Spark Therapeutics and Pfizer Announce Data from 15 Participants with Hemophilia B Showing Persistent and Sustained Factor IX Levels with No Serious Adverse Events

PHILADELPHIA and NEW YORK, May 22, 2018 (GLOBE NEWSWIRE) -- Spark Therapeutics (NASDAQ:ONCE), a fully integrated gene therapy company dedicated to challenging the inevitability of genetic disease, and Pfizer (NYSE:PFE), today announced that, with a cumulative follow-up of more than 18 patient years of observation (5 to 121 weeks), all 15 participants in the ongoing Phase 1/2 clinical trial of investigational SPK-9001 for severe or moderately severe (FIX:C ≤ 2 percent) hemophilia B, had discontinued routine infusions of factor IX concentrates. None of the 15 participants experienced serious adverse events, and there were no thrombotic events or factor IX inhibitors, as of the May 7, 2018 data cutoff. These data will be presented today by Spencer K. Sullivan, M.D., hematologist and clinical investigator, Mississippi Center for Advanced Medicine, at the World Federation of Hemophilia (WFH) World Congress in Glasgow, Scotland, during the “Free Papers: Gene Therapy” session at 10:15 a.m. BST.

“We are pleased to see all 15 participants, notably including the first four participants who have been followed for more than two years, continue to show that a single administration of SPK-9001 has resulted in dramatic reductions in bleeding and factor IX infusions, with no serious adverse events,” said Katherine A. High, M.D., president and head of research & development at Spark Therapeutics. “Our commitment to gene therapy research across our hemophilia programs remains steadfast with the goal of developing a novel therapeutic approach with a positive benefit-risk profile that aims to free patients of the need for regular infusions, while eliminating spontaneous bleeding.”

Based on individual participant history for the year prior to the study, the overall ABR for all 15 participants was reduced by 98 percent (calculated based on data after week four; 97 percent based on data after infusion) to an annual rate of 0.2 bleeds per participant, compared to an annual rate of 8.9 bleeds before SPK-9001 administration. Only one participant experienced a bleeding event four or more weeks after SPK-9001 infusion.

Overall AIR was reduced by 99 percent (calculated based on data after week four; also 99 percent based on data after infusion) for all 15 participants to an annual rate of 0.9 infusions, compared to an annual rate of 57.2 infusions before infusion. Six participants received factor IX infusions following SPK-9001 administration: two for reported spontaneous bleeds, two prior to surgery, one at the end of the study (discretionary, per protocol) and one for prophylaxis for a minor traumatic non-bleeding event.

As of the May 7, 2018 data cutoff, all 13 participants with at least 12 weeks of follow-up after SPK-9001 infusion, the length of time required to achieve steady-state factor IX activity levels, reached stable factor IX levels of more than 12 percent. The range of steady-state factor IX activity level, beginning at 12 weeks through 52 weeks of follow-up for the first 10 participants infused, was 14.3 to 76.8 percent. For the three participants infused with SPK-9001 manufactured using an enhanced process who reached 12 or more weeks of follow-up, the range of steady-state factor IX activity level was 38.1 to 54.5 percent. The two remaining participants are out 11 and 5 weeks, per the May 7, 2018 data cut-off date.

In this open-label, non-randomized and multicenter Phase 1/2 clinical trial, there have been no serious adverse events, no thrombotic events and no factor IX inhibitors developed, and all 15 participants infused with SPK-9001 have discontinued prophylactic clotting factor infusions. Two participants, one having received SPK-9001 manufactured using an enhanced process, reported related adverse events of elevated transaminases and were treated with a tapering course of oral corticosteroids. The events were asymptomatic, and one event has been resolved, as of the May 7, 2018 data cutoff. One additional participant received a tapering course of oral corticosteroids for an increase in liver enzymes (not exceeding the upper limit of normal) temporally associated with falling levels of factor IX activity.

Spark Therapeutics has completed enrollment in the Phase 1/2 clinical trial of SPK-9001 in hemophilia B and expects to complete the transition of the program to Pfizer this summer. Additionally, Spark Therapeutics expects to deliver a batch of drug substance to Pfizer, enabling Pfizer to begin a Phase 3 clinical trial.

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.

About Spark Therapeutics

At Spark Therapeutics, a fully integrated company committed to discovering, developing and delivering gene therapies, we challenge the inevitability of genetic diseases, including blindness, hemophilia and neurodegenerative diseases. We have successfully applied our technology in the first FDA-approved gene therapy in the U.S. for a genetic disease, and currently have three programs in clinical trials, including product candidates that have shown promising early results in patients with hemophilia. At Spark, we see the path to a world where no life is limited by genetic disease. For more information, visit, and follow us on Twitter and LinkedIn.

About Pfizer: Working together for a healthier world®

At Pfizer, we apply science and our global resources to bring therapies to people that extend and significantly improve their lives. We strive to set the standard for quality, safety and value in the discovery, development and manufacture of health care products. Our global portfolio includes medicines and vaccines as well as many of the world's best-known consumer health care products. Every day, Pfizer colleagues work across developed and emerging markets to advance wellness, prevention, treatments and cures that challenge the most feared diseases of our time. Consistent with our responsibility as one of the world's premier innovative biopharmaceutical companies, we collaborate with health care providers, governments and local communities to support and expand access to reliable, affordable health care around the world. For more than 150 years, we have worked to make a difference for all who rely on us. We routinely post information that may be important to investors on our website at In addition, to learn more, please visit us on and follow us on Twitter at @Pfizer and @Pfizer_News, LinkedIn, YouTube and like us on Facebook at

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