On December 11, 2017 Spark Therapeutics (NASDAQ:ONCE), a fully integrated gene therapy company dedicated to challenging the inevitability of genetic disease, and Pfizer Inc. (NYSE:PFE), reported that, with a cumulative follow-up of more than 13 patient years of observation, all 11 participants in the ongoing Phase 1/2 clinical trial of investigational SPK-9001 for the treatment of patients with hemophilia B had discontinued routine infusions of factor IX concentrates and shown sustained steady-state factor IX activity levels with no serious adverse events, thrombotic events or factor IX inhibitors observed (Press release, Pfizer, DEC 11, 2017, View Source [SID1234522561]). Based on individual participant history for the year prior to the study, the overall annualized bleeding rate (ABR) was reduced by 97 percent (calculated based on data after week four; 95 percent based on data after infusion) to a mean of 0.3 (0.5) annual bleeds, compared to a mean of 10.5 bleeds annually before SPK-9001 administration. Overall annualized infusion rate (AIR) was reduced 99 percent (calculated based on data after week four; 97 percent based on data after infusion) to a mean of 0.8 (1.7) annual infusions, compared to a mean of 62.5 infusions per year before SPK-9001 administration. Data on all 11 participants were presented today by Lindsey A. George, M.D., attending physician in the Division of Hematology at Children’s Hospital of Philadelphia and principal investigator of the trial, at the 59th American Society of Hematology (ASH) (Free ASH Whitepaper) Annual Meeting and Exposition in Atlanta.

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"We believe these longer-term data are meeting critical goals of our hemophilia programs," said Katherine A. High, M.D., president and head of research and development at Spark Therapeutics. "Now, with four participants followed for more than 18 months, we continue to see consistent levels of factor IX activity, no serious adverse events, as well as a sustained reduction in both the symptoms of hemophilia and the prophylactic and disease management protocols that were used prior to infusion with SPK-9001."

As of the Nov. 29, 2017 data cutoff, the mean steady-state factor IX activity level at 12 weeks post-administration for the 11 participants was 36 percent of normal (range as of the data cutoff: 15 to 78 percent). As of the data cutoff, the last participant to be infused, who received SPK-9001 manufactured using an enhanced process, was out eight months following SPK-9001 infusion, with a mean factor IX activity level of 60 percent. Spark Therapeutics will enroll up to four additional participants in the current Phase 1/2 clinical trial who will receive SPK-9001 manufactured using an enhanced process to test its comparability to the SPK-9001 received by the first 10 participants enrolled in the ongoing trial.

In this open-label, non-randomized and multicenter Phase 1/2 clinical trial, there were no serious adverse events during or following infusion with SPK-9001, and no participants experienced thrombotic events or developed factor IX inhibitors. Two participants developed an asymptomatic and transient increase in liver enzymes that resolved with a tapering dose of oral corticosteroids. One participant with severe joint disease administered factor for suspected joint bleeding, while a second participant recorded one spontaneous bleed.

About Hemophilia B
Hemophilia, a rare genetic bleeding disorder that causes the blood to take a long time to clot because of a deficiency in one of several blood clotting factors, is almost exclusively found in males. People with hemophilia are at risk for excessive and recurrent bleeding from modest injuries, which have the potential to be life threatening. People with severe hemophilia often bleed spontaneously into their muscles or joints, or rarely into other critical closed spaces such as the intracranial space, where bleeding can be fatal. The incidence of hemophilia B is one in 25,000 male births. People with hemophilia B have a deficiency in clotting factor IX, a specific protein in the blood. Hemophilia B also is called congenital factor IX deficiency or Christmas disease. The current standard of care requires recurrent intravenous infusions of either plasma-derived or recombinant factor IX to control and prevent bleeding episodes. There exists a significant need for novel therapeutics to treat people living with hemophilia.

About the SPK-FIX Program and SPK-9001
SPK-9001 is a novel investigational vector that contains a bio-engineered adeno-associated virus (AAV) capsid and a codon-optimized, high-activity human factor IX gene enabling endogenous production of factor IX.

Spark Therapeutics and Pfizer entered into a collaboration in December 2014 for the SPK-FIX program, including SPK-9001, under which Spark Therapeutics is responsible for conducting all Phase 1/2 studies for any product candidates, while Pfizer will assume responsibility for pivotal studies, any regulatory activities and potential global commercialization of any products that may result from the collaboration.