Macromolecular Diamidobenzimidazole Conjugates Activate STING

Area of Science:

• Immunology and Pharmacology
• Polymer Chemistry and Drug Delivery

Background:

• Stimulator of interferon genes (STING) pathway activation is crucial for cancer and viral infection treatments.
• Dimeric-amidobenzimidazoles (diABZI) are promising small-molecule STING agonists, often conjugated to carriers.
• Previous conjugates utilized enzyme-cleavable linkers, but stable conjugation strategies were unexplored.

Purpose of the Study:

• To evaluate the STING-activating potential of macromolecular diABZI conjugates with stable linkers.
• To develop novel polymer-drug conjugates for enhanced STING agonist delivery.
• To investigate the in vivo efficacy and cellular uptake mechanisms of these new conjugates.

Main Methods:

• Covalent ligation of diABZI to polyethylene glycol (mPEG) chains via amide bonds.
• Synthesis of large dimethylacrylamide (DMA) polymers directly from a diABZI-functionalized RAFT agent.
• In vitro STING activation assays, in vivo tumor growth inhibition studies, and flow cytometry/microscopy for cellular uptake analysis.

Main Results:

• Stable macromolecular diABZI conjugates activated STING in vitro with kinetics comparable to small molecules.
• These conjugates demonstrated significant in vivo tumor growth inhibition.
• Cellular uptake via endocytosis was observed, with colocalization to the ER suggesting effective STING delivery.

Conclusions:

• Stable macromolecular diABZI conjugates possess high immunostimulatory potency.
• These findings support the development of polymer-drug conjugates for STING agonist delivery.
• Endosomal and intracellular trafficking pathways offer alternative routes for STING activation.