Where should siRNAs go: applicable organs for siRNA drugs

RNA interference mediated by small interfering RNAs (siRNAs) has been exploited for the development of therapeutics. siRNAs can be a powerful therapeutic tool because the working mechanisms of siRNAs are straightforward. siRNAs determine targets based on their sequence and specifically regulate the gene expression of the target gene. However, efficient delivery of siRNAs to the target organ has long been an issue that needs to be solved. Tremendous efforts regarding siRNA delivery have led to significant progress in siRNA drug development, and from 2018 to 2022, a total of five siRNA drugs were approved for the treatment of patients. Although all FDA-approved siRNA drugs target the hepatocytes of the liver, siRNA-based drugs targeting different organs are in clinical trials. In this review, we introduce siRNA drugs in the market and siRNA drug candidates in clinical trials that target cells in multiple organs. The liver, eye, and skin are the preferred organs targeted by siRNAs. Three or more siRNA drug candidates are in phase 2 or 3 clinical trials to suppress gene expression in these preferred organs. On the other hand, the lungs, kidneys, and brain are challenging organs with relatively few clinical trials. We discuss the characteristics of each organ related to the advantages and disadvantages of siRNA drug targeting and strategies to overcome the barriers in delivering siRNAs based on organ-specific siRNA drugs that have progressed to clinical trials. Drug development: Refining RNA-based therapeutics to target multiple organsRefining the design and delivery of RNA-based drugs could improve the chances of targeting diseases in complex organs. Gene expression is regulated by small interfering RNAs (siRNAs), which bind to messenger RNA sequences, preventing subsequent gene expression. Drugs based on siRNA show promise as safe and specialised for multiple diseases. Jinju Han and co-workers at the Korea Advanced Institute for Science and Technology in Daejeon, South Korea, reviewed the current status of siRNA drugs. Five siRNAs approved by the US Food and Drug Administration target the liver, while drugs targeting eye conditions and wound healing in the skin are in clinical trials. Targeting complex organs like the brain and lungs remains challenging, because the size of siRNAs and their delivery mechanisms must be adjusted in order to pass safely into target regions.