CD24-dependent innate immune checkpoint targeting chimera disrupts TGF-β-driven immunosuppression to enhance anti-tumor therapy

The immunosuppressive tumor microenvironment (TME) poses formidable challenges for cancer immunotherapies. Among the complex TME landscape, the cytokine TGF-β1 is an attractive soluble target for reinvigoration of anti-tumor immunity due to its pivotal function in immune cell suppression, extracellular matrix remodeling, and epithelial-to-mesenchymal transition (EMT) promotion, while immune checkpoint receptors exemplified by PD-1 and CD24 are promising surface targets. Though adaptive immune checkpoint inhibition is well established in clinical practice, TGF-β blockade or innate immune checkpoint blockade is yet to be harnessed for tumor treatment. Here, leveraging CD24 overexpression on multiple tumor tissues and its unique recycling kinetics, we designed an innate Immune Checkpoint TArgeting Chimera (ICTAC) G01, a bifunctional CD24 antibody-TGF-β1 receptor fusion protein that disrupts TGF-β1 signaling by TGF-β1 degradation instead of simple blockade and simultaneously inhibits the "don't eat me" CD24 signaling. We demonstrated that G01 effectively suppressed TGF-β1-Smad signaling, reversed the EMT, and attenuated fibrotic collagen deposition. Additionally, it antagonized CD24 signaling to unleash robust antibody-dependent effector activity, further reprogramming the immunologically cold TME toward inflammatory phenotype. By selectively targeting malignant cells while sparing CD24-expressing B cells, G01 demonstrated a favorable safety profile. Notably, in patient-derived tumor fragments (PDTFs), G01 also inflamed the TME, underscoring its translational potential. Together, these results establish ICTAC as an effective strategy for tumor-specific receptor-mediated extracellular protein depletion, which supports its application for reversing TGF-β1; and innate immune checkpoint-mediated tumor immunosuppression by concurrent targeting of both surface and soluble tumor-promoting factors.