Hunting a cure, Spark reports steady progress on hemophilia B gene therapy as Pfizer preps for pivotal handoff

After some fine tuning on the manufacturing side, Spark Therapeutics $ONCE says it’s racked up a new round of promising results for its Phase I/II study of a groundbreaking new gene therapy that aims to cure hemophilia B. And the biotech is prepping a handoff of SPK-9001 to its Big Pharma allies at Pfizer $PFE this summer, who are planning to start a Phase III pivotal study.

Katherine High

Researchers are now reporting on 15 patients in the early-stage study getting a replacement factor IX gene to correct the mutation that requires constant care and factor replacement therapy to prevent bleeds. The annualized bleed rate for all of them was cut by 97% and researchers were careful to highlight three patients who are doing fine — with factor IX levels ranging from 38.1% to 54.5% beyond the 12-week mark— after being treated with an enhanced therapy produced by a new manufacturing approach.

The annual infusion rate was slashed to 0.9 infusions, compared to 57.2 infusions before the study. The data were being presented at the World Federation of Hemophilia World Congress in Glasgow today.

For the full group in the Spark study, the range on factor IX was 14.3% to 76.8%. Six of the 15 had to get infusions; two for spontaneous bleeds, two prior to surgery, and one each for a minor trauma and at the end of the study period.

Eliminating these infusions safely and reliably will be key for Spark and Pfizer as they look to field the first hemophilia gene therapy, racing against BioMarin $BMRN and uniQure. Sangamo $SGMO, meanwhile, is using its gene editing tech for hemophilia B. 

Spark gained an historic FDA OK for Luxturna, the first gene therapy approved in the US, which came out with a list price of $850,000. But analysts say that a hemophilia gene therapy could be the first to be marketed for as much as $1.5 million, considering the steep cost of infusions patients undergo.

“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 High, the president and head of research & development at Spark Therapeutics.

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Research Scientist - Immunology
Recursion Pharmaceuticals Salt Lake City, UT
Director of Operations
Atlas Venture Cambridge, MA

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