CLDN18.2 is a surface membrane protein crucial for maintaining tight junctions in gastric mucosal cells and is highly expressed in gastric, esophageal, and pancreatic cancers. Thus, CLDN18.2 is suited for exploration as a clinical target for chimeric antigen receptor T-cell (CAR-T) therapy in these indications. Although CAR-T therapies show promise, a challenge faced in their development for solid tumors is the immunosuppressive tumor microenvironment, often characterized by the presence of immune and stromal cells secreting high levels of transforming growth factor beta (TGF-β). Addition of TGF-β armoring can potentially expand CAR-T activity in solid tumors. We report on the preclinical development of a CLDN18.2-targeting CAR-T showing effectiveness in CLDN18.2-positive gastric, esophageal, and pancreatic tumor models.
The lead lentivirus product contains a unique single-chain variable fragment, CD28 and CD3z costimulatory and signaling domains, and dominant negative TGF-β receptor armoring, enhancing targeting and safety and counteracting suppression. We developed a shortened cell manufacturing process to enhance the potency of the final product, AZD6422.
AZD6422 exhibited significant antitumor activity and tolerability in multiple patient-derived tumor xenograft models with various CLDN18.2 and TGF-β levels, as determined by immunohistochemistry. Efficacy of armored CAR-Ts in tumor models with elevated TGF-β was increased in vitro and in vivo. In vitro restimulation assays established greater persistence and cytolytic function of AZD6422 compared with a traditionally manufactured CAR-T.
AZD6422 was safe and efficacious in patient-derived, CLDN18.2-positive murine models of gastrointestinal cancers. Our data support further clinical development of AZD6422 for patients with these cancers.

Prostate cancer is generally considered an immunologically "cold" tumor type that is insensitive to immunotherapy. Targeting surface antigens on tumors through cellular therapy can induce a potent antitumor immune response to "heat up" the tumor microenvironment. However, many antigens expressed on prostate tumor cells are also found on normal tissues, potentially causing on-target, off-tumor toxicities and a suboptimal therapeutic index. Our studies revealed that six-transmembrane epithelial antigen of prostate-2 (STEAP2) was a prevalent prostate cancer antigen that displayed high, homogeneous cell surface expression across all stages of disease with limited distal normal tissue expression, making it ideal for therapeutic targeting. A multifaceted lead generation approach enabled development of an armored STEAP2 chimeric antigen receptor T cell (CAR-T) therapeutic candidate, AZD0754. This CAR-T product was armored with a dominant-negative TGF-β type II receptor, bolstering its activity in the TGF-β-rich immunosuppressive environment of prostate cancer. AZD0754 demonstrated potent and specific cytotoxicity against antigen-expressing cells in vitro despite TGF-β-rich conditions. Further, AZD0754 enforced robust, dose-dependent in vivo efficacy in STEAP2-expressing cancer cell line-derived and patient-derived xenograft mouse models, and exhibited encouraging preclinical safety. Together, these data underscore the therapeutic tractability of STEAP2 in prostate cancer as well as build confidence in the specificity, potency, and tolerability of this potentially first-in-class CAR-T therapy.