Development of Adamantane-Conjugated TLR7/8 Agonists for Supramolecular Delivery and Cancer Immunotherapy

Theranostics. 2019 Nov 26;9(26):8426-8436. doi: 10.7150/thno.35434. eCollection 2019.


Tumor-associated macrophages (TAMs) are often abundant in solid cancers, assuming an immunosuppressive (M2-like) phenotype which supports tumor growth and immune escape. Recent methods have focused on identification of means (e.g., drugs, nanomaterials) that polarize TAMs to a tumor suppressive (M1-like) phenotype; however, reducing the systemic side effects of these therapies and enabling their delivery to TAMs has remained a challenge. Methods: Here, we develop R848-Ad, an adamantane-modified derivative of the toll-like receptor (TLR) 7/8 agonist resiquimod (R848) through iterative drug screening against reporter cell lines. The adamantane undergoes guest-host interaction with cyclodextrin nanoparticles (CDNPs), enabling drug loading under aqueous conditions and TAM-targeted drug delivery. Therapeutic efficacy and systemic side effects were examined in a murine MC38 cancer model. Results: R848-Ad retained macrophage polarizing activity through agonization of TLR7/8, and the adamantane moiety improved drug affinity for the CDNP. In preclinical studies, nanoformulated R848-Ad resulted in a drastic reduction in measurable systemic effects (loss of body weight) relative to similarly formulated R848 alone while arresting tumor growth. Conclusions: The findings demonstrate the ability of strong nanoparticle-drug interactions to limit systemic toxicity of TLR agonists while simultaneously maintaining therapeutic efficacy.

Keywords: cyclodextrin; drug delivery; drug screening; immunotherapy; macrophage; nanoparticle.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Adamantane / chemistry
  • Animals
  • Cell Proliferation / drug effects
  • Cyclodextrins / chemistry
  • Female
  • Imidazoles / pharmacology
  • Immunotherapy / methods*
  • Macrophages / drug effects
  • Macrophages / metabolism
  • Mice
  • Mice, Inbred C57BL
  • Nanoparticles / chemistry
  • RAW 264.7 Cells
  • Toll-Like Receptor 7 / agonists*
  • Toll-Like Receptor 8 / antagonists & inhibitors*


  • Cyclodextrins
  • Imidazoles
  • TLR8 protein, mouse
  • Toll-Like Receptor 7
  • Toll-Like Receptor 8
  • Adamantane
  • resiquimod