Immunosonodynamic Therapy Designed with Activatable Sonosensitizer and Immune Stimulant Imiquimod

Sonodynamic therapy (SDT) has garnered extensive attention as a noninvasive treatment for deep tumors. Furthermore, imiquimod (R837), an FDA-approved toll-like receptor 7 agonist, is commonly used in clinical settings as an immune adjuvant. We prepared an activatable sonodynamic sensitizer platform (MR) based on glutathione-sensitive disulfide bonds linking Leu-MB, the reduced form of methylene blue (MB), and R837 to achieve emcient combinatory SDT and immunotherapy for tumors without harming normal tissues. We also used the amphiphilic polymer C18PMH-PEG to create selfassembled MB-R837-PEG (MRP) nanoparticles for immunosonodynamic therapy (iSDT). iSDT is a cancer treatment that combines activatable SDT and immunotherapy. Our iSDT demonstrated an excellent sonodynamic effect only at the tumor site, demonstrating high specificity in killing tumor cells when compared to SDT reported in the literature. The iSDT improves its tumor-killing effect by inducing an immune response, which is accomplished by secreted immune adjuvants in the tumor site. MRP was selectively activated by glutathione in the tumor microenvironment to release MB and R837, exhibiting excellent antitumor sonodynamic and immune responses. In addition, when combined with an alpha-PD-L1 antibody for immune checkpoint blockade, this therapy effectively inhibited tumor metastasis. Furthermore, mice treated with iSDT and alpha-PD-L1 antibody did not develop tumors even after tumor reinoculation, indicating that long-term immune memory was achieved. The concept of sonodynamic sensitizer preparation as a next-generation iSDT based on a noninvasive synergistic therapeutic modality applicable in the near future is presented in this study.

Automated summary

This study presents the concept of a next-generation sonodynamic sensitizer preparation for immunosonodynamic therapy (iSDT) as a noninvasive synergistic therapeutic modality. By combining sonodynamic therapy and immunotherapy, this method achieves efficient and targeted treatment for tumors. The iSDT specifically activates the sonodynamic effect at the tumor site, showing high specificity in killing tumor cells. Additionally, when combined with an alpha-PD-L1 antibody, this therapy effectively inhibits tumor metastasis.