Replacement therapy is one of the standard therapies used to treat hemophilia, a genetic disorder caused by the absence or defects in blood clotting factors. Hemophilia makes patients highly susceptible to bleeding due to a compromised cascade of clotting reactions that are necessary to “seal” injuries.
Replacement therapy involves supplying the missing clotting factor to the patient from an external source. The lack or deficiencies in factor VIII, IX, and XI cause hemophilia A, B, and C, respectively, and the type of blood clotting factor that the patient needs depends on the type of hemophilia they have.
Sources of clotting factors
Plasma-derived clotting factors
The clotting factor injected into a patient with hemophilia usually derives from human blood or plasma (the clear non-cellular liquid component of the blood). Examples of plasma-derived factor VIII treatments include Hemofil-M, Alphanate, HumateP, and Wilate. AlphaNineSD and Mononine are some plasma-derived products containing factor IX, and Hemoleven is a factor XI concentrate available in Europe but not in the U.S.
Before replacement therapy is administered, the blood is treated extensively to reduce the risk of transmission of blood-borne pathogens such as hepatitis and HIV.
Recombinant clotting factors
In some cases, the clotting factor concentrate can also be derived from recombinant sources, which decreases the risk of infections from human blood-derived pathogens. Examples of such recombinant products used to treat hemophilia A includes Advate and Xyntha.
Rixubis is a recombinant factor IX product that was approved by the U.S. Food and Drug Administration in 2013 as a replacement therapy to treat hemophilia B.
How replacement therapy is administered
Patients and clinicians can decide the timing and frequency of replacement therapy. There are two kinds of therapies based on when the treatment is administered.
Prophylactic replacement therapy is routinely administered as a preventive measure to avoid future bleeding.
On-demand therapy is administered based on the specific needs of the patients — for example, to stop a current bleeding episode.
Usually, on-demand therapy is less expensive and intensive than prophylactic therapy. The timing of on-demand therapy is critical since excessive bleeding can cause extensive damage until the therapy is administered.
A concentrate of clotting factor can be administered to the patient via a drip or a direct intravenous injection at a clinic or at home. Many patients prefer the ease and convenience of taking the infusions at home, which offers other advantages:
- The therapy can be administered quickly when a bleeding incident occurs and significantly reduce the risk of complications from delayed administration.
- The cost of treatment is lower than treatment delivered in a medical setting.
- Patients respond better at home.
Patients should consult with a clinician who can train them how to administer the treatment safely at home.
A clinician can also pre-implant a device in a patient so the patient has access to a vein more easily when administering their replacement therapy. The doctor can explain how to keep the device sterile and reduce the risk of infection.
Potential complications with replacement therapy
Some serious clinical complications that can arise as a result of replacement therapy include:
- A risk of contracting disease if the donor blood is not carefully screened.
- Antibodies that develop against an external clotting factor which can cause a range of clinical complications. These antibodies can attack the clotting factor and destroy it, and therefore negate the effects of the therapy. In such cases, the clinicians may opt to transfuse the clotting factors in larger doses or try alternative sources of clotting factors. These antibodies have been found to develop in 20% to 30% of patients. In some cases, these antibodies can clear out of the body by themselves.
Regardless of potential complications, replacement therapy is the standard treatment for hemophilia.
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