Guest editorial: the promise of gene therapy.(Opinion)

In recent years, research on gene therapy has yielded successes that offer much hope to patients suffering from a spectrum of diseases. I expect great advances in the coming years, but researchers still face obstacles.

One sign of the field's development is the growth of related professional societies. The American Society of Gene Therapy grew 115% between 1999 and 2002, from 1,443 to 3,102 members. Gene therapy societies in other countries have shown similar growth. National Institutes of Health funding for gene therapy research grew 8% between 2002 and 2003, from $379.7 million to $409.8 million.

About 80% of gene therapy trials occur in the United States. Cancer research accounts for 63% of trials, followed by studies of monogenetic disease (12.3%). Yet we're clearly in the early stages of gene therapy research: 66% of trials are in phase I and another 21% are between phases I and II. Only about 3,500 patients have been treated so far.

Despite these small numbers, advances in several important areas have occurred in recent years.

Early research in gene therapy focused on severe combined immunodeficiency (SCID). This led to break-throughs in treating several forms of this disorder, most notably in treating X-linked SCID (X-SCID) through use of a retrovirus to deliver the corrected gene into the patient's hematopoietic stem cells.

Gene therapy has also led to progress in hemophilia treatment. Phase I trial results using an adeno-associated virus injected into muscle to provide factor IX provide hope for patients with this disease.

There has been some success in using gene therapy in the treatment of cystic fibrosis. In a phase II trial, researchers used an adeno-associated virus to deliver the cystic fibrosis transmembrane conductance regulator gene to the lung epithelium.