Potential Hemophilia B Cure Unveiled

Hemophilia B patients may significantly benefit from gene therapy

(RxWiki News) A novel one-time intravenous gene therapy infusion could potentially cure patients with severe hemophilia B. Four patients from the small trial have had such success that they have discontinued traditional treatment.

Hemophilia B is an inherited bleeding disorder in which patients have a deficiency of clotting factor IX. Those with the most severe forms of the disease may experience spontaneous joint bleeds or potentially fatal bleeds in the brain.

Dr. Andrew Davidoff, a co-author of the study from the department of surgery at St Jude Children's Research Hospital, said researchers were pleased to see an increase in factor IX among all study participants.

"I feel that these preliminary results are very encouraging. It clearly shows that this method is safe," Dr. Davidoff said.

During the small study six severe hemophilia B patients in the U.S. and England received a single gene therapy dose of a serotype-8 pseudotyped self-complementary adeno-associated virus (AAV) vector expressing a codon-optimized coagulation factor IX (FIX) transgene.

Though the name sounds complicated, it actually acts as a vehicle to transport the gene to make factor IX to patients, all of which had less than 1 percent of factor IX. Even small percentage increases can have a tremendous impact  in patients with such low levels. Patients received one of three available doses and were followed for between six months and 16 months after treatment.

Researchers found that the treatment increased expression of factor IX in the patients to between 2 percent and 11 percent. Patients have maintained levels that vary between 2 percent and 8 percent two years after receiving the treatment. In previous animal studies, the one-time treatment had lifelong effects. It is believed it also could work long-term in humans, though it has not been proven.

Four out of six of the patients have discontinued traditional prophylaxis treatments that most had previously received two or three times each week, and have remained free of any hemorrhage. The other two patients have successfully decreased the frequency of their treatments from several times a week to once every seven to 10 days. Two patients developed complications that were treated with a short course of steroids.

Additional, larger studies are planned to evaluate the effectiveness of the treatment at the highest dose, which could potentially cure patients with the severe form of hemophilia B.

The study was presented today at the American Society of Hematology's annual meeting in San Diego, Calif.

Review Date: 
December 10, 2011