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

Comparison of Melphalan Combined with Treosulfan or Busulfan as High-Dose Chemotherapy before Autologous Stem Cell Transplantation in AML

Simple Summary

Different consolidation strategies are available for acute myeloid leukemia (AML) patients fit for intensive treatment. For favorable- or intermediate-risk AML, high-dose chemotherapy (HDCT) followed by autologous stem cell transplantation (ASCT) is one of these options. Busulfan plus melphalan is a frequently used and efficient HDCT regimen, but it bears neurotoxic potential and may cause irreversible alopecia, amongst other toxicities. Thus, improving HDCT regimens with lesser toxicity, albeit at comparable anti-leukemic efficacy, is wishful. We combined treosulfan with its more favorable toxicity profile with melphalan for HDCT and compared these patients with a group receiving busulfan/treosulfan. Whereas disease-free and overall survival did not differ significantly, the treosulfan regimen compared favorably, with the absence of neurotoxicity and irreversibly alopecia. Treosulfan serum levels by mass cytometry demonstrated considerable interindividual biovariability. Further studies should explore treosulfan/melphalan for HDCT/ASCT in AML, aiming to improve the quality of life of AML survivors and offer safer consolidation strategies.

Abstract

(1) Background: High-dose chemotherapy (HDCT) before autologous stem cell transplantation (ASCT) in acute myeloid leukemia (AML) patients predominantly combines busulfan with cyclophosphamide or melphalan. Treosulfan compares favorably regarding lower inter-individual bioavailability and neurotoxicity, but so far, had not been studied before ASCT in AML. (2) Methods: This single-center study investigated AML patients undergoing ASCT in CR1 between November 2017 and September 2020. The first 16 patients received busulfan 16 mg/kg b.w. (days −5 to −2) and melphalan 140 mg/m² (day −1) (BuMel). In a subsequent (TreoMel) cohort, 20 patients received treosulfan 14 g/m² (days −4 to −2) and melphalan. Plasma concentrations of busulfan and treosulfan were determined by mass spectrometry. (3) Results: Neutrophil engraftment and platelet recovery were similar, and PFS and OS were comparable. In only the BuMel cohort, patients reported central nervous toxicities, including seizures (6%) and encephalopathy (12%). The mean AUC for busulfan was 1471.32 μM*min, and for treosulfan it was 836.79 mg/L*h, with ranges of 804.1–2082 μM*min and 454.2–1402 mg/L*h. The peak values for busulfan ranged between 880.19–1734 μg/L and for treosulfan between 194.3–489.25 mg/L. (4) Conclusions: TreoMel appears to be safe and effective for pre-ASCT treatment in AML patients. Due to considerable interindividual biovariability, pharmacologic monitoring may also be warranted for the use of treosulfan.

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.

Cytostatic conditioning in experimental allogeneic bone marrow transplantation: Busulfan causes less early gastrointestinal toxicity but Treosulfan results in improved immune reconstitution

BACKGROUND

Acute graft versus host disease (aGVHD) after allogeneic bone marrow transplantation (allo-BMT) is associated with significant morbidity and mortality. We evaluated the impact of the conditioning regimen on aGVHD comparing Treosulfan (Treo) and Busulfan (Bu) with total body irradiation (TBI).

METHODS

Using a haploidentical murine model, B6D2F1 mice conditioned with Bu (100 mg/kg)/Fludarabine (Flu, 500 mg/kg) or Treo (6000 mg/kg)/Flu (500 mg/kg) or TBI with 14 Gy received bone marrow cells and splenocytes (20 × 10(6)) from either syngeneic (B6D2F1) or allogeneic (C57BL/6N) donors in order to analyze aGVHD outcome.

RESULTS

Conditioning with Bu/Flu or Treo/Flu resulted in significantly reduced aGVHD severity and improved survival (p < 0.05) after allo-BMT compared to TBI. On day 5 after allo-BMT, the organ damages of Bu/Flu conditioned animals were significantly reduced in association with diminished expression of tumor necrosis factor in serum compared to Treo/Flu. Interestingly, the early toxicity of Treo/Flu did not result in significantly higher aGVHD severity; furthermore, a significantly improved immune reconstitution of B220-positive B cells was observed at day 42 after Treo/Flu conditioning compared to Bu/Flu.

CONCLUSION

Conditioning with Treo/Flu or Bu/Flu results in decreased aGVHD severity compared to TBI. Moreover, Treo/Flu was associated with improved immune reconstitution despite the early toxicity.

Treosulfan, fludarabine, and 2-Gy total body irradiation followed by allogeneic hematopoietic cell transplantation in patients with myelodysplastic syndrome and acute myeloid leukemia

Allogeneic hematopoietic cell transplantation (HCT) offers curative therapy for many patients with myelodysplastic syndrome (MDS) or acute myeloid leukemia (AML). However, post-HCT relapse remains a major problem, particularly in patients with high-risk cytogenetics. In this prospective phase II trial, we assessed the efficacy and toxicity of treosulfan, fludarabine, and 2 Gy total body irradiation (TBI) as conditioning for allogeneic HCT in patients with MDS or AML. Ninety-six patients with MDS (n = 36: 15 refractory cytopenia with multilineage dysplasia, 10 refractory anemia with excess blasts type 1, 10 refractory anemia with excess blasts type 2, 1 chronic myelomonocytic leukemia type 1) or AML (n = 60: 35 first complete remission [CR], 18 second CR, 3 advanced CR, 4 refractory relapse) were enrolled; median age was 51 (range, 1 to 60) years. Twelve patients had undergone a prior HCT with high-intensity conditioning. Patients received 14 g/m(2)/day treosulfan i.v. on days -6 to -4, 30 mg/m(2)/day fludarabine i.v. on days -6 to -2, and 2 Gy TBI on day 0, followed by infusion of hematopoietic cells from related (n = 27) or unrelated (n = 69) donors. Graft-versus-host disease prophylaxis consisted of tacrolimus and methotrexate. With a median follow-up of 30 months, the 2-year overall survival (OS), relapse incidence, and nonrelapse mortality were 73%, 27%, and 8%, respectively. The incidences of grades II to IV (III to IV) acute and chronic graft-versus-host disease were 59% (10%) and 47%, respectively. Two-year OS was not significantly different between MDS patients with poor-risk and good/intermediate-risk cytogenetics (69% and 85%, respectively) or between AML patients with unfavorable and favorable/intermediate-risk cytogenetics (64% and 76%, respectively). In AML patients, minimal residual disease (MRD; n = 10) at the time of HCT predicted higher relapse incidence (70% versus 18%) and lower OS (41% versus 79%) at 2 years, when compared with patients without MRD. In conclusion, treosulfan, fludarabine, and low-dose TBI provided effective conditioning for allogeneic HCT in patients with MDS or AML and resulted in low relapse incidence, regardless of cytogenetic risk. In patients with AML, MRD at the time of HCT remained a risk factor for post-HCT relapse.

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.

Conditioning with treosulfan and fludarabine followed by allogeneic hematopoietic cell transplantation for high-risk hematologic malignancies

In this prospective study 60 patients of median age 46 (range: 5-60 years), with acute myelogenous leukemia (AML; n = 44), acute lymphoblastic leukemia (ALL; n = 3), or myelodysplastic syndrome (MDS; n = 13) were conditioned for allogeneic hematopoietic cell transplantation with a treosulfan/fludarabine (Flu) combination. Most patients were considered at high risk for relapse or nonrelapse mortality (NRM). Patients received intravenous treosulfan, 12 g/m(2)/day (n = 5) or 14 g/m(2)/day (n = 55) on days -6 to -4, and Flu (30 mg/m(2)/day) on days -6 to -2, followed by infusion of marrow (n = 7) or peripheral blood stem cells (n = 53) from HLA-identical siblings (n = 30) or unrelated donors (n = 30). All patients engrafted. NRM was 5% at day 100, and 8% at 2 years. With a median follow-up of 22 months, the 2-year relapse-free survival (RFS) for all patients was 58% and 88% for patients without high-risk cytogenetics. The 2-year cumulative incidence of relapse was 33% (15% for patients with MDS, 34% for AML in first remission, 50% for AML or ALL beyond first remission and 63% for AML in refractory relapse). Thus, a treosulfan/Flu regimen was well tolerated and yielded encouraging survival and disease control with minimal NRM. Further trials are warranted to compare treosulfan/Flu to other widely used regimens, and to study the impact of using this regimen in more narrowly defined groups of patients.