After years of controversy, gene therapy is poised to become a viable option for a variety of often life-threatening medical conditions, especially those resulting from a single defective gene. Last month, the European Union approved Glybera for treatment of a rare genetic disease, making it the first gene-therapy medicine approved in the Western world. The approval comes amid a flurry of research showing broader promise for the approach in a range of disorders, from a rare form of blindness to hemophilia to heart failure.
Though outright cures are still elusive, gene therapy "is beginning to emerge as a meaningful clinical" strategy, says Stephen J. Russell, director of molecular medicine at the Mayo Clinic in Rochester, Minn.
Gene therapy's tantalizing attraction is that a single treatment has the potential to cure lethal diseases by enabling normal genes to take over for defective ones. The treatment involves loading a functional gene onto a fragment of a deactivated virus that transports the gene to a cell's nucleus, where it is intended to take over.
The idea suffered major setbacks in 1999 when a U.S. teenager died in a gene-therapy trial and again soon after when several children in Europe developed leukemia after receiving gene therapy.
The episodes prompted criticism that researchers had moved too quickly. Scientists returned to the laboratory, hoping to develop better delivery vehicles and to improve both the safety and efficacy of the treatments.
Bluebird Bio, a Cambridge, Mass., gene-therapy startup, expects to launch studies next year for two rare genetic diseases: childhood adrenoleukodystrophy, or ALD, an inherited and lethal neurological disorder; and beta thallasemia, which causes the destruction of red blood cells and leads to life-threatening anemia. Its technique involves extracting a patient's own bone-marrow cells, isolating certain stem cells, and delivering the gene therapy before returning the cells to the body.
Four boys in Paris with ALD have been successfully treated, says Nick Leschly, Bluebird's president and chief executive officer, including two treated nearly six years ago. They are now in their teens and would otherwise likely have died before age 10, he says.
Other gene-therapy efforts include Novartis SA's NOVN.VX -0.43% partnership with the University of Pennsylvania on a treatment for cancer, GlaxoSmithKline's alliance with Italian scientists for a range of disorders, and Celedon Corp.'s clinical trial of a gene therapy in patients with advanced heart failure.
—Ron Winslow
A version of this article appeared December 29, 2012, on page C2 in the U.S. edition of The Wall Street Journal
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