Treatment and Outcomes Associated With Caplacizumab in the Management of Acquired Thrombotic Thrombocytopenic Purpura

Presenting Authors: Justin R. Arnall, PharmD, BCOP, Atrium Health Specialty Pharmacy Service, Charlotte, NC; Donald C. Moore, PharmD, BCPS, BCOP, DPLA, FCCP (Senior Author), Atrium Health Levine Cancer Institute, Charlotte, NC

Co-Authors: Thuy Tran, PharmD, BCOP, CSP, Atrium Health Specialty Pharmacy Service, Charlotte, NC; Nuti Desai, PharmD, WakeMed Cancer Care, Raleigh, NC

BACKGROUND: Despite standard-of-care treatments, mortality rates for acquired thrombotic thrombocytopenic purpura (aTTP) of as high as 20% continue to be reported, identifying a need for improved treatment strategies. Caplacizumab, a humanized monoclonal antibody that targets von Willebrand factor, has shown faster platelet normalization and lower aTTP recurrence rates. Despite its approval based on phase 3 clinical trial results, many questions remain regarding the practical applicability and clinical value of caplacizumab.

OBJECTIVES: The primary objective of this study was to compare aTTP exacerbation or refractory disease between patients with aTTP who received caplacizumab versus those who did not. The secondary objectives include exacerbation, relapse, refractory aTTP, time to platelet normalization, time to recurrence, duration of therapeutic plasma exchange (PEX), and duration of hospitalization.

METHODS: A single-center, retrospective chart review was conducted to evaluate the effectiveness of caplacizumab in patients diagnosed with aTTP between January 1, 2012, and October 31, 2021. Patients meeting the inclusion criteria were stratified by exposure to caplacizumab (largely before and after the drug’s market approval). Patient, disease, and treatment characteristics were analyzed via descriptive statistics. Categorical and continuous outcomes were analyzed using Fisher’s exact test and Wilcoxon rank-sum test, respectively. All statistical tests were 2-sided, and P<.05 was considered statistically significant.

RESULTS: A total of 48 patients (n=16 caplacizumab, n=32 non-caplacizumab) were included in this study. The caplacizumab group was more likely to be African American (75% vs 21%, respectively) and receive rituximab (93.4% vs 34.4%, respectively) compared with the non-caplacizumab group. Other characteristics were similar between the groups. Although not statistically significant, patients in the caplacizumab group were less likely to have aTTP exacerbation or refractory disease compared with the non-caplacizumab group (6% vs 22%, respectively; P=.24). The caplacizumab group had a similar safety profile to the non-caplacizumab group, including all-cause mortality (6% vs 22%, respectively; P=.24). One major bleeding event was reported among the patients who received caplacizumab (not requiring factor support).

CONCLUSION: The study’s findings were consistent with the results reported in previous clinical trials. Based on our findings and previous literature, patients with aTTP may see benefit in the initiation of caplacizumab. We identified a trend in effectiveness outcomes that may suggest a clinical benefit with the addition of caplacizumab. A similar duration of hospitalization between the caplacizumab and non-caplacizumab groups (14 days vs 12 days, respectively) is likely accounted for by the institutional standard of care to taper PEX. These data may be useful in continuing to optimize the role of caplacizumab in the management of aTTP.

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