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Allogenic hematopoietic cell transplant (HCT) is the best curative approach patients with severe aplastic anemia (SAA). Outcome of HCT from haploidentical family donor (HFD) has improved, making it a feasible option for patients lacking HLA-identical donor. However, data on HFD-HCT for younger patients with SAA is sparse. In multicentre retrospective study, we report outcome of 79 patients undergoing HFD-HCT for SAA. All were heavily pre-transfused, median time to HCT12 months and 67% had failed previous therapies. Conditioning was based on Flu-Cy-ATG/TBI with or without thiotepa/melphalan (TT/Mel). Post-transplantation cyclophosphamide (PTCy) and CNI/Sirolimus were employed as GvHD prophylaxis with or without abatacept. Primary graft failure (PGF) was 16.43%, less in those conditioned with TT/Mel. Incidence of acute and chronic GVHD were 26.4% and 18.9%. At a median follow-up of 48 months, the overall survival (OS) and event free survival (EFS) were 61.6% and 58.1% respectively. Both OS/EFS were better in TT/Mel group and with abatacept as GVHD prophylaxis. On multivariate analysis, use of Abatacept was found to favourably impact the outcome variables including GVHD and EFS. Our study suggests that PTCy-based HFD-HCT is a reasonable option for young patients with high-risk SAA, where optimisation of conditioning and GVHD prophylaxis might improve outcomes further.

Background Adaptive or memory natural killer (NK) cells with epigenetic imprints similar to memory T cells have been shown to develop in response to cytomegalovirus (CMV) infection with upregulation of activating receptor NKG2C. These cells have been shown to possess strong anti-tumour efficacy both in-vitro as well as in-vivo. Objectives To determine if reconstitution of adaptive NK cells (CD56dimNKG2C+NKG2A−) in patients with advanced leukemia undergoing haploidentical HCT had any impact on disease progression (DP). Study Design The study cohort comprised of 60 patients with advanced acute leukemia, aged 2-65 years, receiving myeloablative PTCy based haploidentical transplantation from CMV seropositive donors, followed by CTLA4Ig-primed donor lymphocyte infusions (DLI). They were evaluated for the kinetics of reconstitution of adaptive NK cells, both phenotypic and functional, at days +30,+60, +90 and at regular intervals, to 3 years of follow-up, in relation to DP. Reconstitution of adaptive NK cells was compared with a retrospective cohort of patients in the same protocol receiving DLI without CTLA4Ig. Results Non-relapse mortality, acute and chronic GVHD were 5.1%, 10.3% and 14.5%. DP was 17.5% at a median follow-up of 28 months. Adaptive NK cells were significantly higher in patients without DP at days+30, +60 and +90 (p = 0.0001), irrespective of CMV reactivation and remained elevated until 36 months post-HCT. These cells maintained their functional competence as measured by robust interferon-gamma production with higher expressions of KIR, NKG2D and CD57, without any increase in PD1 expression. Grafts from donors with higher adaptive NK cells were associated with a lower risk of DP (p = 0.0001). In multivariate analysis, adaptive NK cell recovery at day +90 had the most favorable impact on DP (HR-0.7). Tregs reconstituted briskly along with the adaptive NK cells and were sustained as well, without compromising the GVL effect. Comparison with a retrospective cohort receiving the same protocol with DLI without CTLA4Ig, showed a superior reconstitution of adaptive NK cells in those receiving CTLA4Ig-DLI (p Conclusion Our study suggests that myeloablative transplantation from CMV seropositive haploidentical donors augmented with CTLA4Ig-primed DLI might favor early and sustained expansion of functionally competent adaptive NK cells irrespective of CMV reactivation, with a favorable outcome.