Research progress on nanoscale drug delivery system of resiquimod for tumor treatment

Resiquimod (R848) belongs to the class of weak base organic compounds that are derivatives of imidazole quinoline and is a potent agonist of Toll-like receptor (TLR) 7/8. R848 can be considered an effective immune adjuvant as it has the ability to activate different immune cells and regulate innate and adaptive immunity. A number of researches done recently have reported R848 potent anti-tumor capacity, especially when combined with other cytotoxic therapies. Nonetheless, some hurdles remain with the clinical use of R848 such as its limited ability to reach the tumor and likelihood of inflammation and autoimmune responses which might result from repeated delivery of high dosages of the drug. Nanoscale drug delivery systems may overcome some of these challenges. Various nanoformulations, including liposomes, polymeric nanoparticles, biocarriers, inclusion compound, metal-organic frameworks and inorganic nanoparticles, as well as several R848 prodrugs or derivatives-baesd nanoparticles, have been incorporated into present R848 delivery platforms. This article reviews the physicochemical properties, immune regulatory mechanisms and nano drug delivery systems of R848, in order to provide reference and support for anti-tumor research and new drug development.