Awareness of the spectrum of clinical disease, autoantibody profiles and tests required to confirm the diagnosis of C1q deficiency are important if this life-threatening immunodeficiency disease is to be managed correctly.

Summary Immune thrombotic thrombocytopenic purpura (iTTP) is an acute, multisystem thrombotic microangiopathy mediated by ADAMTS13 (a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13) autoantibodies. Immunosuppression with anti‐CD20 therapy is the mainstay of treatment. MabThera's patent has now expired and biosimilars have been approved. Eighty‐four consecutive patient episodes over 2 years, prior to and following our switch to Truxima are presented. Day 1 (D1), Day 28 (D28) and 3‐month platelet counts, ADAMTS13 activity, and CD19 levels, adverse reactions and infective complications were recorded. Platelet counts were not significantly different between acute MabThera and Truxima treatment (D1 P = 0.085, D28 P = 0.77, 3 months P = 0.71) and electively (D1 P = 0.79, D28 P = 0.68, 3 months P = 0.99). ADAMTS13 recovery also was not significantly different acutely (D1 P = 0.99, D28 P = 0.27, 3 months P = 0.26) and electively (D1 P = 0.59, D28 P = 0.61, 3 months P = 0.34). CD19% depletion at D1 and 3 months was not significantly different acutely (D1 P = 0.52, 3 months P = 0.56) and electively (D1 P = 0.22, 3 months P = 0.19). Infusion reactions and infective complications were comparable with both therapies. This is the first series of the Rituximab biosimilar Truxima to be reported in iTTP, demonstrating equivalence to MabThera in terms of ADAMTS13 recovery, CD19 depletion, and platelet count at D28 and 3 months post‐administration, with comparable infusion and infective complications. The financial benefit of the biosimilar anti‐CD20 is considerable.

ObjectivesPrimary immune thrombocytopenia (ITP) is a bleeding disorder characterised by an isolated thrombocytopenia in the absence of an alternative diagnosis. The condition is highly heterogeneous with some patients requiring multiple of therapy before achieving response. In this study, we collected data on a large cohort of primary ITP patients with the objective of identifying variables which may predict treatment requirements.MethodsWe collected data on 379 patients, 275 with a confirmed diagnosis of primary ITP included demographics, baseline laboratory results and treatments. These were compared against treatment responses and lines of therapy.ResultsPatients who presented with a platelet count of <30 × 109/L or bleeding symptoms were observed to require more subsequent lines of therapy (P‐value <0.001). 32% of patients (n = 87) received no treatment, and these patients had a significantly higher median count compared to those with required >2 lines of therapy (P‐value <0.001). Superior response rates were demonstrated with thrombopoietin receptor agonists when compared with other agents irrespective of baseline characteristics.ConclusionsPlatelet counts at diagnosis are a potentially strong predictive indicator of subsequent lines of therapy. Patients with bleeding symptoms at diagnosis were more likely to have lower median platelets counts.

INTRODUCTION Immune thrombotic thrombocytopenic purpura (iTTP) is an acute, multisystem thrombotic microangiopathy mediated by immunoglobulin G (IgG) antibodies. These antibodies target the metalloprotease ADAMTS13 (a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13), which is vital for cleavage of von Willebrand factor. The resulting ADAMTS13 deficiency leads to microthrombi through platelet aggregation to Ultra-Large von Willebrand factor. If untreated the mortality rate in iTTP is in excess of 90%, but the use of plasma exchange (PEX) and immunosuppression has significantly reduced this (to between 10%-20%). Rituximab (a humanised anti-CD20 antibody, MabThera; Roche Pharmaceuticals), is now used routinely in iTTP in relapsed/refractory patients, but also acutely to prolong disease free-survival. The pre-emptive administration of rituximab in patients with a low ADAMTS13 has been shown to be effective in preventing clinical relapse. In 2013 the patent for rituximab expired in Europe and will expire in 2018 in the United States. The European Medicine Agency has now approved two Rituximab biosimilars for use in Europe. Biosimilar products are designed to have no meaningful differences from the reference/originator product. Truxima (CT-P10, a rituximab biosimilar) is approved for the treatment of RA, CLL and NHL in Europe, and we began using Truxima in iTTP in May 2017. Many other rituximab biosimilars exist and are in development. METHODOLOGY Here we report a retrospective cohort study of our patients with iTTP. Data from 84 patients was examined from a two-year time period May 2016-and May 2018, based on our pharmacy registry (having switched to the rituximab biosimilar in May 2017). 45 patients were treated with MabThera and 39 with the rituximab biosimilar Truxima. Laboratory parameters recorded included the patient's platelet counts, ADAMTS13 activity, and CD19 levels at D1, D28 and 3months following treatment. In addition, adverse reactions, and infective complications following treatment were also recorded. Statistical analysis was performed and means +/- 90% confidence interval calculated, with clinical equivalency compared based on clinically significant values. RESULTS Following MabThera/Truxima administration on D1, at 28 days the mean platelet count (+/- SEM, x10^9/L) was 263.3 (+/-10.69) in patient treated with MabThera and 263.8 (+/-11.81) with Truxima (90% CI -24.95 to 27.91), and remained similar at 3months at 275.8 (+/- 10.05) and 275.9 (+/- 12.2) respectively (90% CI -25.96 to 26.2). The ADAMTS13 (+/- SEM) at 28 days was 50.87 iu/dL (+/-4.899) in patients treated with MabThera and 50.88 iu/dL (+/- 4.371) for Truxima (90% CI 11.01-11.03), rising to 85.4 iu/dL (+/- 5.237) and 81.35 iu/dL (+/- 4.549) respectively at 3 months (90% CI 15.84-7.71). CD19 levels at 28 days in patients treated with MabThera had fallen to 0.00259 (x10^9/L)(+/- 0.00049) and 0.02151 (+/- 001161) with Truxima (90% CI 0.00073 to 0.037120), and were 0.01782 (+/- 0.01033) and 0.02098 (+/- 0.01042) respectively at 3 months (90% CI -0.02139 to 0.02771), all demonstrating a marked reduction from baseline means of 0.3247(+/-0.05721) and 0.2456 (+/-0.03016) respectively. The median number of infusions in both groups was 4 (range 1-8). Infusion reactions were comparable between both groups, with infusion reactions occurring in 33% of the MabThera treated patients, and 40% in the Truxima group. Infective complications (principally urinary tract infections) were comparable between both groups, 15% in the MabThera group and 18% in the truxima cohort. The mean saving per patient per treatment course cost was >£4000. DISCUSSION Rituximab is now off patent in Europe, and the EMA approval of Biosimilars offers an opportunity for significant cost savings as demonstrated here. Rituximab has been well established in iTTP, and rituximab biosimilars have demonstrated equivalence to the originator in rheumatoid arthritis and follicular lymphoma. Here we report the first published series of the rituximab biosimilar Truxima in iTTP, and demonstrate equivalence in terms of ADAMTS13 recovery, CD19 depletion, and platelet count at 28days and 3 months post administration, in addition to showing comparable infusion and infective complications. Disclosures Cheesman: Celltrion: Other: Speaker Fee; Roche: Other: Advisory board. Scully:Novartis: Honoraria, Other: Member of Advisory Board, Speakers Bureau.