The number of approved, ongoing or completed clinical gene therapy studies worldwide can be found in the Gene Therapy Clinical Trials Worldwide database of the Journal of Gene Medicine. 

By 2021, almost 3200 clinical studies had been conducted. Approximately 67% of the studies conducted focused on the treatment of cancer, approximately 12% were targeted at monogenetic diseases and 6% each at infectious diseases and cardiovascular diseases. Other diseases that are the subject of clinical studies include neurological diseases, eye diseases and inflammatory diseases. More than half of the registered clinical trials are phase I studies. Most of the clinical studies so far have been conducted in the USA. With 110 studies, Germany is in fourth place.