Abstract

Abstract 3036

Poster Board II-1012

The potential role of allogeneic natural killer (NK) cells for therapy of refractory lymphoma is supported by the curative potential of allogeneic transplantation for lymphoid malignancies. Haploidentical donor derived NK cells may overcome Class I MHC Ag mediated inhibition and deliver an NK versus lymphoma effect. In a Phase II study we evaluated allogeneic NK cell infusions with Rituximab and IL-2 in a non-transplant setting to determine the expansion of NK cells in vivo and the clinical response in patients with refractory B-cell non-Hodgkin lymphoma (NHL). Six patients with advanced NHL received conditioning with Rituximab 375mg/m2 days -8,-1,+6,+15; Cyclophosphamide 60 mg/kg IV day -5; Fludarabine 25 mg/m2 IV days -6 through -2 as immunosupression to permit homeostatic expansion of allogeneic donor NK cells. Peripheral blood cells were obtained by lymphapheresis from unmobilized, HLA-haploidentical donors and selected for “killer immunoglobulin receptor” (KIR) ligand mismatch when available (3 out of 6 patients). Donor peripheral blood cells were enriched for NK cells with the Miltenyi CliniMACS device by depletion of T (CD3+) cells. The donor NK cells were then activated by overnight incubation with IL-2 (1,000 U/mL) and infused at a median nucleated cell dose of 2.27 ±0.4 × 107/kg. Subcutaneous IL-2 10×106 units (qod x 6 doses) was given to facilitate NK cell survival and expansion. All patients were evaluable for toxicity and efficacy. Patients tolerated the NK infusion well with only transient grade 1-2 toxicity and 5 received all 6 scheduled doses of IL-2. IL-2 activated donor NK cell products showed > 55% cytotoxicity against K562 targets. After IL-2 therapy, we observed a median absolute lymphocyte count of 980 ±440/μL. All cells were of recipient origin with no detectable donor NK cells. Importantly, in all patients the median number of host regulatory T cells (T regs phenotype CD4+Foxp3+CD127) post treatment was significantly increased compared to pre-treatment (day 14 T regs: 134 ±141 cells/μL versus pre-treatment T regs: 24 ±12 cells/μL; P=0.06). To investigate the possibility of NK trafficking to affected lymph nodes, we performed fine needle aspiration of palpable tumor in 1 patient and demonstrated a low level of donor DNA by RFLP testing (2.5% donor chimerism). Simultaneous absence of NK cells in peripheral blood in the same patient suggested NK cell tissue homing to lymphoma-bearing nodes. Three patients achieved a partial remission (PR), one of whom proceeded to non-myeloablative cord blood allograft 2 month after NK cell infusion; two remain in partial remission after 1 and 4 months of follow-up. The trial failed to achieve prospective statistical parameters established to detect circulating NK cell expansion rate and will be modified.

Conclusions

This “proof of principle” study demonstrated lack of in vivo expansion of haploidentical NK cells in peripheral blood of patients with lymphoma. However, we identified host factors that interfered with NK cell expansion, including T reg proliferation and possibly inadequate immunosupression, and additionally, the finding of donor DNA in sites of tumor suggested donor NK cell localization to extravascular or tumor sites. Novel approaches to adoptive NK cell therapy trials should incorporate strategies to eliminate or prevent T reg expansion using alternate lymphodepleting regimens.

Disclosures

No relevant conflicts of interest to declare.

Author notes

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Asterisk with author names denotes non-ASH members.