A practical guide to the development of microneedle systems - In clinical trials or on the market.

Microneedle systems are a rapidly growing and promising technology for delivery of drugs, such as vaccines, small molecules, or biologics and for aesthetic skin treatment in local clinics; however, they remain relatively new from a regulatory perspective. There are strong demands for established procedures, test requirements for approval, and recent trends that industries/researchers related to microneedle systems can refer to. Some microneedle systems are commercially available, many are currently undergoing clinical trials, and some are pending approval for commercialization. This review focuses on microneedle systems that are either on the market or in clinical trials, their applicability and characteristics, and the critical evaluation and test methods necessary for their development and approval.