Improving\nTargeted Delivery and Antitumor Efficacy\nof TRAIL through Fusion with a B7H3-Antagonistic Affibody

Tumor necrosis factor-related apoptosis-inducing ligand\n(TRAIL)\nis an attractive candidate for anticancer therapeutics due to its\nefficient pro-apoptotic activity against tumor cells and its well-tolerated\nsafety profile. However, the in vivo antitumor efficacy of TRAIL is\noften limited by its poor tumor targeting capacity. Nowadays, the\nB7 homologue 3 (B7–H3) immune checkpoint has emerged as a promising\ntarget for tumor immunotherapy and drug delivery. Here, we report\nthe achievement of tumor-targeted delivery of TRAIL by genetically\nfusing it with a B7H3-antagonistic affibody. The affibody–TRAIL\nfusion protein, named ACT, was easily expressed in Escherichia coli with a high yield and could form\nthe active trimeric state. In vitro ACT showed significantly increased\ncellular binding to multiple B7H3-positive tumor cells and improved\ncytotoxicity by 2–3 times compared to the parent TRAIL. In\nvivo ACT demonstrated a 2.4-fold higher tumor uptake than TRAIL in\nmice bearing B7H3-positive A431 tumor grafts. More importantly, ACT\nexhibited significantly improved antitumor efficacy against tumors\nin vivo. In addition, ACT treatment did not cause body weight loss\nor histopathological changes in the major organs of mice, indicating\nits good safety profile. Overall, our findings demonstrate that targeting\nB7H3 to enhance TRAIL delivery is a viable approach to improve its\ntherapeutic efficacy, and ACT may be a potential agent for targeted\ntherapy of B7H3-positive tumors.