Selective Recruitment of Antibodies to Cancer Cells and Immune Cell‐mediated Killing via In Situ Click Chemistry

Many current cancer immunotherapies function by redirecting immune system components to recognize cancer biomarkers and initiate a cytotoxic attack. The lack of a universal tumor biomarker limits the therapeutic potential of these approaches. However, one feature characteristic of nearly all solid tumors is extracellular acidity. This inherent acidity provides the basis for targeted drug delivery via the pH‐low insertion peptide (pHLIP), which selectively accumulates in tumors in vivo due to a pH‐dependent membrane insertion propensity. Previously, we established that we could selectively decorate cancer cells with antigen‐pHLIP conjugates to facilitate antibody recruitment and subsequent killing by engineered effector cells via antibody‐dependent cellular cytotoxicity (ADCC). Here, we present a novel strategy for opsonizing antibodies on target cell surfaces using click chemistry. We utilize pHLIP to facilitate selective tetrazine ‐ trans‐cyclooctene ligation of human IgGs to the cancer cell surface and induce ADCC. We demonstrate that our approach activates the primary ADCC signaling pathway via CD16a (FcγRIIIa) receptors on effector cells and induces the killing of cancer cell targets by engineered NK cells. This study presents a novel method using the pH‐low insertion peptide (pHLIP) and click chemistry to selectively recruit antibodies to tumor cells, exploiting the tumor's acidic environment. This approach enhances natural killer cell activation and cancer cell killing via antibody‐dependent cellular cytotoxicity, offering an alternative to biomarker‐dependent therapies.