Fludarabine and treosulfan: A novel modified myeloablative regimen for allogeneic hematopoietic stem-cell transplantation with effective antileukemia activity in patients with acute myeloid leukemia and myelodysplastic syndromes

Metformin pretreatment ameliorates busulfan-induced liver endothelial toxicity during haematopoietic stem cell transplantation

The success of Haematopoietic cell transplantation (HCT) is often limited by regimen-related toxicity (RRT) caused by conditioning regimen drugs. Among different conditioning drugs, busulfan (Bu) and treosulfan (Treo), although widely used in HCT, exhibit different toxicity profiles, the mechanism of which is still unclear. Here we investigated the effects of Bu and Treo in endothelial cells. While both Bu and Treo induced DNA damage in endothelial cells, we observed Bu alone to induce oxidative stress and sustained activation of phospho-ERK1/2, leading to apoptosis. However, Treo-treated cells exhibited no oxidative stress/apoptosis of endothelial cells. Screening of pharmacological inhibitors of both ROS and p-ERK revealed that metformin effectively ameliorates Bu-mediated toxicity in endothelial cells. In Balb/c mice, we observed a significant reduction in bone marrow endothelial cells in Bu-treated mice compared to Treo-treated mice. Further, liver sinusoidal endothelial cells (LSEC) was damaged by Bu, which is implicated in liver vasculature and their functional capacity to uptake FITC-albumin. However, Treo-treated mice liver vasculature was morphologically and functionally normal. When mice were pretreated with metformin followed by Bu, LSECs damage was ameliorated morphologically and functionally. Bone marrow transplants done on these mice did not affect the engraftment of donor cells.

Comparative study of treosulfan plus Fludarabine (FT14) with busulfan plus Fludarabine (FB4) for acute myeloid leukemia in first or second complete remission: An analysis from the European Society for Blood and Marrow Transplantation (EBMT) Acute Leukemia Working Party (ALWP)

Different doses of treosulfan plus fludarabine have shown advantage over reduced intensity regimens. However, data comparing higher doses of treosulfan to myeloablative busulfan are limited. Thus, we compared outcomes between FT14 (fludarabine 150/160 mg/m² and treosulfan 42 g/m², or FT14) over FB4 (fludarabine 150/160 mg/m² and busulfan 12.8 mg/kg). We retrospectively studied patients from European Society for Blood and Marrow Transplantation registry: a) adults diagnosed with acute myeloid leukemia (AML), b) recipients of first allogeneic hematopoietic stem cell transplantation (HSCT) from unrelated or sibling donor (2010-2020), c) HSCT at first or second complete remission, d) conditioning with FT14 or FB4. FT14 recipients (n = 678) were older, with higher rates of secondary AML, unrelated donors, peripheral blood grafts, and adverse cytogenetics, but lower percentage of female donor to male recipient compared to FB4 (n = 2025). Analysis was stratified on age. In patients aged < 55 years, FT14 was associated with higher relapse incidence (RI) and lower Leukemia-Free Survival (LFS). In patients aged≥55 years, acute GVHD CI was higher in FB4, without significant differences in other outcomes. Although FT14 has been used for higher-risk HSCT patients, our large real-world multicenter study suggests that FB4 is associated with better outcomes compared to FT14 in younger patients.

Conditioning with fludarabine and treosulfan compared to FLAMSA-RIC in allogeneic stem cell transplantation for myeloid malignancies: a retrospective single-center analysis

Reduced intensity conditioning (RIC) and reduced toxicity conditioning (RTC) regimens enable allogeneic hematopoietic stem cell transplantation (alloSCT) to more patients due to reduction in transplant-related mortality (TRM). The conditioning regimens with fludarabine and treosulfan (Flu/Treo) or fludarabine, amsacrine, cytarabine (FLAMSA)-RIC have shown their efficacy and tolerability in various malignancies. So far, no prospective study comparing the two regimens is available. Two studies compared the regimens retrospectively, in which both provided similar outcome. In this retrospective, single-center analysis, these two regimens were compared with regard to outcome, rate of acute and chronic graft versus host disease (GvHD), and engraftment. 113 consecutive patients with myeloid malignancies who received Flu/Treo or FLAMSA-RIC conditioning prior to alloSCT between 2007 and 2019 were included. Except for age, previous therapies, and remission status before alloSCT, patient characteristics were well balanced. The median follow-up time within this analysis was 44 months. There was no significant difference in absolute neutrophil count (ANC) or platelet engraftment between the two conditioning regimens. Overall survival (OS), the relapse-free survival (RFS), and the TRM were not significantly different between the two cohorts. The rate of GvHD did not differ between the two groups. In summary, this retrospective analysis shows that there is no major difference regarding tolerability and survival between the Flu/Treo and FLAMSA-RIC regimens. Despite several limitations due to uneven distribution concerning age and remission status, we demonstrate that Flu/Treo and FLAMSA-RIC provide similar outcomes and are feasible in older and intensively pre-treated patients.

Survival Advantage of Treosulfan Plus Fludarabine Before Allogeneic Hematopoietic Cell Transplantation for Older or Comorbid Patients With Myeloid Malignancies

We have previously shown an advantage of a myeloablative conditioning regimen with reduced toxicity (Fludarabine 150 mg/m², Treosulfan 42 g/m², FluTreo) compared to a reduced-intensity regimen. We aimed to determine long-term safety and efficacy of FluTreo. We prospectively studied consecutive patients who received FluTreo in our center (2014-2019) on the basis of age (≥50 years), hematopoietic cell transplantation comorbidity index (HCT-CI) ≥2, or both. FluTreo recipients were then compared to a historical control group. We studied 68 FluTreo recipients, with a median age of 58.5 years and HCT-CI of 3. We calculated cumulative incidence (CI) of acute (grade 2-4) and moderate/severe chronic graft-versus-host disease (GVHD) (29.9% and 25%, respectively). The 3-year CI of treatment-related mortality was 19.1%, associated only with acute GVHD (P < .001). With a median follow-up of 27.3 (range 5.7-84.5) months in surviving patients, the 3-year overall survival (OS) was 56.6%, and disease-free survival (DFS) was 54.9%. Median survival has not yet been reached. Among pretransplantation and transplantation factors, only HCT-CI was associated with DFS and OS (P = .022 and P = .043, respectively). FluTreo recipients aged ≥50 with HCT-CI ≤ 2 had favorable DFS and OS compared with patients aged ≥50 with HCT-CI ≤2 after myeloablative conditioning. Our real-world study confirms that HCT with FluTreo expands the transplant population with favorable outcomes compared to previously used conditions. The choice of HCT in patients of a rather older age and comorbidity index needs to be revisited.

Dose intensity for conditioning in allogeneic hematopoietic cell transplantation: can we recommend "when and for whom" in 2021?

Allogeneic hematopoietic stem-cell transplantation is a potentially curative therapy for various hematologic diseases. An essential component of this procedure is the pre-transplant conditioning regimen, which should facilitate engraftment and reduce or eliminate tumor cells. The recognition of the substantial association of a graft-versus- tumor effect and the high toxicity of the commonly used conditioning regimen led to the introduction of more differentiated intensity strategies, with the aim of making hematopoietic stem-cell transplantation less toxic and safer, and thus more applicable to broader populations such as older or unfit patients. In general, prospective and retrospective studies suggest a correlation between increasing intensity and nonrelapse mortality and an inverse correlation with relapse incidence. In this review, we will summarize traditional and updated definitions for conditioning intensity strategies and the landscape of comparative prospective and retrospective studies, which may help to find the balance between the risk of non-relapse mortality and relapse. We will try to underscore the caveats regarding these definitions and analyses, by missing complex differences between intensity and toxicity as well as the broad influences of other factors in the transplantation procedure. We will summarize evidence regarding several confounders which may influence decisions when selecting the intensity of the conditioning regimen for any given patient, according to the individual risk of relapse and non-relapse mortality.

Long-Term Outcomes of Treosulfan- vs. Busulfan-Based Conditioning Regimen for Patients With Myelodysplastic Syndrome and Acute Myeloid Leukemia Before Hematopoietic Cell Transplantation: A Systematic Review and Meta-Analysis

Background

Many studies aimed to evaluate the efficacy and safety of treosulfan-based conditioning regimens for allogeneic hematopoietic cell transplantation (allo-HCT) compared with other regimens, but different outcomes were reported across studies.

Aim

To determine the long-term survival outcomes of treosulfan-based vs. busulfan-based conditioning regimens in myelodysplastic syndrome (MDS)/acute myeloid leukemia (AML) patients.

Methods

PubMed, Embase, and Cochrane library were searched for studies published prior to December 6, 2019. The fixed-effects model was applied for overall survival (OS), leukemia-free survival (LFS), non-relapse mortality (NRM), acute and chronic graft versus host disease (GvHD). Relapse incidence (RI) was pooled by the use of the random-effects model.

Results

Six studies were included (3,982 patients; range, 57-1,956). The pooled HR for OS favored treosulfan (HR=0.80, 95%CI: 0.71-0.90). There was no significant difference in NRM between the two regimens (HR=0.84, 95%CI=0.71-1.01). There was no significant difference in LFS between the two regimens (HR=0.98, 95%CI=0.87-1.12). Treosulfan-based regimens showed a lower risk of aGvHD (HR=0.70, 95%CI=0.59-0.82), but there was no difference for cGvHD (HR=0.94, 95%CI=0.81-1.09). There was no significant difference in RI between the two regimens (HR=0.96, 95%CI=0.71-1.31). There was no publication bias among these studies.

Conclusion

The current meta-analysis determined that treosulfan-based conditioning regimens could improve the OS in patients with MDS and AML, with lower acute graft-versus-host disease incidence, compared with busulfan-based regimens.

Treosulfan-Based Conditioning Regimen for Second Allograft in Patients with Myelofibrosis

Simple Summary

Currently, the only curative therapy in myelofibrosis is allogeneic hematopoietic stem cell transplantation. Donor lymphocyte infusion and second stem cell transplantation are the two main treatment options for myelofibrosis patients who relapse after the first transplantation. The optimal conditioning regimen for the second transplantation in myelofibrosis patients is not well defined. Our study aimed to address this question and showed that treosulfan-based conditioning for second allograft in relapsed myelofibrosis patients resulted in longtime freedom from disease in about 50% of the patients. This data supports the second allogeneic hematopoietic stem cell transplantation with a less toxic treosulfan-based conditioning regimen that is effective in relapsed, donor lymphocyte infusion resistant myelofibrosis patients with long term low transplant-related mortality and relapse rates.

Abstract

Relapse after allogeneic hematopoietic stem cell transplantation (AHSCT) in myelofibrosis (MF) patients remains as a significant issue despite advances in transplantation procedures and significant prolongation in survival. Second AHSCT is a potential treatment option but associated with high treatment-related mortality and novel less toxic conditioning regimens are needed. In 33 MF patients with relapse after AHSCT and failure to donor lymphocyte infusion (DLI) we investigated treosulfan (36–42 g/m²) in combination with fludarabine and anti-thymocyte globulin (ATG) as conditioning regimen for a second AHSCT with matched related (n = 2), unrelated (n = 23), or mismatched unrelated (n = 8) donors. All patients achieved leukocyte engraftment after a median of 11 days, and 56 ± 13% experienced acute GVHD grade II–IV at day 100. The therapy-related mortality at day 100 and at 3 years was 16% and 31%, respectively. The cumulative incidence of relapse at 5 years was 16%, resulting in a 5-year disease-free and overall survival of 45% and 47%, respectively. Treosulfan-based conditioning for second allograft in relapsed MF patients resulted in about 50% of the patients in long-term freedom from disease.

External validation and comparison of multiple prognostic scores in allogeneic hematopoietic stem cell transplantation

Clinical decisions in allogeneic hematopoietic stem cell transplantation (allo-HSCT) are supported by the use of prognostic scores for outcome prediction. Scores vary in their features and in the composition of development cohorts. We sought to externally validate and compare the performance of 8 commonly applied scoring systems on a cohort of allo-HSCT recipients. Among 528 patients studied, acute myeloid leukemia was the leading transplant indication (44%) and 46% of patients had a matched sibling donor. Most models successfully grouped patients into higher and lower risk strata, supporting their use for risk classification. However, discrimination varied (2-year overall survival area under the receiver operating characteristic curve [AUC]: revised Pretransplantation Assessment of Mortality [rPAM], 0.64; PAM, 0.63; revised Disease Risk Index [rDRI], 0.62; Endothelial Activation and Stress Index [EASIx], 0.60; combined European Society for Blood and Marrow Transplantation [EBMT]/Hematopoietic Cell Transplantation-specific Comorbidity Index [HCT-CI], 0.58; EBMT, 0.58; Comorbidity-Age, 0.58; HCT-CI, 0.55); AUC ranges from 0.5 (random) to 1.0 (perfect prediction). rPAM and PAM, which had the greatest predictive capacity across all outcomes, are comprehensive models including patient, disease, and transplantation information. Interestingly, EASIx, a biomarker-driven model, had comparable performance for nonrelapse mortality (NRM; 2-year AUC, 0.65) but no predictive value for relapse (2-year AUC, 0.53). Overall, allo-HSCT prognostic systems may be useful for risk stratification, but individual prediction remains a challenge, as reflected by the scores' limited discriminative capacity.

Clofarabine and Treosulfan as Conditioning for Matched Related and Unrelated Hematopoietic Stem Cell Transplantation: Results from the Clo3o Phase II Trial

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) can be curative for patients with hematologic malignancies. The ideal conditioning regimen before allo-HSCT has not been established. We conducted a Phase II study to evaluate the tolerability and efficacy of clofarabine and treosulfan as conditioning regimen before allo-HSCT. The primary objective was to evaluate the cumulative incidence of nonrelapse mortality (NRM) on day +100. Forty-four patients (36 with acute myelogenous leukemia, 5 with acute lymphoblastic leukemia, 3 with myelodysplastic syndromes) were enrolled. The median patient age was 47 years, and the median duration of follow-up was 27 months. The conditioning regimen was based on clofarabine 40 mg/m² (days -6 to -2) and treosulfan 14 g/m² (days -6 to -4). Allogeneic hematopoietic stem cells were derived from a sibling (n = 22) or a well-matched unrelated donor (n = 22). Graft-versus-host disease (GVHD) prophylaxis consisted of antithymocyte globulin, rituximab, cyclosporine, and a short-course of methotrexate. The regimen allowed for rapid engraftment and a 100-day NRM of 18%, due mainly to bacterial infections. The incidences of grade II-IV acute GVHD and chronic GVHD were 16% and 19%, respectively. The rates of overall survival (OS), progression-free survival, and relapse at 2 years were 51%, 31%, and 50%, respectively. Significantly different outcomes were observed between patients with low-intermediate and patients with high-very high Disease Risk Index (DRI) scores (1-year OS, 78% and 24%, respectively). Our findings show that the use of treosulfan and clofarabine as a conditioning regimen for allo-HSCT is feasible, with a 78% 1-year OS in patients with a low-intermediate DRI score. However, 1-year NRM was 18%, and despite the intensified conditioning regimen, relapse incidence remains a major issue in patients with poor prognostic risk factors.

High-dose melphalan-based sequential conditioning chemotherapy followed by allogeneic haematopoietic stem cell transplantation in adult patients with relapsed or refractory acute myeloid leukaemia

Considering the unsatisfactory results of salvage therapies for patients with relapsed/refractory acute myeloid leukaemia (R/R-AML), their value before allogeneic haematopoietic stem cell transplantation (HSCT) remains questionable. However, direct allogeneic HSCT following established conditioning regimens applied in patients with R/R-AML during active disease has been equally disappointing. In this retrospective observational study, high-dose melphalan, as part of a sequential preparative regimen, followed by a total body irradiation (4 × 2 Gy)-based or a treosulfan-based dose-adapted conditioning therapy for allogeneic HSCT was administered to 292 adult patients (median age 56 years, range 17-74) with primary refractory (144 patients), secondary refractory (97 patients) or relapsed AML (51 patients). Overall survival rates at 3 years were 34%, 29% and 41%, respectively. Risk factors associated with an inferior survival were higher age, transplantation from a human leucocyte antigen-mismatched donor and high disease burden. Patients transplanted with blast infiltration <20% showed a notable survival rate of 51% at 3 years. In particular, patients with primary refractory AML showed a more favourable outcome when transplanted early during their disease course. Thus, high-dose melphalan-based sequential conditioning chemotherapy followed by an allogeneic HSCT is feasible and enables long-term remission to be achieved in a substantial proportion of patients with active R/R-AML.

Pharmacokinetics and Pharmacodynamics of Treosulfan in Patients With Thalassemia Major Undergoing Allogeneic Hematopoietic Stem Cell Transplantation

A treosulfan (Treo)-based conditioning regimen prior to hematopoietic stem cell transplantation (HSCT) has been successfully used in treating hematological malignant and nonmalignant diseases. We report Treo pharmacokinetics (PK) in patients with thalassemia major undergoing HSCT (n = 87), receiving Treo at a dose of 14 g/m² /day. Median Treo AUC and clearance (CL) was 1,326 mg*h/L and 10.8 L/h/m² , respectively. There was wide interindividual variability in Treo AUC and CL (64 and 68%) which was not explained by any of the variables tested. None of the Treo PK parameters were significantly associated with graft rejection or toxicity; however, Treo CL <7.97 L/h/m² was significantly associated with poor overall (hazard ratio (HR) 2.7, confidence interval (CI) (1.09-6.76), P = 0.032) and event-free survival (HR 2.4, CI (0.98-5.73), P = 0.055). Further studies in a larger cohort are warranted to identify the factors explaining the variation in Treo PK as well as to establish a therapeutic range of Treo for targeted dose adjustment to improve HSCT outcome.

Intravenous Busulfan Compared with Treosulfan-Based Conditioning for Allogeneic Stem Cell Transplantation in Acute Myeloid Leukemia: A Study on Behalf of the Acute Leukemia Working Party of European Society for Blood and Marrow Transplantation

Dose intensity of the conditioning regimen has significant impact on the outcomes after stem cell transplantation (SCT) for acute myeloid leukemia. Most studies have shown more relapse, less nonrelapse mortality (NRM), and similar overall survival after reduced-intensity and myeloablative conditioning. There are limited data on the dose equivalence and expected outcomes of treosulfan-based compared with busulfan-based conditioning. We compared SCT outcomes after fludarabine with either intravenous busulfan at a myeloablative dose (FB4, 12.8 mg/kg, n = 1265) or a reduced dose (FB2, 6.4 mg/kg, n = 1456) or treosulfan at 42 g/m² (FT14, n = 403) or 36 g/m² (FT12, n = 168). Median patient age was 48, 60, 57, and 60 years in the FB4, FB2, FT14, and FT12 groups, respectively (P < .0001). Two-year overall survival was 58%, 53%, 53%, and 51%, respectively (P = .25). Multivariate analysis identified advanced age, advanced disease status, and secondary leukemia to be associated with worse survival. Relapse rate was 30%, 35%, 34%, and 40%, respectively. Relapse was more common after FB2, advanced age and disease status, secondary leukemia, and sibling donors. NRM was 17%, 18%, 21%, and 16%, respectively. NRM was least common after FT12 and more common with advanced age and disease status and unrelated donors. Treosulfan-based regimens were associated with lower rates of graft-versus-host disease. There was no difference in any outcome among patients in first complete remission at transplantation. However, there was better survival with treosulfan-based conditioning in advanced leukemia. In conclusion, survival is determined mostly by disease biology and is similar after various regimens. Treosulfan-based conditioning is more similar to myeloablative than to reduced-intensity conditioning but can be administered safely in older patients, with lower rates of graft-versus-host disease and possibly better outcomes in patients with active leukemia.

Missing HLA C group 1 ligand in patients with AML and MDS is associated with reduced risk of relapse and better survival after allogeneic stem cell transplantation with fludarabine and treosulfan reduced toxicity conditioning

Reduced-toxicity conditioning with fludarabine and treosulfan is a dose-intensive regimen with enhanced anti-leukemia effect and acceptable toxicity in AML/MDS. HLA-C regulates natural-killer (NK) cell function by inhibiting Killer immunoglobulin-like receptors (KIR) and is divided into C1 and C2 epitopes. The missing-ligand theory suggests that missing recipient KIR ligands drives NK-alloreactivity after SCT, in the absence of HLA-mismatch by activating unlicensed donor NK cells. We analyzed SCT outcomes in 203 patients with AML/MDS, median age 58 years, given SCT from matched-siblings (n = 97) or matched-unrelated donors (n = 106), using two treosulfan doses (total 36 or 42 g/m² ). 34% expressed one HLA-C group 1 allele (C1C1), 19% one HLA-C group 2 allele (C2C2), and 48% both KIR ligands (C1C2). Median follow-up was 48 months. 5-year relapse, nonrelapse mortality (NRM) and leukemia-free survival (LFS) rates were 38%, 27%, and 36%, respectively. Relapse rates were 43%, 45%, and 26% in patients expressing C1C1, C1C2, and C2C2 ligands, respectively (P = .03). Multivariate-analysis identified chemo-refractory disease (HR 3.1, P = .003), poor cytogenetics (HR 1.7, P = .08), female donor to male recipient (HR 0.4, P = .01) and C2C2 ligands (HR 0.4, P = .04) as independent factors predicting relapse. HLA-C ligands were not associated with GVHD or NRM. LFS was 33%, 30%, and 46%, respectively (P = .07). Chemorefractory disease (HR 3.1, P = .0004) and C2C2 group ligand (HR 0.6, P = .06) independently predicted LFS. Treosulfan dose did not predict any SCT outcome. In conclusion, missing HLA-C group 1 ligand is associated with reduced relapse risk, similar NRM and improved LFS, after HLA-matched SCT with treosulfan conditioning in AML/MDS.

Escalating topotecan in combination with treosulfan has acceptable toxicity in advanced pediatric sarcomas

Patients with advanced pediatric sarcomas have a poor prognosis and novel combination therapies are needed to improve the response rates. Hematological and organ related toxicities have been observed when administering topotecan in combination with, e.g., high dose thiotepa. This study evaluates the toxicity of escalating doses of topotecan alone or in combination with thiotepa or treosulfan. We compared the toxicity including death of complication (DOC) of topotecan alone or in combination with thiotepa or treosulfan in advanced pediatric sarcomas (n = 12). Ten of 12 patients (0.83) suffered from advanced tumors of the Ewing family (i.e., bone or marrow metastases or relapse <24 month after diagnosis, including one neuroepithelial tumor of the kidney) and two from alveolar rhabdomyosarcoma stage IV (0.17). Median age was 15 years (range 5-28). Ratio of female to male was 1:1. Two patients received topotecan alone (1.25 mg/m(2) q 5d and 1.5 mg/m(2) q 5d), three patients received four courses of topotecan (2 mg/m(2) q d 1-5) in combination with thiotepa (100 mg/m(2) q d 1-5), and seven patients received topotecan (2 mg/m(2) q d 1-5) in combination with treosulfan (10g/m(2) q d 3-5). Overall toxicity was not different between all three groups; mean scores were 1.6, 1.8, and 1.7 according to WHO grading (Scale 0-4). Organ related toxicity ranged between 0 and 4 and was not different as well. DOC was 0/2, 1/3, and 0/7 patients respectively. Escalating therapy with topotecan in combination with treosulfan has acceptable toxicity and warrants further investigation in advanced pediatric sarcomas.

Pharmacology of dimethanesulfonate alkylating agents: busulfan and treosulfan

INTRODUCTION

Among the dimethanesulfonates, busulfan, in combination with other alkylating agents or nucleoside analogues, is the cornerstone of high-dose chemotherapy. It is used, and followed hematopoietic stem cell transplantation, for the treatment of various hematologic malignancies and immunodeficiencies. Treosulfan, which is a hydrophilic analogue of busulfan, was the first dimethanesufonate registered for the treatment of ovarian cancer. Recently, treosulfan has been investigated for the treatment of hematologic malignancies in combination with the same second agents before hematopoietic stem cell transplantation.

AREAS COVERED

This work reviews the pharmacological data of these two dimethanesulfonates alkylating agents. Specifically, the article looks at their chemistry, metabolism, anticancer activity, and their pharmacokinetics and pharmacodynamics.

EXPERT OPINION

Busulfan has been investigated widely for more than three decades leading to a large and precise handling of this agent with numerous studies on activity and pharmacokinetics and pharmacodynamics. In contrast, the behavior of treosulfan is still under investigation and not fully described. The complexity of treosulfan's metabolism and mechanism of action gives rise to the need of a deeper understanding of its pharmacological activity in a context of high-dose chemotherapy. Specifically, there is a great need to better understand its pharmacokinetics/pharmacodynamics relationship.

Phase II prospective study of treosulfan-based reduced-intensity conditioning in allogeneic HSCT for hematological malignancies from 10/10 HLA-identical unrelated donor

Different RIC regimens were evaluated prior to allo-HSCT in different hematological malignancies. We conducted this prospective study in adult patients with various hematological malignancies in order to evaluate the toxicity and efficacy of treosulfan-based conditioning, followed by allo-HSCT from 10/10 HLA-identical unrelated donors. Conditioning included treosulfan 12 g/m(2)/day i.v. (day -6 to day -4), fludarabine 30 mg/m(2)/day i.v. (day -6 to day -2), and ATG 2.5 mg/kg/day (day -2 to day -1). PBSC were used as HSC source. We included 56 patients (29 AML, 9 MM, 8 MDS, 6 CLL, 3 ALL, and 1 CML) with a median age of 57 years (18-65.5). Fifty-four (96%) patients engrafted; the cumulative incidence of aGVHD grade ≥II at 3 months reached 31%. The cumulative incidence of cGVHD at 18 months was 34% limited and 8% extensive. The median overall survival (OS) was not reached with a 3-year probability of 52%. The cumulative incidence of relapse at 3 years was 25%, and the cumulative incidence of transplant-related mortality (TRM) at 12 and 24 months was 20% and 23%, respectively. Treosulfan appears to be a good alternative for conditioning of MUD transplant patients with promising results in terms of OS, relapse, and TRM.

Allogeneic hematopoietic SCT in patients with AML following treosulfan/fludarabine conditioning

An alternative reduced-toxicity conditioning regimen for allogeneic transplantation, based on treosulfan and fludarabine, has recently been identified. The safety and efficacy of this new conditioning regimen has been investigated prospectively in patients with AML. A total number of 75 patients with AML in CR were treated with 3 × 14 g/m(2) treosulfan and 5 × 30 mg/m(2) fludarabine, followed by matched sibling or unrelated SCT. Patients were evaluated for engraftment, adverse events, GVHD, and for non-relapse mortality, relapse incidence, overall and disease-free survival (DFS). All patients showed primary engraftment of neutrophils after a median of 20 days. Non-hematological adverse events grade III-IV in severity included mainly infections (59%) and gastrointestinal symptoms (7%). Acute GVHD grade II-IV occurred in 21% and extensive chronic GVHD occurred in 16% of the patients. After a median follow-up of 715 days, the 2-year overall and DFS estimates were 61% and 55%, respectively. The 2-year incidences of relapse and non-relapse mortality reached 34% and 11%, respectively. In summary, our data confirm promising safety and efficacy of the treosulfan-based conditioning therapy in AML patients, ClinicalTrials.gov Identifier: NCT01063660.

Reduced-toxicity conditioning with treosulfan and fludarabine in allogeneic hematopoietic stem cell transplantation for myelodysplastic syndromes: final results of an international prospective phase II trial

BACKGROUND

An alternative reduced-toxicity conditioning regimen for allogeneic transplantation, based on treosulfan and fludarabine, has recently been identified. The rationale for this study was to investigate the efficacy and safety of this regimen prospectively in patients with a primary myelodysplastic syndrome.

DESIGN AND METHODS

A total of 45 patients with primary myelodysplastic syndromes were conditioned with 3×14 g/m(2) treosulfan and 5×30 mg/m(2) fludarabine followed by allogeneic hematopoietic stem cell transplantation. Subtypes of myelodysplastic syndromes were refractory anemia with excess blasts-2 (44%), refractory cytopenia with multilineage dysplasia (27%), refractory anemia (9%), refractory anemia with ringed sideroblasts (4%), refractory cytopenia with multilineage dysplasia and ringed sideroblasts (4%), refractory anemia with excess blasts-1 (2%), and myelodysplastic syndrome with isolated del (5q) (2%). The myelodysplastic syndrome was unclassified in 7% of the patients. Forty-seven percent of the patients had a favorable karyotype, 29% an unfavorable one, and 18% an intermediate karyotype. Patients were evaluated for engraftment, adverse events, graft-versus-host disease, non-relapse mortality, relapse incidence, overall survival and disease-free survival.

RESULTS

All but one patient showed primary engraftment of neutrophils after a median of 17 days. Non-hematologic adverse events of grade III-IV in severity included mainly infections and gastrointestinal symptoms (80% and 22% of the patients, respectively). Acute graft-versus-host disease grade II-IV developed in 24%, and extensive chronic graft-versus-host disease in 28% of the patients. After a median follow-up of 780 days, the 2-year overall and disease-free survival estimates were 71% and 67%, respectively. The 2-year cumulative incidences of non-relapse mortality and relapse were 17% and 16%, respectively.

CONCLUSIONS

Our safety and efficacy data suggest that treosulfan-based conditioning therapy is a promising treatment option for patients with myelodysplastic syndromes. clinicaltrials.gov identifier: NCT01062490.

Intermediate intensity conditioning regimen containing FLAMSA, treosulfan, cyclophosphamide, and ATG for allogeneic stem cell transplantation in elderly patients with relapsed or high-risk acute myeloid leukemia

Lower dosage of total body irradiation (TBI) and chemotherapy in reduced-intensity conditioning (RIC) regimens prior to allogeneic stem cell transplantation have reduced the toxicity of the conditioning and non-relapse mortality. The FLAMSA-RIC protocol for high-risk patients with acute myeloid leukemia (AML) and myelodysplastic syndrome has shown promising results in refractory disease as well as in first complete remission. Still, the RIC protocol containing 4 Gy TBI/cyclophosphamide/anti-thymocyte globulin (ATG) implicates acute toxicity mainly due to TBI preventing its usage in patients with advanced age and/or severe co-morbidities. To increase feasibility and safety of the conditioning, we substituted TBI with treosulfan. Seventeen patients with relapsed or high-risk AML and either advanced age or concomitant disease were treated within a preparative regimen containing a 4-day course of chemotherapy (FLAMSA) followed by RIC comprising of treosulfan, cyclophosphamide, and ATG. After median follow-up of 12 months, the estimated incidences of relapse and non-relapse mortality were 25% and 20%, respectively. One-year overall survival was 62%. In conclusion, FLAMSA-treosulfan/cyclophosphamide/ATG is an intermediate intensity conditioning regimen with acceptable non-relapse mortality for patients with relapsed or high-risk AML. Substituting TBI with treosulfan provides an alternative to treat elderly patients or patients with severe co-morbidities when TBI appears not feasible due to the potential of increased toxicity.

Stem cell transplantation using non-myeloablative conditioning regimen with fludarabine for hematological malignancies

Stem cell transplantation (SCT) is a useful treatment for hematological malignancies, but it is limited to younger patients because of its high treatment-related mortality. Fludarabine (Flu), a novel anticancer agent with potent immunosuppressive activity, used as a conditioning regimen (reduced intensity transplantation; RIST), can decrease treatment-related mortality, as recently reported. However, the best drug combination and the best timing for RIST remain unknown. We herein report the SCT outcomes of 36 patients undergoing Flu treatment at our institution since December 2002 and retrospectively analyze the results. RIST conditioning with Flu was well-tolerated. No severe toxicity related conditioning regimens was observed in our patients, even though there were 10 patients with a history of autologous (n = 5) or allogeneic stem cell transplantation (n = 5). Hematological engraftment was found in 33 patients. The median times for reconstitution of WBCs, RBCs, and platelets were 16 days, 27.5 days and 34 days, respectively. Stable complete donor chimerism after SCT was present in all patients with WBC engraftment, and no patients experienced late rejection. Thirty-two patients were evaluated for acute graft versus host disease (aGVHD). Nine patients had no aGVHD. The incidence of grade I/II and III/IV aGVHD was 78% and 22%, respectively. Skin lesions were the major sites of involvement. Gut involvement was present in 9 patients. All 4 patients with grade IV GVHD had stage four hepatic GVHD. Twenty-two patients were analyzed for chronic GVHD (cGVHD). Twelve patients had no cGVHD, 6 had limited type and 4 had extended type. The overall survival (OS), relapse rate (RR), and non-relapse mortality (NRM) in all patients over 7 years were found to be 41.7%, 20.1%, and 34.6%, respectively. Induction failures were present in 5 cases of AML and 1 case of NHL. Disease progression was the primary cause of death, which occurred in 12 of 21 patients. Six patients died of grade IV GVHD (n = 2) or complicated fungal infection contracted during the GVHD treatment (n = 4). One patient died of secondary MSD, which originated from donor hematopoietic cells. Two patients died of cerebral bleeding and cardiac rapture, respectively. We found that the patients' state on SCT was the most important factor in long-term survival. The OS of standard risk and high risk patients with hematological malignancies were 75% and 30.3%. We concluded that stem cell transplantation using a non-myeloablative conditioning regimen with Flu was a useful therapeutic approach for patients with hematological malignancies.

Preclinical analysis of treosulfan in combination with total body irradiation as conditioning regimen prior to bone marrow transplantation in rats

Treosulfan (Treo) and total body irradiation (TBI) demonstrate a high therapeutic activity in treatment of acute leukemia and lymphoma. We investigated the combination of Treo and TBI prior to bone marrow transplantation (BMT) in rats. Female Lewis rats were treated with Treo on 3 consecutive days followed by TBI with either 5 Gy (n = 28) or 7.5 Gy (n = 48). After conditioning animals received 4 x 10E7 bone marrow cells (BC) from female Lewis rats. Additional 16 rats were transplanted with 4 x 10E7 BC and 1.5 x 10E7 spleen T-cells from female Brown-Norway (BN) rats. Animals were examined daily for clinical signs and toxicity was investigated by necropsy and histology in all animals. Gastrointestinal toxicity was the dose-limiting factor of Treo in combination with TBI. The highest tolerable dose of Treo in combination with 7.5 Gy TBI was 3 x 0.5 g/kg and the highest tolerable dose of Treo in combination with 5 Gy TBI was 3 x 0.6 g/kg. Allogeneic BMT from BN donors resulted in engraftment and survival of 12 out of 16 animals. Gastrointestinal toxicity is the dose-limiting factor in the treatment with Treo and TBI. Furthermore, Treo possesses certain characteristics of a radiosensitizer.

Long-term outcomes in patients with high-risk myeloid malignancies following matched related donor hematopoietic cell transplantation with myeloablative conditioning of BU, etoposide and CY

Patients with high-risk or advanced myeloid malignancies have limited effective treatment options. These include high-dose therapy followed by allogeneic hematopoietic cell transplantation (HCT). We report a single-institution, long-term follow-up of 96 patients, median age 50 (range, 20-60) years, who received HLA-matched related HCT between 1992 and 2007. All patients were treated with a uniform preparatory regimen intended to enhance the widely used regimen of BU and CY that included: BU 16.0 mg/kg (days -8 to -5), etoposide 60 mg/kg (day -4), CY 60 mg/kg (day -2) with GVHD prophylaxis of CsA or FK506 and prednisone. Disease status at transplantation was high-risk AML (n=41), CML in second chronic phase or blast crisis (n=8), myelofibrosis and myeloproliferative disorders (n=8), and myelodysplasia (n=39). Thirty-six percent (n=35) of patients received BM whereas 64% (n=61) received G-CSF-mobilized PBPC. With a median follow-up of 5.6 years (range, 1.6-14.6 years) actuarial 5-year OS was 32% (95% CI 22-42) and 5-year EFS was 31% (95% CI 21-41). Relapse rate was 24% (95% CI 15-33) at 2 and 5 years. Nonrelapse mortality was 29% (95% CI 20-38) at day 100 and 38% (95% CI 29-47) at 1 year. Cumulative incidence of acute (grade II-IV) and extensive chronic GVHD was 27% (95% CI 18-36) and 29% (95% CI 18-40), respectively. There was no statistically significant difference in OS (31 vs 32%, P=0.89) or relapse rates (17 vs 28%, P=0.22) for recipients of BM vs PBPC, respectively. These results confirm that patients with high-risk or advanced myeloid malignancies can achieve long-term survival following myeloablative allogeneic HCT with aggressive conditioning.

Allogeneic hematopoietic stem-cell transplantation in patients with hematologic malignancies after dose-escalated treosulfan/fludarabine conditioning

PURPOSE

Treosulfan was introduced recently as a conditioning agent for allogeneic blood stem-cell transplantation. The favorable nonhematologic toxicity profile at 3 x 10 g/m(2) was the basis for dose escalation in this prospective, multicenter trial.

PATIENTS AND METHODS

Fifty-six patients with various hematologic malignancies who were not eligible for standard conditioning were treated with one of three doses: 10 g/m(2), 12 g/m(2), or 14 g/m(2) of intravenous treosulfan, which was administered on days -6 to -4 combined with fludarabine 30 mg/m(2) on days -6 to -2. Patients in complete remission (CR; 42%) or non-CR (58%) received grafts from matched related (47%) or matched unrelated (51%) donors; one patient had a mismatched related donor (2%).

RESULTS

No engraftment failure occurred. Overall, extramedullary toxicity and the nonrelapse mortality rate at 2 years (20%) were low and did not increase with dose. Cumulative incidence of relapse/progression reached 31%. The overall survival and progression-free survival rates were 64% and 49%, respectively, in the total study population. An inverse dose dependency of relapse incidence was indicated in the subgroup receiving transplantations from matched related donors (P = .0568).

CONCLUSION

Treosulfan-based conditioning was feasible at all three doses. The 3 x 14 g/m(2) dose was selected for additional studies, because it combines desired characteristics of low toxicity and a low relapse rate.

Optimizing reduced-intensity conditioning regimens for myeloproliferative neoplasms

The myeloproliferative neoplasms (MPNs) are a group of clonal disorders that arise from a pluripotent hematopoietic stem cell and are characterized by excess cellular proliferation. These disorders tend to be chronic in nature and can terminate over time into a bone marrow failure syndrome characterized by marrow fibrosis or transform into a leukemic phase. MPNs are predominantly diseases of the elderly and this is one reason why until very recently the standard treatment was supportive care. The only curative modality for these disorders is allogeneic hematopoietic cell transplantation. The introduction of reduced-intensity conditioning regimens now allows this life-saving therapy to be offered to elderly patients who were previously considered ineligible for high-dose conditioning owing to age or comorbidity. In this review, we will summarize the current strategies and future directions regarding the use of reduced-intensity conditioning regimens in the treatment of MPNs.

Busulfan in hematopoietic stem cell transplant setting

This paper focuses primarily on the data published in the last decade about the pharmacokinetics and pharmacodynamics of oral and intravenous (i.v.) busulfan, therapeutic drug monitoring and clinical outcome in hematopoietic stem cell transplant (HCT) patients. Busulfan is commonly used in HCT as it is toxic to the marrow. Busulfan is available as oral or i.v. formulation. The most common significant toxicity of busulfan is sinusoidal obstruction syndrome. Even with the introduction of i.v. busulfan, variability in the systemic concentrations of busulfan after weight-based dosing and the association between busulfan plasma exposure and outcome in HCT patients have led to the continued use of therapeutic drug monitoring of busulfan. New strategies for personalizing busulfan dosing are being studied to maximize the use of busulfan for optimal disease control with the least toxicity to HCT patients. One such strategy currently being evaluated is if busulfan clearance can be accurately predicted by genetic polymorphism of glutathione S-transferase (GST), with the currently available data suggesting that GST polymorphisms cannot be used to personalize busulfan dosing.

Treosulfan/fludarabine as an allogeneic hematopoietic stem cell transplant conditioning regimen for high-risk patients

In recent years, new conditioning regimens have been explored in patients not eligible for conventional transplant with the aim to reduce transplant-related mortality. In a phase II multicentric prospective trial, we investigated the safety and feasibility of the treosulfan-fludarabine combination prior to allogeneic hematopoietic stem cell transplant in patients with various hematological malignancies not eligible for conventional regimens because of previous intensive treatment, older age, and comorbidities. Forty-six consecutive patients, median age 48 years (range 17-69), were enrolled. Sixteen of them were in complete remission, and 20 had a HSCT comorbidity index > or = 1. Forty-four patients had regular and sustained engraftment, and 39 out of 40 evaluable patients developed complete chimerism. Nonhematological toxicity was limited. Risk of transplant-related mortality was 9% (95% CI, 2-17%) at day +100 and plotted at 15% (95% CI, 7-22%) after 7 months. The estimated overall survival and progression-free survival with a median follow-up of 20 months were 51% and 38%, respectively. The estimated 30 months progression-free survival for patients transplanted in remission was 56%. The treosulfan-fludarabine combination is a reduced-toxicity but myeloablative regimen that can be proposed to patients not fitting criteria for conventional transplant regimens. Longer follow-up and further prospective studies are necessary to evaluate this regimen.