A rational mouse model to detect on-target, off-tumor CAR T cell toxicity
Mauro Castellarin, … , Yangbing Zhao, Carl H. June
Mauro Castellarin, … , Yangbing Zhao, Carl H. June
Published July 23, 2020; First published June 16, 2020
Citation Information: JCI Insight. 2020;5(14):e136012. https://doi.org/10.1172/jci.insight.136012.
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Research Article Immunology Therapeutics

A rational mouse model to detect on-target, off-tumor CAR T cell toxicity

Abstract

Off-tumor targeting of human antigens is difficult to predict in preclinical animal studies and can lead to serious adverse effects in patients. To address this, we developed a mouse model with stable and tunable human Her2 (hHer2) expression on normal hepatic tissue and compared toxicity between affinity-tuned Her2 chimeric antigen receptor T cells (CARTs). In mice with hHer2-high livers, both the high-affinity (HA) and low-affinity (LA) CARTs caused lethal liver damage due to immunotoxicity. In mice with hHer2-low livers, LA-CARTs exhibited less liver damage and lower systemic levels of IFN-γ than HA-CARTs. We then compared affinity-tuned CARTs for their ability to control a hHer2-positive tumor xenograft in our model. Surprisingly, the LA-CARTs outperformed the HA-CARTs with superior antitumor efficacy in vivo. We hypothesized that this was due, in part, to T cell trafficking differences between LA and HA-CARTs and found that the LA-CARTs migrated out of the liver and infiltrated the tumor sooner than the HA-CARTs. These findings highlight the importance of T cell targeting in reducing toxicity of normal tissue and also in preventing off-tumor sequestration of CARTs, which reduces their therapeutic potency. Our model may be useful to evaluate various CARTs that have conditional expression of more than 1 single-chain variable fragment (scFv).

Authors

Mauro Castellarin, Caroline Sands, Tong Da, John Scholler, Kathleen Graham, Elizabeth Buza, Joseph A. Fraietta, Yangbing Zhao, Carl H. June

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Figure 6

Low-affinity CARTs spend less time off -tumor than high-affinity CARTs.

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Low-affinity CARTs spend less time off -tumor than high-affinity CARTs. ...
In vivo CART kinetics were captured using IVIS imaging for n = 6 mice per group. (A) T cells were engineered to express a luciferase gene for in vivo luminescent imaging. The dorsal views of the mice that were kept in the same order as in Figure 5B, and luminescence intensity is shown in a blue-to-red spectrum. In addition to luciferase expression, the T cells contained either no CAR expression (negative control) or they were engineered to express a high-affinity (HA) or low-affinity (LA) Her2 CAR. (B) Whole body bioluminescent imaging (BLI) of T cell luciferase. Statistical significance for HA-CAR versus LA-CAR (*) or HA-CAR vs. No CAR (+) was compared by 2-way repeated measures ANOVA with a Tukey’s multiple comparison test. (C) Spatial luciferase expression was measured along a line that starts in the upper left thorax (point A) and ends in the lower right abdomen (point B). Luminescence from the spleen, liver, and tumor appear at the beginning (~0–1.5 cm), middle (~1–3 cm), and end (~2.5–4 cm) of the line, respectively. Mean luminescence along the line was compared between groups by 2-way repeated measures ANOVA with Bonferroni’s multiple comparisons test. Statistical significance is denoted as **P < 0.01 and ++++P < 0.0001.