Abstract PR002: Design of dual-targeted fine-tuned immune restoring (DFIR) CAR-T cell therapy to treat advanced renal cell carcinoma (RCC)

Abstract Solid tumors hijack immune system through tumor-immune cycle. Here, we tackle multiple key steps to achieve a great therapeutic effect for clear cell renal cell carcinoma (ccRCC) treatment. Using direct stochastic optical reconstruction microscopy (dSTORM) and immunohistochemistry (IHC), we first quantified the expression densities of carbonic anhydrase IX (CAIX) and CD70, two tumor associated antigens (TAAs) that are highly expressed in ccRCC despite of stages. We found that targeting both CAIX and CD70 could significantly increase the target tumor population thus addressing tumor heterogeneity. The affinity/avidity fine-tuned anti-CAIX CAR G9 only kills CAIX high tumor cells but not CAIX low normal tissues, successfully mitigating on-target off-tumor (OTOT) toxicities. To combat immunosuppressive tumor microenvironment (TME), we armed CAR-T cells with immune checkpoint inhibitor (ICI) as a payload to prevent CAR-T cells from being exhausted as well as reverse the exhaustion of other tumor infiltrating leukocytes (TILs). In previous clinical trials, the combination of anti-PD-1 nivolumab and anti-cytotoxic T-lymphocyte associated protein 4 (CTLA-4) ipilimumab demonstrated greater benefits for intermediate- and poor-risk RCC patients. Through phage display and antibody engineering, we obtained a novel tetravalent bispecific antibody (BsAb) targeting PD-1 and CTLA-4, which showed superior efficacy compared to nivolumab and ipilimumab combination therapy. This dual-targeted fine-tuned immune restoring (DFIR) CAR-T showed a great level of cytotoxic activity and maintained an active antitumor immunity in a multi-challenge assay compared to CAR-T cells with irrelevant payload. In a humanized ccRCC orthotopic mouse model, we demonstrated that the CAR-T cells with BsAb payload exhibited enhanced tumor control. In summary, anti-CAIX/CD70 DFIR CAR-T cell therapy holds the promise to achieve cures of advanced RCC by addressing tumor heterogeneity, mitigating OTOT toxicity and rewiring immunosuppressive TME. Citation Format: Yufei Wang, Nithyassree Murugan, Gabriella Kastrunes, Hsien-Chi Yuan, Alicia Buck, Matthew Chang, Christian Coherd, Yasmin Nabil Laimon, Marion Grimaud, Atef Fayed, Oanh Pham, George Talbott, Wonyeong Kang, Jiwon Yang, James Keck, James Lim, David Barbie, Wenxin Xu, Jon Wee, Toni K. Choueiri, Sabina Signoretti, Gordon J. Freeman, Wayne A. Marasco. Design of dual-targeted fine-tuned immune restoring (DFIR) CAR-T cell therapy to treat advanced renal cell carcinoma (RCC) [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Innovations in Kidney Cancer Research: From Molecular Insights to Therapeutic Breakthroughs; 2026 Mar 13-16; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2026;86(5_Suppl_2):Abstract nr PR002.