The research and development of innovative drug have progressed remarkably, but the long development circle and high failure rate have become the bottleneck. Drug repurposing, discovering new indications of approved drugs, is a strategy to overcome these obstacles. By exploring new indications for approved drugs, rapid progress has been made in basic research and clinical translation in recent years. Rich resources of drugs, proven security, efficient development workflow and reduced cost are core advantages of this strategy, making the strategy a crucial direction of optimizing the pipeline of drug research and development. This review systematically summarizes drug repurposing cases that have received clinical approval over the past five years, and proposes core strategies for drug repurposing, including approaches based on targets, pathways, drug similarity, post-treatment phenotypes, and clinical side effects, aiming to provide some strategic guidance for drug repurposing efforts.

The innate immune system employs diverse pattern recognition receptors (PRRs) to monitor pathogen-associated molecular patterns (PAMPs) and damage-associated molecular patterns (DAMPs), thereby initiating innate immune responses against pathogenic invasions. This review focuses on RNA, double-stranded DNA (dsDNA), and non-canonical conformational nucleic acid as structural triggers, comprehensively analyzing the immune recognition mechanisms of nucleic acid-sensing PRRs, their disease relevance, and therapeutic advancements. Key receptors highlighted include Toll-like receptors (TLRs), retinoic acid-inducible gene I (RIG-I)-like receptors (RLRs), cyclic GMP-AMP synthase (cGAS), and Z-DNA-binding protein 1 (ZBP1). We elucidate their pivotal roles in antiviral defense, antitumor immunity, and immune homeostasis maintenance, aiming to provide insights for the development of novel PRR-targeted drugs.