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BioMarin’s experimental hemophilia gene therapy, which is expected to be approved by U.S. regulators in August, has continued to prevent bleeding in patients treated four years ago.

However, levels of the key clotting protein the treatment helps produce, Factor VIII, continued to slowly decline, potentially leading to questions as to how long-lasting the benefits might be.


In the latest data, presented Wednesday at the virtual World Federation of Hemophilia meeting, seven patients who got the highest dose of BioMarin’s gene therapy saw a 95% reduction in bleeding episodes sustained over four years. Before treatment, those same patients needed about 140 doses of costly Factor VIII replacement therapy each year. Four years after gene therapy, they needed an average of five doses, a 96% improvement.

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