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Studying Vector-Facilitated Gene Therapy in Hemophilia B Patients

Severe bleeding in patients with hemophilia can have a negative impact on their quality of life and can lead to disability if there is hemorrhaging of the muscle tissue. Researchers are working on new ways of achieving adequate blood clotting factor levels that could prevent excessive bleeding in hemophilia patients.

A recent study was conducted with the help of ten hemophilia B patients who had a factor IX activity level of <2%. In the study, each of the 10 patients received a single infusion of an adeno-associated viral vector with a unique bio-engineered capsid, a factor IX padua transgene, and a liver-specific promoter. The researchers found that the vector derived factor IX activity was sustained in all patients.

Over the course of the 49-week study, there was a significant decrease in the annualized bleeding rates from a mean of 11.1 down to 0.4, as well as a reduction in factor X infusions. After the treatment using vector-facilitated gene transfer, nine of the ten patients experienced no bleeding in the following weeks, with eight of the ten patients requiring no subsequent factor to stop bleeding incidents. The clinical trial yielded positive results in finding that the vector-facilitated gene transfer led to a sustained therapeutic expression of factor IX and the near elimination of bleeding and factor use, with no adverse effects.

While hopeful in light of the results, the scientists reiterate that constant follow-up is going to be needed to determine the long term efficacy of vector-facilitated gene transfer therapy in patients with hemophilia.