More about low-dose rituximab and plasma exchange as front-line therapy for patients with thrombotic thrombocytopenic purpura

ADAMTS13 in the New Era of TTP

Thrombotic thrombocytopenic purpura (TTP) is a life-threatening, often immune-mediated disease that affects 2-13 persons per million per year. Hemolytic anemia, thrombocytopenia, and end-organ damage due to the formation of microthrombi are characteristic of TTP. ADAMTS13 is a disintegrin, metalloproteinase, cleaving protein of von Willebrand factor (VWF) that processes the VWF multimers to prevent them from interacting with platelets and, in turn, to microvascular thrombosis. Prompt diagnosis of TTP is critical yet challenging. Thrombotic microangiopathies have similar clinical presentation. Measurement of ADAMTS13 activity helps in the differential diagnosis. Less than 10% ADAMTS13 activity is indicative of TTP. Laboratory ADAMTS13 activity assays include incubating the test plasma with the substrate (full-length VWM multimers) and detection with direct or indirect measurement of the cleavage product. The purpose of this study is to examine the diagnostic potential, advantages, and weaknesses of the ADAMTS13 potency in TTP.

Efficacy and safety of low-dose rituximab as induction therapy for antineutrophil cytoplasmic antibody-associated vasculitis with renal involvement: a Chinese case series

BACKGROUND

Rituximab (RTX) is a standard therapy for antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV). However, the most frequently used dose may lead to severe adverse effects (SAEs). We explored the efficacy and safety of low-dose RTX in Chinese patients with AAV.

METHODS

A total of 22 Chinese patients diagnosed with AAV with renal involvement, including 8 treated with low-dose RTX (400 mg of RTX total over 4 weeks) and 14 treated with cyclophosphamide (CYC), were evaluated. The baseline clinical and pathological data and laboratory parameters during follow-up at months 1, 3, 6, and 12 were collected retrospectively.

RESULTS

The baseline data showed no significant differences between the two groups. The median peripheral CD19⁺ cell counts in the RTX group decreased from 315.0/μL to 1.5/μL at 2 weeks, and to 2.5/μL at 1 month after the first dose. The median SCr level decreased from 267.8 μmol/L before treatment to 151.45 μmol/L at 1 month, 132.75 μmol/L at 3 months, 123.2 μmol/L at 6 months, and 151.9 μmol/L at 12 months in RTX-treated patients. The improvements in renal function, proteinuria, and ANCA titre were not significantly different between the two groups. The SAE rate was significantly lower in the RTX group (one SAE of pneumonia) compared with the CYC group.

CONCLUSIONS

This is the first report that low-dose RTX could be effective for the treatment of Chinese patients with AAV with renal involvement.

Predictors of relapse and preventative strategies in immune thrombotic thrombocytopenic purpura

INTRODUCTION

Immune-mediated thrombotic thrombocytopenic purpura (iTTP) is a rare autoimmune blood disorder, which presents with microangiopathic hemolytic anemia, thrombocytopenia, and microvascular thrombosis and is caused by severe deficiency of ADAMTS13. iTTP may result in both acute and chronic complications and is rapidly fatal without expedient treatment. Life-time risk of relapse is approximately 40%.

AREAS COVERED

A number of predictors of relapse has been described in the literature. The most well-studied predictor of relapse is persistent ADAMTS13 deficiency; however, it is not a perfect marker. Relapse can be prevented by treatment with immunosuppressive medications, with rituximab being the most studied.

EXPERT OPINION

Patients who recover from iTTP should be regularly assessed, including with ADAMTS13 activity testing. The optimal frequency of assessments has not been established, but every 3 months is recommended. Considering the potential for significant organ damage and mortality associated with iTTP relapse, patients in remission and with persistent ADAMTS13 activity of 10-20% should be prophylactically treated with immunosuppression. Additional markers to precisely identify patients at higher risk of relapse are needed.

Cost savings to hospital of rituximab use in severe autoimmune acquired thrombotic thrombocytopenic purpura

Patients with severe autoimmune thrombotic thrombocytopenic purpura (TTP) experience acute hematologic emergencies during disease flares and a lifelong threat for relapse. Rituximab, in addition to steroids and therapeutic plasma exchange (TPE), has been shown to mitigate relapse risk. A barrier to care in initiating rituximab in the inpatient setting has been the presumed excessive cost of medication to the hospital. Retrospectively reviewing TTP admissions from 2004 to 2018 at our academic center, we calculated the actual inpatient cost of care. We then calculated the theoretical cost to the hospital of initiating rituximab in the inpatient setting for both initial TTP and relapse TTP cohorts, with the hypothesis that preventing sufficient future TTP admissions offsets the cost of initiating rituximab in all patients with TTP. At a median follow-up of 55 months in the initial TTP cohort, rituximab use produced a projected cost savings of $905 906 and would have prevented 185 inpatient admission days and saved 137 TPE procedures. In the relapse TTP setting, rituximab use produced a projected cost savings of $425 736 and would have prevented 86 inpatient admission days and saved 64 TPE procedures. From a hospital cost standpoint, cost of rituximab should no longer be a barrier to initiating inpatient rituximab in both initial and relapse TTP settings.

Treating thrombotic thrombocytopenic purpura without plasma exchange during the COVID-19 pandemic. A case report and a brief literature review

We report the case of a patient diagnosed with a clinical relapse of acquired immune-mediated thrombotic thrombocytopenic purpura (TTP) who was successfully treated with low-dose rituximab plus corticosteroids without the use of plasma exchange (PEx), which was unavailable at the time due to the COVID-19 pandemic. Rituximab 100 mg weekly for 4 weeks was administered, combined with 1 mg/kg of prednisone, obtaining a complete hematological response in 6 weeks. This case suggests that PEx may be unnecessary for a subset of patients with relapsed TTP who are clinically stable without significant end-organ damage. A brief literature review regarding TTP patients treated without plasma exchange is also included.

Application of the French TMA Reference Center Score and the mortality in TTP Score in de novo and relapsed episodes of acquired thrombotic thrombocytopenic purpura at a tertiary care facility in Spain

Acquired thrombotic thrombocytopenic purpura (aTTP) is still associated with a 10% to 20% death rate and its clinical course is characterized by recurrent episodes in up to 50% of cases. Over the last decade, mortality predicting models like the French TMA Reference Center Score and the Mortality In TTP Score (MITS) have been developed in an attempt to personalize treatment. The objective of the present study was to compare the results in both scores of de novo and relapsed aTTP episodes. For such purpose, a total of 29 episodes of aTTP (16 de novo and 13 relapses) were analyzed. All patients were homogeneously diagnosed and treated. First episodes had a higher score in both models in comparison with relapsed aTTP, (MITS median, 1 r: 1-4 vs 0 r: 1-2, P = .038 and French TMA Reference Center Score median, 2 r: 1-3 vs 1 r: 0-1, P = .006). The prevalence of neurological symptoms was significantly higher in the first episodes (P = .001) and patients >60 years old were more common in this group (P = .013), which may have been related to the results. Platelet count at presentation was higher in recurrences than in the first disease episode (P = .016) and ADAMTS13 activity <5% was more frequent in the last group (P = .016). There was no significant difference in the rate of refractoriness or exacerbations. In conclusion, first aTTP episodes had a higher probability of short-term mortality compared to relapsed aTTP episodes according to the MITS and French TMA Reference Center Score.

Comparison of low fixed dose versus standard-dose rituximab to treat thrombotic thrombocytopenic purpura in the acute phase and preemptively during remission

The standard dose of rituximab used in B-cell hematological malignancies, 375 mg/m² weekly, may be excessive for autoimmune conditions. Successful use of a low, fixed dose of 100-200 mg of rituximab, weekly for 4 weeks, has been reported in the literature in the treatment of autoimmune thrombotic thrombocytopenic purpura (aTTP). We retrospectively analyzed our rituximab data in aTTP over a 13-year-period for 39 patients, with the aim of comparing response and outcomes with a standard lymphoma-dose course versus a low fixed 100 mg-dose course. Compared to the standard dose (17 patients, 17 courses of 4 infusions), our patients who received a low dose (8 patients, 9 courses of 4 infusions) had a possibly lower baseline risk but did achieve a similar time to remission and number of plasma exchange procedures to remission. Preemptive low-dose courses for ADAMTS13 activity <50 % during remission (6 patients, 10 courses of 4 infusions) achieved a median peak ADAMTS13 activity of 99 %, in a median of 1 month, with no clinical relapses. Our results provide additional evidence for the efficacy of low-dose rituximab, with the benefit of much lower cost, less infusion time, and theoretically lower risk of toxicity.

Expert statement on the ICU management of patients with thrombotic thrombocytopenic purpura

Thrombotic thrombocytopenic purpura (TTP) is fatal in 90% of patients if left untreated and must be diagnosed early to optimize patient outcomes. However, the very low incidence of TTP is an obstacle to the development of evidence-based clinical practice recommendations, and the very wide variability in survival rates across centers may be partly ascribable to differences in management strategies due to insufficient guidance. We therefore developed an expert statement to provide trustworthy guidance about the management of critically ill patients with TTP. As strong evidence was difficult to find in the literature, consensus building among experts could not be reported for most of the items. This expert statement is timely given the recent advances in the treatment of TTP, such as the use of rituximab and of the recently licensed drug caplacizumab, whose benefits will be maximized if the other components of the management strategy follow a standardized pattern. Finally, unanswered questions are identified as topics of future research on TTP.

When targeted therapies alleviate the burden of TPE: The example of immune-mediated TTP

Thrombotic thrombocytopenic purpura is a rare and severe disease that manifests as a thrombotic microangiopathy with severe thrombocytopenia and variable multiorgan failure. The disease relies on a severe deficiency in a disintegrin and metalloprotease with thrombospondin type-1 repeats, 13^th member (ADAMTS13), the von Willebrand factor (vWF) cleaving protease which can be either inherited (congenital TTP) or immune-mediated (iTTP). In iTTP, the therapeutic strategy has long relied on therapeutic plasma exchange alone which still represents the only way to deliver large amounts of ADAMTS13 without risking fluid overload. Yet, several therapeutic strategies have been developed in recent years and are about to transform the standard of care of iTTP. The immunosuppressive regimen now increasingly encompasses the administration of frontline rituximab to all patients. Moreover, the impressive results of the anti-vWF nanobody caplacizumab in phase 2 and 3 studies have recently prompted its approval by health authorities for the initial treatment of the disease. The increasing use of these highly effective targeted therapies should translate in a reduced need for therapeutic plasma exchange and an improvement in the prognosis of the disease. Nevertheless, and until the development of a recombinant ADAMTS13, this cornerstone therapy remains irreplaceable.

Caplacizumab as an emerging treatment option for acquired thrombotic thrombocytopenic purpura

Thrombotic thrombocytopenic purpura (TTP) is a rare disease with a mortality rate of over 90% if left untreated. Therapeutic plasma exchange (PEX) is the mainstay of treatment of acquired TTP (aTTP), and with the introduction of PEX, the mortality rate declined dramatically below 20%. Although PEX together with corticosteroids are the backbone of the upfront management of patients with aTTP with successful outcomes, patients may remain refractory and/or relapse following an initial response to this treatment. There are some therapeutic options, which can be used among these patients, helping in improving outcomes of aTTP. Caplacizumab (formerly ALX-0081 or ALX-0681) is a humanized single-variable domain immunoglobulin that recognizes the human von Willebrand factor (vWF) A1 domain and inhibits the vWF-platelet glycoprotein 1b-alpha (GP1b-α) interaction. The drug was first developed for the prevention of thrombosis in high-risk patients with acute coronary syndrome undergoing percutaneous coronary intervention; however, drug development for this indication has been discontinued. Recently, caplacizumab received its first approval following Phase II TITAN and Phase III HERCULES trials in the European Union (EU) for the treatment of acute episode of aTTP in adult patients, in addition to PEX and immunosuppression. This review focuses on the use of caplacizumab as an emerging treatment option in patients with aTTP.

Relapsed/refractory acquired thrombotic thrombocytopenic purpura in a patient with Sjögren syndrome: Case report and review of the literature

RATIONALE

Thrombotic thrombocytopenic purpura (TTP) is a rare, fatal disorder which could be caused by autoimmune diseases. However, TTP secondary to Sjögren syndrome (SS) is extremely rare.

PATIENT CONCERNS

A 47-year- old woman with an 8-year history of SS was admitted due to skin ecchymosis and bleeding gums. Then she gradually developed fever and headache.

DIAGNOSES

Laboratory investigations suggested anemia, thrombocytopenia, increased lactic dehydrogenase, and a disintegrin-like metalloproteinase with thrombospondin motif type 1 member 13 (ADAMTS13) activity deficiency with high inhibitor titers. Acquired TTP was thus diagnosed.

INTERVENTIONS

Plasma exchange (PE) was the first choice for treatment, while glucocorticoid, cyclosporine A (CSA), rituximab, and intravenous immunoglobulin (IVIG) were used simultaneously. Bortezomib, a selective proteasome inhibitor and thereby inducing apoptosis in both B-cells and plasma cells, was added.

OUTCOMES

She was discharged from the hospital and then treated with prednisone of 40 mg/d and hydroxychloroquine. The patient remained in full remission.

LESSONS

We conclude that bortezomib should be considered for patients with TTP refractory to PE, steroids, and rituximab due to its efficacy and relatively favorable side effect profile.

Pathophysiology of thrombotic thrombocytopenic purpura

The discovery of a disintegrin-like and metalloproteinase with thrombospondin type 1 motif, member 13 (ADAMTS13) revolutionized our approach to thrombotic thrombocytopenic purpura (TTP). Inherited or acquired ADAMTS13 deficiency allows the unrestrained growth of microthrombi that are composed of von Willebrand factor and platelets, which account for the thrombocytopenia, hemolytic anemia, schistocytes, and tissue injury that characterize TTP. Most patients with acquired TTP respond to a combination of plasma exchange and rituximab, but some die or acquire irreversible neurological deficits before they can respond, and relapses can occur unpredictably. However, knowledge of the pathophysiology of TTP has inspired new ways to prevent early deaths by targeting autoantibody production, replenishing ADAMTS13, and blocking microvascular thrombosis despite persistent ADAMTS13 deficiency. In addition, monitoring ADAMTS13 has the potential to identify patients who are at risk of relapse in time for preventive therapy.

Management of thrombotic thrombocytopenic purpura

Daily therapeutic plasma exchange (TPE) transformed the historically fatal prognosis of acquired, anti-ADAMTS13 antibody-mediated thrombotic thrombocytopenic purpura (TTP), leading to the current overall survival rates of >80%. However, relapses occur in up to 40% of patients and refractory disease with fatal outcomes still occurs, typically within the first days of management. In this context, the introduction of rituximab has been the second major breakthrough in TTP management. Rituximab is now routinely recommended during the acute phase, typically in patients with a suboptimal response to treatment, and increasingly as frontline therapy, with high response rates in the following weeks. In more severe patients, salvage strategies typically include twice daily TPE, pulses of cyclophosphamide, as well as splenectomy in the more desperate cases. In this life-threatening and debilitating disease, relapses can be efficiently prevented in patients with a severe acquired ADAMTS13 deficiency and otherwise in remission with the use of rituximab. In the coming years, the TTP therapeutic landscape should be enriched by original strategies stemming from clinical experience and new agents that are currently being evaluated in large, international, clinical trials. Promising agents under evaluation include caplacizumab (an inhibitor of the glycoprotein-Ib/IX-Von-Willebrand factor axis), N-acetylcysteine, recombinant ADAMTS13, and anti-plasmocyte compounds.

Thrombotic thrombocytopenic purpura

Thrombotic thrombocytopenic purpura (TTP; also known as Moschcowitz disease) is characterized by the concomitant occurrence of often severe thrombocytopenia, microangiopathic haemolytic anaemia and a variable degree of ischaemic organ damage, particularly affecting the brain, heart and kidneys. Acute TTP was almost universally fatal until the introduction of plasma therapy, which improved survival from <10% to 80-90%. However, patients who survive an acute episode are at high risk of relapse and of long-term morbidity. A timely diagnosis is vital but challenging, as TTP shares symptoms and clinical presentation with numerous conditions, including, for example, haemolytic uraemic syndrome and other thrombotic microangiopathies. The underlying pathophysiology is a severe deficiency of the activity of a disintegrin and metalloproteinase with thrombospondin motifs 13 (ADAMTS13), the protease that cleaves von Willebrand factor (vWF) multimeric strings. Ultra-large vWF strings remain uncleaved after endothelial cell secretion and anchorage, bind to platelets and form microthrombi, leading to the clinical manifestations of TTP. Congenital TTP (Upshaw-Schulman syndrome) is the result of homozygous or compound heterozygous mutations in ADAMTS13, whereas acquired TTP is an autoimmune disorder caused by circulating anti-ADAMTS13 autoantibodies, which inhibit the enzyme or increase its clearance. Consequently, immunosuppressive drugs, such as corticosteroids and often rituximab, supplement plasma exchange therapy in patients with acquired TTP.

Rituximab as first-line treatment for acquired thrombotic thrombocytopenic purpura

Objective To investigate the efficacy and safety of rituximab (RTX) as first-line treatment of acquired thrombotic thrombocytopenic purpura (aTTP). Methods Twenty-five patients with acute aTTP and/or severe a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13 (ADAMTS13) deficiency were admitted to our centre from April 2009 to March 2015. Fourteen patients received RTX plus standard therapy (plasma exchange and corticosteroids) at acute episodes. Haemoglobin, platelet count, schistocytes, lactate dehydrogenase levels, ADAMTS13 activity and its inhibitors, and the ratio of B lymphocytes in the peripheral blood, were monitored. The number of plasma exchange (PEXs), total plasma volume, remission time, relapse ratio, and adverse effects were recorded. Results The median number of PEXs was 5 (2-17) sessions and median total plasma volume was 168.43 ml/kg (62.86-469.52 ml/kg). Patients achieved haematological remission at a median of 15 days (5-22 days), and the median time of immunological remission was 2 weeks (2-8 weeks) with a median follow-up of 13 months (3-61 months). ADAMTS13 activity significantly increased after 2 weeks. The B lymphocyte percentage in peripheral blood was reduced 1 week after the first dose of RTX infusion compared with before treatment (2.21% ± 5.23% vs 18.47% ± 7.34%, P = 0.000 [the result of statistical software]), and began to gradually increase 9 months later. Severe adverse effects and relapsing TTP were not observed during therapy and follow-up. However, one patient who had sustained immunological remission died of severe pneumonia 7 months later. Conclusion Although our study was limited by its small sample number and it was a non-controlled, clinical trial, it showed potential benefits of RTX therapy for acute aTTP. RTX may be administered as a first-line therapy for lowering patients' relapse rate in the long term. Randomized, controlled trials of RTX for aTTP are required.