Spark, Pfizer Announce Data From Initial Subjects In Hemophilia B Trial

(RTTNews) - Spark Therapeutics (ONCE) and Pfizer Inc. (PFE) announced that new data will be presented on June 11 at the European Hematology Association's (EHA) 21st Congress. These data will show encouraging initial observations for the first subjects dosed in the Phase 1/2 clinical trial of SPK-9001, the lead investigational compound in the SPK-FIX program, which is being studied for the treatment of Hemophilia B. SPK-9001, a novel bio-engineered adeno-associated virus (AAV) capsid expressing a codon-optimized high-activity human Factor IX variant, was developed using Spark's proprietary technology platform for selecting, designing, manufacturing and formulating highly optimized gene therapies.

Data available today demonstrate that the first three subjects enrolled in the study experienced AAV-mediated Factor IX activity levels following one administration of SPK-9001 at the initial dose level (5 x 1011 vg/kg) studied in the trial. Factor IX activity levels in the first two subjects, without prior history of liver disease, rose consistently through the first four weeks post-administration.

At the time of abstract submission, the first subject stabilized at 28% of normal at eighteen weeks, and the second subject at 30% of normal at seven weeks post-administration. Factor IX activity level in the third subject, with a history of liver disease, also rose consistently and was at 16% of normal at three weeks post-administration. Data from a natural history of patients with hemophilia suggest that circulating factor activity levels sustained at a threshold of greater than or equal to 12% of normal generally are considered to be sufficient to reduce the risk of joint bleeds and the need for prophylactic clotting factor infusions.

Over the combined 28 weeks of observation reported in the abstract, none of the three subjects received regular infusions of Factor IX concentrates to prevent bleeding events. Only one precautionary infusion has taken place due to a suspected ankle bleed in one subject two days after administration of vector. SPK-9001 has been well-tolerated and no subjects have needed, or received, immunosuppression.