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.