In the United States and other wealthy countries, most patients receive recombinant factor VIII, Walsh said.
In general, the therapy works well, he noted. But a major problem is that some children develop antibodies against the replacement factor VIII soon after they begin treatment.
One question has been whether the source of the factor VIII — donor blood or DNA technology — makes a difference, explained Dr. Donna DiMichele, of the U.S. National Heart, Lung, and Blood Institute.
One of the new studies was designed to answer that question, said DiMichele, who wrote an editorial published with the findings.
An international team of researchers randomly assigned 264 young children newly diagnosed with severe hemophilia to start replacement therapy with either blood-derived or recombinant factor VIII.
Overall, 37 percent of children on the recombinant therapy developed antibodies. That compared with 23 percent of kids on blood-based therapy.
Lead researcher Dr. Flora Peyvandi said the findings suggest blood-derived factor VIII is the “better choice” for children beginning therapy.
The findings do not apply to patients who’ve been on therapy for a while, according to Peyvandi, of the University of Milan, in Italy.
If a child is going to develop antibodies, that usually happens within the first 50 infusions, she explained.
But Walsh and DiMichele expressed doubts about whether blood-derived factor VIII is better for children just beginning therapy.
For one, DiMichele said, the risk of developing antibodies might be lower, but it’s still significant.
Walsh agreed, and also pointed to safety concerns.
The blood supply is thoroughly tested, and considered very low-risk. “But,” Walsh said, “anytime a ‘new’ virus comes out that could be spread through blood transfusions — like the Zika virus — patients worry. You’re always looking over your shoulder.”
He and DiMichele both predicted that doctors will vary in their opinions, and their advice to patients.
Meanwhile, the emicizumab study suggests an entirely different solution to the antibody problem, Walsh said.
The drug is a lab-generated antibody that “mimics” the form of factor VIII, which allows it to do the protein’s job. It’s designed, in part, to get around the problem of factor VIII antibodies.
DiMichele called the drug “ingenious.”
“The fact that they could even do this is remarkable,” she said.
The new trial tested the drug in just 18 patients with severe hemophilia. But over three months, 72 percent had no bleeding episodes. And it was just as effective in patients who’d developed antibodies to factor VIII as those who were antibody-free.
The study was sponsored by Japanese drug maker Chugai Pharmaceutical, one of the companies developing emicizumab. Larger trials are underway, according to the company.
Emicizumab is easier to take than factor VIII replacement. It requires one weekly injection, versus several IV infusions per week. Young children on factor VIII often need a catheter device implanted under the skin to allow the frequent infusions.
The new findings “should be very exciting for patients and parents,” DiMichele said. “But we still need much more information.”
Researchers need to show the drug is effective and safe in the longer term, she said. It’s also unclear whether it not only prevents bleeding episodes, but treats them when they do happen — as factor VIII replacement can.
“Does this represent a sea change?” Walsh said. “We’ll see.”
The ultimate hope, he noted, is to use gene therapy to potentially cure hemophilia. Researchers are already working on it, he added.
Both studies were published May 26 in the New England Journal of Medicine.