Ex Vivo–expanded Natural Killer Cells Demonstrate Robust Proliferation In Vivo in High-risk Relapsed Multiple Myeloma Patients

Abstract

Highly activated/expanded natural killer (NK) cells can be generated via stimulation with the HLA-deficient cell line K562 genetically modified to express 41BB-ligand and membrane-bound interleukin (IL)15. We tested the safety, persistence and activity of expanded NK cells generated from myeloma patients (auto-NK) or haplo-identical family donors (allo-NK) in heavily pretreated patients with high-risk relapsing myeloma. The preparative regimen comprised bortezomib only or bortezomib and immunosuppression with cyclophosphamide, dexamethasone and fludarabine. NK cells were shipped overnight either cryopreserved or fresh. In 8 patients, up to 1×108 NK cells/kg were infused on day 0 and followed by daily administrations of IL2. Significant in vivo expansion was observed only in the 5 patients receiving fresh products, peaking at or near day 7, with the highest NK cell counts in 2 subjects who received cells produced in a high concentration of IL2 (500 units/mL). Seven days after infusion, donor NK cells comprised > 90% of circulating leukocytes in fresh allo-NK cell recipients, and cytolytic activity against allogeneic myeloma targets was retained in vitro. Among the 7 evaluable patients, there were no serious adverse events that could be related to NK cell infusion. One patient had a partial response and in another the tempo of disease progression decreased; neither patient required further therapy for 6 months. In the 5 remaining patients, disease progression was not affected by NK cell infusion. In conclusion, infusion of large numbers of expanded NK cells was feasible and safe; infusing fresh cells was critical to their expansion in vivo.

Preservation of cell-based immunotherapies for clinical trials

“…The use of fresh versus cryopreserved cells is likely due to observed poor post-thaw viability and functionality of NK cells [49,50,58,59]. In one study directly comparing fresh NK cells and NK cells that had been frozen, thawed and re-cultured, it was shown that the cryopreserved cells did not show proliferation in the patients who received the cellular therapy [50]. It is noteworthy that cryopreserved NK cells were shown to have fair viability (70%) but poor cytotoxicity after thawing [60].…”

Donor Natural Killer Cells and Their Therapeutic Potential in Allogeneic Hematopoietic Stem Cell Transplantation

“…Up to now, clinical NK cell doses can be reached even up to 10 8 NK cells/kg [165]. However, there are numerous factors that may affect the effector function of expanded NK cells.…”

Dissecting the multiple myeloma-bone microenvironment reveals new therapeutic opportunities

“…Expansion, and activation of human NK cells ex vivo has been demonstrated in the presence of human leukocyte antigen (HLA) deficient cell line K562 genetically modified to express an activated T-Cell ligand (41BBL) and interleukin-15 (IL-15.) Safe auto- or allo-transplant of educated NK cells has been demonstrated in patients [106]. Similarly to T-cells, CAR-NK cells are also under investigation for the treatment of myeloma, with CS1 as a potential therapeutic target [107].…”