People with severe hemophilia don’t produce enough clotting proteins on their own, requiring regular infusions in order to prevent or control bleeding. While safe and effective, the infusions can be expensive and time–consuming, and repeated bleeds can result in damaged joints.

Hemophilia patients from St. Michael’s Hospital are taking part in a small gene therapy trial based in the United States, in which participants have gone weeks, months and in one case a year without any bleeds.

“The results so far are wonderful, even better than what we had dared to hope,” said Dr. Jerry Teitel, medical director of the Hemophilia Treatment Program at St. Michael's. Dr. Teitel, who is a collaborator with the lead researchers at the Children's Hospital in Philadelphia, called it a “revolutionary therapy.”

Dr. Teitel said preliminary data from the first nine patients suggests that a single dose of the experimental gene therapy may help patients with hemophilia B, who have a deficiency of blood clotting factor IX. He stressed that the treatment was still experimental and that the long–term effectiveness and safety had not been proven. Of the nine patients, four are Canadian, from St. Michael’s.

One of those patients, John Konduros, 53, a bakery owner from Cambridge, Ont., hasn’t had a bleed or a need for treatment since his gene therapy on June 6, 2016. The IV procedure took about one hour. In the IV bag were engineered genes encased in inactivated viruses that signaled his body to produce its own clotting factor IX.

Konduros was diagnosed with hemophilia shortly after he was born, as his older brother also had the disease, so he has spent a lifetime being careful not to hurt himself. When he hit himself shoveling snow a couple of years ago he was in hospital for 10 days and couldn’t walk properly for six months.

He said the gene therapy has made him less anxious about the future.

“You spend so much time looking after yourself, avoiding injuries, that to have no bleeds nine to 10 months later is almost too good to be true,” he said. “It’s still hard for me to believe. You go in for a one–hour IV drip and, like one of the doctors in Philadelphia said, ‘You leave your hemophilia at the door.’”