Now, `Gunsights' For Gene Therapy's Magic Bullets

IN THE FIVE YEARS SINCE DOCTORS BEGAN testing gene therapy, the results have been disappointing. It's easy enough to arm cells with a therapeutic gene and inject them into patients so that the doctored cells will secrete a beneficial product--say, a certain enzyme--into the bloodstream. But it's hard to get sufficient quantities of the enzyme to the sites where it's needed. To date, there have been no cases where gene therapy has definitively saved lives.

Inder Verma, co-director of the Salk Institute's Laboratory of Genetics in La Jolla, Calif., says there may be a better delivery system. Described in the August Proceedings of the National Academy of Science, it combines a harmless mouse virus with an antibody that will bind only to receptors in liver cells. Give the virus an altered gene, expose it to liver cells in vitro, and it binds to the correct receptor and passes along the gene.

In principle, such an approach could deliver a variety of medications, including clotting factor for hemophiliacs. And by pairing the virus with different antibodies, Verma believes he can target any organ in the body. Human tests could be three to five years away.

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