Initial US tertiary health care system experience using caplacizumab in patients with immune thrombotic thrombocytopenic purpura

Several international registries have reported on the efficacy of caplacizumab for the treatment of immune thrombotic thrombocytopenic purpura (iTTP). Similar real-world data from the United States (US) are limited. In this single center retrospective study, we sought to describe caplacizumab prescribing patterns and review clinical outcomes for US patients with iTTP. Subjects were eligible for inclusion if they were diagnosed with acute iTTP and received care at University of Pittsburgh Medical Center-affiliated hospitals from 2012 to 2022. Subjects were divided into an historical cohort who received standard of care therapy alone, and early and late administration cohorts (EA and LA) who received caplacizumab within and greater than 72 h of admission, respectively, plus standard of care. Clinical data were collected from the electronic record. Thirty-two subjects were included: 16 historical, 12 EA, and 4 LA subjects. Refractoriness occurred more frequently in the LA and historical cohorts as compared to the EA cohort (4 (100%) vs. 6 (38%) vs. 3 (25%), p = 0.02). The LA cohort also experienced longer lengths of hospital stay, required more TPE procedures, and were exposed to the greatest amount of donor plasma (p < 0.05 for all) as compared to the other cohorts. Time to platelet count normalization was longest in the LA cohort (p = 0.013). There were no significant between-group differences in bleeding events. Because we are unable to predict which patients will develop refractoriness, we recommend frontline administration of caplacizumab to all patients with iTTP.