After decades of research, gene therapies have begun reshaping the treatment of cancers and rare inheritable diseases with medicines that can modify or correct mutations embedded in people's genetic code.Hemgenix is the first such treatment for hemophilia and several other drugmakers are working on gene therapies for the more common form of the disorder, hemophilia A.Hemophilia almost always strikes males and is caused by mutations in the gene for a protein needed for blood clotting.Small cuts or bruises can be life-threatening, and many people need treatments once or more a week to prevent serious bleeding.The FDA said it granted approval based on two small studies, including one that showed those taking the drug had increased levels of the clotting protein, reduced need for standard treatment and a 54% drop in bleeding problems."