Abstract 2302: An ‘off the shelf,’ GMP-grade, IL-2-independent NK cell line expressing the high-affinity Fc-receptor to augment antibody therapeutics
Authors: Boissel Laurent , Klingemann Hans , Campbell Kerry , Nichols Karen , Toneguzzo Frances , Marcus Paula , Williams Brent , Keating Armand , Soon-Shiong Patrick 
Published: July 2016

A number of approved IgG1 monoclonal antibodies (mAb) used in cancer therapy, including trastuzumab, cetuximab, and rituximab, depend on natural killer (NK) cell-mediated antibody dependent cell-mediated cytotoxicity (ADCC) to induce cancer cell death, mediated through the Fcγ receptor (FcγR). Multiple studies report that survival benefit is significantly improved in cancer patients receiving IgG1 antibody therapy who have NK cells that express the high-affinity FcγRIIIa receptor (CD16-158V). Only 12% of the normal human population, however, is homozygous for expression of this high-affinity variant CD16. We hypothesized that infusion of an NK-92 cell line modified to express CD16-158V (high-affinity NK cells [haNK]) in combination with an IgG1 mAb may result in superior antitumor effects compared with IgG1 mAb alone.

A GMP-grade plasmid-transfected variant of NK-92 expressing the high-affinity CD16 receptor was developed utilizing a novel transfection vector containing the erIL-2 gene, enabling the resulting haNK cells to grow independently of IL-2. Using limiting dilution, clones having identical surface molecule expression to the parent cell line were generated and shown to have long-term expression of CD16. The haNK cells displayed high ADCC in combination with rituximab, trastuzumab, and daratumumab against target cell lines that were not killed by the parental NK-92 cells. Of note, despite non-viral transfection, the plasmid is fully integrated into chromosome 5. The haNK cell line secretes about 200 pg/106 cells of IL-2, and like the parental NK-92 cell line, produces enough IFNγ to potentially stimulate an adaptive immune response. A GMP-grade master cell bank of haNK cells has been established; haNK cells can be cryopreserved with retention of ADCC activity.

In vivo studies demonstrated the efficacy of haNK cells. In a multiple myeloma model of CD38+ NCI-H929 cells xenografted into NOD/SCID gamma null (NSG) mice, treatment with haNK cells plus the anti-CD38 mAb daratumumab led to prolonged survival versus mice treated with haNK cells plus an isotype control (log rank p = 0.0169), demonstrating therapeutically relevant in vivo ADCC. haNK cells have also been transfected with various CARs using mRNA, thereby enabling this platform to make a bispecific effector cell product.

In summary, haNK cells are a potent and versatile platform for cellular immunotherapy, and clinical trials of these novel “off the shelf” high-affinity NK cells are scheduled for 2016.

Citation Format: Laurent Boissel, Hans Klingemann, Kerry Campbell, Karen Nichols, Frances Toneguzzo, Paula Marcus, Brent Williams, Armand Keating, Patrick Soon-Shiong. An ‘off the shelf,’ GMP-grade, IL-2-independent NK cell line expressing the high-affinity Fc-receptor to augment antibody therapeutics. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2302.