Researchers conducted the first study of the use of caplacizumab for thrombotic thrombocytopenic purpura (TTP) outside of a clinical trial setting in a retrospective analysis, the results of which are published in Blood.
Caplacizumab, an anti-von Willebrand factor-based therapy, has been approved in recent years for treatment of immune-mediated TTP in the United States and the European Union.
The study was based on data obtained from 2018 to 2020 from 22 hospitals across the United Kingdom (UK) included in the UK TTP Registry. A total of 85 patients with TTP were evaluated for baseline characteristics and treatment outcomes with caplacizumab. Outcomes of interest were based on endpoints from the phase 3 HERCULES clinical trial (ClinicalTrials.gov Identifier: NCT02553317) and compared with historical data from prior to the availability of caplacizumab.
All patients presented with ADAMTS13 activity level less than 20 IU/dL, and all but 1 had a level less than 10 IU/dL. The baseline median platelet count was 13 × 109/L. All patients received caplacizumab, and nearly all (n=84) were additionally treated with rituximab and glucocorticoid therapy; 26% required intubation.
The median time to administration of caplacizumab after beginning plasma exchange was 2 days (interquartile range [IQR], 1-3). The median follow-up time in this analysis was 80 days (IQR, 59-166).
Platelet normalization occurred in 95% of patients given caplacizumab, compared with 100% of patients from the historical cohort (P =.31). Platelet normalization with caplacizumab occurred at a median of 4 days (IQR, 3-8) after the first plasma exchange, compared with 6 days (IQR, 4-10) from historical data (P =.011).
Plasma exchange was given for a median of 7 days with caplacizumab, compared with 9 days from historical data (P =.007). Median hospital stays were 12 days with caplacizumab and 14 days in the historical data cohort (P =.62).
A total of 31 adverse events were reported in 26 patients with caplacizumab. Slightly more than half (55%) of these events were bleeding episodes, 16% were thrombotic events, and 6% of patients died from causes deemed related to TTP and unrelated to caplacizumab therapy.
The researchers reported that outcomes from this study were comparable to data from the HERCULES clinical trial, although a post-hoc analysis of HERCULES showed a lower rate of thromboembolic events. Median plasma exchange duration was also slightly longer in this real-world study than the 5.8 days seen with the HERCULES study.
“This real-world evidence from the largest series of TTP patients receiving caplacizumab, outside of the pivotal studies, provides confirmation of the therapeutic benefits of caplacizumab and its inherent bleeding risk,” concluded the researchers in their report.
Disclosures: Some authors have declared affiliations with or received grant support from the pharmaceutical industry. Please refer to the original study for a full list of disclosures.
Dutt T, Shaw R, Stubbs M, et al. Real-world evidence of caplacizumab use in the management of acute TTP. Blood. Published online November 4, 2020. doi:10.1182/blood.2020007599