Radiation-Activated Resiquimod Prodrug Nanomaterials for Enhancing Immune Checkpoint Inhibitor Therapy
Jiali Sun, Haochen Yao, Xitong Ren, Linjie Cui, Linlin Liu, Guoqing Wang, Zhaohui Tang
Abstract
Immune checkpoint inhibitor (ICI) therapy is effectively employed in treating various malignancies. However, the response rate is constrained to 5-30%, which is attributed to differences in immune responses across different tumors. Overcoming all obstacles of multistep immune activation with monotherapy is difficult. Here, maleimide-modified resiquimod (R848) prodrug nanoparticles (MAL-NPs) are reported and combined with radiotherapy (RT) and anti-PD1 to enhance ICI therapy. MAL-NPs can promote antigen endocytosis by dendritic cells and are radio-reduced to produce R848. When combined with RT, MAL-NPs can augment the concentration of nanoparticles at tumor sites and be selectively radio-reduced within the tumor, thereby triggering a potent antitumor immune response. The systemic immune response and long-term memory efficacy induced by MAL-NPs + RT + anti-PD1 significantly inhibit the abscopal tumor growth and prevent tumor recurrence. This strategy can achieve systemic therapy through selective training of the tumor immune microenvironment, offering a new approach to overcome the obstacles of ICI therapy.