FDA approves Hemgenix the first gene therapy for hemophilia B

Hemgenix is approved for the treatment of adults with hemophilia B who currently use factor IX prophylaxis therapy, or have current or historical life-threatening hemorrhage or have repeated, serious spontaneous bleeding episodes. In the ongoing clinical trial, Hemgenix reduced the rate of annual bleeds and 94 percent of patients discontinued factor IX prophylaxis and remained prophylaxis-free.

Hemophilia B is a rare, lifelong bleeding disorder caused by a single gene defect, resulting in insufficient production of factor IX, a protein primarily produced by the liver that helps blood clots form. Treatments for moderate to severe hemophilia B include prophylactic infusions of factor IX replacement therapy to temporarily replace or supplement low levels of blood-clotting factor and, while these therapies are effective, those with hemophilia B must adhere to strict, lifelong infusion schedules. They may also still experience spontaneous bleeding episodes as well as limited mobility, joint damage or severe pain as a result of the disease. For appropriate patients, Hemgenix allows people living with hemophilia B to produce their own factor IX, which can lower the risk of bleeding.

The FDA approval is supported by results from the ongoing HOPE-B trial, the largest gene therapy trial in hemophilia B to date. Results from the study demonstrated that Hemgenix allowed patients to produce mean factor IX activity of 39 percent at six months and 36.7 percent at 24 months post infusion. Seven to 18 months post-infusion, the mean adjusted annualized bleeding rate (ABR) for all bleeds was reduced by 54 percent compared to the six-month lead-in period on factor IX prophylactic replacement therapy (4.1 to 1.9). In addition, 94 percent (51 out of 54) of patients treated with Hemgenix discontinued use of prophylaxis and remained free of previous continuous routine prophylaxis therapy. The most common side effects (incidence greater than 5%) were liver enzyme elevations, headache, elevated levels of a certain blood enzyme, flu-like symptoms, infusion-related reactions, fatigue, nausea and feeling unwell.