ADAMTS13 RECOVERY IN ACUTE THROMBOTIC THROMBOCYTOPENIC PURPURA AFTER CAPLACIZUMAB THERAPY. THE SPANISH REGISTRY

• There is no delay in ADAMTS13 recovery after PEX start in caplacizumab-treated iTTP patients from the Spanish registry.

• Caplacizumab allows suspending PEX earlier, thus creating the impression that there is a delay in ADAMTS13 recovery after PEX end.

Caplacizumab prevents the interaction between von Willebrand factor and platelets, and is used to treat immune thrombotic thrombocytopenic purpura (iTTP). Its administration has been associated with a delay in ADAMTS13 activity restoration after plasma exchange (PEX) suspension. We analyzed the outcomes of 113 iTTP episodes, 75 of which were treated with caplacizumab, in 108 patients from the Spanish Registry of Thrombotic Thrombocytopenic Purpura. Caplacizumab shortened the time to platelet count normalization and reduced PEX requirement, exacerbations and relapses. There was no difference in the time to achieve ADAMTS13 activity ≥20% after PEX end between caplacizumab-treated and non-treated episodes (14.5 [7.7-27.2] vs. 13.0 [8.0-29.0] days, median [IQR], P=.653). However, considering the 36 episodes where caplacizumab started <=3 days after iTTP diagnosis, the time to ADAMTS13 restoration from PEX end was higher than in those episodes where caplacizumab started >3 days after iTTP diagnosis (20.0 [12.0-43.0] vs. 11.0 [3.5-20.0] days, P = .003), or than in non-caplacizumab-treated episodes (P=.033). This finding could be related to a significantly shorter duration of PEX in early caplacizumab-treated episodes than in late caplacizumab-treated episodes (5.5 [4.0-9.0] vs. 15.0 [11.0-21.5] days, P <.001) or non-caplacizumab-treated episodes (11.0 [6.0-26.0] days, P < .001). There were no differences in time to ADAMTS-13 restoration from PEX start (28.0 [17.2-47.5], 27.0 [19.0-37.5] and 29.5 [15.2-45.0] days in early caplacizumab-treated, late caplacizumab-treated and non-caplacizumab-treated episodes). Early administered caplacizumab does not prevent the requirement for immunosuppression but has beneficial effects by shortening PEX requirement without major safety concerns.