The anti-von Willebrand factor nanobody caplacizumab was licensed for adults with immune-mediated thrombotic thrombocytopenic purpura (iTTP) based on prospective controlled trials. However, few data are available on post-marketing surveillance. We treated 90 iTTP patients with a compassionate frontline "triplet regimen" associating therapeutic plasma exchange (TPE), immunosuppression with corticosteroids and rituximab, and caplacizumab. Outcomes were compared to 180 historical patients treated with the standard frontline treatment (TPE and corticosteroids, with rituximab as salvage therapy). The primary outcome was a composite of refractoriness and death within 30 days since diagnosis. Key secondary outcomes were exacerbations, time to platelet count recovery, the number of TPE and the volume of plasma required to achieve durable remission. The percentage of patients in the triplet regimen with the composite primary outcome was 2.2% vs. 12.2% in historical patients (p=0.01). One elderly patient in the triplet regimen died of pulmonary embolism. Patients from this cohort experienced less exacerbations (3.4% vs. 44%, p<0.01); they recovered durable platelet count 1.8 times faster than historical patients (95% confidence interval, 1.41-2.36, p<0.01), with fewer TPE sessions and lower plasma volumes (p<0.01 both). The number of days in hospital was 41% lower in the triplet regimen than in the historical cohort (13 days vs. 22 days, p <0.01). Caplacizumab-related adverse events occurred in 46 patients (51%), including 13 major or clinically relevant non-major hemorrhagic events. Associating caplacizumab to TPE and immunosuppression, by addressing the three processes of iTTP pathophysiology, prevents unfavorable outcomes and alleviates the burden of care.
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