Spark Therapeutics and Pfizer Inc. announced that the US Food and Drug Administration (FDA) has granted breakthrough therapy designation to SPK-9001, the lead investigational candidate in the companies’ SPK-FIX program, in development for the treatment of haemophilia B. SPK-9001, a novel bio-engineered adeno-associated virus (AAV) capsid expressing a codon-optimized, high-activity human factor IX variant, is being investigated in an ongoing Phase 1/2 trial as a potential one-time therapy.

Breakthrough therapy designation is intended to expedite the development and FDA review of drugs to treat a serious or life-threatening disease or condition. The designation requires preliminary clinical evidence that the investigational therapy may offer substantial improvement over existing therapies on at least one clinically significant endpoint.

In addition to SPK-9001, Spark Therapeutics previously received breakthrough therapy designation for voretigene neparvovec, which is being developed for the potential treatment of inherited retinal disease (IRD) caused by mutations in the RPE65 gene.

“We are extremely pleased to have been granted breakthrough therapy designation for SPK-9001, which has shown early promise in achieving our goal of eliminating the need for regular infusions to control and prevent bleeding episodes in patients with haemophilia B through a potentially one-time, intravenous administration of a highly optimized gene therapy,” said Jeffrey D. Marrazzo, chief executive officer of Spark Therapeutics. “Together with Pfizer, we look forward to working closely with the FDA to bring SPK-9001 to patients as quickly and responsibly as possible.”

Haemophilia is a rare genetic bleeding disorder that causes the blood to take a long time to clot as a result of a deficiency in one of several blood clotting factors, and occurs almost exclusively in males. People with haemophilia face specific risks as they are not able to form blood clots efficiently and are at risk for excessive and recurrent bleeding from modest injuries, which have the potential to be life threatening. People with severe haemophilia often bleed spontaneously into their muscles or joints. The incidence of haemophilia B is one in 25,000 male births. People with haemophilia B have a deficiency in clotting factor IX, a specific protein in the blood. Haemophilia B is also called congenital factor IX deficiency or Christmas disease. 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 haemophilia.

Spark Therapeutics' proprietary technology platform for selecting, designing, manufacturing and formulating highly optimized gene therapies was applied to developing compounds in the SPK-FIX program. The SPK-FIX program leverages a long history of haemophilia gene therapy research and clinical development conducted by Spark Therapeutics and its founding scientific team over nearly three decades. SPK-9001 is a novel bio-engineered adeno-associated virus (AAV) capsid expressing a codon-optimized, high-activity human factor IX variant enabling endogenous production of factor IX. SPK-9001 is being developed under a collaboration with Pfizer. Spark Therapeutics and Pfizer entered into a collaboration in 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.