A small hemophilia A gene therapy trial signals early safety and efficacy

Red blood cells

A gene therapy for hemophilia A, an inherited bleeding disorder, helped reduce internal bleeding events among several participants in a small clinical research trial. The study was partially supported by NHLBI and published in the New England Journal of Medicine.

Every year, about 400 babies in the U.S. are born with hemophilia A, an X-linked condition that can prevent blood from properly clotting and lead to sustained bleeding. In a trial with 18 men with hemophilia A, researchers grouped study participants into four sections to assess the safety and early efficacy of a gene therapy designed to help the body form blood clots. They followed each participant for about two to three years and found no major safety concerns following the initial therapy. The therapy helped support 16 out of 18 trial participants with gene expression for clotting. Before the trial, participants experienced an average of eight to nine bleeding events each year. After the trial, they experienced less than one, a 91.5% reduction. The researchers will continue to follow study participants to assess the safety and effectiveness of this gene therapy.