Hematopoietic Stem Cell Transplantation for Severe Aplastic Anemia Using Alemtuzumab and Cyclophosphamide as Conditioning Regimen.

Cyclophosphamide (Cy) with/without antithymocyte globulin (ATG) as conditioning regimen for allogeneic hematopoietic stem cell transplantation (AlloHSCT) is the treatment of choice for young patients with severe aplastic anemia (SAA). In developing countries, and particularly in Brazil, ATG costs limit its use in AlloHSCT for SAA patients. Alternative low-cost regiments, like busulfan (BU) with Cy as conditioning regimen is still associated with a significant rate of rejection, especially in heavily transfused patients, and long-term infertility. Alemtuzumab (Cam) was reported as an alternative to ATG for SAA patients, with similar activity and a lower cost.

In order to study the effect of the combination of Cy and Cam, we reviewed all AlloHSCT performed for SAA using this conditioning regimen. Between April 2007 and Mai 2009, fifteen patients with SAA (defined by Camitta criteria) underwent an AlloHSCT in our institution. Median age at transplantation was 25 (range 5-42) years. All but one patient had positive CMV serology. Median number of transfusions was 20 (range 10-67). One patient received a second AlloHSCT due to a late (> 4 years) graft rejection. Patients received an unmanipulated bone marrow (n=11) or peripheral blood (n=4) graft as stem cell source and all but one patient were transplanted with an HLA-identical sibling. Median number of nucleated cell infused was 2.86 (range 1.65-6.50)x10 8/kg. Cyclosporin alone (n=10) or in combination with methotrexate (n=5) was used as GVHD prophylaxis.

Thirteen out of 15 patients presented neutrophil recovery with a median time to > 0.5×10 9 neutrophil/L of 23 (range 13-30) days. Platelet recovery (> 20×10 9 platelets/L) occurred in thirteen patients with a median time of 16.5 (range 9-45) days. Acute graft versus host disease (GVHD) was observed in just one patient (grade II). None of 12 patients alive 100-days after AlloHSCT presented chronic GVHD. Seven patients presented CMV reactivation. One patient did not engrafted and other presented a late (14 months) rejection. One patient became pregnant after alloHSCT and gave birth to a healthy child. With a median follow-up of 315(range 4-782) days, two patients died and the estimate 1-year overall survival rate is 87%. One patient died due to complications of a CNS bleeding that occurred hours before marrow infusion and the other of GI infection while still on neutropenia.

Use of cyclophosphamide and alemtuzumab as conditioning regimen is a valid option in SAA patients undertaking AlloHSCT, with significant lower rates of acute and chronic GVHD. Nevertheless, a longer follow-up is required to properly evaluate rejection incidence.

Off Label Use: Drug: Alemtuzumab Off-label Use: Aplastic Anemia.