CTLA4Ig-primed donor lymphocyte infusions following haploidentical transplantation improve outcome with a distinct pattern of early immune reconstitution as compared to conventional donor lymphocyte infusions in advanced hematological malignancies.

CTLA4Ig has a unique property to spare or even potentiate natural killer (NK) cell-mediated cytotoxicity, whilst inhibiting T cell activation. We explored the efficacy of prophylactic DLI following CTLA4Ig (CTLA4Ig-DLI group, n = 75), compared to conventional DLI (DLI group, n = 50), in patients with advanced hematological malignancies receiving PTCy-based haploidentical transplantation. Acute and chronic GVHD in the CTLA4Ig-DLI group were 9.6% and 15.3% compared to 18.8% [p = 0.09] and 36.5% [p = 0.01] in the DLI group. Both non-relapse mortality (4% vs 14.4%) and disease progression (DP) (15.7% vs 31.1%) were lower in CTLA4Ig-DLI group (p = 0.04). GVHD and progression-free survival was significantly improved in the CTLA4Ig-DLI group (p = 0.001). The recovery of CD56dimNK cells, NKG2A-KIR + NK subsets and Tregs was significantly better in the CTLA4Ig-DLI group at all time points and memory T cells at day +90. Immune recovery in relation to DP showed distinct patterns, with T cell subsets in the DLI group and NKG2A-KIR+NK cells in CTLA4Ig-DLI group having favorable impact. CTLA4Ig-DLI was thus associated with an improved outcome, possibly on account of the distinct pattern of immune recovery shown with this novel approach.