NEJM Publishes Data from Study of Gene Therapy in Hemophilia B

Mathew Shanley

The New England Journal of Medicine has published interim data from Spark Therapeutics' Phase 1/2 clinical trial of SPK-9001 in patients with hemophilia B.

The paper, titled “Hemophilia B Gene Therapy with a High Specific Activity Factor IX Variant,” explores the investigational gene therapy when administered as a single intravenous infusion.

The company collaborated with Pfizer in December 2014 for the SPK-FIX program, under which Spark is responsible for conducting all Phase 1/2 studies, any regulatory activities and potential global commercialization of the adeno-associated viral (AAV) vector with human factor IX gene, or any other products that may result from the partnership.

In June 2016, Spark presented an earlier version of the data from the trial at the 21st Congress of the European Hematology Association (EHA).

Hemophilia B, a rare genetic disorder, is characterized by the inability of a patient’s blood to properly clot as the result of reduced factor IX activity. People with the condition are at risk for excessive, recurrent and potentially life-threatening bleeding episodes from minor injuries. The current standard-of-care for the disease includes repeated intravenous infusions of either plasma-derived or recombinant factor IX, which assists in controlling and preventing bleeding episodes.

The highlights published in NEJM include interim data as of July 25, 2017 and concludes that the first 10 adult male participants, after 492 weeks of follow-up, experienced a mean steady-state factor IX activity of 34% of normal after a single administration of the drug, with a range of 14%-81%. Additionally, the annualized bleeding rate (ABR) of these patients was reduced 97%, with a mean rate of 11.1 events per year at baseline to 0.4 events per year after administration of the vector (p=0.02).

“The data suggest a one-time infusion of SPK-9001 has the potential to safely sustain factor IX coagulant activity level that may result in the termination of baseline prophylaxis factor infusions, significantly reduce bleeding, and nearly eliminate the need for exogenous factor IX concentrate infusions,” said Katherine A. High, M.D., president and head of Research and Development at Spark Therapeutics and co-author of the paper in a press release.

No serious adverse events (AEs) were reported in the trial, and no patients experienced thrombotic events or developed IX inhibitors. It was noted, however, that 2 enrolled participants did develop asymptomatic and transient increases in live enzymes that were resolved with a tapering dose of oral corticosteroids.

“People who live with hemophilia today face a lifelong need for vigilant monitoring and recurrent factor concentrate infusions to prevent spontaneous, potentially life-threatening bleeds and to protect their joints,” said High. “The discipline required to execute the usual prophylactic regimen can exact a heavy toll on quality of life, and these regimens result in significant costs to patients, families and the health care system.”

At present, the incidence of hemophila B is 1 in every 25,000 male births.

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