Treatment of Myeloid and Lymphoid Malignancies with Highly Purified Alloreactive CD56+CD3− NK-Cells and Haploidentical Stem Cell Transplantation: Promising Results of a Phase I Study.

NK cell alloreactivity can mediate strong graft versus leukemia (GvL) effects following haploidentical hematopoietic stem cell transplantation (HSCT). In an attempt to further improve the antileukemic effectiveness of this approach, we have adoptively transferred high numbers of alloreactive donor NK cells during the early phase after transplantation.

Method: In a phase-II study, 10 patients (6 AML, 1 MDS, 1 HD, 1 CML, 1 ALL, median age 38 yrs, range 17–48 yrs) were transplanted in late phases of their disease (5 pts. as 2^nd transplantation) and received purified NK cells from their haploidentical donors at day +2 after HSCT. Conditioning consisted of 12 Gy fTBI, Thiotepa (10mg/kg), Fludarabine (5 x 30 mg/qm) and OKT3 (day −4 to +2). Two patients received a reduced conditioning with Fludarabine and OKT3 alone. NK cells were isolated from the CD34- fraction using an automated two-step procedure of CD3+ depletion and subsequent CD56+ selection.

Results: No severe technical problems occurred and a mean of 12,1 x 10E8 (16,74 x10E6/kg, range 6,12 to 27,2 x10E6/kg) CD34+ cells was selected in high purity (95,9 %) with a very low T-cell content (mean 1,83 x10E4/kg CD3+ cells, 4,5 Log depletion). A mean of 5,7 x10E8 (6,7 x 10E6/kg) CD56+CD3− NK cells was transferred (yield 70,36%, purity 70%). The mean number of contaminating CD3+ cells was 3,2 x10E4/kg (3,6 Log depletion).No severe acute toxicity attributable to NK cell infusion was observed. Hematopoietic recovery was fast with leukocytes > 1/nl between day 5 and 11. Seven patients developed early grade II GvHD of the skin which promptly resolved after CSA and steroids. One patient developed late graft rejection five months after reduced conditioning, received a 2^nd graft from a different donor, engrafted but unfortunately died due to pneumonia one month after the second transplantation. One pt with CML died due to adenovirus infection at day 140. One pt. with HD in 5^th CR died due to pneumonia at day 85. One patient showed a relapse of the AML three months after transplant. She received a DLI with NK cells form the donor but died due to disease progression one month after. Interestingly, leukemic cells from this patient proved to be resistant to donor NK cell mediated lysis. Five of 9 patients are alive and in CCR with a median follow up of 192 days, the two patients with the longest follow up are in very good condition and free of GvHD at day +1271 and +1019. Our data show for the first time that the early adoptive transfer of high numbers of HLA-mismatched NK cells is safe and feasible.