Inhibition of the cGAS/STING Pathway for the Treatment of Colitis and Other Inflammatory Diseases

Abstract

The cGAS/STING pathway is of paramount importance in healthy immune function due to its role in antiviral and antitumoral immunity. However, chronic or aberrant overactivation of cGAS/STING can cause tissue damage and cell death, leading to serious autoimmune disorders and inflammatory diseases. Thus, STING pathway inhibition in the inflamed tissue may be a viable therapeutic strategy. This work explores the use of nanoparticle carries and albumin hitchhiking to block cGAS/STING signaling in order to illicit a therapeutic effect in a murine model of colitis. First, we formulated PLGA nanoparticles containing the cGAS inhibitor RU.521 and the STING inhibitor H-151, and we demonstrated the capacity of these STING-pathway inhibiting nanoparticles (SPINs) to inhibit cGAS/STING signaling in mouse and human macrophages and monocytes. Additionally, formulating these SPINs with a benzylated excipient polymer resulted in increased drug loading and extended drug release, while maintaining the inhibitory capacity. To build upon this work, we designed and tested ROS-quenching poly(propylene sulfide) SPINs, which potently inhibit STING signaling and have a protective effect in oxidative in environments. We observed a trending decrease in STING-driven inflammatory signaling in the colons of mice with DSS-induced colitis when these SPINs were administered orally or rectally every-other-day. After increasing oral administration to daily and including an empty PPS control, we again observed trending decreases in decrease in STING-driven inflammatory signaling. Finally, we explored albumin hitchhiking as an alternative drug delivery mechanism for colitis, which has never before been exploited for drug delivery in this disease context. We demonstrated that three different albumin-binders accumulate in the inflamed colon in the context of DSS-induced colitis: the albumin-binding dye Evans Blue, a Cy7-labeled albumin-binding nanobody, and a Cy5-labelled albumin-binding lipid-conjugated siRNA. Overall, the work presented here introduces promising new strategies for STING pathway inhibition, which may be relevant for the treatment of many inflammatory diseases, including colitis. Herein, we have developed modular hydrolytic and ROS-quenching platforms to deliver small molecule STING pathway inhibitors, tested them in a murine model of colitis, and importantly, we have presented albumin hitchhiking as a hitherto unexplored drug delivery strategy for colitis.