In 1990, for the first time, Blease and Andresco attempted gene therapy on a four-year-old girl with the deficiency of the enzyme

The first clinical gene therapy was given to a girl suffering from SCID (severe combined immunodeficiency). The disorder is caused due to the deletion of the gene for the enzyme adenosine deaminase (ADA). The deficiency of ADA results in the production of a chemical which selectively destroys the lymphocytes of the immune systems. The scientists introduced a healthy ADA gene into the body of the girl. In 1990, for the first time, Michaele Blease and W. French Andresco of National Institute of Health, Bethesda, U.S.A. attempted gene therapy.