Two decades of clinical gene therapy--success is finally mounting.

Human gene therapy has made substantial progress since the initiation of the first clinical trials 20 years ago. Here, we summarized important applications of gene transfer protocols in the treatment of various human diseases using different viral vectors. Recent successful trials on the treatment of ocular diseases and inherited immune deficiencies are particularly encouraging and have raised hopes that human gene therapy as a standard treatment option will finally become a reality. While immune responses and insertional mutagenesis pose obstacles for this novel form of molecular medicine, continuous progress suggests that a wider range of diseases can be treated with gene therapy in the future.