Caplacizumab appears to be safe and effective among patients with acquired thrombotic thrombocytopenic purpura (aTTP) treated in the real-world setting, according to a study published in Blood Advances.

aTTP, which is characterized by acute onset microangiopathic hemolytic anemia with profound thrombocytopenia, can be fatal in up to 90% of cases when left untreated. The standard treatments, including immunosuppressive drugs and plasma exchange (PEX), do not consistently yield optimal outcomes, indicating a need for novel treatment options.

Caplacizumab, a novel nanobody that inhibits von Willebrand factor (VWF)–platelet aggregation, was compared with placebo plus PEX in 2 clinical trials. One trial (HERCULES; Identifier: NCT02553317), which gave the option to maintain experimental treatment for more than 30 days after PEX, showed positive outcomes, leading to treatment approval in Germany in 2018.

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Because real-world evidence is necessary to determine whether a novel therapy is likely to be effective in the wider population, researchers conducted a retrospective study to evaluate the settings in which caplacizumab is used, as well as the outcomes yielded.

Data from 60 patients were included in this study and results were compared to those of the HERCULES trial, which included 145 patients. The mean age was 45.7 years (range, 22-83), 70% of patients were women, 98.3% of patients were White, and the median body mass index was 27. Forty-eight (80%) patients received rituximab, compared with 63 of the 145 (43%) patients included in the HERCULES trial leading to drug approval (P <.0001); the mean number of days of PEX treatment was 11.8, and the mean number of days of both PEX and caplacizumab treatment was 5.3.

The median follow-up was 108.5 days. Fifty-six patients (93.3%) had clinical response, 2 (3.3%) did not, and 2 (3.3%) had insufficient follow-up. The majority of patients (57; 95%) reached final platelet normalization within the follow-up period with a median time to normalization after diagnosis of 12 days.

While 2 patients did not receive PEX treatment, their platelets normalized within 3 and 4 days, respectively, of initiating treatment, suggesting that, in some cases, PEX is not necessary.

One patient died of aTTP-related complications.

“This real-word evidence allows us to generalize the effectiveness of caplacizumab to treat acute episodes of aTTP beyond the internal validity of randomized trials,” the authors wrote.  


Völker LA, Kaufeld J, Miesbach W, et al. Real-world data confirm the effectiveness of caplacizumab in acquired thrombotic thrombocytopenic purpura. Blood Adv. 2020;4(13):3085-3092.