Abstract 6606: Develop dual-targeted CAR-T cells to achieve RCC cures

Abstract

Clear cell renal cell carcinoma (ccRCC) is the major type of RCC and is among the 10 most common cancers in both men and women. ccRCC is characterized by the loss of chromosome 3p, where the von-Hippel-Lindau (VHL) gene is found. Its gene product, pVHL suppresses the hypoxia inducible factor (HIF) transcription factors and the deletion of VHL leads to HIF hyperactivation, upregulating the expression of many downstream genes involved in angiogenesis, metabolism, and cell-cycle regulation. Two gene products, carbonic anhydrase IX (CAIX) and CD70 which we are pursuing as therapeutic targets are downstream genes of the HIF-1α pathway and thus commonly overexpressed in ccRCC. Despite the development of checkpoint blockade inhibitors (CBIs) for the treatment of this disease, curative therapies are rare. Chimeric Antigen Receptor (CAR)-T cells are a new type of “living drug”, in which T cells are engineered to express a single chain variable antibody fragment (scFv) linked to an intracellular signaling motif that includes CD3ζ (z) activation domain (first generation), with CD28 or 41BB (second generation), or both (third generation) costimulatory domains. CAR-T cells have proven to be a powerful, clinically translatable immunotherapy for hematologic malignancies. However, these results have not been translatable to solid tumors due to inefficient homing of CAR-T cells, the suppressive tumor microenvironment (TME), and on-target off-tumor toxicities resulting from the sharing of CAR-T target epitopes on healthy tissues. To translate CAR-T cell therapy to ccRCC, we developed dual-targeted CAR-T cells against both CAIX and CD70, in which dual CAR can target double positive (CAIX+ CD70+) and single positive (CAIX+ CD70-, CAIX- CD70+) tumor cell populations to address this heterogeneity. By IHC staining, we demonstrated that these two target antigens are overexpressed in ccRCC and represent circa 90% of the tumor cell population regardless of disease stages. Here we build on our previous findings and demonstrate that 41BB CAR and CD4/CD8 CAR-T cell mixtures exhibit the superior efficacy and persistence in our ccRCC orthotopic NSG-SGM3 mouse model compared to other CAR constructs and CD8 alone. A panel of dual-targeted CARs have been encoded in our 41BB CAR construct and assessed in vitro and in vivo by using Celigo imaging cytometry assay and humanized ccRCC orthotopic NSG-SGM3 mouse model respectively. Dual-targeted anti-CAIX/CD70 CD4/8 CAR-T cells outperformed singly-targeted CAR-T cells with elevated efficacy. In summary, anti-CAIX/CD70 CAR-T cells hold a great promise to achieve ccRCC cures. Citation Format: Yufei Wang, Marion Grimaud, Alicia Buck, Atef Fayed, Matthew Chang, Rebecca Jennings, Maura Sticco-Ivins, Miriam Ficial, Leo L. Chan, Sabina Signoretti, Quan Zhu, Wayne A. Marasco. Develop dual-targeted CAR-T cells to achieve RCC cures [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 6606.

Evolution of cell therapy for renal cell carcinoma

“…Our in vitro and in vivo preclinical studies using humanized mice bearing human RCC [ 132 ] have been encouraging from the standpoint of antitumor efficacy and minimal on-target off-tumor side effects [ 28 , 133 – 135 ]. Besides CAIX, oncofetal antigen 5T4 (with overexpression found in over 75% of RCC patient samples) [ 22 ] and the CD70 (overexpressed in about 40% of RCC patients) [ 86 , 88 , 136 ], are relevant targets to be further explored for the development of new cell immunotherapies for RCC management.…”

“…Another preclinical study evaluating allogeneic cells identified CD70 CAR-T binding epitopes that exhibited important antitumor activity against RCC cell lines and in a xenograft mouse model of RCC derived from patients [ 31 ]. Moreover, we developed dual-targeted anti-CAIX/CD70 CAR-T cells to enlarge the target cell population and mitigate tumor heterogeneity [ 87 , 88 ].…”

Affinity fine-tuning anti-CAIX CAR-T cells mitigate on-target off-tumor side effects

“…In our study comparing G9 to G250, we observed superior in vivo antitumor efficacy as well as boosted in vivo expansion, better ex vivo migration and a wider therapeutic window of G9. To further enhance tumor killing efficacy and decrease the OTOT of CAIX targeted CAR-T cells, we have designed an anti-CAIX/CD70 dual-targeted CAR-T cell therapy that is activated in the presence of either CAIX or CD70, thus killing CAIX low expressing tumor cells and preventing potential antigen escape [59].…”