A pilot study of cord blood-derived natural killer cells as maintenance therapy after autologous hematopoietic stem cell transplantation

Natural killer (NK) cell based immunotherapy is an emerging strategy in hematologic malignancies because allogeneic NK cells can provide potent antitumor immunity without inducing graft-versus-host disease. Thus, we expanded cord blood-derived NK (CB-NK) cells ex vivo from random (MHC mismatched and KIR mismatched) donors, and investigate the feasibility and efficacy of repeated infusions CB-NK cells as maintenance therapy after autologous hematopoietic stem cell transplantation (ASCT). Thirty-one patients with acute myeloid leukemia and high-risk lymphoma received ASCT and the adoptive CB-NK cell multiple infusions for maintenance therapy. Patients received a median dose of 5.98 x 107/kg (range, 1.87-17.69 x 107/kg) CB-NK cells and 23 patients completed four infusions, 8 patients received three infusions. Only mild infusion reactions occurred in 15.5% of 116 infusions. Compared to a contemporaneous cohort of 90 patients who did not receive NK cell therapy, the adoptive transfer of CB-NK cells as maintenance treatment showed a tendency of difference in decreasing the relapse rate between CB-NK group and control group (9.7% vs 24.4%). The patients who receiving NK cell infusions had a better PFS and OS than controls (4 year PFS, 84.4 +/- 8.3% vs 73.5 +/- 5.4%; and 4 year OS, 100% vs 78.1 +/- 5.4%) . These findings demonstrate safety and validity of maintenance therapy using CB-NK cells multiple infusions after ASCT, and it is worthy of further clinical trial verification.