Impact of Different In Vivo T Cell Depletion Strategies on Outcomes Following Hematopoietic Stem Cell Transplantation for Idiopathic Aplastic Anaemia: A Study on Behalf of the EBMT SAA Working Party

To determine the optimal serotherapy regimen in idiopathic aplastic anaemia stem cell transplantation, we analysed 1837 patients who underwent either in vivo T cell depletion with either ATG (n=1283) or Alemtuzumab (n=261) or no serotherapy (n=293) as part of their conditioning regimen. All patients had either undergone a matched sibling or matched unrelated donor stem cell transplant (at least 6 out of 6). Data was obtained retrospectively from the EBMT SAA database, between the periods 2000-2013. The major endpoints were graft versus host disease, overall survival and event free survival. Events were classified as graft failure, secondary malignancy, relapse and requirement for second transplant. The median follow up was 34 months in the ATG group, 30.9 months in the Alemtuzumab group and 47.9 months in the no serotherapy group. Rate of grade 2-4 acute GVHD was 19.1% without serotherapy; this was higher than that observed with both ATG (13.3%, p Figure 1. Figure 1. Disclosures Snowden: Celgene: Other: Educational support, Speakers Bureau; Janssen: Other: Educational support, Speakers Bureau; MSD: Consultancy, Other: Educational support, Speakers Bureau; Sanofi: Consultancy. Dufour:Pfizer: Consultancy. Risitano:Pfizer: Consultancy; Novartis: Research Funding; Rapharma: Consultancy, Research Funding; Alnylam: Consultancy, Research Funding; Alexion Pharmaceuticals: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding. Off Label Use: this paper includes discussion of the use of alentuzumab for GVHD prophylaxis, which is currently off-label.