Approval of the drug may depend on the conclusions the FDA makes regarding safety concerns raised by its blood products advisory committee, which met on April 4 to review the treatment.
N9-GP is a long-acting recombinant coagulation factor IX, a molecule missing in patients with hemophilia B. This treatment helps the blood to clot, thereby providing temporary bleeding control.
Its safety and effectiveness was evaluated in clinical studies involving 115 patients with severe or moderately severe hemophilia B. Results showed that N9-GP was effective in routine prophylaxis, treatment of bleeding episodes, and surgery.
Indeed, compared to other factor IX products, N9-GP presented five times longer half-life (long-lasting action in the body). Patients treated with this drug showed a higher level of factor IX in their blood, even with less frequent dosings.
The trials also found that treatment with N9-GP 40 IU/kg once-weekly maintained patients’ factor IX activity levels above 15 percent, and reduced the median annualized bleeding rate. The treatment also prevented joint bleeding and improved patients’ quality of life.
The treatment was well-tolerated, with no safety concerns observed.
However, the FDA’s advisory committee raised two concerns regarding the approval of N9-GP. One was whether the assessment of brain function in the clinical studies was adequate to detect all clinically important neurological signs or symptoms. The other was whether the number of patients enrolled in the trials was sufficient to evaluate N9-GP’s safety.
In March, the Committee for Medicinal Products for Human Use (CHMP), which is under the European Medicines Agency (EMA), recommended marketing authorization in Europe for N9-GP, as a treatment and preventive therapy for bleeding in patients age 12 and older with hemophilia B (congenital factor IX deficiency). The treatment, if approved, will be available in Europe under the brand name Refixia, and as a powder and solvent for solution for injection (500 IU, 1,000 IU, and 2,000 IU).
N9-GP was designated as an orphan medicinal product in Europe in May 2009.
Hemophilia B is caused by a missing or defective protein called factor IX, which plays an important role in blood clotting. As such, hemophilia B patients bleed longer than other people when injured. The main treatment for this disease consists of the delivery of externally produced factor IX by intravenous administration.