Bispecific antibody mimicking factor VIIIa (FIX-FX bridging) Pregnancy: No clinical studies in pregnant women; use during pregnancy only if potential benefit to the mother outweighs risk to the fetus. Women of childbearing potential should use effective contraception during and for at least 6 months after stopping treatment.

Emicizumab

Brand names: Hemlibra

Emicizumab is a humanised bispecific monoclonal antibody used for routine prophylaxis to prevent or reduce bleeding episodes in haemophilia A, including patients with factor VIII inhibitors.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: Loading: 3 mg/kg once weekly for the first 4 weeks; Maintenance (from week 5): 1.5 mg/kg once weekly OR 3 mg/kg every two weeks OR 6 mg/kg every four weeks

Route: Subcutaneous injection

Frequency: Loading dose once weekly x4 weeks, then maintenance at selected interval

Max: A volume greater than 2 mL per injection should not be administered

For routine prophylaxis of bleeding in haemophilia A. Treatment initiated under supervision of a physician experienced in haemophilia/bleeding disorders. The loading regimen is the same irrespective of the chosen maintenance regimen; maintenance regimen selected on physician and patient/caregiver preference to support adherence. Dose (mg) = bodyweight (kg) x dose (mg/kg). Discontinue prophylactic bypassing agents the day before starting; FVIII prophylaxis may continue for the first 7 days. Do not combine the 30 mg/mL and 150 mg/mL concentrations in the same syringe. Intended for long-term prophylaxis; no dose adjustments recommended during treatment. Paediatric: no dose adjustments recommended (same weight-based regimen); no data in patients under 1 year of age.

Dose adjustments

Renal

No dose adjustments recommended in mild renal impairment; limited data in moderate renal impairment; not studied in severe renal impairment.

Dose auto-extracted from UK Summary of Product Characteristics (SPC) via the eMC; US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

Contraindications

Hypersensitivity to the active substance or to any of the excipients

Side effects

Injection site reactions (very common)
Arthralgia (very common)
Headache (very common)
Diarrhoea; myalgia; pyrexia; urticaria; rash (common)
Thrombotic microangiopathy; superficial thrombophlebitis; cavernous sinus thrombosis; skin necrosis; angioedema (uncommon)

Interactions

Activated prothrombin complex concentrate (aPCC): risk of thrombotic microangiopathy and thromboembolism when a cumulative average of >100 U/kg/24 h of aPCC is given for 24 hours or more
Interferes with intrinsic-pathway clotting-based laboratory tests (aPTT, aPTT-based single-factor and Bethesda assays, ACT); do not use these tests to monitor

Clinical monograph

How it works

It bridges activated factor IX and factor X, mimicking the cofactor function of missing factor VIII and thereby restoring effective coagulation.

Prescribing in practice

Thrombotic microangiopathy and thromboembolism have occurred when activated prothrombin complex concentrate was used concurrently, so co-administration should be avoided where possible and managed cautiously.
It interferes with activated partial thromboplastin time-based coagulation assays, so factor VIII activity and inhibitor measurement require assays not affected by emicizumab.
Breakthrough bleeding management with bypassing agents must follow specialist haemophilia centre guidance because of the altered bleeding risk.

Monitoring

Monitor clinically for bleeding and thrombotic events, and use only coagulation assays validated for use during emicizumab therapy.

Counselling the patient

Tell any treating clinician you are on emicizumab so that standard clotting tests are interpreted correctly.
Report signs of a clot or unusual bruising or bleeding to your haemophilia centre.

Evidence & guidelines

Emicizumab prophylaxis in haemophilia A is supported by the HAVEN trial programme and recommended by NICE.

Reference: NICE TA577; NICE TA585; UKHCDO; BSH; SmPC; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Curated clinical cross-links plus same-class fallbacks.

Calculators

Pathways