In–Situ‐Sprayed Dual‐Functional Immunotherapeutic Gel for Colorectal Cancer Postsurgical Treatment

Surgery remains the most preferred treatment options for colorectal cancer (CRC). Paradoxically, local recurrence and distant metastasis are usually accelerated postsurgery as a consequence of local and systemic immunosuppression caused by surgery. Therefore, modulating tumor postoperative immune microenvironment and activating systemic antitumor immunity are necessary supplementaries for CRC therapy. Here, an in‐situ‐sprayed immunotherapeutic gel loaded with anti‐OX40 antibody (iSGels@aOX40) is reported for CRC postsurgical treatment. The iSGel is formed instantly after spraying with strong adhesion ability via crosslinking between tannic acid (TA) and poly(l‐glutamic acid)‐g‐methoxy poly(ethylene glycol)/phenyl boronic acid (PLG‐g‐mPEG/PBA). TA not only serves as one component of the iSGel but also relieves the postsurgical immunosuppressive microenvironment by inhibiting the activity of cyclo‐oxygenase‐2 (COX‐2). The aOX40 serves as an immune agonistic antibody and is released from the iSGel in a constant manner lasting for over 20 days. In a subcutaneous murine CRC model, the iSGels@aOX40 results in complete inhibition on tumor recurrence. In addition, the cured mice show resistance to tumor re‐challenge, suggesting that immune memory effects are established after the iSGels@aOX40 treatment. In an orthotopic CRC peritoneal metastatic model, the iSGels@aOX40 also remarkably inhibits the growth of the abdominal metastatic tumors, suggesting great potential for clinical CRC therapy. An in‐situ‐sprayed immunotherapeutic gel loaded with anti‐OX40 antibody (iSGels@aOX40) is designed for colorectal cancer (CRC) postsurgical treatment. After spraying at the tumor resection bed, the iSGels@aOX40 gradually releases tannic acid (TA) and aOX40, both inhibiting postoperative inflammation and immunosuppression at the tumor resection bed, and stimulating constant T‐cell activation for tumor eradication.