A Deep Dive into FEIBA's Composition
FEIBA, or Factor Eight Inhibitor Bypassing Activity, is a medication for individuals with hemophilia A or B who have developed inhibitors to standard factor replacement therapies. Unlike recombinant products, FEIBA is derived from pooled human plasma. This involves rigorous screening of donors and plasma for infectious agents, followed by a manufacturing process that includes viral removal and inactivation steps like vapor heat treatment and nanofiltration to enhance safety.
The Active Ingredients: A Symphony of Clotting Factors
FEIBA's primary active component is its "Factor VIII inhibitor bypassing activity", which is provided by a mix of plasma proteins. The key active ingredients are vitamin K-dependent coagulation factors: Factors II, IX, and X are mostly in their non-activated forms, while Factor VII is mainly activated (FVIIa). It also contains small amounts of other proteins, including Factor VIII coagulant antigen and traces of proteins from the kinin-generating system. Anticoagulant proteins like protein C and protein S are present to help maintain hemostatic balance. FEIBA does not contain heparin. Inactive ingredients include sodium chloride and trisodium citrate.
How FEIBA Works: Bypassing the Blockade
In hemophilia, a deficiency of Factor VIII or IX impairs blood clotting. Inhibitors are antibodies that can neutralize standard factor replacement therapies. FEIBA acts as a "bypassing agent" by providing components, particularly activated Factor VII (FVIIa) and the combination of prothrombin (Factor II) and Factor Xa, to activate the coagulation cascade downstream of the blocked factors. This generates thrombin, which forms a fibrin clot to stop bleeding, effectively bypassing the inhibitors.
Clinical Applications and Administration
FEIBA is used in hemophilia A and B patients with inhibitors to control and prevent bleeding, manage perioperative bleeding, and for routine prophylaxis. It is not for patients without inhibitors. Administration is intravenously after reconstituting the lyophilized powder with sterile water.
Comparison with Other Bypassing Agents
FEIBA and recombinant Factor VIIa (rFVIIa), or NovoSeven, are the two main bypassing agents for inhibitor patients. They differ in origin and composition.
| Feature | FEIBA (Anti-Inhibitor Coagulant Complex) | NovoSeven (Recombinant Factor VIIa) |
|---|---|---|
| Source | Human Plasma | Recombinant (lab-created) |
| Composition | A complex of mainly non-activated Factors II, IX, X and mainly activated Factor VII | Contains only activated recombinant Factor VII |
| Mechanism | Bypasses inhibitors by providing multiple factors (FII, FX, FVIIa) to generate thrombin | Bypasses inhibitors by directly activating Factor X on the platelet surface |
| Administration | Administered as an intravenous infusion | Administered as an intravenous infusion |
Studies like FENOC suggest similar efficacy for joint bleeds, but individual responses vary.
Important Safety Considerations
As a plasma-derived product, FEIBA has a theoretical, though minimized by manufacturing processes, risk of transmitting infectious agents. A significant risk is the black box warning for thrombotic events (blood clots), including stroke and pulmonary embolism, especially in patients with clot risk factors. Severe allergic reactions are also possible. Common side effects include nausea, vomiting, anemia, and diarrhea.
Conclusion
FEIBA is composed of activated and non-activated coagulation factors from screened human plasma. Its composition allows it to bypass inhibitory antibodies, providing a crucial treatment for hemophilia with inhibitors. Despite risks like thrombotic events, it remains a vital option for managing bleeding in these patients.
For more information, consult the official prescribing information or a qualified healthcare provider. An authoritative source for further reading is the FEIBA Prescribing Information on the FDA's website.
