Similar outcome after allogeneic stem cell transplantation with a modified FLAMSA conditioning protocol substituting 4 Gy TBI with treosulfan in an elderly population with high-risk AML

Early blast clearance during sequential conditioning prior to allogeneic stem cell transplantation in patients with acute myeloid leukaemia

For patients with relapsed or refractory AML, sequential conditioning prior to allogeneic stem cell transplantation (alloSCT) is an established and potentially curative treatment option. Early response to treatment during conditioning indicates chemotherapy-responsive disease and may have prognostic value. We retrospectively evaluated blast clearance on day 5 after melphalan, administered 11 days prior to alloSCT as part of a sequential conditioning in 176 patients with active AML. Overall survival (OS) was 52% (95% confidence interval [CI] 45%-60%), and relapse-free survival (RFS) was 47% (95% CI 40%-55%) at 3 years. Patients who achieved early blast clearance did not show a significant improvement in OS and RFS (OS, hazard ratio [HR] HR 0.75, p 0.19; RFS, HR 0.71, p 0.09, respectively), but had a significantly lower non-relapse mortality rate (HR 0.46, p 0.017). HLA-mismatched donor, older age, adverse genetic risk and higher comorbidity scores were associated with inferior survival outcomes. A high initial blast count was only associated with inferior prognosis in patients receiving chemotherapy-only compared to total body irradiation containing conditioning therapy. These results indicate that for patients transplanted with active AML, sensitivity to chemotherapy might be of less importance, compared to other disease- and transplant-related factors.

Smart Conditioning with Venetoclax-Enhanced Sequential FLAMSA + RIC in Patients with High-Risk Myeloid Malignancies

Up to 50% of patients with high-risk myeloid malignancies die of relapse after allogeneic stem cell transplantation. Current sequential conditioning regimens like the FLAMSA protocol combine intensive induction therapy with TBI or alkylators. Venetoclax has synergistic effects to chemotherapy. In a retrospective survey among German transplant centers, we identified 61 patients with myeloid malignancies that had received FLAMSA-based sequential conditioning with venetoclax between 2018 and 2022 as an individualized treatment approach. Sixty patients (98%) had active disease at transplant and 74% had genetic high-risk features. Patients received allografts from matched unrelated, matched related, or mismatched donors. Tumor lysis syndrome occurred in two patients but no significant non-hematologic toxicity related to venetoclax was observed. On day +30, 55 patients (90%) were in complete remission. Acute GvHD II°-IV° occurred in 17 (28%) and moderate/severe chronic GvHD in 7 patients (12%). Event-free survival and overall survival were 64% and 80% at 1 year as well as 57% and 75% at 2 years, respectively. The off-label combination of sequential FLAMSA-RIC with venetoclax appears to be safe and highly effective. To further validate these insights and enhance the idea of smart conditioning, a controlled prospective clinical trial was initiated in July 2023.

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.

Evaluation of six different types of sequential conditioning regimens for allogeneic stem cell transplantation in relapsed/refractory acute myelogenous leukemia - a study of the Acute Leukemia Working Party of the EBMT

The Acute Leukemia Working Party (ALWP) of the EBMT assessed the outcome of allogeneic stem cell transplantation (alloSCT) in patients with relapsed/refractory AML (r/rAML) evaluating six sequential conditioning regimens (SR) groups. A total of 2132 patients were included. LFS at 2 years was 28.9%, 33.6%, 35.3%, 20.6%, 24.4%, and 27% for the FLAMSA-TBI4, FLAMSA-Chemo, Mel-Flu-TBI8, Mel-Treo-Flu, Thio-ETO-Cy-Bu2-Flu, and Clo-ARAC-(Bu2/TBI4)-Cy groups, respectively. In patients <55 years of age Mel-Flu-TBI8 had the best LFS, which was statistically significant only in comparison to the Mel-Treo-Flu group, while in patients ≥55 years LFS was best with FLAMSA-Chemo without significant differences compared to FLAMSA-TBI4 and Mel-Flu-TBI8. Furthermore, best NRM rates were obtained with the two FLAMSA regimens groups. Our study suggests that in younger (<55 years) patients a more intense regimen might be used whereas in older (≥55 years) patients the focus might be more on tolerability.

Sequential treatment with FLAG-IDA/treosulfan conditioning regimen for patients with active acute myeloid leukemia

Sequential protocols combining salvage chemotherapy with reduced intensity conditioning (RIC) and allogeneic hematopoietic cell transplantation (alloHCT) for high-risk acute myeloid leukemia (AML) have been studied more than a decade. Purpose of this retrospective analysis was to evaluate the anti-leukemic efficacy and toxicity of FLAG-IDA protocol (fludarabine, cytarabine, and idarubicin) followed by treosulfan-based conditioning for patients with active AML. From January 2014 to November 2019, a total of 29 active AML patients [median age, 64 years (range, 23-73)] were treated. All patients completed protocol regimen and were transplanted. Five patients (17%) had grade 3-4 toxicities; therefore, treosulfan was substituted with total body irradiation (TBI) non-myeloablative conditioning. Six (20%) patients died within 30 post-transplant days, all from infectious complications. Out of 23 evaluable patients on day 30, 22 (96%) achieved complete hematologic remission with full donor chimerism. Non-relapse mortality (NRM) rates at 1 and 3 years were 22% and 49%, respectively. Median overall survival (OS) was 12 (95% CI, 4-20) months. OS and disease-free survival were 50% and 46% at 1 year and 28% and 17% at 2 years, respectively. Age, gender, disease burden, number of previous lines, and comorbidity score did not predict survival. Sequential strategy combining FLAG-IDA and treosulfan may offer a salvage option for few selected patients with active AML; however, high NRM presents a major obstacle to treatment success. Future efforts should focus on reducing NRM by moderating regimen intensity and by better selection of patients.

The FLAMSA concept-past and future

The FLAMSA reduced intensity (RIC) concept, also known as "sequential therapy", is a conceptual platform for the treatment of leukemia separated in several parts: induction therapy, a sequence of antileukemic and immunosuppressive conditioning for allogeneic stem cell transplantation, and immune restitution supported by donor lymphocyte transfusions. The antileukemic part consists of fludarabine, cytosine arabinoside, and amsacrine (FLAMSA); non-cross reactive agents like fludarabine and amsacrine have been successfully used in cases of refractoriness and relapse. Immunosuppressive conditioning and transplantation follow after only 3 days of rest. This way, the toxicity of allogeneic transplantation could be reduced and the anti-leukemia effects by using allogeneic immune cells could be optimized. This review summarizes available data on efficacy and toxicity of this approach. Further, possible strategies for improvements are discussed in order to provide better chances for elderly and frail patients and patients with advanced and high-risk disease. Among others, several new agents are available that target molecular changes of leukemia for induction of remission and allow for bridging the time after transplantation until adoptive immunotherapy becomes safe and effective.

Sequential therapy for patients with primary refractory acute myeloid leukemia: a historical prospective analysis of the German and Israeli experience

Primary refractory acute myeloid leukemia (AML) is associated with a dismal prognosis. The FLAMSA-reduced intensity conditioning protocol (total body irradiation or treosulfan-based) has been described as an effective approach in patients with refractory leukemia undergoing allogeneic hematopoietic cell transplantation. A modified protocol (without amsacrine) has also recently been used. We retrospectively analyzed the transplantation characteristics and outcomes of all consecutive patients between the years 2003 and 2017 (n=51) diagnosed with primary refractory AML who underwent transplantation at the University of Cologne and the Tel Aviv Medical Center. Median age was 54 years and median follow up was 37 months. Median time to neutrophil and platelet engraftment was 13 (range, 8-19) and 13 (range, 7-30) days, respectively. None of the patients had primary graft failure. Incidences of grade 2-4 and grade 3-4 acute graft-versus-host disease (GvHD), overall and moderate-severe chronic GvHD were 50% (95%CI: 41-67%), 12% (95%CI: 3-25%), 61% (95%CI: 47-72%), and 42% (95%CI: 34-51%), respectively. Anti-thymocyte globulin administration was associated with lower incidence of acute GvHD (HR: 0.327; P=0.02). Non-relapse mortality at three months and three years were 6% and 16%, respectively. Relapse incidences were 6% and 29%, respectively. Overall survival rates at three months, three and five years were 90%, 61%, and 53%, respectively. Chronic GvHD disease was associated with a decreased mortality rate (HR: 0.397; P=0.045). We conclude that sequential therapy in patients with primary refractory acute myeloid leukemia is safe and provides a remarkable anti-leukemic effect with durable survival and should be considered for every patient with primary refractory disease.

Pre-formulation investigations for establishing a protocol for treosulfan handling and activation

INTRODUCTION

Treosulfan is an alkylating agent that is used for the treatment of ovarian cancer and for conditioning prior to stem cell transplantation. It is a prodrug that is activated non-enzymatically to two active epoxides.

OBJECTIVES

To optimize a protocol for both in vivo samples handling and in vitro drug preparation. Treosulfan stability was tested in biological fluids at different conditions as well as for its cytotoxicity on cell lines.

RESULTS

Plasma samples can be safely frozen for a short period up to 8 h, however; for longer periods, samples should be acidified. Urine samples and cell culture media can be safely frozen regardless their pH. For in vitro investigations, incubation of treosulfan at 37 °C for 24 h activated 100% of the drug. Whole blood acidification should be avoided for the risk of hemolysis. Finally; treosulfan cytotoxicity on HL-60 cells has increased following pre-incubation for 24 h at 37 °C compared to K562 cell line.

CONCLUSION

The stability profiling of treosulfan provided a valuable reference for handling of biological samples for both in vivo and in vitro studies. These results can be utilized for further investigations concerning the drug kinetics and dynamics in addition to the development of new pharmaceutical formulations.

Reduced Relapse Incidence with FLAMSA-RIC Compared with Busulfan/Fludarabine for Acute Myelogenous Leukemia Patients in First or Second Complete Remission: A Study from the Acute Leukemia Working Party of the European Society for Blood and Marrow Transplantation

Busulfan/fludarabine (BuFlu) is a widely used conditioning regimen for patients with myeloid malignancies. The sequential FLAMSA (fludarabine + Ara-C + amsacrine chemotherapy) protocol followed by either cyclophosphamide and total body irradiation (FLAMSA-TBI) or cyclophosphamide and busulfan (FLAMSA-Bu) has shown remarkable activity in high-risk acute myelogenous leukemia (AML) patients. Here we compare the outcomes of AML patients transplanted in first complete remission (CR1) or second complete remission (CR2) after conditioning with BuFlu or FLAMSA. Eligible patients had their first allogeneic stem cell transplantation for AML in CR1 or CR2 between January 2005 and June 2016. Donors were matched related or unrelated with up to 1 mismatch. Conditioning consisted of either BuFlu or FLAMSA. Propensity score matching was applied and comparisons were performed using weighted Cox regression. BuFlu conditioning was used in 1197 patients, whereas FLAMSA-TBI and FLAMSA-Bu were used in 258 and 141 patients, respectively. Median follow-up of survivors was 24.72 months. In univariate analysis, relapse incidence (RI) was 30.3%, 21.9%, and 23.1% in the BuFlu, FLAMSA-TBI, and FLAMSA-Bu groups, respectively (P < .01), and nonrelapse mortality at 2 years was 16.1%, 16.4%, and 26.7%, respectively (P < .01). Leukemia-free survival (LFS) at 2 years was 53.6%, 61.6%, and 50.1%, respectively (P = .03). Weighted Cox regression revealed that FLAMSA-TBI compared with BuFlu was associated with lower RI (hazard ratio [HR], .64; 95% confidence interval [CI], .42 to .98; P = .04) and a trend for better LFS (HR, .72; 95% CI, .49 to 1.06; P = .09). These results suggest that compared with BuFlu, conditioning with FLAMSA-TBI leads to reduced RI at 2 years in AML patients transplanted in CR1 or CR2.

Bridging Strategies to Allogeneic Transplant for Older AML Patients

Treatment options for older patients with intermediate or high-risk acute myeloid leukemia (AML) remain unsatisfactory. Allogeneic stem cell transplantation, the treatment of choice for the majority of younger AML patients, has been hampered in elderly patients by higher treatment related mortality, comorbidities and lack of a suitable donor. With the higher availability of suitable donors as well as of reduced intensity conditioning regimens, novel low intensity treatments prior to transplantation and optimized supportive care, the number of older AML patients being successfully transplanted is steadily increasing. Against this background, we review current treatment strategies for older AML patients planned for allogeneic stem cell transplantation based on clinical trial data, discussing differences between approaches with advantages and pitfalls of each. We summarize pre-treatment considerations that need to be taken into account in this highly heterogeneous older population. Finally, we offer an outlook on areas of ongoing clinical research, including novel immunotherapeutic approaches that may improve access to curative therapies for a larger number of older AML patients.

A new intensive conditioning regimen for allogeneic hematopoietic stem cell transplantation in patients with refractory or relapsed acute myeloid leukemia

To explore the efficacy, and safety of the intensive conditioning regimen consisting of cladribine, cytarabine (Ara-C), and granulocyte colony-stimulating factor (G-CSF) plus modified busulfan (Bu) combined with cytoxan (Cy) (BuCy), prior to allogeneic hematopoietic stem cell transplantation (allo-HSCT) in patients with refractory, or relapsed acute myeloid leukemia (R/R AML).Thirty-Six R/R AML patients scheduled to receive allo-HSCT were consecutively, enrolled in this prospective study, and treated using intensive conditioning regimen consisting of CLAG plus modified BuCy. Median follow-up duration was 11.25 (range 0.5 - 21.0) months and the last follow up date was August 15, 2017.All patients (100%) achieved white blood cell (WBC) recovery within a median time of 16.00 (13.25 - 18.00) days, and 34 of them (94%) attained platelet (PLT) recovery within a median time of 13.50 (9.25 - 19.75) days. Incidence of acute graft-versus-host disease (aGVHD) was 50.00%, with median time of 71.50 (41.00 - 401.25) days. Three patients developed Grade I; nine, Grade II; 5, Grade III; and 1, Grade IV aGVHD. The incidence of chronic GVHD (cGVHD) was 44.40%, with median time of 255.00 (120.00 - 390.00) days. Four patients developed limited cGVHD, and 12, extensive cGVHD. One-year accumulating leukemia free survival (LFS), and overall survival (OS) rates between 52.9 ± 8.8% to 69.4 ± 7.7%, respectively. Eighteen (50%) patients were infected with cytomegalovirus; 2 (5.6%), with Epstein-Barr virus (EBV), 7 (19.4%), with hemorrhagic cystitis; 13 (36.1%), with bacteria; and 8 (22.2%), with fungus.Intensive conditioning regimen of CLAG plus modified BuCy for allo-HSCT may be effective and well-tolerated in R/R AML patients.