Abstract 2488: PET imaging of innate immunity activation In Vivo with redox-tuned 4-[18F]fluoro-1-naphthol

Abstract

Abstract High redox potential reactive oxygen and nitrogen species (ROS/RNS), such as O2 free radicals, superoxide, and hypochlorous acid, generated by activities of the NADPH oxidase-2 (NOX2)/myeloperoxidase (MPO) axis and related enzymes, are key effector molecules of innate immunity in physiological and diseased inflammatory states. Other lower energy species (H2O2, NO) provide adjuvant signaling functions. NOX2- and MPO-derived high energy radicals are known to oxidize naphthol species, wherein the naphthol products bind to proximate proteins and activated myeloid cells. Herein, we present 4-[18F]fluoro-1-naphthol ([18F]4FN), a novel redox-tuned radiopharmaceutical that selectively detects by positron emission tomography (PET) high energy radicals produced by activated innate immunity. The products of human MPO plus H2O2, but not H2O2 alone, rapidly and completely oxidized [18F]4FN. All-trans-retinoic acid-differentiated HL-60 "neutrophil-like" human cells activated with phorbol-12-myristate-13-acetate (PMA) retained [18F]4FN 5-fold over unstimulated cells. 4-ABAH, an MPO-specific inhibitor, or DPI, a broad oxidase inhibitor, blocked cellular retention by >95%. [18F]4FN PET/CT imaging readily discriminated foci of inflammation in vivo in three distinct murine models of acute inflammation: endotoxin-induced whole-body toxic shock, PMA-induced mild contact dermatitis of the ear, and lipopolysaccharide (LPS)-induced ankle arthritis. Mechanistically, in mice in vivo, 4-ABAH reduced inflammation-induced [18F]4FN retention, and Cybb-/- (Nox2-/-) gene-deletion strongly and significantly abrogated PMA-induced [18F]4FN retention. Thus, [18F]4FN shows promise as a robust redox-tuned reporter for imaging activation states of innate immunity by PET/CT, is ready for translation. [18F]4FN PET imaging may find application in a variety of inflammatory states associated with cancer therapy, immunotherapy-related adverse events, as well as other diseases, including arthritis, hepatitis, atherosclerosis, COVID-19, as well as up-staging and monitoring multi-organ inflammation. Citation Format: Seth T. Gammon, Federica Pisaneschi, Vincenzo Paolillo, Sarah Qureshy, David Piwnica-Worms. PET imaging of innate immunity activation In Vivo with redox-tuned 4-[18F]fluoro-1-naphthol [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2488.