London researchers have made a rare breakthrough in a rare disease: hemophilia A. In the small-scale clinical study, patients received injections of a missing gene that promotes the production of the factor VIII clotting protein absent in these patients. Results reported in NEJM showed that six of the 7 patients in the high-dose cohort maintained normal levels of factor VIII after a full year. Also amazing, those in the high-dose cohort had an average of 16 bleeding events per year prior to therapy and this was reduced to 1 event per year after therapy. These findings are particularly significant because prior gene therapy studies have shown effectiveness only in hemophilia B sufferers, not hemophilia A, where a different clotting protein is the culprit.