Secretion of bispecific protein of anti-PD-1 fused with TGF-β trap enhances antitumor efficacy of CAR-T cell therapy

Xianhui Chen; Shuai Yang; Si Li; Yun Qu; Hsuan-Yao Wang; Jiangyue Liu; Zachary S Dunn; Gunce E Cinay; Melanie A MacMullan; Fangheng Hu; Xiaoyang Zhang; Pin Wang

doi:10.1016/j.omto.2021.03.014

Secretion of bispecific protein of anti-PD-1 fused with TGF-β trap enhances antitumor efficacy of CAR-T cell therapy

Mol Ther Oncolytics. 2021 Apr 2:21:144-157. doi: 10.1016/j.omto.2021.03.014. eCollection 2021 Jun 25.

Authors

Xianhui Chen¹, Shuai Yang², Si Li¹, Yun Qu³, Hsuan-Yao Wang¹, Jiangyue Liu⁴, Zachary S Dunn³, Gunce E Cinay⁵, Melanie A MacMullan³, Fangheng Hu³, Xiaoyang Zhang³, Pin Wang^{1

3

4}

Affiliations

¹ Department of Pharmacology and Pharmaceutical Sciences, University of Southern California, Los Angeles, CA, USA.
² Department of Biochemistry and Molecular Biology, University of Southern California, Los Angeles, CA, USA.
³ Mork Family Department of Chemical Engineering and Materials Sciences, University of Southern California, Los Angeles, CA, USA.
⁴ Department of Molecular Microbiology and Immunology, University of Southern California, Los Angeles, CA 90089, USA.
⁵ Department of Biomedical Engineering, University of Southern California, Los Angeles, CA, USA.

Abstract

Despite the remarkable success of chimeric antigen receptor-modified T (CAR-T) cell therapy for blood malignancies, the clinical efficacy of this novel therapy in solid tumor treatment is largely limited by the immunosuppressive tumor microenvironment (TME). For instance, immune checkpoints (e.g., programmed cell death protein 1 [PD-1]/programmed death ligand 1 [PD-L1]) in TME play an important role in inhibiting T cell proliferation and functions. Transforming growth factor β (TGF)-β secreted by cancer cells in TME induces regulatory T cells (Tregs) and inhibits cytotoxic T cells. To overcome the inhibitory effect of immune checkpoints, we have previously engineered CAR-T cells to secrete anti-PD-1 to block the PD-1/PD-L1 pathway activity, a step demonstrating superior antitumor efficacy compared with conventional CAR-T cells. In this study, we engineered CAR-T cells that secrete bispecific trap protein co-targeting PD-1 and TGF-β, with the aim of further improving antitumor immunity. Compared with conventional CAR-T cells and anti-PD-1-secreting CAR-T cells, data from in vitro and in vivo experiments showed that CAR-T cells with trap protein secretion further attenuated inhibitory T cell signaling, enhanced T cell persistence and expansion, and improved effector function and resistance to exhaustion. In the xenograft mouse model, CAR-T cells with trap protein secretion exhibited significantly enhanced antitumor immunity and efficacy. With these observations, we demonstrate the potential of trap protein self-secreting CAR-T cells as a potent therapy for solid tumors.

Keywords: PD-1; PD-L1; amored CAR-T cells; chimeric antigen receptor; immune checkpoint; tumor growth factor beta; tumor microenvironment.