Specialists hail new era in hemophilia treatment

Despite gains, hemophilia B remains hard to treat

The much rarer hemophilia B (the type that affected members of European royal families who descended from Queen Victoria) has proved more difficult to treat than hemophilia A. An estimated 1 in 5,600 males in the United States are born with hemophilia A, compared with 1 in 19,300 males born with hemophilia B. The conditions rarely affect females.

Recombinant factor IX products that replace a missing protein have been improved and can now be given every 7 or 14 days, instead of twice a week, Dr. Key said. As for the future, so-called rebalancing therapies are in phase 3 trials and look promising: “Instead of trying to beef up the proclotting proteins, you’re trying to knock down the anticlotting proteins. ‘Rebalancing’ is a good way to think of it.”

These treatments are also agnostic – like Hemlibra – to the presence of inhibitors, he said.

These drugs could be available within a few years, Dr. Key said. “The major concern is always going to be a risk of thrombosis or clotting. Some of that has only become apparent through clinical trials and require a return to the drawing board to redesign the dosing to hit the safe, sweet spot that prevents bleeds but doesn’t cause clots.”

Dr. Ma agreed that clots are a significant risk from rebalancing agents. “I don’t know that I would put a factor IX patient without an inhibitor on a rebalancing therapy, because we already have pretty darn good therapies for them,” she said. However, factor IX patients with inhibitors do need better treatments, “and we’re all looking forward to the next approved drugs there.”
 

Hoopla for gene therapy, with questions, as well

The prospect of gene therapy for hemophilia, meanwhile, continues to draw attention as phase 3 trials continue. Potentially, gene therapy could be given just once to patients with hemophilia A or hemophilia B and provide bleeding control indefinitely, Dr. Ma said.

However, Dr. Key wondered whether gene therapy may be useful in hemophilia A, since emicizumab has worked so well. “I just don’t see the tsunami of patients who are wanting to undergo gene therapy in the first few years. I think there’ll be relatively slow uptake due to a lot of factors, including reimbursement.”

Hematologist Amar H. Kelkar, MD, of Dana-Farber Cancer Institute in Boston, is also skeptical that a groundswell of patients will embrace gene therapy, even if one-time treatment lasts for years. Current treatments are working well for many patients, Dr. Kelkar said in an interview, “and comfort with novel therapies may be slow within the community, especially if the treatment effect is expected to be transient. This is the same community that was hit hard by contaminated blood products during the HIV crisis, so it may be hard to convince a large number of patients to adopt a new type of therapy. There’s also the issue of the projected high upfront cost of gene therapies. Of course, I’d love to be wrong, especially if cost issues for the patients can be mitigated.”

Moving forward, both Dr. Ma and Dr. Key urged hematologists to send their hemophilia patients to Hemophilia Treatment Centers so they can get specialized care. There are about 140 of these federally funded centers around the country, according to the National Hemophilia Foundation. Many are located in children’s hospitals.

Hemophilia treatment now requires a subspecialty degree of knowledge that’s difficult for a hematologist in general practice to master, Dr. Ma said. “If you have a patient with hemophilia, and you’re in private practice for general hematology/oncology, please send them to a Hemophilia Treatment Center for something like a once-a-year check-in to make sure that the patient is getting comprehensive care.”

Dr. Ma discloses relationships with Takeda (research funding and consultation). Dr. Key discloses relationships with BioMarin and Takeda (advisory board), Novo Nordisk (grants review committee), and Uniqure (steering committee). Dr. Kelkar has no disclosures.