Background CAR T cell activity in solid tumors is limited by off-tumor toxicity, antigen heterogeneity, poor persistence, and functional suppression resulting from the tumor microenvironment (TME). To address these challenges, we have developed AB-1015, an autologous, integrated circuit T (ICT) cell product for the potential treatment of ovarian cancer. The AB-1015 DNA cassette includes two functional modules: an ’AND’ logic gate targeting ALPG/P and MSLN designed to limit off-tumor toxicity through dual tumor antigen recognition, and a dual shRNA-miR targeting FAS and PTPN2 to resist TME suppression and to improve ICT cell function. The AB-1015 DNA cassette is inserted into the T cell genome at a defined genomic site, GS94, via CRISPR integration of transgenes by electroporation (CITE).
Methods The dual-antigen specificity of AB-1015 was evaluated in vivo using a dual flank tumor xenograft model where one tumor expressed both ALPG and MSLN, and the contralateral tumor expressed MSLN alone. To model priming antigen heterogeneity that AB-1015 may encounter in the tumor, we utilized an admixed co-culture system where varying proportions of ALPG+MSLN+ target cells were spiked into cultures that were otherwise MSLN+. In addition, AB-1015 anti-tumor activity and the capability to overcome TME were also assessed in vivo using an intraperitoneal OVCAR3 ovarian xenograft model and a subcutaneous MSTO-FASL xenograft model.
Results AB-1015 demonstrated specific activity against ALPG+MSLN+ tumors but had no effect against MSLN+ tumors in the in vivo dual flank specificity model. In the in vitro heterogeneity assay, AB-1015 was able to eliminate admixed co-cultures where as few as 5% of the target cells expressed ALPG+MSLN+. In the intraperitoneal OVCAR3 ovarian xenograft model, AB-1015 showed potent anti-tumor activity as demonstrated by decrease in bioluminescent signal from the tumors treated with AB-1015. Furthermore, in the subcutaneous MSTO-FASL xenograft model, AB-1015 could resist FASL suppression via shRNA knockdown of FAS. As a result, AB-1015 is capable of completely clearing these otherwise difficult-to-treat tumors in this model.
Conclusions AB-1015 is specific for ALPG/P+MSLN+, demonstrates superior potency compared with logic gated T cells alone, and is resistant to ovarian TME suppression in preclinical studies. Based on these promising preclinical data, AB-1015 is being studied in a phase I clinical trial (NCT05617755).
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