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The benefits of caplacizumab in acute immune mediated TTP (iTTP) are well established. We identified a delay in normalisation of ADAMTS13 activity (>30%) in a subgroup of caplacizumab treated patients which was not evident in the pre-caplacizumab era. Caplacizumab treated patients (n=64) achieved ADAMTS13 activity >30% at median 31 days post PEX, compared to 11.5 days in the non-caplacizumab group (n=50, p=0.0004). 18/64 (28%) caplacizumab treated patients had an ADAMTS13 activity 30% (median 139 days after completing PEX). 18/64 (28%) of patients receiving extended caplacizumab (31-58 days) failed to achieve ADAMTS13 activity >30% at time of stopping caplacizumab compared to 4/47 (8.5%) of historical controls at similar timepoint (30+28 days, p30% within 30+28 days was 6 times more likely in caplacizumab treated patients (OR 6.3, p=0.0006). ADAMTS13 antigen level

Rituximab, an anti-CD20 monoclonal antibody, can be used to treat immune thrombotic thrombocytopenic purpura (iTTP) during acute presentation or disease relapse. Undesirable side-effects include severe hypersensitivity reactions, particularly anaphylaxis and rituximab-induced serum sickness, with a minority not maintaining a response to treatment. Alternative humanised anti-CD20 treatments, obinutuzumab and ofatumumab, have been used. A review of the UK TTP Registry showed 15 patients received these drugs over 26 treatment episodes (eight obinutuzumab and 18 ofatumumab). Indications for alternative anti-CD20 treatment were severe infusion-related reactions, acute rituximab-induced serum sickness and a short duration of disease remission. All patients achieved disease remission (ADAMTS13 [A disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13] activity ≥30 iu/dl) after a median 15 days and 92% of episodes achieved complete remission (≥60 iu/dl). Seven patients required further treatment for disease relapse with a median relapse-free survival of 17.4 months. All patients continued to respond to re-treatment with the preceding drug when relapse occurred. There were four adverse events in 26 treatment episodes (15%) - two infections and two infusion reactions. These results suggest that obinutuzumab and ofatumumab may be considered as an alternative option to rituximab in the treatment of iTTP with a comparable safety profile, absence of significant hypersensitivity reactions and sustained normalisation of ADAMTS13.

Post-COVID syndrome (PCS), or long COVID, is an increasingly recognized complication of acute SARS-CoV-2 infection, characterized by persistent fatigue, reduced exercise tolerance, chest pain, shortness of breath, and cognitive slowing. Acute COVID-19 is strongly linked with an increased risk of thrombosis, which is a prothrombotic state quantified by an elevated von Willebrand factor (VWF) antigen (Ag)/ADAMTS13 ratio that is associated with severity of acute COVID-19 infection. We investigated whether patients with PCS also had evidence of a prothrombotic state associated with symptom severity. In a large cohort of patients referred to a dedicated post-COVID-19 clinic, thrombotic risk, including VWF(Ag)/ADAMTS13 ratio, was investigated. An elevated VWF(Ag)/ADAMTS13 ratio (≥1.5) was present in nearly one-third of the cohort and was 4 times more likely to be present in patients with impaired exercise capacity, as evidenced by desaturation ≥3% and/or an increase in lactate level >1 from baseline on a 1-minute sit-to-stand test and/or a 6-minute walk test (P < .0001). Of 276 patients, 56 (20%) had impaired exercise capacity, of which 55% (31/56) had a VWF(Ag)/ADAMTS13 ratio ≥1.5 (P < .0001). Factor VIII and VWF(Ag) were elevated in 26% and 18%, respectively, and support a hypercoagulable state in some patients with PCS. These findings suggest possible ongoing microvascular/endothelial dysfunction in the pathogenesis of PCS and suggest a role for antithrombotic therapy in the treatment of these patients.

Intravenous immunoglobulin (IVIg) is a common therapy for patients with immune thrombocytopenia (ITP). The initial response rate for IVIg is 80%[1][1] and is typically rapid, with some patients responding in 24 hours, although usually in 2–4 days.[2][2] When IVIg is used alone, the response is