Natural killer (NK) cells represent a new frontier in adoptive cell immunotherapies. NK cells possess an innate ability to recognise and kill cancer cells, and unlike CAR T cells, can be administered in an ‘off-the-shelf’ allogeneic setting. Supplementing NK cells with Chimeric Antigen Receptors (CAR) further enhances their therapeutic capacity, with initial trials outlining remarkable safety and efficacy1.

NK cell expansions have been complicated through inaccessibility to feeder cells for NK cell stimulation. Addressing this bottleneck, we developed bi-cistronic Sleeping Beauty-based plasmids for the  in-house generation of feeder cells. The plasmids contain multiple genes encoding membrane-bound cytokines and co-stimulatory domains, along with antibiotic resistance genes for the convenient selection of transfectants. Feeder cells are rapidly acquired, circumventing iterative transduction processes, high costs, and intellectual property agreements. The plasmids are publicly available through Addgene, allowing for global distribution and GMP-compliant derivation2.

Our feeder cells selectively expand NK cells and can recycle neglected PBMC in CAR T cell manufacturing into highly pure NK cell populations for downstream combination therapies. Stimulating 5 million non-T cell PBMC with our feeder cells can induce 70,000-fold expansions and yield over 7 billion NK cells in 14 days. The NK cells are cytotoxic and express CD16 Fc receptors for enhancement with tumour-binding IgG. Co-expanded NK cells and CAR T cells synergise in vivo and improve pre-clinical tumour clearance and survival in an immunosuppressive breast cancer model. Furthermore, we demonstrate successful transduction of NK cells with CAR, thereby allowing dual antigen-recognition by CAR NK cell and CAR T cells for treatment of blood and solid cancers.