Non Malignant Disorders

This phase II trial investigates how well a naive T cell depleted graft work for the reduction of graft versus host disease in patients with non-malignant diseases requiring hematopoietic cell transplantation. Giving chemotherapy and total-body irradiation before a donor peripheral blood stem cell transplant helps stop the growth of cells in the bone marrow, including normal blood-forming cells (stem cells) and cancer cells. It may also stop the patient's immune system from rejecting the donor's stem cells. When the healthy stem cells from a donor are infused into the patient, they may help the patient's bone marrow make stem cells, red blood cells, white blood cells, and platelets. The donated stem cells may also replace the patient's immune cells and help destroy any remaining cancer cells.

This study is designed to estimate the efficacy and toxicity of familial HLA mismatched bone marrow transplants in patients with non-malignant disease who are less than 21 years of age and could benefit from the procedure.

One of the major challenges to improve the outcome of hematopoietic stem cell transplantation (HSCT) is the reduction of toxicity and non-relapse mortality caused by the pre-transplant conditioning regimen, while maintaining efficacy. Treosulfan (TREO) (L-treitol-1,4-bis-methanesulfonate) is a busulfan analogue with a distinct site of alkylation that results in a more favourable toxicity profile in comparison with busulfan and total body irradiation. TREO is the prodrug of L-epoxybutane, a water-soluble bifunctional alkylating agent with remarkable myeloablative and immunosuppressive properties. The use of TREO, in combination with other chemotherapy agents, as part of the conditioning regimen for hematopoietic stem cell transplantation (HSCT) in children has progressively increased during the last decade for both malignant and non-malignant disorders. Data on TREO pharmacokinetics in the pediatric population are still scarce. To date, only a few studies, including small numbers of pediatric patients, have investigated the PK profile of TREO. These studies reported high variability of TREO pharmacokinetics, and the relationship between TREO exposure, toxicity and clinical outcome is still unresolved. Therefore, therapeutic drug monitoring with a personalized approach may be an important tool to optimize outcomes in the pediatric population. The aim of the investigators' study is to characterize TREO PK/PD profiles in children undergoing HSCT and to evaluate the relationship between TREO exposure and early toxicity and clinical outcome.

The hypothesis for this study is that a preparative regimen that maximizes host immunosuppression without myeloablation will be well tolerated and sufficient for engraftment of donor hematopoietic cells. It is also to determine major toxicities from these conditioning regimens, within the first 100 days after transplantation.