AB‑3028, a Dual‑antigen AND‑gated, TGF‑β–resistant CAR T Therapy

AB-3028 represents a next-generation approach to solid-tumor CAR T therapy tailored to the unique challenges of metastatic castration-resistant prostate cancer. CAR T cells, transformative in hematologic malignancies, have struggled in solid tumors due to heterogeneous antigen expression, on-target off-tumor risks, suppressive cytokines like TGF-β, and chronic stimulation that drives exhaustion. AB-3028 was engineered to counter these barriers with a tri-module, non-viral DNA cassette that integrates tumor selectivity, TME resistance, and persistence.

At the core of AB-3028 is a sequential AND logic gate that requires dual-antigen recognition before full activation, a strategy designed to limit off-tumor toxicity while mitigating single-antigen escape. By enforcing a two-signal sequence, this gating tightens the therapeutic window: tumor cells co-expressing the selected antigens trigger potent activity; cells expressing only one antigen elicit minimal response. Complementing this gate is an shRNA–miR module that knocks down FAS and TGFβR2, aiming to reduce FasL-mediated apoptosis and uncouple CAR T cells from TGF-β suppression, two dominant inhibitory axes in the prostate cancer microenvironment and bone stroma. The third element, a synthetic pathway activator, is intended to strengthen T-cell functional persistence under repeated antigen encounter, supporting metabolic fitness and resistance to exhaustion.

Preclinical evaluation proceeded along three pillars: antigen biology, logic fidelity, and functional durability under TME pressure. Tumor antigen expression was first assessed by IHC in mCRPC patient samples and cell lines to establish physiologic targets and co-expression patterns. Dual-antigen specificity was then tested in vitro using target cells engineered to express either single antigens or the dual-antigen combination, and in vivo using a stringent dual-flank xenograft design where single-antigen and dual-antigen tumors grow on opposite flanks. Across these assays, AB-3028 showed strong activity against dual-antigen cells and minimal activity against single-antigen controls, providing evidence that the sequential gate operates as intended and reduces the risk of off-tumor activation.

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