Caplacizumab 💊
🩸 Caplacizumab is used in acute acquired thrombotic thrombocytopenic purpura (aTTP) in combination with plasma exchange and immunosuppression.
⚠️ Always check the BNF for the latest prescribing information before initiation.
🧬 Mode of Action
- Caplacizumab is a humanised single-variable-domain antibody fragment (nanobody).
- Binds to the A1 domain of von Willebrand factor (vWF).
- Prevents interaction between vWF multimers and platelets.
- Reduces formation of platelet-rich microthrombi in small vessels.
In aTTP, severe ADAMTS13 deficiency leads to ultra-large vWF multimers causing widespread microvascular thrombosis. Caplacizumab directly interrupts this pathway while immunosuppression treats the underlying autoimmune process.
📌 Indication
- Acute acquired thrombotic thrombocytopenic purpura (aTTP)
- Used alongside:
- Daily plasma exchange (PEX)
- Corticosteroids
- Often rituximab
💉 Dose & Administration
Always confirm dosing in the BNF or product literature.
| Drug |
Initial Dose |
Ongoing Dose |
Route |
| Caplacizumab |
10 mg IV bolus prior to first plasma exchange |
10 mg subcutaneously daily after each plasma exchange, continued for 30 days after stopping PEX (extend if persistent ADAMTS13 deficiency) |
IV then SC |
⚠️ Monitoring
- Platelet count (daily during acute phase)
- ADAMTS13 activity (where available)
- Signs of bleeding
- Renal and neurological status (disease monitoring)
🔁 Interactions
- Increased bleeding risk with:
- Anticoagulants
- Antiplatelets
- Thrombolytics
⚠️ Contraindications
- Active clinically significant bleeding
- Hypersensitivity to the drug or excipients
🩺 Cautions
- Recent surgery
- High bleeding risk
- Severe hepatic impairment
- Careful perioperative planning (withhold prior to elective surgery)
💥 Adverse Effects
- Epistaxis and mucosal bleeding (common)
- Gingival bleeding
- Injection site reactions
- Headache
- Rare but serious bleeding events
📖 NICE Guidance
🧠 Clinical Pearls
- aTTP is a haematological emergency — start plasma exchange immediately if suspected.
- Caplacizumab reduces time to platelet normalisation and lowers relapse risk.
- It does not treat the underlying autoimmunity — immunosuppression remains essential.
- Bleeding risk must be balanced against thrombotic risk.
📝 Revisions
- Updated to reflect NICE TA667 indication (aTTP only).
- Corrected previous incorrect asthma indication.
