Gene Therapy Shows Promise For Hemophilia, But Could Be Most Expensive U.S. Drug Ever

Jack Grehan, who was born with hemophilia, used to inject himself every couple of days with a protein he needs for his blood to clot. But not anymore.

"It's been absolutely brilliant and life-changing for me," says Grehan, 26, of Billinge in North West England. He received an experimental gene therapy in 2017 that, at least for now, has eliminated his need for regular injections. "I can just go about my day and not have to worry."

Based on experiences like Grehan's, the company that developed the therapy is seeking approval in Europe and the United States to start selling the first gene therapy for hemophilia. That's generating excitement among patients, patient advocates and doctors.

"Not to have to worry about hemophilia any longer — I think it's essentially transformational for many patients," says Dr. John Pasi of the Royal London Hospital and the London School of Medicine and Dentistry. Pasi led the recently published study Grehan took part in.

Others are more cautious.

"This is really exciting, but also raises a lot of questions," says Meg Bradbury...