Molecular Medicine Program and Department of Immunology, Guggenheim 18, Mayo Foundation, 200 First Street SW, Rochester, MN 55905, USA.
Reports that two young children developed leukemia after being treated for immunodeficiency with their own retrovirally modified bone-marrow cells delivered a severe blow to confidence in gene therapy as a treatment. Two reports, published since the trial was initiated, now take away some of the mystery as to why these events happened and allay fears for the safety of gene therapy across all therapeutic applications.