model (C-indices: 0.62, 0.55, 0.60, and 0.54, respectively) (P < 0.001). In conclusion, combining disease- and patient-related factors provides better survival stratification for patients with AML/MDS receiving AHSCT.

The combination of the DNA-alkylating agents busulfan (Bu) and cyclophosphamide is the most commonly used myeloablative pretransplantation conditioning therapy for myeloid leukemias. However, it is associated with significant nonrelapse mortality, which prohibits dose escalation to control relapse. We hypothesized that combining these two drugs with an epigenetic modifier would increase antileukemic efficacy without jeopardizing patient safety. A preclinical study was performed to determine the synergistic cytotoxicity of Bu, 4-hydroperoxycyclophosphamide (4HC), and the hypomethylating agent decitabine (DAC) in human acute myeloid leukemia (AML) cell lines. Exposure of KBM3/Bu250 6 (P53-null) and OCI-AML3 (P53-wild-type) cells to Bu+4HC inhibited cell proliferation by ∼35-39%; addition of DAC increased the inhibition to ∼60-62%. The observed synergistic interactions correlated with DNA damage response activation, increased the production of reactive oxygen species, and decreased mitochondrial membrane potential, release of mitochondrial proapoptotic proteins into the cytoplasm, and induction of caspase-dependent programmed cell death. The Bu+4HC+DAC combination further caused chromatin trapping of DNMT1 with a concomitant increase in DNA damage. In contrast, FMS-like tyrosine kinase 3 internal tandem duplications (FLT3-ITD)-positive AML cell lines were not sensitized to Bu+4HC by inclusion of DAC; addition of the FLT3 kinase inhibitor sorafenib sensitized the FLT3-ITD-positive MV4-11 and MOLM13 cell lines to the triple drug combination by inhibiting the FLT3 signal transduction pathway. Our results therefore provide a rationale for the development of personalized conditioning therapy for patients with P53-mutated and FLT3-ITD-positive AML., (Published by Elsevier Inc.)

We studied if the inclusion of early post-stem cell transplantation (SCT) minimal residual disease (MRD) assessments improved prognostication in patients with acute myeloid leukemia (AML). Two hundred sixty-nine AML patients in morphological complete remission (CR) who underwent a first SCT were included if they had evaluable pre-SCT MRD assessment by multiparametric flow cytometry. Post-SCT MRD assessments were performed at days +30, +100, and +180. The primary outcome was 1-year relapse incidence (RI). Of 269 patients in CR, 83 (30.8%) had detectable MRD pre-SCT. Post-SCT, during routine disease assessment time points, 9 of 241 evaluable patients (3.7%) at day +30, 6 of 191 evaluable patients (3.1%) at day +100, and 4 of 133 evaluable patients (3%) at day +180 were MRD positive while in CR. MRD positivity at day +30 predicted the highest risk of relapse at 1 year (group 1, 1-year RI 78%). Among MRD-negative patients at day +30, either adverse risk category by European Leukemia Net (ELN) or intermediate risk who were aged ≥60 years and/or pre-SCT MRD-positive represented the intermediate-risk group (group 2, 1-year RI 29%). The remaining patients represented the low-risk group (group 3, 1-year RI 5%). For patients in CR beyond day +30 post-SCT, detectable MRD at any time point predicted impending relapse within 2 months. Early post-SCT MRD assessment-combined with pre-SCT MRD assessment, ELN risk category, and age-improves risk stratification for relapse in AML patients post-transplant. Studies aimed at preventing impending relapse in this high-risk population are urgently needed., (Copyright © 2018 The American Society for Blood and Marrow Transplantation. Published by Elsevier Inc. All rights reserved.)

In patients with AML with FMS-like tyrosine kinase 3 (FLT3) mutations, the significance of minimal residual disease (MRD) detected by PCR before allogeneic stem cell transplantation (SCT) on outcomes after transplant remains unclear. We identified 200 patients with FLT3-AML who underwent SCT at our institution. Disease status at transplant was: first or second complete remission (CR1/CR2, n = 119), high-risk CR (third or subsequent CR, marrow hypoplasia, or incomplete count recovery) (CR-HR, n = 31), and morphological evidence of active disease (AD, n = 50). The median follow-up was 27 months, and the 2-year overall and progression-free survival were 43% and 41%, respectively. Relapse was highest in the AD group (85%) and the CR-HR FLT3 MRD positive group (72%), followed by CR-HR FLT3 MRD negative (58%), CR1/CR2 FLT3 MRD positive (39%), and lowest in the CR1/CR2 FLT3 MRD negative group (23%). On multivariate analysis, independent factors influencing the risk of relapse were detectable morphological disease and FLT3 MRD by PCR pre-transplant. Factors that did not influence the relapse risk included: age, graft type, graft source, type of FLT3 mutation, or conditioning intensity. Morphologic and molecular remission status at the time of transplant were key predictors of disease relapse and survival in patients with FLT3-AML., (© 2017 Wiley Periodicals, Inc.)

We hypothesized that IV busulfan (Bu) dosing could be safely intensified through pharmacokinetic (PK-) dose guidance to minimize the inter-patient variability in systemic exposure (SE) associated with body-sized dosing, and that this should improve outcome of AML/MDS patients undergoing allogeneic stem cell transplantation. To test this hypothesis, we treated 218 patients (median age 50.7 years, male/female 50/50%) with fludarabine 40 mg/m 2 once daily x4, each dose followed by IV Bu, randomized to 130 mg/m 2 (N=107) or PK-guided to average daily SE, AUC of 6000 μM min (N=111), stratified for remission status and allo-grafting from HLA-matched donors. Toxicity and GvHD rates in the groups were similar; the risk of relapse or treatment-related mortality remained higher in the fixed-dose group throughout the 80-month observation period. Further, PK-guidance yielded safer disease control, leading to improved overall and PFS, most prominently in MDS patients and in AML patients not in remission at allogeneic stem cell transplantation. We conclude that AML/MDS patients receiving pretransplant conditioning treatment with our 4-day regimen may benefit significantly from PK-guided Bu dosing. This could be considered an alternative to fixed-dose delivery since it provides the benefit of precise dose delivery to a predetermined SE without increasing risk(s) of serious toxicity and/or GvHD.

Our aim was to improve outcome prediction after allogeneic hematopoietic stem cell transplantation in acute myeloid leukemia by combining cytogenetic and molecular data at diagnosis with minimal residual disease assessment by multicolor flow-cytometry at transplantation. Patients with acute myeloid leukemia in first complete remission in whom minimal residual disease was assessed at transplantation were included and categorized according to the European LeukemiaNet classification. The primary outcome was 1-year relapse incidence after transplantation. Of 152 patients eligible, 48 had minimal residual disease at the time of their transplant. Minimal residual disease-positive patients were older, required more therapy to achieve first remission, were more likely to have incomplete recovery of blood counts and had more adverse risk features by cytogenetics. Relapse incidence at 1 year was higher in patients with minimal residual disease (32.6% versus 14.4%, P=0.002). Leukemia-free survival (43.6% versus 64%, P=0.007) and overall survival (48.8% versus 66.9%, P=0.008) rates were also inferior in patients with minimal residual disease. In multivariable analysis, minimal residual disease status at transplantation independently predicted 1-year relapse incidence, identifying a subgroup of intermediate-risk patients, according to the European LeukemiaNet classification, with a particularly poor outcome. Assessment of minimal residual disease at transplantation in combination with cytogenetic and molecular findings provides powerful independent prognostic information in acute myeloid leukemia, lending support to the incorporation of minimal residual disease detection to refine risk stratification and develop a more individualized approach during hematopoietic stem cell transplantation., (Copyright© Ferrata Storti Foundation.)

Pretransplant conditioning regimens critically determine outcomes in the setting of allogeneic stem cell transplantation (allo-SCT). The use of nucleoside analogs such as fludarabine (Flu) in combination with i.v. busulfan (Bu) has been shown to be highly effective as a pretransplant conditioning regimen in acute myeloid leukemia (AML), chronic myeloid leukemia (CML), and myelodysplastic syndrome (MDS). Because leukemia relapse remains the leading cause of death after allo-SCT, we studied whether clofarabine (Clo), a nucleoside analog with potent antileukemia activity, can be used to complement Flu. In a preliminary report, we previously showed the safety and efficacy of Clo ± Flu with i.v. Bu in 51 patients with high-risk AML, CML, and MDS. The study has now been completed, and we present long-term follow-up data on the entire 70-patient population, which included 49 (70%), 8 (11%), and 13 (19%) patients with AML, MDS, and CML, respectively. Thirteen patients (19%) were in complete remission, and 41 patients (59%) received matched unrelated donor grafts. Engraftment was achieved in all patients. Sixty-three patients (90%) achieved complete remission. There were no deaths reported at day +30, and the 100-day nonrelapse mortality rate was 4% (n = 3). Thirty-one percent of patients (n = 22) developed grades II to IV acute graft-versus-host disease, and the median overall survival and progression-free survival times were 2.4 years and .9 years, respectively. Our results confirm the safety and overall and progression-free survival advantage of the arms with higher Clo doses and lower Flu doses, which was most prominent in the AML/MDS group., (Copyright © 2016 The American Society for Blood and Marrow Transplantation. Published by Elsevier Inc. All rights reserved.)

The adverse prognosis of internal tandem duplication in the FMS-like tyrosine kinase 3 gene(s) (FLT3-ITD) in patients with acute myelogenous leukemia (AML) may depend on allelic burden. We compared postremission treatment with chemotherapy and hematopoietic stem cell transplantation (HSCT) in 169 FLT3-ITDmut intermediate cytogenetic risk AML patients with allelic ratio evaluable at diagnosis who achieved first complete remission (CR1) with induction therapy. To minimize selection bias, the analysis was limited to patients who remained in CR1 for at least 4 months (median time to HSCT) after achieving CR1, and propensity score matching was implemented. Sensitivity analysis including patients who remained in CR1 for at least 3 months was applied as well. HSCT in CR1 was associated with longer relapse-free survival (RFS) and overall survival (OS), with 3-year estimated rates of 18% and 24%, respectively (P < .001), for patients receiving chemotherapy and 46% and 54%, respectively (P < .001), for those undergoing HSCT. Multivariate regression models showed that HSCT remained statistically significant with improved RFS and OS independent of FLT3-ITD allelic ratio and NPM1 status. Irrespective of postremission therapy, relapse remains the main reason for treatment failure, with a 3-year incidence of 68% in chemotherapy recipients versus 41% in HSCT recipients. Allogeneic HSCT improved disease outcomes compared with chemotherapy after propensity score matching was applied. The improvement observed for RFS (hazard ratio [HR], 0.55; P = .09) and OS (HR, 0.58; P = .10) with HSCT as postremission therapy in patients who remained in CR1 for at least 4 months did not reach statistical significance; however, the sensitivity analyses including patients who remained in CR1 for at least 3 months showed significant improvement in both RFS (HR, 0.31; P = .002) and OS (HR, 0.27; P = .02) after propensity score matching. Our results indicate that HSCT in CR1 for AML FLT3-ITDmut patients is associated with longer RFS and OS. Innovative transplantation strategies to improve relapse incidence are urgently needed., (Copyright © 2016 American Society for Blood and Marrow Transplantation. Published by Elsevier Inc. All rights reserved.)

Chimerism testing after allogeneic hematopoietic stem cell transplantation (allo-HSCT) in patients with acute myeloid leukemia (AML) and myelodysplastic syndromes (MDS) represents a promising tool for predicting disease relapse, although its precise role in this setting remains unclear. We investigated the predictive value of T lymphocyte chimerism analysis at 90 to 120 days after allo-HSCT in 378 patients with AML/MDS who underwent busulfan/fludarabine-based myeloablative preparative regimens. Of 265 (70%) patients with available T lymphocyte chimerism data, 43% of patients in first or second complete remission (CR1/CR2) at the time of transplantation had complete (100%) donor T lymphocytes at day +90 to +120 compared with 60% of patients in the non-CR1/CR2 cohort (P = .005). In CR1/CR2 patients, donor T lymphocyte chimerism ≤ 85% at day +90 to +120 was associated with a higher frequency of 3-year disease progression (29%; 95% confidence interval [CI], 18% to 46% versus 15%; 95% CI, 9% to 23%; hazard ratio [HR], 2.1; P = .04). However, in the more advanced, non-CR1/CR2 cohort, mixed T lymphocyte chimerism was not associated with relapse (37%; 95% CI, 20% to 66% versus 34%; 95% CI, 25% to 47%; HR, 1.3; P = .60). These findings demonstrate that early T lymphocyte chimerism testing at day +90 to +120 is a useful approach for predicting AML/MDS disease recurrence in patients in CR1/CR2 at the time of transplantation., (Copyright © 2015 American Society for Blood and Marrow Transplantation. Published by Elsevier Inc. All rights reserved.)

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., (Published by Elsevier Inc.)

The mismatched minor histocompatibility antigens present on Y chromosome (H-Y) in male recipients receiving stem cells from female donors may contribute to the graft-versus-leukemia effect and results in a reduced relapse rate, especially in patients with high-risk disease. We retrospectively compared the outcomes of male patients with acute myeloid leukemia who received an allogeneic hematopoietic stem cell transplant (HSCT) from female donors (F-M) (174 patients) versus other gender combinations (667 patients). Median age was 50 years (range, 18 to 74 years). For the whole group, the 1-year cumulative incidence of relapse was significantly lower in F-M group (34.1% versus 41.3%, P = .044), whereas nonrelapse mortality (NRM) was higher (23.2% versus 15.7%, P = .004). For patients younger than 50 years beyond first complete remission, the F-M group was associated with lower relapse rate (42.5% versus 55.2%, P = .045) whereas NRM was not significantly different (35.8% versus 25.5%, P = .141). Although survival was not significantly improved, transplantation from a female donor for male recipient was associated with a lower relapse rate. When relapse is the most common concern for treatment failure, especially for younger patients, a female donor for a male recipient might be beneficial to decrease relapse rate after transplantation. Future studies are needed to explore how the H-Y mismatch may improve survival after transplantation., (Copyright © 2015 American Society for Blood and Marrow Transplantation. Published by Elsevier Inc. All rights reserved.)

Clofarabine (Clo), fludarabine (Flu), and busulfan (Bu) are used in pretransplantation conditioning therapy for patients with myeloid leukemia. To further improve their efficacy in FMS-like tyrosine kinase 3 internal tandem duplications (FLT3-ITD)-positive acute myeloid leukemia (AML), we investigated their synergism with sorafenib (Sor). Exposure of FLT3-ITD-positive MV-4-11 and MOLM 13 cells to Bu+Clo+Flu+Sor resulted in synergistic cytotoxicity; no such synergism was observed in the FLT3-wild type THP-1 and KBM3/Bu250(6) cell lines. The drug synergism in MV-4-11 cells could be attributed to activation of DNA damage response, histone 3 modifications, inhibition of prosurvival kinases, and activation of apoptosis. Further, the phosphorylation of kinases, including FLT3, MAPK kinase (MEK), and AKT, was inhibited. The FLT3-ITD substrate STAT5 and its target gene PIM 2 product decreased when cells were exposed to Sor alone, Bu+Clo+Flu, and Bu+Clo+Flu+Sor. The level of the proapoptotic protein p53 upregulated modulator of apoptosis (PUMA) increased, whereas the level of prosurvival protein MCL-1 decreased when cells were exposed to Bu+Clo+Flu+Sor. The interactions of PUMA with MCL-1 and/or BCL-2 were enhanced when cells were exposed to Bu+Clo+Flu or Bu+Clo+Flu+Sor. The changes in the level of these proteins, which are involved in mitochondrial control of apoptosis, correlate with changes in mitochondrial membrane potential. Bu+Clo+Flu+Sor decreased mitochondrial membrane potential by 60% and caused leakage of cytochrome c, second mitochondria-derived activator of caspases (SMAC)/direct IAP Binding protein with low pI (DIABLO), and AIF from the mitochondria to the cytoplasm, caspase activation, and cell death, suggesting the activation of apoptosis. Analogous, synergistic cytotoxicity in response to Bu, Clo, Flu, and Sor was observed in mononuclear cells isolated from FLT3-ITD-positive AML patients. Although our previous studies were aimed at standardizing the conditioning regimen, the new findings suggest that patients with abnormal expression of FLT3 might further benefit from individualizing treatment through the addition of Sor to Bu+Clo+Flu, thereby providing personalized pretransplantation therapy., (Copyright © 2014 American Society for Blood and Marrow Transplantation. Published by Elsevier Inc. All rights reserved.)

This study was conducted to retrospectively compare the clinical outcomes after transplantation of T cell-depleted (TCD) and unmodified allografts in patients with acute myeloid leukemia (AML) in first complete remission (CR1). Patients received TCD grafts at Memorial Sloan-Kettering Cancer Center (MSKCC, N = 115) between 2001 and 2010 using the following preparative regimens: hyperfractionated total body irradiation (HFTBI)+thiotepa+fludarabine; HFTBI+thiotepa+cyclophosphamide; or i.v. busulfan+melphalan+fludarabine. TCD was performed by 1 of 2 immunomagnetic CD34(+) cell selection methods for peripheral blood grafts or by soybean lectin agglutination followed by sheep red blood cell-rosette depletion for bone marrow grafts. No additional graft-versus-host disease (GVHD) prophylaxis was administered. Patients received unmodified grafts at M.D. Anderson Cancer Center (MDACC, N = 181) after conditioning with busulfan+fludarabine and GVHD prophylaxis with tacrolimus+mini-methotrexate. Patients with unrelated or human leukocyte antigen-mismatched donors received anti-thymocyte globulin (ATG) at both centers, with some recipients of matched related donor TCD transplants also receiving ATG, depending upon the preparative regimen. TCD graft recipients were more likely to be older, receive a mismatched transplant, and have peripheral blood used as the graft source. The incidences rates of grades 2 to 4 acute GVHD and chronic GVHD were significantly lower in the TCD graft group (5% versus 18%, and 13% versus 53%). Three-year relapse-free and overall survival rates were 58% and 57%, respectively, in recipients of TCD grafts, and 60% and 66% in recipients of unmodified grafts (P = not significant). Survival and relapse-free survival are similar after TCD and conventional transplants from related/unrelated donors in patients with AML in CR1, but TCD significantly reduces GVHD., (Copyright © 2013 American Society for Blood and Marrow Transplantation. Published by Elsevier Inc. All rights reserved.)

Risk stratification is important to identify patients with acute myelogenous leukemia (AML) who might benefit from allogeneic hematopoietic stem cell transplantation (allo-HSCT) in first complete remission. We retrospectively studied 150 patients with AML and diagnostic cytogenetic abnormalities who underwent myeloablative allo-HSCT while in first complete remission to evaluate the prognostic impact of persistent cytogenetic abnormalities at allo-HSCT. Three risk groups were identified. Patients with favorable/intermediate cytogenetics at diagnosis (n = 49) and patients with unfavorable cytogenetics at diagnosis but without a persistent abnormal clone at allo-HSCT (n = 83) had a similar 3-year leukemia-free survival of 58%-60% despite the higher 3-year relapse incidence (RI) in the latter group (32.3%, versus 16.8% in the former group). A third group of patients with unfavorable cytogenetics at diagnosis and a persistent abnormal clone at allo-HSCT (n = 15) had the worst prognosis, with a 3-year RI of 57.5% and 3-year leukemia-free survival of only 29.2%. These data suggest that patients with AML and unfavorable cytogenetics at diagnosis and a persistent abnormal clone at allo-HSCT are at high risk for relapse after allo-HSCT. These patients should be considered for clinical trials designed to optimize conditioning regimens and/or to use preemptive strategies in the posttransplantion setting aimed at decreasing RI., (Copyright © 2013 American Society for Blood and Marrow Transplantation. Published by Elsevier Inc. All rights reserved.)

Complete remission (CR) is the gold standard for assessing outcomes following chemotherapy for acute myelogenous leukemia (AML). "CRp," a response criterion defined as fulfillment of all criteria for CR except platelet count recovery to ≥100 × 10(9)/L, is associated with inferior outcomes following chemotherapy. The prognostic importance of CRp before allogeneic stem cell transplantation (allo-SCT) remains unknown. We analyzed a cohort of AML (n = 334) and myelodysplastic syndrome (MDS; n = 10) patients to determine the prognostic significance of achieving CR versus CRp before allo-SCT. At time of transplantation, 266 patients were in CR (CR1 and ≥CR2) and 78 in CRp (CR1p and ≥CR2p). Median follow-up was 38 months (3-131 months). Overall survival, progression-free survival, and nonrelapse mortality (NRM) were most favorable in patients transplanted in CR (CR1 or ≥CR2) compared with CRp (CR1p or ≥CR2p). Achieving CR is therefore associated with improved posttransplantation outcomes compared with achieving CRp and is a significant prognostic factor that needs to be considered when evaluating AML/MDS patients for clinical trials and allo-SCT., (Copyright © 2011 American Society for Blood and Marrow Transplantation. Published by Elsevier Inc. All rights reserved.)

The optimal pretransplant regimen for acute myeloid leukemia (AML) or myelodysplastic syndrome (MDS) in patients ≥ 55 years of age remains to be determined. The myeloablative reduced-toxicity 4-day regimen i.v. busulfan (Bu) (130 mg/m(2)) and i.v. fludarabine (Flu) (40 mg/m(2)) is associated with low morbidity and mortality. We analyzed 79 patients ≥ 55 years of age (median, 58 years) with AML (n = 63) or MDS (n = 16) treated with i.v. Bu-Flu conditioning regimens between 2001 and 2009 (median follow-up, 24 months). The patients who received this regimen had a good performance status. The 2-year overall survival (OS) rates for patients in first complete remission (CR1), second CR (CR2), or refractory disease and for all patients at time of transplantation were 71%, 44%, 32%, and 46%, respectively; 2-year event-free survival (EFS) rates for patients in CR1, CR2, or refractory disease at time of transplantation and for all patients were 68%, 42%, 30%, and 44%, respectively. One-year transplant-related mortality (TRM) rates for patients who were in CR or who had active disease at the time of transplantation were 19% and 20%, respectively. Grade II-IV acute graft-versus-host (aGVHD) disease was diagnosed in 40% of the patients. Our results suggest that age alone should not be the primary reason for exclusion from receiving myeloablative reduced-toxicity conditioning with i.v. Bu-Flu preceding transplantation in patients with AML/MDS., (Copyright © 2011 American Society for Blood and Marrow Transplantation. Published by Elsevier Inc. All rights reserved.)

Objective: To report the case of a clinically significant drug interaction between intravenous busulfan and oral metronidazole observed through busulfan therapeutic drug monitoring (TDM)., Case Summary: A 7-year-old boy with a history of myelodysplasia that progressed to acute myeloid leukemia received busulfan with therapeutic drug monitoring (TDM), clofarabine, and thiotepa as a pretransplant conditioning regimen for a cord blood transplant. The patient received metronidazole the day after a busulfan test dose of 0.5 mg/kg was administered. On the day of the first busulfan therapeutic dose, TDM was performed and the clearance of busulfan was significantly decreased by 46%. After 2 doses of busulfan therapy, the course area under the curve was exceeded, requiring discontinuation of busulfan. Metronidazole is not known to affect glutathione or the glutathione S-transferase A1 (GSTA1) enzyme system or cytochrome P450 (CYP) 3A4., Discussion: Busulfan is a bifunctional alkylating agent widely used in pretransplant conditioning regimens in patients undergoing stem cell transplantation for hematologic malignancies. Busulfan metabolism is best described by hepatic conjugation to glutathione by GSTA1, although some CYP-dependent pathways have been described. Currently there is 1 publication describing the drug interaction between oral busulfan and oral metronidazole, in which concomitant use of metronidazole resulted in higher busulfan trough concentrations and higher risk of veno-occlusive disease. Our case represents a possible drug interaction based on the Horn Drug Interaction Probability Scale., Conclusions: Though the mechanistic basis for this interaction is unknown, the risks and benefits of using metronidazole during and in close proximity to busulfan should be carefully considered and therapeutic alternatives to metronidazole should be used when appropriate.

We retrospectively analyzed the outcomes of all acute myelogenous leukemia (AML) patients in first remission (n = 44; median age = 48 years; high-risk cytogenetics = 59%) who received unrelated donor hematopoietic cell transplantation (HCT) with myeloablative conditioning regimen of i.v. busulfan, fludarabine, and antithymocyte globulin (ATG) between January 2002 and November 2009 at our institution. Donor-recipient pairs were matched by high-resolution HLA-A, -B, -C, -DRB1, and -DQB1 typing (10/10 matches, n = 41; 9/10 matches, n = 3). With a median follow-up of 34 months, actuarial 3-year event-free survival (EFS) and overall survival (OS) is 70% and 78%, respectively. The 3-year EFS and OS in patients with and without poor risk cytogenetics is similar (63% versus 82%, P = 0.43 and 78% versus 82%, P = .89, respectively). The 3-year EFS and OS is also similar in patients above age 55 year versus patients age 55 year or younger (80% versus 67%, P = .47 and 80% versus 78%, P = .81, respectively). The 100-day and 3-year cumulative incidence of transplant-related mortality is 5% and 15%, respectively. Six patients have relapsed, and 3 of them are alive and in remission after salvage therapy, with a median follow-up of 23 months. These results indicate that the majority of AML patients eligible for this treatment can achieve long-term disease control., (2011 American Society for Blood and Marrow Transplantation. Published by Elsevier Inc. All rights reserved.)

Although a combination of i.v. busulfan (Bu) and fludarabine (Flu) is a safe, reduced-toxicity conditioning program for acute myelogenous leukemia/myelodysplastic syndromes (AML/MDS), recurrent leukemia posttransplantation remains a problem. To enhance the conditioning regimen's antileukemic effect, we decided to supplant Flu with clofarabine (Clo), and assayed the interactions of these nucleoside analogs alone and in combination with Bu in Bu-resistant human cell lines in vitro. We found pronounced synergy between each nucleoside and the alkylator but even more enhanced cytotoxic synergy when the nucleoside analogs were combined prior to exposing the cells to Bu. We then designed a 4-arm clinical trial in patients with myeloid leukemia undergoing allogeneic stem cell transplantation (allo-SCT). Patients were adaptively randomized as follows: Arm I-Clo:Flu 10:30 mg/m(2), Arm II-20:20 mg/m(2), Arm III-30:10 mg/m(2), and Arm IV-single-agent Clo at 40 mg/m(2). The nucleoside analog(s) were/was infused over 1 hour once daily for 4 days, followed on each day by Bu, infused over 3 hours to a pharmacokinetically targeted daily area under the curve (AUC) of 6000 μMol-min ± 10%. Fifty-one patients have been enrolled with a minimum follow-up exceeding 100 days. There were 32 males and 19 females, with a median age of 45 years (range: 6-59). Nine patients had chronic myeloid leukemia (CML) (BC: 2, second AP: 3, and tyrosine-kinase inhibitor refractory first chronic phase [CP]: 4). Forty-two patients had AML: 14 were induction failures, 8 in first chemotherapy-refractory relapse, 7 in untreated relapse, 3 in second or subsequent relapse, 4 were in second complete remission (CR), and 3 in second CR without platelet recovery (CRp), 2 were in high-risk CR1. Finally, 1 patient was in first CRp. Graft-versus-host disease (GVHD) prophylaxis was tacrolimus and mini-methorexate (MTX), and those who had an unrelated or 1 antigen-mismatched donor received low-dose rabbit-ATG (Thymoglobulin™). All patients engrafted. Forty-one patients had active leukemia at the time of transplant, and 35 achieved CR (85%). Twenty of the 42 AML patients and 5 of 9 CML patients are alive with a projected median overall survival (OS) of 23 months. Marrow and blood (T cell) chimerism studies at day +100 revealed that both in the lower-dose Clo groups (groups 1+2) and the higher-dose Clo groups (groups 3+4), the patients had a median of 100% donor (T cell)-derived DNA. There has been no secondary graft failure. In the first 100 days, 1 patient died of pneumonia, and 1 of liver GVHD. We conclude that (1) Clo ± Flu with i.v. Bu as pretransplant conditioning is safe in high-risk myeloid leukemia patients; (2) clofarabine is sufficiently immunosuppressive to support allo-SCT in myeloid leukemia; and (3) the median OS of 23 months in this high-risk patient population is encouraging. Additional studies to evaluate the antileukemic efficacy of Clo ± Flu with i.v. Bu as pretransplant conditioning therapy are warranted., (Copyright © 2011 American Society for Blood and Marrow Transplantation. Published by Elsevier Inc. All rights reserved.)

DNA alkylating agents alone or with ionizing radiation have been the preferred conditioning treatment in allogeneic hematopoietic stem cell transplantation (allo-HSCT). In search of less toxic alternatives, we hypothesized that combination of busulfan (Bu), fludarabine (Flu) and clofarabine (Clo) would provide superior efficacy. At low concentrations, these drugs show synergistic cytotoxicity in Bu-resistant AML KBM3/Bu250(6) cells. Similar molecular responses were observed in other AML cell lines and in primary explanted AML cells. The [Clo+Flu+Bu] combination activates an intense DNA damage response through the ATM pathway, leading to cell cycle checkpoint activation and apoptosis. Phosphorylations of SMC1 and SMC3, and methylations of histones 3 and 4, are much more pronounced in cells exposed to [Clo+Flu+Bu] than [Clo+Flu], suggesting their relevance in the efficacy of the triple-drug combination. A possible mechanism for these observed synergistic effects involves the capability of [Clo+Flu] to induce histone methylations and subsequent chromatin remodeling, which may render the genomic DNA more accessible to Bu alkylation. The Bu-mediated DNA cross-linking may provide a feedback loop which perpetuates the DNA damage response initiated by [Clo+Flu] and commits the cells to apoptosis. Our results provide a conceptual mechanistic basis for exploring this triple-drug combination in pretransplant conditioning therapy for allo-HSCT., (Published by Elsevier Inc.)

We hypothesized that standardized systemic drug delivery would improve treatment safety and provide better leukemia control. We therefore developed an intravenous busulfan formulation and combined it with fludarabine instead of cyclophosphamide in preparation for allogeneic stem cell transplantation (alloSCT). We used a Bayesian method to compare the outcomes of 67 acute myeloid leukemia (AML)/myelodysplastic syndrome (MDS) patients who received intravenous busulfan-cyclophosphamide (BuCy2) with 148 subsequent AML/MDS patients who received busulfan-fludarabine (Bu-Flu). The groups had comparable pretreatment characteristics, except that the Bu-Flu patients were older, more often had unrelated donors and had a shorter follow-up. A greatly improved outcome in the Bu-Flu group is unlikely to be explained by improved supportive care during this time period. Overall, the data support replacing BuCy2 with or without antithymocyte globulin (ATG) with Bu-Flu with or without rabbit-ATG for AML or MDS. We further suggest that the high level of safety and fast recovery from conditioning therapy-related side effects after the Bu-Flu regimen makes it a suitable platform technology for testing additional adjuncts for improved posttransplant immune recovery and long-term disease control in patients who are at high risk of rapidly recurrent disease after alloSCT. The extremely low one-year treatment-related mortality as well as high overall and event-free survival of patients in the Bu-Flu group indicate that it is time to revisit the value of alloSCT compared with conventional maintenance chemotherapy for patients in first complete remission of AML/MDS.

We postulated that fludarabine (Flu) instead of cyclophosphamide (Cy) combined with i.v. busulfan (Bu) as preconditioning for allogeneic hematopoietic stem cell transplantation (HSCT) would improve safety and retain antileukemic efficacy. Sixty-seven patients received BuCy2, and subsequently, 148 patients received Bu-Flu. We used a Bayesian method to compare outcomes between these nonrandomized patients. The groups had comparable pretreatment characteristics, except that Bu-Flu patients were older (46 versus 39 years, P < .01), more often had unrelated donors (47.3% versus 20.9%, P < .0003), and had shorter median follow-up (39.7 versus 74.6 months). To account for improved supportive care and other unidentified factors that may affect outcome ("period" effects), 78 acute myelogenous leukemia (AML) patients receiving Melphalan-Flu (MF), treated in parallel during this time (1997-2004) were used to estimate the period effect. The MF patients' outcomes worsened during this period. Therefore, the period effect is unlikely to explain the greatly improved outcome with Bu-Flu. Patients transplanted with Bu-Flu in the first complete remission (CR1) had a 3-year overall survival and event-free-survival (EFS) of 78% and 74%, respectively, whereas CR1 patients younger than age 41 had a 3-year EFS of 83%. These results support replacing BuCy +/- ATG with Bu-Flu +/- rabbit-antithymocyte globulin (ATG), and warrant a prospective comparison between allogeneic HSCT and conventional induction/consolidation chemotherapy for AML in CR1.

Allogeneic progenitor cell transplantation is the only curative therapy for patients with refractory acute myelogenous leukemia or myelodysplastic syndromes. To identify prognostic factors in these patients, we performed a retrospective analysis of transplantation outcomes. Patients were selected if they had undergone an allogeneic transplantation between January 1988 and January 2002 and were not in remission or first untreated relapse at the time of transplantation. A total of 135 patients were identified. The median age was 49.5 years (range, 19-75 years). At the time of transplantation, 39.3% of patients had not responded to induction therapy, 37% had not responded to first salvage therapy, and 23.7% were beyond first salvage. Forty-one patients (30%) received unrelated donor progenitor cells. Eighty patients (59%) received either a reduced-intensity or a nonmyeloablative regimen. A total of 104 (77%) of 135 patients died, with a median survival time of 4.9 months (95% confidence interval, 3.9-6.6 months). The median progression-free survival was 2.9 months (95% confidence interval, 2.5-4.2 months). A Cox regression analysis showed that Karnofsky performance status, peripheral blood blasts, and tacrolimus exposure during the first 11 days after transplantation were predictive of survival. These data support the use of allogeneic transplantation for patients with relapsed or refractory acute myelogenous leukemia/myelodysplastic syndromes and suggest that optimal immune suppression early after transplantation is essential for long-term survival even in patients with refractory myeloid leukemias.

Postulating favorable antileukemic effect with improved safety, we used intravenous busulfan and fludarabine as conditioning therapy for allogeneic hematopoietic stem cell transplantation (HSCT) for acute myelogenous leukemia (AML) and myelodysplastic syndrome (MDS). Fludarabine 40 mg/m2 and intravenous busulfan 130 mg/m2 were given once daily for 4 days, with tacrolimus-methotrexate as graft-versus-host disease (GVHD) prophylaxis. We treated 74 patients with AML and 22 patients with MDS; patients had a median age of 45 years (range, 19-66 years). Only 20% of the patients were in first complete remission (CR) at transplantation. Donors were HLA-compatible related (n = 60) or matched unrelated (n = 36). The CR rate for 54 patients with active disease was 85%. At a median follow-up of 12 months, 1-year regimen-related and treatment-related mortalities were 1% and 3%, respectively. Two patients had reversible hepatic veno-occlusive disease. Actuarial 1-year overall survival (OS) and event-free survival (EFS) were 65% and 52% for all patients, and 81% and 75% for patients receiving transplants in CR. Recipient age and donor type did not influence OS or EFS. Median busulfan clearance was 109 mL/min/m2 and median daily area-under-the-plasma-concentration-versus-time-curve was 4871 micromol-min, with negligible interdose variability in pharmacokinetic parameters. The results suggest that intravenous busulfan-fludarabine is an efficacious, reduced-toxicity, myeloablative-conditioning regimen for patients with AML or MDS undergoing HSCT.

Intensity of the preparative regimen is an important component of allogeneic transplantations for myelodysplasia (MDS) or acute myelogenous leukemia (AML). We compared outcomes after a truly nonablative regimen (120 mg/m2 fludarabine, 4 g/m2 cytarabine, and 36 mg/m2 idarubicin [FAI]) and a more myelosuppressive, reduced-intensity regimen (100 to 150 mg/m2 fludarabine and 140 or 180 mg/m2 melphalan [FM]). We performed a retrospective analysis of 94 patients with MDS (n = 26) and AML (n = 68) treated with FM (n = 62) and FAI (n = 32). The FAI group had a higher proportion of patients in complete remission (CR) at transplantation (44% versus 16%, P =.006), patients in first CR (28% versus 3%, P =.008), and HLA-matched sibling donors (81% versus 40%, P =.001). Median follow-up is 40 months. FM was significantly associated with a higher degree of donor cell engraftment, higher cumulative incidence of treatment-related mortality (TRM; P =.036), and lower cumulative incidence of relapse-related mortality (P =.029). Relapse rate after FAI and FM was 61% and 30%, respectively. Actuarial 3-year survival rate was 30% after FAI and 35% following FM. In a multivariate analysis of patient- and treatment-related prognostic factors, progression-free survival was improved after FM, for patients in CR at transplantation, and for those with intermediate-risk cytogenetics. Survival was improved for patients in CR at transplantation. In conclusion, FM provided better disease control though at a cost of increased TRM and morbidity.

Sixty-two adults underwent marrow or blood stem cell transplantation from an HLA-matched related donor using high-dose thiotepa, busulfan, and cyclophosphamide (TBC) as the preparative regimen for treatment of advanced myelodysplastic syndrome (MDS) (refractory anemia with excess blasts with or without transformation) or acute myelogenous leukemia (AML) past first remission. All evaluable patients engrafted and had complete donor chimerism. A grade 3-4 regimen-related toxicity occurred in eight (13%) patients, and a diagnosis of MDS was the only independent risk factor for grade 3-4 regimen-related toxicity (hazard ratio 9.25, P = 0.01). Day-100 treatment-related mortality (TRM) was 19%. Poor-prognosis cytogenetics increased the risk of day-100 TRM (hazard ratio 11.4, P = 0.003), and use of tacrolimus for graft-versus-host disease prophylaxis reduced the risk of day-100 TRM (hazard ratio 0.13, P = 0.027). For all patients, the three-year relapse rate was 43% (95% CI, 28%-58%). Refractoriness to conventional induction chemotherapy prior to transplantation was an independent risk factor for relapse (hazard ratio 10.8, P = 0.02). Three-year survival was 26% (95% CI, 14%-37%); survival rates were 29% for those transplanted for AML in second remission, 31% transplanted for AML in relapse, and 17% with MDS, and there were no independent risk factors for survival. TBC is an active preparative regimen for advanced AML. Patients with advanced MDS appeared to have a higher risk of toxicity and early mortality, and alternative preparative regimens should be considered for these patients.

Pretransplant conditioning therapy with i.v. BuCy followed by allogeneic hematopoietic stem cell transplantation (BMT) was investigated in a phase II trial in patients with acute myeloid leukemia (AML) or myelodysplastic syndrome (MDS). We gave i.v. Bu at a dose of 0.8 mg/kg every 6h x 16 doses, followed by Cy 60 mg/kg daily for 2 days. Twenty-six AML patients (18 males/eight females) were treated, only eight of whom were in CR1. The rest were either refractory to induction chemotherapy (four patients) or in a more advanced stage of their disease (14 patients). In addition, nine patients with MDS (1M/8F) were treated. Their median age was 41 years (range 21-64). Engraftment to > or =500 neutrophils/microl was reached at 14 days (range 10-29 days) post BMT, and the median time of neutropenia was only 11 days (range 4-28 days). The most common regimen-related toxicity was grade 2-3 nausea. In the post-BMT period (including BMT day +30), two patients died, one each from pulmonary hemorrhage secondary to CMV pneumonia and hepatic veno-occlusive disease (VOD), for an early treatment-related mortality (TRM) of 5.7%. Three patients developed VOD and two of them died. There was no direct regimen-related pulmonary or neurologic toxicity. Overall, the clinical side-effect spectrum was analogous to what would be expected from a high-dose oral Bu-based regimen; there was no unique toxicity experienced with the used solvent system. The disease-free survival in the high-risk subgroup (all patients not in CR1) at 1 and 2 years post transplant was 44% and 31%, respectively. The 13 patients still alive in CR have been followed for a median of 24 months (range 18-32). Pharmacokinetic analysis showed very good interdose reproducibility, and limited interpatient variability in area under the plasma concentration vs time curve, peak concentration, and clearance of Bu after this i.v. formulation. We conclude, that this new i.v. Bu formulation is well tolerated; it has an impressive safety profile, and we suggest that it should be considered as appropriate replacement for oral busulfan in pretransplant conditioning therapy prior to allogeneic BMT for patients with AML or MDS.

Altered p53 tumor suppressor genes have been described in various human malignancies, including in chronic myelogenous leukemias (CML) and acute myelogenous leukemias (AML), as well as their derivative cell lines. It has been proposed that this gene mutation may be less frequent in myeloid leukemia patients than in myeloid leukemia cells lines and that the latter acquire these mutations during growth in vitro. We investigated this possibility by studying p53 gene alterations in matched samples of fresh leukemic cells and their respective derivative cell lines obtained from two CML blast crisis and one AML patient. No gross structural abnormalities were detected in the p53 gene in any of the samples analyzed. Discrete mutations in the gene in the two CML blast crisis samples and in all three derivative cell lines were, however, detected by polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) analyses and DNA sequencing. Cytogenetic analyses revealed either numerical or structural, as well as numerical, abnormalities of chromosome 17 in their karyotypes. Cells from the two CML blast crisis patients had two different mutations which were maintained as the sole mutations in the cell lines. The mutation detected in the AML cell line was, however, not detectable in the parental fresh leukemic cells. Our findings demonstrate that p53 mutations and chromosome 17 abnormalities occurring in CML blast crisis patients persist in long-term cell lines but that mutations not detectable in AML patients may indeed be acquired in cell lines established from them in vitro.

Sublines of a human myeloid leukaemia cell line, KBM-3, with increasing degrees of resistance to the antileukaemic agent 4'-(9-acridinlylamino) methanesulphon-m-anisidide (m-AMSA) were evaluated for their response to this drug using a clonogenic assay to measure cell survival and alkaline elution to assess m-AMSA induced DNA strand breakage. Polyacrylamide gel electrophoresis was used to map the protein profiles of the various cell lines. The resistant lines were obtained by intermittent exposure of the KBM-3 cells to the highest tolerated concentration of m-AMSA so that the culture would be repopulated only by the most resistant subpopulation after each exposure. Two distinct phases were apparent during the development of resistance. During the first 14 months of intermittent exposure to maximally tolerated concentrations of m-AMSA, the cells developed low-degree m-AMSA resistance (5-7-fold as compared with the parent line, as measured by cell survival). This low-degree resistance was characterised by a somewhat suppressed level of DNA strand breakage and no measurable change in cellular protein levels. Subsequently, a single escalation of the m-AMSA retreatment concentration resulted in a cell population that was approximately 100-fold resistant, as assessed by cloning. This rapid phenotypic change temporally coincided with the acquisition of an almost complete refractoriness to m-AMSA-induced DNA strand breakage and the loss of a cellular 76 kDa protein. We suggest that the loss of this protein is important for the development of a highly m-AMSA resistant phenotype.

Normalization of granulocyte counts was obtained with low-dose cytosine arabinoside (Ara-C) in a patient with acute myelogenous leukemia (AML, FAB-M2) who had relapsed on maintenance therapy containing conventional doses of Ara-C and was clinically resistant to high-dose Ara-C treatment. The patient's leukemic cells exhibited an abnormal karyotype (45, X-Y, t[8q; 21q]). To determine whether the response to low-dose Ara-C was a result of induced leukemic cell differentiation, the mature peripheral blood granulocytes were isolated and fused with mitotic chinese hamster ovary (CHO) cells to induce premature chromosome condensation. Karyotypic evaluation of the granulocyte prematurely condensed chromosomes (PCC) during response to low-dose Ara-C demonstrated the presence of cells with 45 chromosomes. This result strongly suggests that part of this patient's response to low-dose Ara-C was a result of induced maturation of the leukemic clone.

The human myelogenous leukemia cell line HL-60 was made resistant to amsacrine (m-AMSA) by repeated exposure in vitro to increasingly large doses of the drug. Resistance to m-AMSA developed in a triphasic process and was accompanied by a slightly slower growth rate and cloning efficiency and a more differentiated morphological phenotype. Extensive chromosomal rearrangement also took place. Among other chromosomal aberrations, one of the No. 6 homologues showed an added segment on the long arm in the form of an homogeneously staining region. One of the homologues of chromosome 14 in every cell showed a deletion of the distal end of the long arm that was replaced by an unidentified homogeneously staining segment. Membrane-associated 170 kd glycoprotein was not overexpressed in the resistant cells, which together with an absence of cross-resistance to Vinca alkaloids and anthracyclines points toward a mechanism of resistance different from multidrug resistance. The ability of resistant cells to respond to differentiation-inducing agents was not significantly changed as compared with that of the parental line. Growth of resistant cells in the absence of m-AMSA for over 200 population doublings within a period of more than 1.5 years did not result in reversion of the resistance, suggesting a stable genomic change. Resistance was not due to a decrease in the bioavailability of the drug. Uptake of [14C]m-AMSA by either whole cells or isolated nuclei of resistant cells exceeded that of the parental cell line, and outward transport of the drug was not more active; thus there were higher levels of intracellularly bound drug. The cell line represents an excellent model for studies of the mechanisms of resistance to m-AMSA and its modulation in human myelogenous leukemia.

Benzisoquinolinedione (nafidimide; NSC 308847) is an investigational drug currently in phase I clinical testing. We have studied the antileukemic activity in vitro, the cellular drug transport, and the molecular mechanism of action with DNA of this new compound. By agarose gel electrophoresis, we verified that nafidimide is an intercalating agent, through its alteration of the electrophoretic migration of DNA products produced by the relaxing action of DNA topoisomerase I. Concentrations of up to 100 microM of nafidimide did not produce topoisomerase I-mediated DNA cleavage. Nafidimide produced DNA single-strand breaks (SSB), double-strand breaks, and DNA-protein cross-links in human myeloid leukemia cells (measured with filter elution). The ratio of SSB/DNA-protein cross-links was 1.32 +/- 0.36, a value similar to that produced by 4'-(9-acridinylamino)methanesulfon-m-anisidide (m-AMSA), suggesting that nafidimide, like m-AMSA, produced protein-associated DNA-strand breaks through a topoisomerase II-mediated reaction. The production of double-strand breaks by nafidimide also suggests the involvement of topoisomerase II in the drug-induced DNA cleavage. The cytotoxic activity of nafidimide was quantified in human myeloid leukemia cell lines differing by a factor of 70 in their cytotoxic sensitivity to m-AMSA. The m-AMSA-resistant line was less than 2-fold resistant to nafidimide. Cellular drug uptake was rapid and reached a steady state level in 30 min at 37 degrees C. At the end of exposure, drug egress was rapid, as was the disappearance of the DNA SSB. Rapid cellular uptake of nafidimide, with low retention at the end of exposure and rapid rejoining of DNA SSB suggest that prolonged cellular exposure may be necessary for optimal antitumor effect. In vitro cloning data suggest that nafidimide may be a therapeutic option for patients with leukemia resistant to m-AMSA.