Chiron’s Hemophilia Gene Therapy in Trials

Hemophilia is a hereditary bleeding disorder that plagued the descendants of Britain’s Queen Victoria. One major form of the disease is caused by a defect in a gene that normally produces a factor vital to forming blood clots. In the most severe cases, any small cut or bruise can cause excessive bleeding. The condition is treated now by using injections to supply the missing blood factor, but the repeated bleeding takes its toll on patients, especially when it flows into joints. More than 15,000 Americans suffer from this painful and crippling disease.

Fortunately, the gene responsible for hemophilia A has been isolated, and it is an obvious target for gene therapy. The theory is simple: If you can somehow get working copies of a healthy gene into patients, the new genes should begin producing the missing clotting factor--eliminating the bleeding episodes and the continual need for injections to stop them.

However, gene therapy has proved difficult to accomplish in a variety of hereditary disorders, with only a few partial successes to date.

Chiron, an Emeryville, Calif., biotechnology company, has taken the plunge with a new gene therapy for hemophilia A. The company attaches the healthy gene to a disabled mouse virus, which can carry the gene into a patient’s cells but cannot itself cause disease.

In studies of hemophilic animals, the virus successfully carried healthy genes into cells, which were able to crank out the clotting factor for a year or longer, according to Dr. Deborah Hulft, Chiron’s director of clinical development.

Last week, at the University of Pittsburgh, a 50-year-old man became the first patient to receive the new therapy. The first trial could include as many as 20 patients with severe hemophilia at six medical centers, including UC Davis. In the first phase, Chiron and its university collaborators will determine the best dosage and check for safety. Results are expected in a year, Hulft said.