Spark Therapeutics (NASDAQ: ONCE), the biotechnology company focused on gene therapy, said Tuesday its experimental treatment for hemophilia A reduced bleeds and the need for therapeutic infusions by 97% in a trial of 12 patients. It plans to start a late-stage clinical trial in the fourth quarter.
At the highest dose in the study, which the company plans to use in its phase 3 trial, five of seven patients saw levels of the protein important in hemophilia A restored to an average of 30% of normal, the company said when it reported second-quarter financial results. Two patients, though, had an immune response that caused the level of that protein to decline to less than 5%.
Hemophilia is a rare disorder in which the blood doesn't clot properly. It's currently treated with drugs that replace proteins — called Factor VIII, for hemophilia A, and Factor IX, for the less common hemophilia B — known as clotting factors. About 20,000 people in the U.S. are estimated to have hemophilia, according to the Centers for Disease Control and Prevention.
New approaches, from Spark and competitors like BioMarin, aim to deliver healthy copies of the gene that makes the proteins important in hemophilia. The goal of what's called gene therapy is to dramatically improve, or even cure, the disease with just one treatment (hence, the stock symbol, "ONCE")
Spark's stock has gained more than 50% this year, following a massive drop in December on an earlier look at four patients in this clinical trial.
Shares opened Tuesday tumbled $24.34, or 31.4%, to $53.27
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