Acquired thrombotic thrombocytopenic purpura (TTP) is the deficiency of von Willebrand factor–cleaving protease ADAMTS13 and is characterized by low platelets and red blood cell count. Caplacizumab is a bivalent single-domain antibody and anti–von Willebrand factor designed to treat thrombotic thrombocytopenic purpura and thrombosis. This study aims to investigate the efficacy of caplacizumab in the treatment of acute TTP.

This double-blind, controlled trial included a total of 145 patients with TTP. The patients were randomized to receive caplacizumab or placebo during plasma exchange and for 30 days thereafter. The primary endpoint of the study was the time to normalization of platelet count, along with the discontinuation of daily plasma exchange. Treatment-related adverse events were also considered.

The findings suggested that the median time to normalization of platelet count was shorter with caplacizumab than with a placebo. Patients assigned to caplacizumab exhibited 1.55-fold normalization of the platelet count, as compared to those who received placebo. The prevalence of patients with a composite outcome event was 74% lower in the caplacizumab than in the placebo group. Treatment-related adverse events (mucocutaneous bleeding) occurred in 65% of the patients in the caplacizumab group and 48% of those in the placebo group.

The research concluded that caplacizumab resulted in faster normalization of platelet count than placebo, but it was also associated with a higher risk of mucocutaneous bleeding.