Gene-therapy approach to hemophilia finds success in study, Spark stock surges

Spark Therapeutics Inc. stock surged Wednesday afternoon after the company announced positive results from a study of a gene-therapy approach to hemophilia. The drug, developed and tested in a collaboration with Pfizer Inc. , involves a single injection meant to help those suffering from hemophilia B, a disease that keep blood from clotting and is typically treated with regular and costly infusions. The study followed 10 adult males for 492 weeks and found that the number of episodes of bleeding decreased from an average of 11.1 a year before administration to 0.4 per year after, while infusions were reduced by 99%. The results were published in The New England Journal of Medicine on Wednesday, the companies said in a news release. Spark shares jumped as much as 9% in late trading after the announcement Wednesday, while Pfizer shares were unchanged.

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