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107 Armoring NKG2D CAR T cells with IL-18 improves in vivo anti-tumor activity
  1. Eytan Breman,
  2. Ann-Sophie Walravens,
  3. Isabelle Gennart,
  4. Amelie Velghe,
  5. Thuy Nguyen,
  6. Benjamin Violle,
  7. Fanny Huberty,
  8. Nancy Ramelot,
  9. Laure Twyffels,
  10. Emilie Gauthy,
  11. Hannes Iserentant and
  12. David Gilham
  1. Celyad Oncology, Mont-Saint-Guibert, Belgium


Background Whilst 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.

Methods A 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.

Results Armored 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).

Conclusions Armoring 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.


  1. Chmielewski M, Abken H. Cell Reports 2017;21(11): 3205–32192.

  2. Hu B, Ren J, Luo Y, Keith B, Young R, Scholler J, Zhao Y, June C. Cell Reports 2017; 20(13): 3025–30333.

  3. Dinarello C, Novick D, Kim S, Kaplamski G. Frontiers in Immunology 2013;4;289

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