Real-world data for caplacizumab outcomes matched those seen in randomized controlled trials (RCTs) for the treatment of immune-mediated thrombotic thrombocytopenic purpura (iTTP), according to the results of a retrospective study.
Data collected from 2018 to 2020 were assessed for 85 patients (4 of them children) receiving caplacizumab at 22 United Kingdom hospitals, according to a report published online in Blood.
Researchers Tina Dutt, PhD, from the Liverpool (England) University Hospitals NHS Foundation Trust, and her colleagues compared patient characteristics and outcomes in these real-world clinical settings to those of caplacizumab trial endpoint results and to historical outcomes in the precaplacizumab era.
Acquired thrombotic thrombocytopenic purpura is an immune-mediated deficiency of the von Willebrand factor–cleaving protease (ADAMTS13), which allows unrestrained adhesion of von Willebrand factor multimers to platelets, leading to thrombocytopenia, hemolytic anemia, and tissue ischemia.
Standard management of iTTP has focused on the replacement of ADAMTS13 and the removal of autoantibodies using plasma exchange and immunosuppression, an approach which has reduced the mortality of acute TTP from greater than 90% to between 10% and 20%, according to the report.
Caplacizumab is a novel anti–von Willebrand factor immunoglobulin fragment that inhibits this interaction between von Willebrand factor multimers and platelets and is now added to the standard treatment regimen. The drug has been assessed in two pivotal multicenter RCTs that led to European Union and U.S. Food and Drug Administration approval.
Benefits and risk
Eighty-four of 85 patients received steroid and rituximab as well as plasma exchange along with caplacizumab treatment. All patients had ADAMTS13 activity at presentation less than 20 IU/dL, with 99% of patients (84/85) having ADAMTS13 activity less than 10 IU/dL, confirming a clinical diagnosis of acute TTP, according to the researchers.
The median time to platelet count normalization (3 days), the median duration of plasma exchange (7 days), and the median hospital stay (12 days) were all comparable with the RCT data, according to the researchers. In addition, the median duration of plasma exchange and time from beginning plasma exchange to platelet count normalization were favorable, compared with historical outcomes (P < .05).
TTP recurred in 5 of the 85 patients, all of whom had persistent ADAMTS13 activity less than 5 IU/dL.
There were 31 adverse events reported in 26 patients, 17 of these (55%) were bleeding episodes, and 5 of 31 (16%) were thrombotic events (2 unrelated to caplacizumab). The overall mortality was 6% (five patients), with no deaths attributed to caplacizumab. In four of the five deaths, caplacizumab was introduced more than 48 hours after plasma exchange initiation (range 3-21 days).
“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,” the researchers concluded.
Dr. Dutt and several of her colleagues reported receiving honoraria from Sanofi for serving on advisory boards, as well as speaker fees from Sanofi and Alexion.