Successful Haematopoietic Stem Cell Transplantation for LRBA Deficiency with Fludarabine, Treosulfan, and Thiotepa-Based Conditioning.

LRBA deficiency is an inborn error of immunity defined by autoimmunity, lymphoproliferation, recurrent infections, cytopenia, and inflammatory bowel disease. Despite recent advances in managing this disease with targeted biologic therapy, haematopoietic stem cell transplant (HSCT) remains the only cure. However, great variability exists between protocols used to transplant patients with LRBA deficiency. We describe a cohort of seven patients with LRBA deficiency who underwent HSCT using a myeloablative, reduced toxicity regime of fludarabine, treosulfan, and thiotepa at two transplantation centres from 2016 to 2019. Data were collected both retrospectively and prospectively, measuring time to engraftment, infectious complications, incidence of graft versus host disease, and post-transplantation chimerism. Six of seven patients survived transplantation, and four of six surviving patients achieving treatment-free survival. We thus recommend that HSCT with fludarabine, treosulfan, and thiotepa-based conditioning be considered in patients with LRBA deficiency.

Impact of fludarabine and treosulfan on ovarian tumor cells and mesothelin chimeric antigen receptor T cells.

In addition to their immunosuppressive effect, cytostatics conditioning prior to adoptive therapy such as chimeric antigen receptor (CAR) T cells may play a role in debulking and remodeling the tumor microenvironment. We investigated in vitro the killing efficacy and impact of treosulfan and fludarabine on ovarian cancer cells expressing mesothelin (MSLN) and effect on MSLN-targeting CAR T cells. Treosulfan and fludarabine had a synergetic effect on killing of SKOV3 and OVCAR4 cells. Sensitivity to the combination of treosulfan and fludarabine was increased when SKOV3 cells expressed MSLN and when OVCAR4 cells were tested in hypoxia, while MSLN cells surface expression by SKOV3 and OVCAR4 cells was not altered after treosulfan or fludarabine exposure. Exposure to treosulfan or fludarabine (10 µM) neither impacted MSLN-CAR T cells degranulation, cytokines production upon challenge with MSLN + OVCAR3 cells, nor induced mitochondrial defects. Combination of treosulfan and fludarabine decreased MSLN-CAR T cells anti-tumor killing in normoxia but not hypoxia. In conclusion, treosulfan and fludarabine killed MSLN + ovarian cancer cells without altering MSLN-CAR T cells functions (at low cytostatics concentration) even in hypoxic conditions, and our data support the use of treosulfan and fludarabine as conditioning drugs prior to MSLN-CAR T cell therapy.

Impact of busulfan versus treosulfan dose intensity in myelofibrosis undergoing hematopoietic cell transplantation.

One key aspect of allogeneic hematopoietic cell transplantation (HCT) is pretransplant conditioning, balancing risk for relapse versus non-relapse mortality. Conditioning regimens with different alkylators at different doses can influence outcome, but data are missing for myelofibrosis, a challenging cohort of patients usually presenting at older age and with comorbidities. We evaluated in a multicenter retrospective study the comparative efficacy and safety of busulfan versus treosulfan in combination with fludarabine for myelofibrosis patients undergoing HCT. This study included 1115 patients (busulfan, n = 902; treosulfan, n = 213) receiving first HCT between 2005 and 2021. Patients were generally balanced for key patient characteristics. Overall survival at 4 years was 62% for the busulfan group versus 58% for the treosulfan group (p = .22). Impact on outcome was dose-dependent. Overall survival was 65% (95% CI, 61%-69%) for reduced intensity busulfan versus 69% (95% CI, 54%-84%) for reduced intensity treosulfan, 53% (95% CI, 44%-63%) for higher intensity busulfan, and 55% (95% CI, 46%-63%) for higher intensity treosulfan. Incidence of relapse was similar across intensity groups. In multivariable analysis, the hazard for death (with reduced intensity busulfan as reference) was 0.88 (95% CI, 0.39-2.01) for reduced intensity treosulfan (p = .77), 1.42 (95% CI, 0.96-2.10) for higher intensity busulfan (0.08), and 1.61 (95% CI, 1.14-2.26) for higher intensity treosulfan (p = .006). In terms of non-relapse mortality, comparison was not significantly different, while the hazard ratio for higher intensity treosulfan was 1.48 (95% CI, 0.98-2.23; p = .06). Here, we showed comparable outcomes and improved survival in myelofibrosis undergoing HCT with reduced intensity busulfan or treosulfan.

Outcomes from hematopoietic stem cell transplantation following treosulfan-based conditioning: A clinical and pharmacokinetic analysis.

BACKGROUND: The aims of this study are to report our experience with treosulfan-based conditioning regimens for patients with non-malignant hematologic conditions, correlating clinical outcomes at different time points post-transplant with treosulfan exposure (AUC). METHODS: This study was a single-center observational study investigating overall survival (OS), disease-free survival (DFS), and event-free survival (EFS) end-points post-transplant. The consequences of treosulfan AUC with respect to toxicity, correction of underlying disease, and long-term chimerism were also explored using pharmacokinetic analysis. RESULTS: Forty-six patients received 49 transplants with treosulfan and fludarabine-based conditioning between 2005 and 2023. Twenty-four patients also received thiotepa. Donor chimerism was assessed on either whole blood or sorted cell lines at different time points post-transplant. Thirty-nine patients received treosulfan pharmacokinetic assessment to evaluate cumulative AUC, with five infants receiving real-time assessment to facilitate daily dose adjustment. OS, DFS, and EFS were 87%, 81%, and 69%, respectively. Median follow-up was 32.1 months (range 0.82-160 months) following transplant. Lower EFS was associated with patient age (<1 year; p = .057) and lower cumulative treosulfan dose (<42 g/m2; p = .003). Stable donor chimerism in B-cell, NK-cell, and granulocyte lineages at 1-year post-transplant were more prevalent in patients receiving thiotepa conditioning. Two infants required daily dose adjustment to treosulfan to avoid high AUC. CONCLUSIONS: Excellent clinical outcomes and stable chimerism were observed in this patient series. The addition of thiotepa conferred no significant toxicity and trended toward sustained ongoing donor engraftment. Correlating treosulfan AUC with long-term patient outcomes is required.

Determinants of Interpatient Variability in Treosulfan Pharmacokinetics in AML Patients Undergoing Autologous Stem Cell Transplantation.

Limited data on treosulfan pharmacokinetics in adults, particularly regarding autologous stem cell transplantation (ASCT) in acute myeloid leukemia (AML), is available to date. Furthermore, correlations between treosulfan exposure, toxicity, and clinical outcome remain understudied. In this single-center retrospective study, we analyzed data from 55 AML patients who underwent HDCT with treosulfan (14 g/m2) and melphalan (140 mg/m2 or 200 mg/m2) (TreoMel) between August 2019 and November 2023 at the University Hospital of Bern. We assessed treosulfan pharmacokinetics and correlations with several physiological parameters with potential impact on its interpatient variability. We further analyzed how treosulfan exposure correlates with toxicity and clinical outcomes. Women above 55 years showed higher area under the curve (AUC) levels (median: 946 mg*h/L, range: 776-1370 mg*h/L), as compared to women under 55 (median: 758 mg*h/L, range: 459-1214 mg*h/L, p = 0.0487). Additionally, women above 55 showed higher peak levels (median: 387 mg/L, range: 308-468 mg/L), as compared to men of the same age range (median: 326 mg/L, range: 264-395 mg/L, p = 0.0159). Treosulfan levels varied significantly with body temperature, liver enzymes, hemoglobin/hematocrit., and treosulfan exposure correlated with diarrhea severity in women over 55 (p = 0.0076). Our study revealed age- and gender-related variability in treosulfan pharmacokinetics, with higher plasma levels observed in female patients above 55. Moreover, our data suggest that treosulfan plasma levels may vary with several physiological parameters and that higher treosulfan exposure may impact toxicity. Our study underlines the need for further research on treosulfan pharmacokinetics, especially in older patients undergoing HDCT in the ASCT setting.

Busulfan-fludarabine- or treosulfan-fludarabine-based myeloablative conditioning for children with thalassemia major.

Significant advances in supportive care for patients with transfusion-dependent thalassemia major (TDT) have improved patients' life expectancy. However, transfusion-associated iron overload remains a significant barrier to long-term survival with good quality of life. Today, allogeneic hematopoietic stem cell transplantation (HSCT) is the current curative standard of care. Alongside selection of the best available donor, an optimized conditioning regimen is crucial to maximize outcomes for patients with TDT undergoing HSCT. The aim of this retrospective analysis was to investigate the role of busulfan-fludarabine-based and treosulfan-fludarabine-based conditioning in TDT patients undergoing HSCT. We included 772 patients registered in the European Society for Blood and Marrow Transplantation (EBMT) database who underwent first HSCT between 2010 and 2018. Four hundred ten patients received busulfan-fludarabine-based conditioning (median age 8.6 years) and 362 patients received treosulfan-fludarabine-based conditioning (median age 5.7 years). Patient outcomes were retrospectively compared by conditioning regimen. Two-year overall survival was 92.7% (95% confidence interval: 89.3-95.1%) after busulfan-fludarabine-based conditioning and 94.7% (95% confidence interval: 91.7-96.6%) after treosulfan-fludarabine-based conditioning. There was a very low incidence of second HSCT overall. The main causes of death were infections, graft-versus-host disease, and rejection. In conclusion, use of busulfan or treosulfan as the backbone of myeloablative conditioning for patients with TDT undergoing HSCT resulted in comparably high cure rates. Long-term follow-up studies are warranted to address the important issues of organ toxicities and gonadal function.

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.

A retrospective study of treosulfan versus busulfan-based conditioning in pediatric patients.

OBJECTIVES: To compare the outcomes of treosulfan-based vs busulfan-based conditioning regimens in allogeneic hematopoietic stem cell transplantation (HSCT) in pediatric patients. METHODS: Retrospective study of all consecutive patients (2012-2019) treated with allogenic HSCT and treosulfan- or busulfan-based conditioning regimens at a single center. RESULTS: A total of 101 HSCT were included: 66 HSCT with busulfan and 35 with treosulfan. In malignant diseases (n = 62), busulfan-based conditioning was more commonly employed than treosulfan: 82.3% vs 17.7%. However, the use of treosulfan for malignant diseases increased over time: 6.5% of HSCT in 2012-2015 vs 29% of HSCT in 2015-2019 (p = .02). The cohort of treosulfan had more children under 1-year of age than the busulfan cohort (31 vs 13%; p = .033). The percentage of patients who received serotherapy was 73 and 89% in the nonmalignant and malignant groups, respectively. The engraftment, time to neutrophil, and platelet engraftment were not significantly different between the busulfan and the treosulfan cohorts. Rate of grade II-IV acute GvHD was significantly higher in the busulfan cohort than the treosulfan cohort (39% vs 15%; p = .016). No differences were observed in endothelial damage complications, chronic GvHD, relapse, overall survival, and transplant-related mortality. CONCLUSIONS: Busulfan-based conditioning regimens are used more frequently for children undergoing allogenic HSCT, but treosulfan-based conditioning is gaining acceptance. Treosulfan-based conditioning is associated with lower rates of acute GvHD, and no significant differences on overall survival were observed compared with busulfan.

Busulfan and cyclophosphamide-based conditioning regimen still holds the promise of being a safe and efficacious regimen for allogeneic transplantation in patients with transfusion-dependent thalassemia, even in high risk.

Busulfan and cyclophosphamide (BuCy)-based regimen has been used as a standard myeloablative chemotherapy for haematopoietic stem cell transplantation in thalassemia. However, treosulfan-based conditioning regimen has emerged due to concerns of toxicities. We retrospectively analysed the safety and efficacy of fludrabine/Bu/Cy/antithymocyte globulin (ATG) versus treosulfan/thiotepa/fludrabine regimens for Hematopoietic Stem Cell Transplant (HSCT) in transfusion-dependent thalassemia (TDT) conducted at our institute (2013-2021). In 75 patients, 36 (48%) received Flu/Bu/Cy/ATG whereas 39 (52%) received Treo/Thio/Flu. Median age was 6 (1-12) and 9 (1-15) years, respectively. Number of patients with Classes I, II, and III were 14, 10, and 12 in Flu/Bu/Cy/ATG versus 2, 19, and 18 in Treo/Thio/Flu group, respectively. Graft was growth factor mobilized bone marrow in Flu/Bu/Cy/ATG versus peripheral blood stem cell in Treo/Thio/Flu group. Mean stem cell dose was 3.82 (2.2-9.1) versus 5 (1.65-8.01) 106 /kg in Flu/Bu/Cy/ATG versus Treo/Thio/Flu group, respectively. Neutrophils and platelets engrafted at a median of 16 (14-21) and 16 (9-47) days in Flu/Bu/Cy/ATG and 15 (10-20) and 13 (9-41) days in Treo/Thio/Flu group. Median duration of follow-up was 28 (23-32.9) months. Five (6.6%) patients had rejection (all secondary). Venoocclusive disease was observed in 2 (5.7%) versus 4 (10.3%) patients (p = .047), respectively. Flu/Bu/Cy/ATG had 4 (11.4%) patients with acute GVHD versus 15 (38.5%) patients which had significant impact on survival (p = .038). We observed chronic GVHD in 4 (11.4%) and 11 (28.2%) patients, respectively, with significant impact on survival (p = .031). Four (5.1%) patients had TRM in Treo/Thio/Flu group, in contrast to none in Flu/Bu/Cy/ATG group. Mixed chimerism was common in Flu/Bu/Cy/ATG {20 (57.1%)} versus Treo/Thio/Flu group {12 (30.1%)}. Five-year Event Free Survival (EFS) and OS of entire cohort were 87% + 4% and 94% + 3%, respectively. Estimated TFS, EFS, OS of Flu/Bu/Cy/ATG versus Treo/Thio/Flu was 97.1% + 2.9% versus 89.2% + 5.1% (p = .251), 97 + 3% versus 80.7 + 6% (p = .041) and 100% versus 90.4 + 5% (p = .067), respectively. In our experience, Flu/Bu/Cy/ATG regimen is safe and effective even in high-risk TDT. However, one needs to be vigilant for mixed chimerism.

Treosulfan compared with reduced-intensity busulfan improves allogeneic hematopoietic cell transplantation outcomes of older acute myeloid leukemia and myelodysplastic syndrome patients: Final analysis of a prospective randomized trial.

The phase III study was designed to compare event-free survival (EFS) after treosulfan-based conditioning with a widely applied reduced-intensity conditioning (RIC) busulfan regimen in older or comorbid patients with acute myeloid leukemia (AML) or myelodysplastic syndrome (MDS) undergoing allogeneic hematopoietic cell transplantation (HCT). A previously reported confirmatory interim analysis of the randomized clinical study including 476 patients demonstrated statistically significant noninferiority for treosulfan with clinically meaningful improvement in EFS. Here, the final study results and pre-specified subgroup analyses of all 570 randomized patients with completed longer-term follow-up are presented. Patients presenting HCT-specific comorbidity index >2 or aged ≥50 years were randomly assigned (1:1) to intravenous (IV) fludarabine with either treosulfan (30 g/m2 IV) or busulfan (6.4 mg/kg IV) after stratification by disease risk group, donor type, and participating institution. The primary endpoint was EFS with disease recurrence, graft failure, or death from any cause as events. EFS of patients (median age 60 years) was superior after treosulfan compared to RIC busulfan: 36-months-EFS rate 59.5% (95% CI, 52.2-66.1) vs. 49.7% (95% CI, 43.3-55.7) with a hazard ratio (HR) of 0.64 (95% CI, 0.49-0.84), p = 0.0006. Likewise, overall survival (OS) with treosulfan was superior compared to busulfan: 36-month-OS rate 66.8% vs. 56.3%; HR 0.64 (95% CI, 0.48-0.87), p = 0.0037. Post hoc analyses revealed that these differences were consistent with the confirmatory interim analysis, and thereby the treosulfan regimen appears particularly suitable for older AML and MDS patients.

Evaluation of the drug-drug interaction potential of treosulfan using a physiologically-based pharmacokinetic modelling approach.

AIMS: The aim of this work is the development of a mechanistic physiologically-based pharmacokinetic (PBPK) model using in vitro to in vivo extrapolation to conduct a drug-drug interaction (DDI) assessment of treosulfan against two cytochrome p450 (CYP) isoenzymes and P-glycoprotein (P-gp) substrates. METHODS: A PBPK model for treosulfan was developed de novo based on literature and unpublished clinical data. The PBPK DDI analysis was conducted using the U.S. Food and Drug Administration (FDA) DDI index drugs (probe substrates) midazolam, omeprazole and digoxin for CYP3A4, CYP2C19 and P-gp, respectively. Qualified and documented PBPK models of the probe substrates have been adopted from an open-source online model database. RESULTS: The PBPK model for treosulfan, based on both in vitro and in vivo data, was able to predict the plasma concentration-time profiles and exposure levels of treosulfan applied for a standard conditioning treatment. Medium and low potentials for DDI on CYP3A4 (maximum area under the concentration-time curve ratio (AUCRmax = 2.23) and CYP2C19 (AUCRmax = 1.6) were predicted, respectively, using probe substrates midazolam and omeprazole. Treosulfan was not predicted to cause a DDI on P-gp. CONCLUSION: Medicinal products with a narrow therapeutic index (eg, digoxin) that are substrates for CYP3A4, CYP2C19 or P-gp should not be given during treatment with treosulfan. However, considering the comprehensive treosulfan-based conditioning treatment schedule and the respective pharmacokinetic properties of the concomitantly used drugs (eg, half-life), the potential for interaction on all evaluated mechanisms would be low (AUCR < 1.25), if concomitantly administered drugs are dosed either 2 hours before or 8 hours after the 2-hour intravenous infusion of treosulfan.

Allogeneic hematopoietic cell transplantation in patients with myelodysplastic syndrome using treosulfan based compared to other reduced-intensity or myeloablative conditioning regimens. A report of the chronic malignancies working party of the EBMT.

Allogeneic haematopoietic-cell transplantation (allo-HCT) is a potentially curative therapy for high-risk myelodysplastic syndrome (MDS). Reduced-intensity conditioning (RIC) is usually associated with lower non-relapse mortality (NRM), higher relapse rate and similar overall-survival (OS) as myeloablative-conditioning (MAC). Fludarabine/treosulfan (FT) is a reduced-toxicity regimen with intense anti-leukaemia activity and a favourable toxicity profile. We investigated post-transplant outcomes in 1722 MDS patients following allo-HCT with FT (n = 367), RIC (n = 687) or MAC (n = 668). FT and RIC recipients were older than MAC recipients, median age 59, 59 and 51 years, respectively (P < 0·001) but other disease characteristics were similar. The median follow-up was 64 months (1-171). Five-year relapse rates were 25% (21-30), 38% (34-42) and 25% (22-29), after FT, RIC and MAC, respectively, (P < 0·001). NRM was 30% (25-35), 27% (23-30) and 34% (31-38, P = 0·008), respectively. Five-year OS was 50% (44-55), 43% (38-47), and 43% (39-47), respectively (P = 0·03). In multivariate analysis, FT was associated with a lower risk of relapse (HR 0·55, P < 0·001) and better OS (HR 0·72, P = 0·01). MAC was associated with higher NRM (HR 1·44, P = 0·001). In conclusion, FT is associated with similar low relapse rates as MAC and similar low NRM as RIC, resulting in improved OS. FT may be the preferred regimen for allo-HCT in MDS.

Haploidentical Stem Cell Transplant With Post-transplant Cyclophosphamide for Chediak-Higashi Syndrome: A Very Rare Case Report.

Chediak-Higashi syndrome is a rare immunodeficiency disorder for which hematopoietic stem cell transplant (HSCT) is the only curative treatment option. HSCT only corrects the hematologic and immunologic manifestations of the disease but neurologic complications may still progress after transplant. Haploidentical HSCT (haplo-HSCT) has evolved as a feasible alternative for patients with primary immunodeficiency. More recently, there has been use of haplo-HSCT with post-transplant cyclophosphamide. However, only 4 cases of Chediak-Higashi syndrome have been reported using this approach. Here, the authors describe a case of a 17-month-old boy who was successfully treated by haplo-HSCT with reduced-toxicity conditioning (fludarabine/treosulfan/melphalan) and post-transplant cyclophosphamide.

Treosulfan in platinum-resistant ovarian cancer.

OBJECTIVES: Treosulfan is offered as last-line treatment in patients with end-stage ovarian cancer. This retrospective study aimed to evaluate the response rates, overall survival, and adverse events of treosulfan in this patient population. METHODS: The study included patients with end-stage platinum-resistant ovarian cancer treated with treosulfan from October 2015 to October 2020 at the Department of Oncology, Lillebaelt Hospital, University Hospital of Southern Denmark, Vejle, Denmark. Patients were included for treatment if their cancer had progressed and if other treatment options were limited. Patients receiving treosulfan as first-line treatment were excluded from the study. Response rates were evaluated according to the combined criteria of CA125 and Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1. Kaplan-Meier survival analyses were used to illustrate progression-free and overall survival. Adverse events were graded 1-5 according to the Common Terminology Criteria for Adverse Events version 5.0. RESULTS: Sixty-seven patients with a median age of 72 years (range 33-92) were identified. Sixty-three (94%) patients were diagnosed with serous adenocarcinoma. Fifty-seven (85%) patients were Federation of International Gynecology and Obstetrics (FIGO) stage III or IV at the time of diagnosis. The median number of treatments prior to treosulfan treatment was 3 (range 1-8). One patient had a complete response (2%), eight patients had a partial response (13%), and 22 patients (35%) had stable disease as the best response. The median duration of response (complete or partial) was 239 days (range 43-572). Median progression-free survival was 63 days (95% CI 41 to 77). The most common adverse events were anemia (83%), fatigue (83%), anorexia (62%), nausea (57%), and constipation (41%). CONCLUSIONS: Treosulfan is an alternative for the treatment of relapsed ovarian cancer when other treatment options are limited, with response rates of approximately 15%. In general, the treatment was well tolerated. Taking the mild adverse events and the response rates into account, palliative treosulfan mainly seems beneficial for patients with performance status 0-1.

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.

Improved Outcomes after Allogenic Hematopoietic Stem Cell Transplantation with Fludarabine/Treosulfan for Patients with Myelodysplastic Syndromes.

While allogeneic hematopoietic stem cell transplantation (allo-HCT) currently offers the only curative option for patients with myelodysplastic syndrome (MDS), there is still a high risk of relapse or transplant-related complications. We collected data on all patients who had undergone allo-HCT at our center (Copenhagen University Hospital) between 2000 and 2018. In total, 215 patients with MDS (n = 196) or chronic myelomonocytic leukemia (n = 19) were included. Estimated 1-year overall survival (OS) was 70.3% (95% confidence interval [CI], 64.2% to 77.0%), and the median survival was 7.7 years (95% CI, 4.7 to indeterminable). There was a significant improvement in OS over time (P = .011, comparing 2000 to 2010, 2010 to 2014, and 2014 to 2018). Treatment was standardized throughout the study period, allowing comparison between patients receiving nonmyeloablative (NMA, n = 124), standard myeloablative (SMA, n = 36), and fludarabine and treosulfan (FluTreo, n = 55) conditioning. FluTreo has myeloablative properties but lower toxicity and replaced standard myeloablative conditioning at our center in 2014. The FluTreo group was significantly older and had more comorbidities than the SMA group but similar disease severity. One-year OS was 84.0% (95% CI, 74.3% to 94.9%), 58.3% (95% CI, 44.3% to 76.9%), and 68.3% (95% CI, 60.2% to 77.5%) for FluTreo, SMA, and NMA, respectively (P = .04). In univariate analysis, Revised International Scoring System (IPSS-R) (high versus low), donor sex mismatch, and cytomegalovirus status mismatch were significant factors for OS. In multivariate analysis of OS including age, IPSS-R, and HCT specific comorbidity index, NMA was borderline inferior to FluTreo (P = .073) while SMA was significantly inferior to FluTreo with a hazard ratio of 6.89 (95% CI, 2.53 to 18.77, P < .001). The introduction of FluTreo allowed us to administer a myeloablative regimen to a broader patient group and shows promising results.

Treosulfan-Based Conditioning Regimen in Haematopoietic Stem Cell Transplantation with TCRαß/CD19 Depletion in Nijmegen Breakage Syndrome.

Nijmegen breakage syndrome (NBS) is a DNA repair disorder characterized by combined immunodeficiency and a high predisposition to malignancies. HSCT appears to cure immunodeficiency, but remains challenging due to limited experience in long-term risks of transplant-associated toxicity and malignancies. Twenty NBS patients received 22 allogeneic HSCTs with TCRαß/CD19+ graft depletion with fludarabine 150 mg/m2, cyclophosphamide 20-40 mg/kg and thymoglobulin 5 mg/kg based conditioning regimens (CRs). Twelve patients additionally received low-dose busulfan 4 mg/kg (Bu group) and 10 patients (including 2 recipients of a second HSCT) treosulfan (Treo group) 30 g/m2. Overall and event-free survival were 0.75 vs 1 (p = 0.16) and 0.47 vs 0.89 (p = 0.1) in the Bu and Treo groups, respectively. In the Bu group, four patients developed graft rejection, and three died: two died of de novo and relapsed lymphomas and one died of adenoviral hepatitis. The four living patients exhibited split chimerism with predominantly recipient myeloid cells and predominantly donor T and B lymphocytes. In Treo group, one patient developed rhabdomyosarcoma. There was no difference in the incidence of GVHD, viral reactivation, or early toxicity between either group. Low-dose Bu-containing CR in NBS leads to increased graft failure and low donor myeloid chimerism. Treo-CR followed by TCRαß/CD19-depleted HSCT demonstrates a low level of early transplant-associated toxicity and enhanced graft function with stable donor chimerism.

Risk stratification of pulmonary toxicities in the combination of whole lung irradiation and high-dose chemotherapy for Ewing sarcoma patients with lung metastases: a review.

BACKGROUND: Whole lung irradiation (WLI) represents an important part of multimodal therapy in Ewing sarcoma (EwS) patients diagnosed with pulmonary metastases. This review discusses pulmonary toxicity in EwS patients with pulmonary metastases treated with WLI, who received different modes of high-dose chemotheray (HD-Cth). METHODS: Literature was compiled using the Cochrane Library, PubMed database, and the National Institute of Health (NIH) clinical trials register. Relevant patient information, including nature of HD-Cth, acute and late lung toxicities, and pulmonary function disorders, was selected from the above databases. RESULTS: Nine reports with a total of 227 patients, including 57 patients from a single randomized trial were included in this review. No acute or chronic symptomatic pulmonary toxicities were observed in patients that received WLI after HD busulfan-melphalan (HD-Bu/Mel), but 8% of these patients were diagnosed with asymptomatic restrictive lung disease. Grade 1 or 2 acute or chronic lung adverse effects were observed in up to 30% of patients that received WLI after HD treosulfan/Mel (HD-Treo/Mel) or HD etoposide (E)/Mel. Interstitial pneumonitis was present in 9% of patients treated concurrently with E/Mel and total body irradiation (TBI) with 8 Gy. Radiation doses as well as time between HD-Cth and WLI were both identified as significant risk factors for pulmonary function disorders. CONCLUSION: The risk of adverse lung effects after WLI depends on several factors, including cumulative radiation dose and dose per fraction, HD-Cth regimen, and time interval between HD-Cth and WLI. A cumulative radiation dose of up to 15 Gy and a time interval of at least 60 days can potentially lead to a reduced risk of pulmonary toxicities. No evident adverse lung effects were registered in patients that received simultaneous therapy with HD-Cth and TBI. However, pulmonary function testing and lung toxicity reports were lacking for most of these patients.

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.

High leukemia-free survival after TBI-based conditioning and mycophenolate mofetil-containing immunosuppression in patients allografted for chronic myelomonocytic leukemia: a single-center experience.

This retrospective single-center analysis studied the impact of the conditioning and the graft-versus-host disease (GVHD) prophylaxis on outcome in unselected patients allografted for chronic myelomonocytic leukemia (CMML) and acute myeloid leukemia (AML) secondary to documented prior CMML. A total of 44 patients (median age 61 years) allografted between 2002 and 2019 in our institution were analyzed. Fifteen patients had secondary AML. The conditioning regimen was fractionated 6-8 Gy total body irradiation (TBI) in combination with fludarabine in 33 (75%) patients. Eleven patients (25%) received alkylator-based conditioning therapy without TBI. For GVHD prophylaxis, a calcineurin inhibitor (CNI) backbone in combination with methotrexate (MTX) or mycophenolate mofetil (MMF) was applied in 21 and 23 patients, respectively. All patients allografted from an unrelated donor (UD) received antithymocyte globuline. In univariate analysis of the entire cohort, TBI-based conditioning and MMF-containing immunosuppression were associated with improved leukemia-free survival (LFS, HR 0.16, P < 0.001 and HR 0.41, P = 0.030, respectively). After stratification according to conditioning and GVHD prophylaxis into four groups (TBI-MMF [n = 17], TBI-MTX [n = 16], alkylator-MMF [n = 6], alkylator-MTX [n = 5]), TBI-MMF was associated with improved overall survival (OS) and LFS (P = 0.001 and P < 0.001, respectively). Patient and disease characteristics did not differ between the groups. The associations of TBI-based conditioning and MMF with prolonged LFS were observed across the CMML (n = 29), secondary AML (n = 15), and UD allograft (n = 34) subgroups. In summary, our study suggests that allografting based on intermediate-dose TBI conditioning and MMF-containing GVHD prophylaxis is associated with increased disease control in CMML. Larger (registry-based) studies are warranted to confirm our findings.