Over 1600 clinical trials have been conducted using gene therapy approaches.
The Journal of Gene Medicine maintains an excellent publicly accessable database of all such studies. Despite the number of trials, progress into actual clinical products has been slow.
However, increasingly more and more clinical trials are reaching phase III and have a good chance of becoming licensed products for a range of diseases.
In humans the most successful set of trials to date have been for the severe immune deficiency disease ADA-SCID. Much of this work is being conducted by the Centre for Immunodeficiency in London.
In 2012, Glybera, an AAV based gene therapy for lipoprotein lipase deficiency (LPLD) was licensed for use in humans. In doing so it became the first licensed gene therapy product in the US or Europe.
Although not relevant to human disease, two gene therapy products have been licensed for use as veterinary medicinces. Novartis Animal Health have developed a DNA Vaccine against Infectious Salmon Anaemia and VGX Animal Health developed LifeTide, a growth hormone releasing hormone therapy aimed at improving health in farmed pigs.
Gene Therapy clinical trials by phase. Taken from the Journal of Gene Medicine Website.