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posted on 2024-06-04, 14:20 authored by Siok Ping Yeo, Lindsay Kua, Jin Wei Tan, Joanna Kristyn Lim, Fiona HS Wong, May Delos Santos, Chek Meng Poh, Angeline XH Goh, Xin Yu Koh, Xiaohua Zhou, Ravisankar Rajarethinam, Qingfeng Chen, Zhisheng Her, Ivan D. Horak, Lionel Low, Kar Wai Tan B7H3.CAR EBVSTs targets MDSCs. A, Flow cytometric histograms of IL10, TGFβ, iNOS, and B7-H3 in MDSCs generated from 2 healthy donors (left). Median fluorescence intensities (MFI) of B7-H3 expressed on MDSCs from 2 healthy donors and the NCI-H1299 cell line (right). B, Cytotoxicity of UT or B7H3.CAR EBVSTs against allogeneic MDSCs. Data compiled from coculture of effector EBVSTs generated from 2 donors and target MDSCs generated from 2 other donors. C, Proliferation of UT and B7H3.CAR EBVSTs after anti-CD3/CD28 stimulation in the presence of allogeneic MDSCs. Each datapoint represents proliferation from each E:T donor pair. Proliferation index was calculated by normalizing percentages of proliferated cells against that of the no MDSC control condition. For B and C, UT versus B7H3.CAR EBVSTs groups were compared using Student unpaired t test. *, P < 0.05; **, P < 0.01; ***, P < 0.001. Error bars denote means ± SD where applicable.
Funding
Agency for Science, Technology and Research (A*STAR)
History
ARTICLE ABSTRACT
Encouraged by the observations of significant B7-H3 protein overexpression in many human solid tumors compared to healthy tissues, we directed our focus towards targeting B7-H3 using chimeric antigen receptor (CAR) T cells. We utilized a nanobody as the B7-H3–targeting domain in our CAR construct to circumvent the stability issues associated with single-chain variable fragment–based domains. In efforts to expand patient access to CAR T-cell therapy, we engineered our nanobody-based CAR into human Epstein-Barr virus–specific T cells (EBVST), offering a readily available off-the-shelf treatment. B7H3.CAR-armored EBVSTs demonstrated potent in vitro and in vivo activities against multiple B7-H3–positive human tumor cell lines and patient-derived xenograft models. Murine T cells expressing a murine equivalent of our B7H3.CAR exhibited no life-threatening toxicities in immunocompetent mice bearing syngeneic tumors. Further in vitro evaluation revealed that while human T, B, and natural killer cells were unaffected by B7H3.CAR EBVSTs, monocytes were targeted because of upregulation of B7-H3. Such targeting of myeloid cells, which are key mediators of cytokine release syndrome (CRS), contributed to a low incidence of CRS in humanized mice after B7H3.CAR EBVST treatment. Notably, we showed that B7H3.CAR EBVSTs can target B7-H3–expressing myeloid-derived suppressor cells (MDSC), thereby mitigating MDSC-driven immune suppression. In summary, our data demonstrate that our nanobody-based B7H3.CAR EBVSTs are effective as an off-the-shelf therapy for B7-H3–positive solid tumors. These cells also offer an avenue to modulate the immunosuppressive tumor microenvironment, highlighting their promising clinical potential in targeting solid tumors.
Clinical application of EBVSTs armored with B7-H3–targeting CARs offer an attractive solution to translate off-the-shelf CAR T cells as therapy for solid tumors.
