(066) Efficacy and Safety of Caplacizumab for the Treatment of Acquired Thrombotic Thrombocytopenic Purpura

Poster Abstract:

Background: Caplacizumab is a von Willebrand factor-directed monoclonal antibody fragment approved for the treatment of patients with acquired thrombotic thrombocytopenic purpura (aTTP). The addition of caplacizumab to standard of care treatment has been associated with improved time to normalization of platelet count and clinical outcomes. In January 2020, caplacizumab was added to standard of care therapy for all aTTP patients treated at our institution.

Objective: The objective of this study is to assess the efficacy and safety of caplacizumab with standard therapy compared to standard therapy alone in patients with aTTP.

Methods: This is a single-center, retrospective study of patients with aTTP admitted from August 2016 to March 2023. Individual patients could contribute to multiple encounters if they had separate admissions for treatment of aTTP. Electronic health records were used to collect patient baseline characteristics, aTTP treatment history, and clinical outcomes over 12 months. The primary outcome is time to platelet normalization. Secondary outcomes include composite endpoint of thromboembolic events, one-year mortality, and aTTP exacerbation, mortality, thromboembolic events, bleeding events, intensive care unit and overall lengths of stay, number of plasma exchange sessions, rates of remission, exacerbation, and time to relapse.

Results: A total of 103 patient encounters were included in the analysis, 74 (71.8%) received standard therapy alone and 29 (28.2%) received caplacizumab in combination with standard therapy. There was no difference in time to platelet normalization (median 3.3 days vs. 2.7 days, p=0.22). The composite endpoint of thromboembolic events, mortality, and exacerbation was significantly reduced in the patients treated with caplacizumab (24.1% vs. 54.1%, p=0.006). Moreover, caplacizumab was associated with a significantly reduced rate of exacerbation compared to standard of care alone (13.8% vs. 37.8%, p=0.02). There was no difference in bleeding events between caplacizumab and standard of care (20.7% vs. 16.2%, p=0.58). No difference was observed for all other outcomes.

Discussion/

Conclusions: This study did not demonstrate a difference in time to platelet normalization from the addition of caplacizumab to standard of care treatment for treatment of aTTP. However, patients with aTTP treated with caplacizumab experienced substantially reduced incidence of composite efficacy outcomes and aTTP exacerbation alone. Overall, results indicate the need for further investigation into the use of caplacizumab for treatment of aTTP.

References (must also be included in final poster): Scully M, Cataland SR, Peyvandi F, et al. Caplacizumab Treatment for Acquired Thrombotic Thrombocytopenic Purpura. N Engl J Med. 2019;380(4):335-346.