Developing a new drug molecule is not only time-consuming and expensive, but also mostly a failing process. However, improving bioavailability, targetability, efficacy or safety of old drugs could be more effective way to use them in clinic. For these purposes, so many strategies including individualising drug therapy, nanoparticle-based drug delivery systems, drug conjugates, therapeutic drug monitoring, stimuli-sensitive targeted therapy are investigated intensely. Depending on the desired application or targeted site, nanoparticles can be administrated as orally, locally, topically and systemically. Currently, the Food and Drug Administration and the European Medicines Agency approved nanoparticles are mostly aimed to treat cancer. Although some of these formulations were approved by Food and Drug Administration and/or European Medicines Agency to use in clinic, most of them have fell down to pass either pre-clinical or clinical trials. To have high approval rate, failure reasons need to be better understand.