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Gene therapy's heady days of introducing the gene for adenosine deaminase into immune cells to treat a life-threatening congenital defect, as was done in the first gene therapy trial in 1990, have given way to an atmosphere of caution. In 1999, Jesse Gelsinger died of multiple organ failure four days after receiving adenovirus-based therapy for a rare liver disorder. In 2002, a child developed leukemia after receiving retroviral therapy for X-linked severe combined immunodeficiency (X-SCID), and another child in the same trial was similarly diagnosed the following year (with the possibility of a third recently reported). In June it was reported that a promising trial for hemophilia was halted because of apparent adverse immunological reactions to both the vector and the transgene.
The cause of Gelsinger's death, while not definitively established, may have been the high numbers of viral particles infused during the dose-escalation study. The X-SCID ...
