APE1/Ref-1: multifunctional biology, selective inhibition, and the path to clinical translation

INTRODUCTION: Apurinic/apyrimidinic endonuclease 1/redox factor-1 (APE1/Ref-1) is a multifunctional stress-response regulator that coordinates genome maintenance, redox signaling, RNA biology, and cellular metabolism. Its expression and subcellular localization further determine disease states and severity. The growing appreciation of its biological complexity and clinical relevance makes APE1/Ref-1 an increasingly attractive therapeutic target for redox-stress-related diseases. AREAS COVERED: In this review, we aim to consolidate information on the structural and mechanistic basis of APE1/Ref-1 redox and repair functions, while recognizing emerging evidence in DNA/RNA-forming G-quadruplex (rG4) biology, RNA metabolism, protein homeostasis, and mitochondrial function. We discuss mechanisms regulating APE1/Ref-1 expression, activity, and trafficking, which dynamically influence function in physiological and disease contexts. We specifically emphasize therapeutic strategies including redox-specific inhibition, endonuclease-targeted approaches, and genetic perturbations that result in distinct effects across disease models. EXPERT OPINION: Evolving understanding of APE1/Ref-1 biology has accelerated therapeutic development, particularly through redox-selective targeting strategies. Small-molecule inhibitors such as APX3330 and new-generation analogs like APX2009 and APX2014 have advanced into therapeutic applications spanning cancer, inflammatory disorders, and ocular diseases. Continued investigation into the context-dependent and multifunctional roles of APE1/Ref-1, together with the progression of mechanism-informed therapeutic design, is steadily strengthening the translational potential of APE1/Ref-1-directed therapies.