Effect of Caplacizumab in the Recovery of ADAMTS13 Level in Patients with Autoimmune Thrombotic Thrombocytopenic Purpura. Analysis from the Spanish Registry (REPTT)

INTRODUCTION Treatment of immune thrombotic thrombocytopenic purpura (iTTP) includes plasma exchanges (PEX) and immunosuppressive treatment with steroids with or without rituximab (RTX). Actually, caplacizumab (CPZ) has been included in this scheme of treatment, because of its effect in decreasing clinical response time, exacerbations and refractoriness. A longer time to recovery of ADAMTS13 levels has recently been described in a group of patients from United Kingdom in subjects treated with caplacizumab. We analysed the behaviour of ADAMTS13 recovery in patients from the Spanish TTP registry (REPTT). METHODS Retrospective, multicentre, non-interventional study. Data collected by the Spanish PTT Registry (REPTT) from September-2018 to February-23. The objective is to describe the efficacy of standard therapy with and without CPZ with regard to recovery of ADAMTS13 levels higher than 20%. Episodes evaluable for ADAMTS13 >20% recovery were those with data available 48 hours or more after last PEX. Data about clinical response, clinical remission, exacerbations and relapses will be described. Qualitative variables described in percentages, quantitative in median and interquartile range (IQR). RESULTS We included 178 patients from REPTT, but only 164 were analysed. Reasons for exclusion were 5 were congenital TTP, 3 patients were younger than 16 years-old, and 6 patients because of lack of data. The 164 patients presented 172 episodes whose characteristics are described in Table 1. Clinical remission rate did not differ between groups, 95% CPZ vs 97% no CPZ, with a median time of 41 days (36-50) vs 43 days (38-50), respectively. A median of 11 PEX (IQR:6-20) were required to get clinical remission, lower in CPZ group (CPZ 10 PEX, IQR:5-18 vs no CPZ 12 PEX, IQR: 7-23, p=0.044). In 49 of the 103 CPZ episodes, CPZ was introduce in the 3 first days from diagnosis (CPZ3). In this group, number of PEX was critically reduced (CPZ 6 PEX, IQR: 4-9 vs no CPZ 12 PEX, IQR: 7-23; p