Caplacizumab for Acute Thrombotic Thrombocytopenic Purpura

Acute thrombotic thrombocytopenic purpura (aTTP) is a rare microangiopathic hemolytic anemia. Standard of care currently includes plasma exchange and immunosuppressive agents, including glucocorticoids, vincristine, and rituximab. Even with these therapies, relapse occurs in 36% of patients, and mortality ranges from 10% to 20%. Caplacizumab is a novel agent approved for the treatment of adult patients with aTTP in conjunction with plasma exchange and immunosuppressive therapies. It works by binding to the A1 domain of von Willebrand factor (VWF), blocking platelets from binding to VWF and aggregating. In clinical trials, patients who received caplacizumab compared with placebo were more likely to have a normalization of their platelet count, a lower rate of recurrence, and a lower incidence of the composite of aTTP-related death, recurrence, or major thromboembolic event. The side effect profile is rather benign and includes epistaxis, headache, and gingival bleeding. Caplacizumab is only available through specialty pharmacy services due to its high cost. Providers should be aware of and prepared for the prior authorization process required to assist their patients in gaining access to the medication. Currently, there is no formal consensus regarding caplacizumab's place in therapy for patients with aTTP, but it remains an option for refractory cases.