Boosting blood-cell production does little good for patients whose blood cells are malformed, such as those of sickle cell anemics. The ultimate goal of gene therapy is not to compensate for genetic diseases but to erase them completely. Preliminary work published in the September 6 issue of Science offers a reason to hope that goal may be possible. A team led by Allyson Cole-Strauss and Kyonggeun Yoon of Thomas Jefferson University in Philadelphia experimented on cells containing a mutant gene that causes sickle cell anemia. To make their genetic drug, they combined DNA for the normal version of this gene with RNA for the same gene.
When they injected the drug into the diseased cells, the RNA/DNA particles homed in on the particular stretch of the genome that matched their codes and formed triple-stranded DNA that covered the mutation. The cells' normal DNA-repair machinery then apparently replaced the mutation with the normal code--thus permanently curing 10 to 20 percent of the cells. The researchers still have to demonstrate that this technique works in human cells and in human bodies.
While scientists and the public slowly allow optimism to creep back into discussions about gene therapy, investors and biotechnology companies are unabashedly bullish once more. By July, 216 clinical trials of gene therapies were planned or under way, according to the Pasteur Institutein Paris. "Biotech firms of every kind are scrambling to reposition themselves as genomics companies," says Joan E. Kureczka, an industry publicist.
Gene therapy may emerge a winner in this round, though the match will likely draw on for years to come. The longer the search and the larger the investment, however, the more expensive that treatments will be when they do arrive. The greatest challenges to the medical wonders promised by gene therapy may well turn out to be economic rather than scientific.