Albumin fusion for hemophilia
Fact-checked by What is albumin fusion for hemophilia?
Albumin fusion is a molecular technology used to create replacement therapies for hemophilia with an extended half-life — treatments that last longer in the body. Using albumin fusion for hemophilia treatments is one way to extend how long replacement factors remain in the body, allowing less frequent dosing than standard replacement products.
Hemophilia occurs when genetic mutations disrupt the production or function of specific clotting factors — proteins that help stop bleeding by forming clots. In hemophilia A, the disrupted protein is factor VIII (FVIII), while in hemophilia B, it is factor IX (FIX). Factor replacement therapies, a cornerstone of hemophilia treatment, provide the body with a working version of the affected factor.
When used prophylactically, or to prevent bleeds, standard half-life replacement therapies require frequent dosing — typically two to four times weekly for hemophilia A and one to two times weekly for hemophilia B — to maintain factor levels adequate for proper blood clotting. Extended half-life products are modified to help the clotting factor last longer in the body, in some cases reducing infusions to once a week or every two weeks. There are several technologies that can achieve this, including albumin fusion.
How does albumin fusion work in hemophilia?
Albumin is the most abundant protein found in plasma, the liquid portion of blood. It acts as a molecular ferry that carries other molecules through the bloodstream, including naturally occurring molecules, such as hormones, and external molecules, such as medications.
The liver produces albumin and releases it into the bloodstream. Albumin is very stable in circulation, with a half-life of about three weeks. This means the amount of albumin in circulation decreases by about half over that period.
This long half-life is largely due to neonatal Fc receptors, proteins that bind to albumin and help protect it from degradation by recycling it back into circulation.
Albumin fusion therapies take advantage of this stability to increase the half-life of drugs. Essentially, the process involves attaching, or fusing, albumin to a medication. The fused therapy can then benefit from albumin’s Fc receptor-mediated recycling, leading to slower breakdown and a longer time in circulation.
Extended-half-life albumin fusion therapies have been explored for treating multiple conditions. In the context of hemophilia, albumin is attached to clotting factors to extend the half-life of replacement therapies.
Albumin fusion in hemophilia therapies
Currently, Idelvion (albutrepenonacog alfa) is the only U.S.-approved hemophilia therapy that uses albumin fusion technology. The medication, which contains a lab-made version of FIX fused to albumin, is used to prevent and control bleeds in adults and children with hemophilia B. It is also approved in the European Union, Canada, and other regions.
CSL Behring developed Idelvion, which is administered as an intravenous (into-the-vein) infusion. The albumin-fused FIX product has a median half-life of about 100 hours (more than four days) and a recommended initial dosing schedule of once weekly. Depending on the response to treatment and other health factors, doctors may recommend adjusting the frequency, so some people receive infusions less often.
While albumin fusion for hemophilia B has reached the market, ongoing research is also looking at this technology for hemophilia A replacement therapies.
Potential side effects of albumin fusion therapies
Albumin is not expected to trigger abnormal immune responses when used as part of fusion therapies. No specific side effects have been clearly attributed to albumin fusion technology itself in hemophilia.
The most common side effects of Idelvion, which overlap with those of other standard half-life FIX products that don’t use albumin fusion, include:
- headache
- dizziness
- allergic reactions (hypersensitivity)
- rash
However, because only one approved medication uses the technology, all possible albumin fusion side effects may not yet be established.
Hemophilia News Today is strictly a news and information website about the disease. It does not provide medical advice, diagnosis, or treatment. This content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this website.
