Improving Targeted Delivery and Antitumor Efficacy of TRAIL through Fusion with a B7H3-Antagonistic Affibody

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is an attractive candidate for anticancer therapeutics due to its efficient pro-apoptotic activity against tumor cells and its well-tolerated safety profile. However, the in vivo antitumor efficacy of TRAIL is often limited by its poor tumor targeting capacity. Nowadays, the B7 homologue 3 (B7–H3) immune checkpoint has emerged as a promising target for tumor immunotherapy and drug delivery. Here, we report the achievement of tumor-targeted delivery of TRAIL by genetically fusing it with a B7H3-antagonistic affibody. The affibody–TRAIL fusion protein, named ACT, was easily expressed in Escherichia coli with a high yield and could form the active trimeric state. In vitro ACT showed significantly increased cellular binding to multiple B7H3-positive tumor cells and improved cytotoxicity by 2–3 times compared to the parent TRAIL. In vivo ACT demonstrated a 2.4-fold higher tumor uptake than TRAIL in mice bearing B7H3-positive A431 tumor grafts. More importantly, ACT exhibited significantly improved antitumor efficacy against tumors in vivo. In addition, ACT treatment did not cause body weight loss or histopathological changes in the major organs of mice, indicating its good safety profile. Overall, our findings demonstrate that targeting B7H3 to enhance TRAIL delivery is a viable approach to improve its therapeutic efficacy, and ACT may be a potential agent for targeted therapy of B7H3-positive tumors.