Cd8-Depleted Donor Lymphocyte Infusions Can Boost Immune Reconstitution After Haploidentical Stem Cell Transplantation Following Reduced-Intensity Conditioning Regimen.

Haploidentical stem cell transplantation (SCT) can be used in relapsed haematological malignancies for patients lacking a matched sibling or unrelated donor. Major barriers of this strategy are the poor immune reconstitution and the high risk of relapse. Here, we report results of a phase I–II trial evaluating early add-backs of CD8-depleted donor lymphocytes (DLIs) (from 1x10^4 up to 1x10^5 cells/kg starting at day+45 up to day +105 at monthly intervals) after a reduced intensity conditioning (RIC) regimen [thiotepa (10 mg/kg), fludarabine (120 mg/sqm), cyclophosphamide (60 mg/kg) and TBI (2 Gy)]. Ex-vivo and in-vivo TCD were carried out by CD34+ cell selection using the CliniMACS device and alemtuzumab (15mg/m2, day-2), respectively. Twenty-one patients [n= 10 NHL (n=5 CLL, n=5 high-grade NHL), n=7 HL, n=1 MM, n=1 ALL, n=2 AML] were transplanted with advanced disease: 16 (76%) failed a previous autograft and 13 (62%) had refractory disease. A median of 10.4x10^6/Kg CD34+, 1x10^4/kg CD3+, 10x10^4/kg CD19+, 0.9 x10^4/kg NK+ were infused. All patients engrafted with full donor chimerism from day +90. At a median follow-up of 12 months (range, 4–41 months), 12 of 21 pts are alive (7 CR, 2 PR and 3 PD) and 9 died [n=3 infection with GVHD (+610, +187, +253), n=6 disease]. The estimated 2-year overall survival was 49%: pts transplanted in remission had better outcome (83% versus 31%, p=0.13). The estimated 2-year cumulative incidence of TRM and relapse were 27% and 58%, respectively. CMV reactivation and hospital readmissions for opportunistic infections occurred in 76% and 57% of patients, respectively. For CD8 depletion of donor leukaphereses, a new depletion protocol using clinical grade CD8 microbeads (Miltenyi) was applied. This procedure is efficient to reduce the content of CD8 T cells by 3 logs while the median cell recovery of CD3+, CD4+, CD56+/CD3+, CD 20+ was 60%, 86%, 54%, 72%, respectively. Before DLIs, only 2 of 21 patients (10%) developed acute GVHD (no grade III–IV). A total of 36 CD8-depleted DLIs were administered to 17 pts without any acute toxicity. Following DLIs, 6 pts (35%) developed acute GVHD (grade II) and 5 (30%) chronic GVHD (n=2 limited, n=3 extensive). Overall, the incidence of acute GVHD is higher (50% vs 22%, p=0.33) in pts receving larger numbers of donor cells (10–15x10^4/kg versus 3–5x10^4/kg CD8-depleted DLIs). The median values of CD4+/uL, CD8+/uL and NK+ were 100, 280 and 680 at 4 months and 220, 200, 500 at 6 months after SCT in patients receiving CD8-depleted DLIs. Measurable TREC/ucg DNA (mean value 316; mean value donors 3740) and polyclonal T cell repertoire, evaluated by spectratyping, were observed at 9 months in patients younger than 40 years and/or without GVHD. Our results suggest that: