An Enzyme-Responsive Imiquimod Prodrug for Precision Immune Activation within the Tumor Microenvironment

Area of Science:

• Oncology
• Immunology
• Drug Delivery

Background:

• Small-molecule immune modulators like imiquimod (IMQ) are alternatives to biologics for cancer immunotherapy.
• Current IMQ use is limited to topical applications due to systemic toxicity risks from widespread Toll-like receptor (TLR) expression.

Purpose of the Study:

• To develop a prodrug for selective delivery of IMQ within the tumor microenvironment.
• To overcome the limitations of systemic IMQ administration and extend its use to various solid tumors.

Main Methods:

• Designed a β-glucuronidase-responsive, albumin-binding prodrug to mask IMQ's immunogenicity.
• Administered the prodrug to immunocompetent mice to assess systemic side effects and tumor-specific drug release.
• Evaluated the prodrug's impact on immune cell polarization and antibody levels within the tumor microenvironment.

Main Results:

• The prodrug allowed systemic administration without eliciting severe inflammatory side effects.
• Tumor-specific release of IMQ was achieved via β-glucuronidase-catalyzed activation.
• Controlled delivery promoted M1 macrophage polarization, T cell activation, and increased IgG levels exclusively in malignant tissues.

Conclusions:

• Targeting tumor microenvironment specificities enables selective delivery of small-molecule immune modulators.
• This approach offers a promising strategy for developing safer and more effective cancer immunotherapies.