CPPsite3: An updated large repository of experimentally validated cell-penetrating peptides

Over the past two decades, cell-penetrating peptides (CPPs) have emerged as key intracellular drug delivery vehicles. This review provides a systematic overview of advancements in CPP research, encompassing both experimental techniques and computational resources crucial for their discovery. Our primary focus is on CPPsite3, a meticulously curated repository that currently houses 6788 entries, representing 4285 unique CPPs. This updated version builds upon CPPsite and CPPsite2, both of which have been extensively utilized by the scientific community for designing CPPs and developing robust prediction methods. Furthermore, we explore the clinical applications of CPPs, specifically highlighting those currently undergoing clinical use. This comprehensive review aims to be a vital resource for the drug delivery research community.