http://science.sciencemag.org/content/352/6289/1059.full

DEVELOPMENT OF GENE THERAPY. Forty-four years have elapsed since an article appeared in Science on the possible therapeutic benefits of gene therapy (1). The early history was marked by poor trial design and a need for greater attention to basic aspects of viral gene transfer and disease biology (2). After some tragic setbacks and years of research to redesign existing vectors and identify safer ones, several trials have recently delivered promising results in regard to both safety and efficacy in several immunodeficiency disorders (3, 4), hemophilia B (5), a form of congenital blindness (6, 7), beta-thalassemia (8), and metachromatic leukodystrophy (9). We presume that gene therapy for at least one disorder currently in clinical trials will be established as safe and efficacious and that will lead to U.S. Food and Drug Administration (FDA) approval in the next 3 years.