For the study, George and her colleagues delivered one dose of the gene therapy each into 10 hemophilia B patients’ livers. This is where the body normally produces the so-called factor IX protein that allows blood to clot properly.
The dose contained a “bioengineered payload” of the gene that codes for a naturally occurring clotting factor that’s eight to 10 times stronger than the normal factor and known as factor IX-Padua.
All of the patients benefited from the gene therapy, the researchers said. It moved them out of the severe disease category and almost eliminated bleeding in their joints, a persistent prior problem.
Eight of the 10 did not require any additional standard treatments, and 9 of the 10 didn’t experience bleeding problems after the gene therapy. None experienced serious complications, according to the study.
The research was published Dec. 7 in the New England Journal of Medicine.
“What’s transformative about this [study] is they converted people who were at risk of having these bleeds to now having levels of clotting factor where they can pretty much do anything they want,” said Dr. Matthew Porteus. He’s an associate professor of pediatrics-stem cell transplantation at Stanford University School of Medicine.
“Patients will really be able to live essentially normal lives, even playing sports like soccer, which we now discourage patients with hemophilia from playing,” added Porteus, who wrote an editorial accompanying the study.
“But this is a study on 10 patients and now the challenge is to expand it to many more,” he said.
Another hurdle is that about one-third of hemophilia B patients have a pre-existing immunity to the virus that delivers this type of gene therapy, making them ineligible to receive it, George and Porteus noted.
Researchers are also trying to develop a similar gene therapy for hemophilia A, which has proven more challenging.
The potential price tag of the hemophilia B gene therapy is an issue, but George and Porteus said it could be offset by eliminating the need for standard treatments. These can cost between $100,000 and $500,000 a year.
Only two gene therapies are approved for use in the United States — both for blood cancers. And “less than a handful” are in use around the world, Porteus said. They typically cost between $400,000 and $1 million for each therapy.
“That’s obviously raised some eyebrows and given some people sticker shock,” he added.
“But even at $800,000 to $1 million, that could end up being cost-effective over the lifetime of a patient. That being said, how to price and reimburse gene therapies is an active area of discussion and there’s no true consensus,” Porteus said.