By Dr. David Clark

Dear Dr. Clark:
What treatments are received by patients with inhibitors?
Liz

Dear Liz,

Please talk to your doctor.  I assume that you might be asking for your son, but it could be also for you. Female bleeders can develop inhibitors.
 
Rebalancing agents, concizumab, marstacimab and fitusiran, are coming to market we will see them in a year or two.
 
For low inhibitor titers (levels), the inhibitor can sometimes be overwhelmed by larger doses of factor. For some patients, that seems to work and may even tamp down the inhibitor. For others, it will only make the inhibitor worse.
 
Immune Tolerance Induction (ITI) is used to try to tolerize the immune system toward the factor VIII or IX. In ITI, they get more frequent infusions of higher doses of factor. This works to eliminate the inhibitor in about 70% of hemophilia A inhibitor patients. However, it doesn’t work that well for hemophilia B.
 
The three main treatments to restore clotting in B inhibitor patients are FEIBA, NovoSeven and Sevenfact. FEIBA is plasma-derived and contains a range of activated clotting factors, including factor IX. However, many B inhibitor patients develop allergic reactions to factor IX, so they can’t use FEIBA. NovoSeven and Sevenfact are both recombinant activated factor VII (FVIIa) products. Although the backbones of the FVIIa proteins are the same, they are made in different organisms, so they are glycosylated differently. Glycosylation refers to the carbohydrate side chains (chains of sugar molecules) bound to the proteins.
 
Remember that “every patient is different.” Some patients respond better to NovoSeven and some respond better to Sevenfact. It’s trial and error.
 
I hope that helps. Let me know if you have questions.
 
Dave