Emicizumab is a bispecific monoclonal antibody used for the treatment of hemophilia A with inhibitors. It restores blood coagulation function by bridging factors IXa and X.
How to Use Emicizumab
Route of Administration and Frequency
Subcutaneous Injection: For subcutaneous use only; intravenous or intramuscular injection is prohibited.
Standard Regimen:
A loading dose of 3 mg/kg once weekly for the first 4 weeks.
After 4 weeks, one of the following maintenance regimens may be selected (determined by healthcare providers based on factors such as patient compliance):
1.5 mg/kg once weekly;
3 mg/kg once every two weeks;
6 mg/kg once every four weeks.
Key Points for Injection Procedure
Injection Sites: Select the outer upper arm, thigh, or abdomen (avoiding scars, bruises, or damaged skin). Change the injection site each time.
Pre-Injection Inspection: The medicinal solution should be a colorless to pale yellow liquid. Do not use if particles are present or the solution has changed color.
Injection Tools: A sterile 1 mL or 2/3 mL syringe (with a Luer-lock connector) paired with a 26G injection needle is required.
Management of Missed Doses
If a scheduled dose is missed, administer the missed dose as soon as possible before the next scheduled dose. After that, resume the original weekly regimen; do not administer a double dose to make up for the missed one.
Dose Adjustment and Precautions for Emicizumab
Basis for Dose Adjustment
Insufficient Efficacy: If ≥ 2 spontaneous bleeding episodes still occur after 24 weeks of treatment, consider increasing the maintenance dose to 3 mg/kg per week.
Risk of Concomitant Medication: When used in combination with activated prothrombin complex concentrate (aPCC), a cumulative dose of > 100 U/kg within 24 hours may trigger thrombotic microangiopathy or thrombotic events. In such cases, aPCC should be discontinued, and the need to adjust the emicizumab dose should be evaluated.
Interference with Laboratory Monitoring
Emicizumab may shorten the results of tests based on the intrinsic coagulation pathway (such as aPTT), but does not affect coagulation factor tests based on chromogenic substrate assays or immunoassays.
Clinically, it is necessary to avoid relying on aPTT to guide anticoagulant therapy or factor replacement dosing.
Emicizumab Use in Special Populations
Pediatric Patients
Age of Application: Infants (over 1 month old) to adolescents. For patients with a body weight ≥ 40 kg, refer to the adult regimen.
Dose: The same as the adult dose (calculated by body weight). Clinical studies have shown that the zero-bleeding rate in children under 12 years old reaches 87%.
Note: Self-injection is not recommended for children under 7 years old; the injection should be administered by healthcare providers or guardians.
Pregnancy and Lactation
Pregnancy: No human data are available. Emicizumab should be used only when the benefit outweighs the risk. It is recommended to use the medication during contraception.
Lactation: IgG may pass into breast milk. The necessity of treatment and potential risks to the infant should be weighed.
