Ex Vivo T Cell Depleted HLA-Matched PBSCT with Post-Transplant Activated Donor-Derived NK Cell Infusions for High-Risk Acute Lymphoblastic Leukemia

Relapse is the primary cause of treatment failure following allogeneic HCT. Preclinical data demonstrates that large numbers of activated NK cells can be generated ex vivo using artificial APCs (aAPC), that these activated NK cells readily kill pediatric leukemia, and that activity is independent of KIR mismatch. The post-transplant period may be favorable for expansion and survival of adoptively transferred NK cells potentially providing an additional anti-leukemia effect. We initiated a Phase I trial to assess safety and feasibility of administration of escalating doses of donor-derived activated NK cell infusions (NK-DLI) following myeloablative HLA-matched T-cell depleted PBSCT. Donors underwent apheresis for filgrastim mobilized PBSC. The product was T cell depleted and CD34/CD56 selected. The CD56+ fraction was cultured for 9–11 days with a K562 based aAPC expressing 4-1BBL and IL-15Ra plus rhIL-15 to generate the NK-DLI. T cell add back to the CD34 selected graft ranged from 1-2 x 10e4 T cells/kg. NK-DLI was administered at days 21 and 49 (+/- 3 days) post-transplant. Patients received a myeloablative preparative regimen (TBI 1200 cGy and cyclophosphamide 60 mg/kg x 2 days). Recipients of unrelated donor products received GVHD prophylaxis with tacrolimus and were dose escalated separately. The starting dose for NK-DLI was 1 x 105 NK cells/kg for unrelated donor recipients and 1 x 106 NK cells/kg for related donor recipients. Six patients with high-risk ALL underwent transplant (Table). The median time to neutrophil and platelet engraftment was 9 and 12 days respectively. Median whole blood and CD3 donor chimerism at day 28 was 91% (range, 49-100%) and 52% (range, 0-97%). Despite achieving primary engraftment, one patient had absence of donor lymphoid engraftment and underwent a second RIC T-replete HCT to treat secondary rejection. Another subject received DLI to treat mixed chimerism. Although persistence or engraftment of infused NK-DLI cannot be definitely determined, in 5 of 6 recipients, the absolute NK value post-infusion was a median of 2.8 fold higher (range 1.7-4.3) than the pre-infusion value. Two subjects had grade 1 GVHD. All subjects received the second NK infusion off any immunosuppression. With limited follow up, all patients remain disease free (2-12 months post-HCT). Infusion of ex-vivo, aAPC expanded NK-DLI is feasible and can be safely performed following myeloablative allogeneic HCT in patients with high-risk leukemia. Accrual and follow-up are ongoing.Tabled 1Pt#Age (yrs)/SexDonorDisease statusCD34 dose/kg (x106)NK dose/kgDay of NK cell infusionNK associated toxicity123/MMRDCR34.651 x 10623; 75Grade 1 GVHD224/MMUDCR35.141 x 10524; 87Grade 1 GVHD325/FMRDCR38.691 x 10623None418/MMRDCR24.881 x 10622; 54None518/MMUDCR49.451 x 10524Too early66/MMUDCR3101 x 10526Too earlyDisease status: CR=complete remission # Open table in a new tab