On May 22, 1989, Dr. Steven A. Rosenberg and his team at the National Cancer Institute (NCI) performed the first human gene therapy trial when they used a retrovirus to introduce the gene coding for resistance to neomycin into human tumor-infiltrating lymphocytes before infusing them into five patients with advanced melanoma.

The results of this proof-of-concept experiment with marked TIL cells, first performed on a 52-year-old truck driver from Indiana, demonstrated that the engineered virus can be used safely in humans and also elucidated the prolonged survival of the transferred cells in the patient.

This study demonstrated the feasibility of using retroviral gene transduction in humans and set the stage for further studies. Since then, over 900 clinical trials have been completed, are ongoing or have been approved worldwide. These trials have been designed to establish feasibility and safety, to demonstrate the reality of expression of therapeutic protein(s) in vivo by the genes transferred and, in some cases, to show therapeutic benefit.