Abstract 4235: A combination of CAR-NK and CAR-T cells results in rapid and persistent anti-tumor efficacy while reducing CAR-T cell mediated cytokine release and T-cell proliferation
Guangnan Li, Xiumin Wu, Ivan H. Chan, James Trager
Abstract
Abstract CAR-NK cells show rapid and potent anti-tumor cytotoxic activity even at very low effector-to-target ratios, however, they do not typically expand upon encounter with antigen and lack long term persistence commonly associated with CAR-T cells. Conversely, CAR-T cells generally exhibit persistent killing activity, even though they are activated somewhat more slowly. In addition, the explosive expansion of CAR-T cells is frequently associated with a variety of toxicities (e.g. CRS, CRES, etc.). To address these shortcomings, Nkarta has developed a novel platform to combine both CAR-NK and CAR-T cells as a novel cancer therapeutic. To evaluate the overall outcomes of combining CAR-NK and CAR-T cells as an anti-tumor therapy, we have developed two novel in vitro assays: (a) IncuCyte-based matrixed cytotoxicity assay, which allows direct assessment of tumor killing kinetically with different E:T and NK:T ratios; (b) IncuCyte-based tumor re-challenge assay, which provides a convenient and quick assessment of anti-tumor persistence. For proof-of-concept studies, a CD19 directed CAR (CAR19) was retrovirally engineered into NK and T cells. Our newly developed assays revealed that the combination of CAR-NK and CAR-T cells clearly outperformed CAR19-NK or CAR19-T cells alone in anti-tumor efficacy and persistence. Additionally, the combination also showed an improved cytokine profile. To further investigate the cellular mechanism(s) underlying the beneficial effects of combining CAR-NK and CAR-T cells, we performed FACS-based phenotyping and a Violet Cell Trace based proliferation assay. When challenged with tumor cells, the presence of CAR19-NK cells reduced the proliferation of CAR19-T cells. Surprisingly, the presence of CAR19-T cells could trigger the proliferation of CAR19-NK cells. Finally, we evaluated the NK plus T platform in vivo with a Nalm6 xenograft model. Treatment with CAR19-NK cells combined with a low dose of CAR19-T cells (5e5 cells/animal) delayed tumor progression. Combined treatment with a medium dose of CAR19-T cells (2.5e6 cells/animal) largely prevented tumor relapse, and consequently enhanced the overall survival of the animals. In summary, our in vitro and in vivo studies strongly demonstrate that the NK plus T platform can harness the advantages of both CAR-NK and CAR-T cells, allowing for both rapid and persistent killing while potentially minimizing the toxicities associated with CAR-T cells. Citation Format: Guangnan Li, Xiumin Wu, Ivan H. Chan, James B. Trager. A combination of CAR-NK and CAR-T cells results in rapid and persistent anti-tumor efficacy while reducing CAR-T cell mediated cytokine release and T-cell proliferation [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 4235.