107 Armoring NKG2D CAR T cells with IL-18 improves in vivo anti-tumor activity

Abstract

BackgroundWhilst delivering impressive clinical efficacy in certain hematological malignancies, Chimeric Antigen Receptor (CAR) T cell therapy has yet to deliver significant clinical impact across a broader array of cancer indications. Armoring CAR T through the co-expression of immune modifying cytokines is an approach that may aid anti-cancer activity but is currently at an embryonic stage of development. In this study, the potential benefit of expressing IL-18 alongside a NKG2D CAR was assessed.MethodsA series of retroviral vectors encoding the NKG2D CAR (a fusion of NKG2D with CD3z), a cell surface tag to facilitate cell selection and tracking (truncated CD19) either with or without full length IL-18 were compared. In certain vectors, a single shRNA targeting CD3z was included to generate allogeneic CAR T versions. All transgenes were delivered as a single vector expressed under the control of the retroviral promoter with individual 2A elements ensuring equimolar levels of protein expression. T cells transduced with the individual vectors were challenged in vitro and in vivo to determine the impact of IL-18 upon NKG2D CAR directed function.ResultsArmored NKG2D CAR T cells that included the IL-18 transgene showed high levels of IL-18 secretion in culture and increased levels of interferon gamma secretion upon antigen challenge as compared to non-armored NKG2D CAR T cells. Armored NKG2D CAR T cells also showed prolonged sequential target cell killing as compared to non-armored CAR T versions. Importantly, in an in vivo stress test where the dose of non-armored NKG2D T cells was reduced to a level where minimal anti-tumor activity and survival above control was seen using an established THP-1 model, armored CAR T cells showed enhanced anti-tumor activity (as determined by bioluminescence) and overall survival. Interestingly, at high doses of armored CAR T cells, toxicity was seen in some tumor bearing models. This toxicity was abrogated by systemic infusion of human IL-18 binding protein (IL-18BP).ConclusionsArmoring NKG2D CAR T cells with IL-18 resulting in increased in vitro and in vivo target-dependent anti-tumor activity. The transient toxicity observed with high doses of the armored CAR T in tumor bearing models was eliminated by IL-18BP. Together, these observations imply that armoring NKG2D CAR T cells with IL-18 is likely to drive improved anti-tumor activity of the CAR T cell in line with previous publications1 2 while the presence of systemic IL-18BP3 should negate possible toxicities arising from high level constitutive expression of the cytokine.ReferencesChmielewski M, Abken H. Cell Reports 2017;21(11): 3205–32192.Hu B, Ren J, Luo Y, Keith B, Young R, Scholler J, Zhao Y, June C. Cell Reports 2017; 20(13): 3025–30333.Dinarello C, Novick D, Kim S, Kaplamski G. Frontiers in Immunology 2013;4;289

First-in-classTransactivator-Free, Doxycycline-inducible IL-18-engineered CAR-T cells for relapsed/refractory B-cell lymphomas

“…Despite the promising therapeutic effect of TRUCKs that overexpress cytokines in hard-to-treat tumors, their continuous immunomodulatory action can also lead to serious toxicities. Sustained administration of IL-12 and IL-15 has been linked to severe toxicity events (38, 39), while the constitutive expression of IL-18 has been associated not only with specific toxicity events (30) but also with the onset of autoimmune disorders (31) and IFNγ-independent toxicities (32). Therefore, it is essential to control the expression of these cytokines in CAR-T cells to achieve an appropriate balance between efficacy and safety.…”

“…As for most cytokines, unregulated release of IL-18 can lead to potential safety issues, since a continuous delivery of IL-18 promotes constant (and non-tissue-specific) IFNγ secretion, creating a permanent environment of acute inflammation that might lead to toxicity (30), autoimmune disorders (31) as well as IFNγ-independent toxicities (32). Therefore, a controlled/regulated release of IL-18 is highly desirable.…”