Allogeneic hematopoietic stem-cell transplantation for sickle cell disease

Area of Science:

• Hematology
• Immunology
• Transplantation Medicine

Background:

• Myeloablative allogeneic hematopoietic stem-cell transplantation (HSCT) is curative for pediatric sickle cell disease (SCD) but poses significant toxicity risks in adults.
• Graft rejection and graft-versus-host disease (GVHD) are major challenges limiting the success of HSCT in adult SCD patients.

Purpose of the Study:

• To evaluate the safety and efficacy of a nonmyeloablative HSCT protocol in adult patients with severe sickle cell disease.
• To determine if this modified HSCT approach can overcome the toxicity and immunological barriers associated with traditional myeloablative HSCT.

Main Methods:

• Ten adult patients with severe SCD received nonmyeloablative HSCT using CD34+ peripheral-blood stem cells from HLA-matched siblings.
• The conditioning regimen included 300 cGy total-body irradiation and alemtuzumab, followed by post-transplant immunosuppression with sirolimus.

Main Results:

• All 10 patients survived at a median follow-up of 30 months.
• Nine patients achieved stable, mixed donor lymphohematopoietic engraftment, reversing the SCD phenotype with improved hemoglobin levels.
• No cases of acute or chronic GVHD were observed; adverse events included narcotic-withdrawal syndrome and sirolimus-related complications.

Conclusions:

• A nonmyeloablative HSCT protocol combining total-body irradiation, alemtuzumab, and sirolimus is effective in achieving stable mixed chimerism and reversing the SCD phenotype in adults.
• This approach represents a less toxic alternative to myeloablative HSCT for adult SCD patients, mitigating risks of GVHD and graft rejection.