Comparison of Allogeneic Matched Related Haematopoietic Stem Cell Transplantation After a Reduced Intensity Conditioning Regimen With Standard of Care in Adolescents and Adults With Severe Sickle Cell Disease

Although the survival of children with sickle cell disease (SCD) has dramatically improved over the last decades in the US and Europe, mortality remains high in adults. Moreover, many children and most adults develop a chronic debilitating condition due to organ damage. Allogeneic hematopoietic stem cell transplantation (HSCT) is currently the unique curative approach; it allows the cure of more than 95% of children transplanted from a matched related donor (MRD) after a myeloablative conditioning regimen.To date, few studies have addressed the role of HSCT in SCD adults, due to the risk of graft versus host disease (GVHD) and to the toxicity expected in older patients with a higher risk of organ damage. The development of safe, non-myeloablative conditioning regimens that allow stable mixed chimerism and avoid GVHD appears as an attractive option for HSCT to cure adults with severe SCD. The investigators design a prospective multicenter trial targeting patients over 15 years with severe SCD, and compare non-myeloablative transplant (when a matched related donor (MRD) is identified) versus no HSCT (for patients lacking MRD). The main objective is to assess the benefit of HSCT on the 2-year event free survival compared to standard care. The primary endpoint is the 2-year event free survival.