Gene Therapy to Treat Hemophilia

By Nancy Steinbach

This is the VOA Special English SCIENCE REPORT.

American researchers report limited success using gene therapy to treat the genetic blood disease hemophilia.

Hemophilia results when a gene fails to produce the protein needed for the blood to clot, or change from a liquid to a solid. The defective gene is passed from parents to children. People with hemophilia suffer uncontrolled bleeding. This can result in pain, tissue swelling and permanent damage to joints and muscles.

One in every ten-thousand males has the most common kind of hemophilia. It is extremely rare for females to have it. Patients can be treated with the missing clotting substance. They generally can lead normal lives.

Scientists say gene therapy may be a possible way to cure hemophilia in the future. Most gene therapies use a virus to place a good copy of a gene into a cell that needs it. The new gene helps the body operate normally. For people with hemophilia, this means that clotting genes placed in the body would result in blood cells that clot normally.

Researchers consider hemophilia the best disease for gene therapy because it is caused by a single defective gene. Also, only a small increase in the missing clotting substance could provide good results. Scientists at the Beth Israel Deaconess Medical Center in Boston, Massachusetts carried out the experiment. They reported the results in the New England Journal of Medicine. They tested gene therapy in six patients with severe hemophilia.

First, they removed skin cells from the patients' arms. The researchers grew the cells in the laboratory. They added copies of the needed gene taken from healthy people. Then they created hundreds of millions of genetically changed cells. They placed these cells into the patients' stomachs.

After four months, the amount of blood clotting substance in the blood increased in four of the six patients. Some of the patients reported a decrease in bleeding problems. However, ten months later, the clotting substance was no longer in the patients' blood. It is not clear if the implanted cells died or the added genes stopped working.

The researchers say the study showed that gene therapy is safe for people with the most common kind of hemophilia. But others expressed concern about the treatment because the effects were only temporary.

This VOA Special English SCIENCE REPORT was written by Nancy Steinbach.