Immune-restoring CAR-T cells display antitumor activity and reverse immunosuppressive TME in a humanized ccRCC mouse model

One of the major barriers that have restricted successful use of chimeric antigen receptor (CAR) T cells in the treatment of solid tumors is an unfavorable tumor microenvironment (TME). We engineered CAR-T cells targeting carbonic anhydrase IX (CAIX) to secrete anti-PD-L1 monoclonal antibody (mAb), termed immune-restoring (IR) CAR G36-PDL1. We tested CAR-T cells in a humanized clear cell renal cell carcinoma (ccRCC) orthotopic mouse model with reconstituted human leukocyte antigen (HLA) partially matched human leukocytes derived from fetal CD34+ hematopoietic stem cells (HSCs) and bearing human ccRCC skrc-59 cells under the kidney capsule. G36-PDL1 CAR-T cells, haploidentical to the tumor cells, had a potent antitumor effect compared to those without immune-restoring effect. Analysis of the TME revealed that G36-PDL1 CAR-T cells restored active antitumor immunity by promoting tumor-killing cytotoxicity, reducing immunosuppressive cell components such as M2 macrophages and exhausted CD8+ T cells, and enhancing T follicular helper (Tfh)-B cell crosstalk.

Abstract 886: Fine-tuned CAIX targeted CAR-T cells exhibit superior efficacy and mitigate on-target off-tumor side effects

Chimeric Antigen Receptor (CAR) T cell therapy is a new type of “living drug” that has proven to be a powerful immunotherapy for hematologic malignancies. To date, there are six CAR-T products approved by the FDA for hematologic malignancies, four targeting CD19, and two targeting B-cell maturation antigen (BCMA). However, this success has not yet been transferred to solid tumors. A major hurdle is the on-target off-tumor toxicities due to the shared expression of target antigen on normal tissues. Carbonic anhydrase IX (CAIX) is highly expressed in clear cell renal cell carcinoma (ccRCC); however, it is also expressed on bile duct at a lower physiological level leading to off-tumor toxicity of CAIX targeted therapies. The first anti-CAIX CAR-T studies, using the 1st generation G250 CAR-T cells plus IL-2 to treat patients with metastatic ccRCC, caused severe liver enzyme abnormalities in the treated patients after CAR-T cell infusions. To understand CAIX expression on tumor and normal tissues, we quantified CAIX expression on ccRCC patient samples and healthy bile duct tissues using direct stochastic optical reconstruction microscopy (dSTORM) which provides single-molecule resolution. Tet-On inducible CAIX expressing cell lines were established to mimic various CAIX densities on normal tissue and tumor samples. Using biolayer interferometry (BLI) and avidity analyzer, we identified a low-affinity, high-avidity anti-CAIX CAR G9. G9 CAR-T cells only kill CAIX high ccRCC tumor cells but not CAIX low normal cholangiocytes, and exhibited a CAIX density dependent response to Tet-On inducible CAIX expressing cell lines. Compared to high-affinity G250 CAR-T cells, G9 showed a better safety profile and a wider therapeutic window. G9 demonstrated a superior ex vivo efficacy on ccRCC patient derived organotypic tumor spheroids (PDOTS) 3D cultures which recapitulate ccRCC patient tumor microenvironment (TME), as well as low toxicity on cholangiocyte derived organotypic spheroids (CDOS). In summary, affinity/avidity fine-tuned CAIX targeted CAR-T cell therapy holds promise to achieve cures of ccRCC by efficaciously killing tumor cells and mitigating on-target off-tumor toxicity on normal tissues.

Citation Format: Yufei Wang, Alicia Buck, Gabriella Kastrunes, Rabia Abbas, Michael Lynch, Zhou Zhong, Song-My Hoang, Andras Miklosi, Kun Huang, Jae-Won Cho, Marion Grimaud, Cecile Razimbaud, Matthew Chang, Atef Fayed, Audrey Apollon, Nithyassree Murugan, Ze-Hua Li, Tran Thai, Luann Zerefa, Brandon Piel, Elena Ivanova, Amy Cameron, Quang-De Nguyen, Zhu Zhu, Kevin Wei, Yasmin Nabil Laimon, Aseman Bagheri Sheshdeh, Sabina Signoretti, David A. Braun, Catherine J. Wu, Toni K. Choueiri, Jon Wee, Cloud P. Paweletz, Martin Hemberg, Aedin C. Culhane, David A. Barbie, Gordon J. Freeman, Wayne A. Marasco. Fine-tuned CAIX targeted CAR-T cells exhibit superior efficacy and mitigate on-target off-tumor side effects [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 886.

Abstract 2814: Anti-CAIX Immune Restoring (IR) CAR-T cells display superior antitumor activity and reverse immunosuppressive TME in a humanized ccRCC orthotopic mouse model

Chimeric Antigen Receptor (CAR) T cell therapy is a new type of “living drug” that has proven to be a powerful, clinically translatable immunotherapy for hematologic malignancies. To date, there are five CAR-T products approved by FDA, four CD19 targeted CAR-T cells, and one targeting B-cell maturation antigen (BCMA). However, this success has not yet been transferred to solid tumors. A major challenge is the immunosuppressive tumor microenvironment (TME). Development of immunotherapies has traditionally been hampered by discrepancies observed between in vitro and in vivo studies and actual clinical trial outcomes. The lack of clinically relevant mouse models for human immunotherapy testing is often seen as the primary cause. Existing clear cell renal cell carcinoma (ccRCC) in vivo models poorly recapitulate the tumor microenvironment (TME). Here we report a ccRCC orthotopic humanized NSG-SGM3 mouse model (ccRCC-hNSG-SGM3) with reconstituted human lymphocytes and bearing human ccRCC skrc-59 cells under the kidney capsule. Human leukocyte antigen (HLA) matched CD34+ human stem cells were used for the humanization to reduce T cell alloreactivity against skrc-59 human ccRCC cells. Tumors were harvested, sorted for CD45+ tumor infiltrating leukocytes (TILs) and single cell RNA sequencing (scRNAseq) was performed to profile the TME in ccRCC-hNSG-SGM3. By comparing to patient data from prospective clinical trials of the anti-PD-1 monoclonal antibody (mAb) nivolumab in advanced ccRCC, the results demonstrated that CD45+ TILs from ccRCC-hNSG-SGM3 reconstitute most CD45+ cell types, including dendritic cells, exhausted CD8 T cells, and regulatory T cells (Tregs), that are observed in advanced ccRCC patient TME. Furthermore, we generated HLA matched Immune Restoring (IR) CAR-T cells which can secrete anti-PD-L1 monoclonal antibody (mAb) locally to restore active antitumor immunity, and we assessed the efficacy and safety of IR CAR-T cells in this model. Anti-CAIX CAR-T cells armored with anti-PD-L1 mAb showed superior efficacy in tumor regression and significantly decreased TIL exhaustion compared to irrelevant CAR or irrelevant payload in this model. In addition, in situ hybridization (ISH) results showed CAR-T cells infiltration in tumor but no CAR-T cells were observed in normal tissues. In summary, the ccRCC-hNSG-SGM3 system is able to model the advanced ccRCC TME and provides a powerful tool for ccRCC TME study and immunotherapy assessment. IR CAR-T cells exhibited superior tumor regression and reversed immunosuppressive TME in humanized mice.

Citation Format: Yufei Wang, Alicia Buck, Marion Grimaud, Aedin Culhane, David Braun, Sreekumar Kodangattil, Cecile Razimbaud, Matthew Chang, Atef Fayed, Audrey Apollon, Gabriella Kastrunes, Luann Zerefa, Brandon Piel, Elena Ivanova, Dennis Bonal, Kristen Jones, Quang-De Nguyen, Zhu Zhu, Kevin Wei, Nicholas Hayden, Madison O'Donnell, Ying Huang, Rebecca Jenning, Miriam Ficial, Maura Aliezah Sticco-Ivins, Sabina Signoretti, Catherine Wu, Toni Choueiri, Jon Wee, Cloud Paweletz, David A. Barbie, Gordon Freeman, Wayne A. Marasco. Anti-CAIX Immune Restoring (IR) CAR-T cells display superior antitumor activity and reverse immunosuppressive TME in a humanized ccRCC orthotopic mouse model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2814.

Anti-CAIX BBζ CAR4/8 T cells exhibit superior efficacy in a ccRCC mouse model

Improving CAR-T cell therapy for solid tumors requires a better understanding of CAR design and cellular composition. Here, we compared second-generation (BBζ and 28ζ) with third-generation (28BBζ) carbonic anhydrase IX (CAIX)-targeted CAR constructs and investigated the antitumor effect of CAR-T cells with different CD4/CD8 proportions in vitro and in vivo. The results demonstrated that BBζ exhibited superior efficacy compared with 28ζ and 28BBζ CAR-T cells in a clear-cell renal cell carcinoma (ccRCC) skrc-59 cell bearing NSG-SGM3 mouse model. The mice treated with a single dose of BBζ CD4/CD8 mixture (CAR4/8) showed complete tumor remission and remained tumor-free 72 days after CAR-T cells infusion. In the other CAR-T and control groups, tumor-infiltrating T cells were recovered and profiled. We found that BBζ CAR8 cells upregulated expression of major histocompatibility complex (MHC) class II and cytotoxicity-associated genes, while downregulating inhibitory immune checkpoint receptor genes and diminishing differentiation of regulatory T cells (Treg cells), leading to excellent therapeutic efficacy in vivo. Increased memory phenotype, elevated tumor infiltration, and decreased exhaustion genes were observed in the CD4/8 untransduced T (UNT) cells compared with CD8 alone, indicating that CD4/8 would be the favored cellular composition for CAR-T cell therapy with long-term persistence. In summary, these findings support that BBζ CAR4/8 cells are a highly potent, clinically translatable cell therapy for ccRCC.

Abstract 62: Development of dual-targeted fine-tuned immune restoring (DFIR) CAR T cell therapy for clear cell renal cell carcinoma (ccRCC)

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. Treatment of RCC has improved dramatically over the last decade, however, a curative treatment for advanced RCC remains rare. Chimeric Antigen Receptor (CAR) T cell therapy is a new type of “living drug”. The FDA approval of CAR-T cell therapies have ushered this new type of cellular immunotherapy into mainstream cancer therapy for hematologic malignancies. To date, these results have not been translatable to solid tumors due to inefficient homing of CAR-T cells, the immunosuppressive tumor microenvironment (TME), and on-target off-tumor toxicities due to shared antigens on normal tissues. Carbonic anhydrase IX (CAIX) is a therapeutic target against ccRCC that is under the control of HIF1α and becomes overexpressed on the surface of ccRCC cells because of VHL inactivation. The first anti-CAIX CAR-T study using the 1st generation G250-CD3 CAR-T cells plus IL-2 to treat patients with metastatic ccRCC was terminated due to hepatitis that developed after CAR-T cell infusions. The on-target off-tumor side effects were attributed to low expression of CAIX on healthy bile duct cells. To translate CAR-T cell therapy to ccRCC, we designed dual-targeted fine-tuned immune restoring (DFIR) CAR-T cells. The DFIR-CAR T cells secreted immune checkpoint inhibitor (ICI) monoclonal antibodies at the tumor site and exhibited superior efficacy and safety profiling. Increased efficacy is achieved through anti-CD70/CAIX dual-targeting CAR which allows the CAR-T cell activation in response to either antigen to mitigate solid tumor heterogeneity. Elevated safety is addressed through fine-tuned CARs which have the affinities of the scFv targeting moieties tailored so that they are activated only by high density tumor associated antigens (TAAs) but not the same antigens expressed at physiologic levels on normal tissues. The ICI payloads act globally on the TME, not only to prevent CAR-T cell exhaustion but also to restore anti-tumor activity of the educated tumor infiltrated lymphocytes (TILs) that have accumulated in the TME. In summary, our DFIR CAR-T cell therapy holds the promise to achieve cures of ccRCC by killing heterogenous ccRCC cells, mitigating against on-target off-tumor toxicity, reversing TME immunosuppression and restoring host anti-tumor immunity. We believe that DFIR-CAR T cells are ready to be translated to the clinic upon completion of pre-IND studies.

Citation Format: Yufei Wang, Alicia Buck, Marion Grimaud, Sreekumar Kodangattil, Cecile Razimbaud, Atef Fayed, Matthew Chang, Aedin Culhane, David A. Braun, Toni K. Choueiri, Catherine J. Wu, Kevin S. Wei, Leo L. Chan, Brandon P. Piel, Elena V. Ivanova, Cloud P. Paweletz, David A. Barbie, Rebecca Jennings, Miriam Ficial, Maura Aliezah Sticco-Ivins, Sabina Signoretti, Gordon J. Freeman, Quan K. Zhu, Wayne A. Marasco. Development of dual-targeted fine-tuned immune restoring (DFIR) CAR T cell therapy for clear cell renal cell carcinoma (ccRCC) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 62.