Universal solid tumor therapy with CD5-deleted, DSG2-directed CAR-T cells.

Abstract

2539 Background: CAR-T cell therapy has been curative for many patients with refractory, progressive hematologic cancers, resulting in several FDA approvals. However, this therapy has not been successful for solid cancers, reflecting the need for suitable antigen targets for each disease and solutions to immunological barriers in solid tumors. Here, we have identified the desmosomal cadherin, desmoglein 2 (DSG2), as an effective CAR-T cell therapy target in epithelia-derived solid tumors. DSG2 contributes to cell proliferation, migration, and other emerging tumor-promoting pathways, resulting in its upregulation in nearly all solid cancers and correlating with poor prognosis. Moreover, we explored CRISPR-Cas9-mediated elimination of the inhibitory receptor CD5 to enhance in vivo CAR-T cell expansion and solid tumor efficacy. Methods: DSG2-directed CAR-T cells were generated from human T cells using a scFv derived from a murine hybridoma targeting the extracellular domain of DSG2 in a 3 rd generation CAR design with CD28, 4-1BB, and CD3ζ signaling domains. CD5 elimination employed electroporation of complexed gRNA-Cas9 ribonucleoprotein (RNP). DSG2 expression was characterized in human cancers and cell lines and CAR-T cell activity was examined in vitro by cytokine production and target cell cytolysis. In vivo efficacy studies employed cancer xenografts in NSG mice treated with CAR-T cells. Safety studies employed a human DSG2 transgenic mouse treated with syngeneic murine CAR-T cells for clinical, serum biomarkers, and histopathological evaluation. Results: In vitro studies revealed recognition and lysis of solid cancer cell lines and effector cytokine production. Administration of DSG2-directed CAR-T cells eliminated metastatic cell-derived xenografts, patient-derived xenografts, and orthotopic tumors derived from various solid cancers, including colorectal, pancreatic, lung, prostate, breast, and liver. Moreover, elimination of CD5 enhanced the expansion of DSG2-directed CAR-T cells in vivo, resulting in curative efficacy at sub-therapeutic CAR-T cell doses. Safety studies revealed no toxicity in any human DSG2 transgenic mouse tissues. Conclusions: These studies reveal the robust antitumor activity of DSG2-directed CAR-T cells in solid tumors, which is enhanced by CD5 deletion, without toxicity in a human transgenic mouse model. Thus, CD5-deleted DSG2-directed CAR-T cells are a promising therapeutic approach that may be safe and effective for all solid cancers.