Novel TROP2-targeted CAR T cells with high specificity and sustained efficacy for solid tumors in animal models.

e14563 Background: CAR T cell therapy, successful in hematological malignancies, encounters challenges against solid tumors due to immune exhaustion and senescence within the tumor microenvironment. The imperative need for an optimal tumor target antigen is evident in advancing CAR T therapy. TROP2, a membrane-associated glycoprotein, is highly expressed in diverse cancers, including cervical, bladder, esophageal, ovarian, and endometrial cancers. TROP2 overexpression, approaching 100% in cervical and hormone-resistant prostate cancer, correlates inversely with prognosis and survival, presenting TROP2 as a promising CAR T therapy target. This study engineered the novel TROP2 antibody R4702, featuring a distinct binding epitope from Sacituzumab and Datopotamab, to develop TROP2-specific CAR T cells and evaluated their efficacy against a spectrum of solid tumors. Methods: Expansion of CAR T Cells and Cytotoxicity: CAR T cells were created through lentivirus-mediated genetic engineering with the TROP2 antibody, followed by 10 days of expansion. T cell differentiation was evaluated, and luciferase-encoding target cells incubated with varying CAR T cell ratios overnight were quantified luciferase activity. In Vivo Efficacy and Persistence: CAR T cells were adoptively transferred into ASID mice with tumors. In vivo tumor imaging used luciferase activity, and calipers monitored tumor size weekly. CAR T cell persistence assessed their ability to suppress rechallenged tumor growth. Results: R4702, a novel TROP2-specific antibody, displayed high binding affinity to a distinct epitope. Post- ex vivo expansion, R4702 CAR T cells showed a substantial increase (100 to 200-fold) over 10 days, with a high expression level (50~80%) of R4702 CAR on T cells. Over 60% of R4702 CAR T cells displayed a less differentiated status, characterized by a CD62L+ population comprising TSCM and TCM. In vitro cytotoxicity revealed potent and specific efficacy against various TROP2-positive cancer cell lines, with no observed killing activity against TROP2-negative cells. In vivo efficacy of R4702 CAR T cells demonstrated 100% tumor growth inhibition within 30 days post-treatment across diverse xenograft models. Importantly, R4702 CAR T cells exhibited enduring anti-tumor efficacy against successive tumor challenges in xenograft models of pancreatic, gastric, NSCLC, TNBC, and ovarian cancers. In a head-to-head comparison with Sacituzumab and Datopotamab CAR T, R4702 demonstrated superior anti-tumor efficacy to Sacituzumab and comparable efficacy with Datopotamab in the BxPC-3 CDX model of pancreatic cancer. Conclusions: A novel TROP2-specific R4702 CAR T cell, developed, showcased robust tumor-killing capabilities. The anti-tumor activity persisted upon repeated tumor challenges across various xenograft models, underscoring the potential of R4702 CAR T cells as a promising therapeutic strategy.