Treosulfan-based preparative regimens for allo-HSCT in childhood hematological malignancies: a retrospective study on behalf of the EBMT pediatric diseases working party.

This retrospective analysis evaluated 51 children (0.7-17 years; median eight) with high-risk or advanced hematological malignancies, including 18 (35%) patients undergoing second/third hematopoietic SCT (allo-HSCT), not eligible for standard myeloablative regimens and transplanted from matched sibling (MSD) (n=24) or matched unrelated (MUD) (n=27) donors. Preparative regimens were based on treosulfan (TREO) i.v., a structural analog of BU, given at total dose of 30 g/m(2) (n=21) or 36-42 g/m(2) (n=30) in combination with, fludarabine, cyclophosphamide, melphalan and/or VP-16 according to diagnosis, and risk factors. Deaths due to early regimen-related toxicity (RRT) did not occur. Nonrelapse mortality was 8% at 1 year and 16% after 4 years. Myeloid engraftment was achieved in 94%, complete donor chimerism in 90% of patients. A 4-year incidence of relapse was 24%, and was significantly lower after MUD-HSCT (8%) than after MSD-HSCT (39%), but similar in children undergoing first (28%) or second/third HSCT (17%). A 4-year disease-free survival was 61%, but it was significantly better in myeloid (73%), than in lymphoid malignancies (41%). Thus, children with high-risk and advanced hematological malignancies and high-risk of life-threatening RRT can be transplanted effectively and safely using TREO-based regimens. Particularly favorable results were achieved in myeloid malignancies and in children undergoing second HSCT.

Pharmacokinetics of high-dose i.v. treosulfan in children undergoing treosulfan-based preparative regimen for allogeneic haematopoietic SCT.

Pharmacokinetic studies of high-dose treosulfan were carried out in seven paediatric patients (age range: 2-15 years) undergoing treosulfan-based conditioning regimen prior to allogeneic haematopoietic SCT. Treosulfan was administered intravenously in a daily dose of 10, 12 or 14 g/m(2) within 2 h. Five out of seven patients received 12 g/m(2). The plasma concentrations of treosulfan and its quantity eliminated with urine were determined using a validated HPLC method with refractometric detection. Pharmacokinetic parameters were evaluated following first dose using a two-compartment disposition model. These studies demonstrated a dose-dependent increase of area under the concentration (AUC) and maximum concentrationplasma (C(max)), but there was variability of these parameters. Rapid clearance of tresoulfan was observed, especially in 10 and 12 g/m(2) doses. Terminal half-life (t(0.5)) of treosulfan was in the range of 1.71-2.15 h, but the mean percent of parent drug eliminated with urine was 30%, range 16.3-45.4% of the total dose eliminated during the first 12 h after administration. The results of this study confirmed the linear pharmacokinetics of treosulfan, as used in children. However, variability of pharmacokinetic results observed in children studied demonstrates the need for pharmacokinetic evaluation in each paediatric patient undergoing the treosulfan-based preparative regimen, including those using different doses. This approach could enable further reduction of the risk of early and late organ toxicity related to high-dose treosulfan in paediatric patients.