Caplacizumab

Caplacizumab is a humanized single-domain antibody (nanobody) that targets von Willebrand factor (VWF) and is used in the treatment of acquired thrombotic thrombocytopenic purpura (aTTP). It works by binding the A1 domain of VWF, inhibiting the interaction between ultra-large VWF multimers and platelets, which reduces the formation of microthrombi in small blood vessels. Caplacizumab is intended to be used in combination with plasma exchange and immunosuppressive therapy to accelerate platelet count recovery and reduce the risk of TTP-related organ damage.

Indications and administration vary by region, but the approved use is for adults with acquired TTP in addition to plasma exchange and immunosuppressive therapy. The typical dosing regimen starts with a 10 mg intravenous loading dose before the first plasma exchange, followed by 10 mg administered subcutaneously once daily during the plasma exchange period and for 30 days after the last plasma exchange. Treatment duration may be adjusted based on clinical response and bleeding risk. Caplacizumab is not indicated for inherited TTP due to ADAMTS13 deficiency.

Adverse effects are mainly related to its anti-platelet mechanism and include bleeding, such as epistaxis and other mucocutaneous bleeding, as well as headaches and injection-site reactions. Because the drug can increase bleeding risk, it is used with caution in patients with active or high-risk bleeding and may interact with other anticoagulant or antiplatelet therapies. Caplacizumab was developed by Ablynx and is marketed as Cablivi; regulatory approvals have been granted in multiple regions, with labeling emphasizing its role as an adjunct to plasma exchange and immunosuppression in adults with acquired TTP.