Pharmacology · Coagulation factor replacement and haemophilia agents
Emicizumab !
A bispecific antibody that bridges factors IXa and X, doing factor VIII's job. Given under the skin to prevent bleeds in haemophilia A.
Updated 2026-11-01
Mechanism of action
Emicizumab is a bispecific antibody. One arm binds activated factor IX and the other binds factor X, placing them side by side so factor X is activated without factor VIII. It stands in for factor VIII's function rather than replacing the protein.
- One arm grabs factor IXa
- The other arm grabs factor X
- Factor X is activated without factor VIII
Pharmacokinetics
- Absorption
- Given by subcutaneous injection
Indications
- Haemophilia A, to prevent or reduce the frequency of bleeding episodes Haemophilia A and B →
Adverse effects
Common
- Injection-site reactions
- Headache
- Joint pain
Contraindications
- Hypersensitivity to emicizumab
Key interactions
- Activated prothrombin complex concentrate (aPCC)
- Risk of thrombotic microangiopathy and thrombosis
- Laboratory clotting and inhibitor tests
- Standard methods can mislead; the laboratory must be told the patient uses emicizumab
What is monitored
- Breakthrough bleeds and what was used to treat them
- Signs of thrombotic microangiopathy (confusion, low urine, jaundice)
Administration and safety
- Subcutaneous injection; patients and caregivers can learn to give it at home
- It prevents bleeds but does not treat an acute bleed; a plan for breakthrough bleeds is agreed with the haematology team
Nursing care
- Teach injection technique and site rotation
- Make sure the patient carries information that they receive emicizumab, for emergency teams and laboratories
- Warn about the danger of using aPCC without haematology advice
Pregnancy and breastfeeding
There are no adequate data in pregnancy; women of childbearing age are advised to use contraception during treatment.
Test yourself
Think of the answer, then tap the question to see it.
How does emicizumab replace factor VIII's function?
It binds factor IXa and factor X at the same time, so X is activated.
By which route is it given?
Subcutaneous injection, which patients can learn to give at home.
Which combination can cause thrombotic microangiopathy?
Emicizumab with activated prothrombin complex concentrate.
Related drugs
Related conditions
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Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: Emicizumab-kxwh Injection: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2022); Treatment of Hemophilia | Hemophilia | CDC (Centers for Disease Control and Prevention, 2026); eEML - Electronic Essential Medicines List (World Health Organization, 2025); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026).
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