Abstract LB335: Establishment of the effective dose of the STAT3 inhibitor WP1066 used in combination with STING activation for reprograming the preclinical glioma microenvironment

Abstract

Purpose: Trials of immunotherapy in diffuse glioma patients have been mostly unsuccessful. We therefore sought to determine the combined effects of the signal transducer and activator of transcription 3 (STAT3) inhibitor WP1066 and the STING agonist IACS-8803 in a preclinical model of glioma. Experimental Design: C57BL/6 mice (n=9-10/group) with orthotopically engrafted GL261 cells were treated orally with WP1066, a blood-brain-barrier penetrant inhibitor of STAT3, in combination with the STING agonist IACS-8803 administered directly into the tumor. Analysis of treatment effects included immunoblots, ubiquitination, multiplex immunohistochemistry, and NanoString immune phenotyping of glioma-infiltrating immune cells. Results: The STING agonist 8803 at 2.5µg/mouse, in combination with WP1066 dosed at 30mg/kg with a 12-hour delay, increased animal subject median survival (MS) to 58 days, in contrast to monotherapy (WP1066=25 days, 8803=29 days) or control (25 days) (p=0.002 of combo relative to all other groups). Dose escalation of WP1066 to 60 mg/kg, administered simultaneously with 8803, completely abrogated the therapeutic combinatorial effect. Five ubiquitin-binding domains were predicted on STING using the UbPred program; concentrations of 5µM or higher of WP1066 induced polyubiquitination of phosphorylated STING. Immune profiling during the therapeutic window demonstrated a multi-pathway induction of anti-tumor immunity. Conclusions: Co-administration of a reduced effective dose of WP1066 is necessary with STING agonist 8803 to effectively enhance the anti-glioma immune reactivity in the tumor microenvironment. Citation Format: Hinda Najem, Shashwat Tripathi, Moloud Sooreshjani, Lisa Hurley, Corey Dussold, Victor Arrieta, Martina Ott, Jun Wei, Michael Curran, Anantha Marisetty, Waldemar Priebe, Leondias C. Platanias, Maciej S. Lesniak, Charles D. James, Craig Horbinski, David M. Ashley, Amy B. Heimberger. Establishment of the effective dose of the STAT3 inhibitor WP1066 used in combination with STING activation for reprograming the preclinical glioma microenvironment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr LB335.