Should we consider caplacizumab as routine treatment for acute thrombotic thrombocytopenic purpura? An expert perspective on the pros and cons

INTRODUCTION

Immune thrombotic thrombocytopenic purpura (iTTP) is a rare and life-threatening disorder. Caplacizumab has been the latest drug incorporated into the initial treatment of acute episodes, allowing for faster platelet recovery and a decrease in refractoriness, exacerbation, thromboembolic events, and mortality. However, caplacizumab is also associated with a bleeding risk and higher treatment costs, which prevent many centers from using it universally.

AREAS COVERED

Studies that included iTTP and/or caplacizumab to date were selected for this review using PubMed and MEDLINE platforms. We describe outcomes in the pre-caplacizumab era and after it, highlighting the benefits and risks of its use early in frontline, and also pointing out special situations that require careful management.

EXPERT OPINION

It is clear that the availability of caplacizumab has significantly and favorably impacted the management of iTTP patients. Whether this improvement is cost-effective still remains uncertain, and data on long-term sequelae and different healthcare systems will help to clarify this point. In addition, evidence of the bleeding/thrombotic risk of iTTP patients under this drug needs to be better addressed in future studies.

Therapeutic modalities in thrombotic thrombocytopenic purpura management among Jehovah's Witness patients: A review of reported cases

INTRODUCTION

Devout members of the Jehovah's Witness faith flatly refuse transfusions of white blood cells, red blood cells, platelets, and plasma. The latter agent is a mainstay in the treatment of thrombotic thrombocytopenic purpura (TTP). Alternative treatment options for Jehovah's Witness patients are needed and reviewed herein.

METHODS

Cases of TTP treatment among Jehovah's Witnesses were obtained from the published literature. Key baseline and clinical data were extracted and summarized.

RESULTS

A total of 13 reports spanning a 23-year period and 15 TTP episodes were identified. Median (IQR) age was 45.5 (29.0-57.5) and 12/13 (93%) patients were female. Neurologic symptoms were present in 7/15 (47%) episodes at presentation. Disease confirmation with ADAMTS13 testing was present in 11/15 (73%) of episodes. Corticosteroids and rituximab were employed in 13/15 (87%) and 12/15 (80%) of cases, respectively, with apheresis-based therapy employed in 9/15 (60%) episodes. For eligible cases, caplacizumab was used in 4/5 (80%) episodes; average time to platelet response was shortest in these cases. Sources of exogenous ADAMTS13 accepted by patients in this series included cryo-poor plasma, FVIII concentrate, and cryoprecipitate.

CONCLUSIONS

Successful management of TTP within the boundaries of the Jehovah's Witness faith is possible.

Real-world data of the use and experience of caplacizumab for the treatment of acquired thrombotic thrombocytopenic purpura: Case series

PURPOSE

Caplacizumab was licensed for acquired thrombotic thrombocytopenic purpura (aTTP) based on prospective controlled trials. Real-world evidence is crucial in rare diseases. We aim to describe a patient population with aTTP, receiving caplacizumab in a real-world setting, reporting their outcomes, including safety and tolerability, and contrasting them with a historical cohort from our center.

METHODS

We describe data collected retrospectively from 2012 to 2022 for 16 patients with aTTP (8 received caplacizumab and 8 the historical standard-of-care). Patients' characteristics and outcomes were compared between groups.

RESULTS

Patients' demographic and baseline characteristics were similar in both groups. Caplacizumab led to a rapid normalization of the platelet count of 3.5 (IQR, 2-6) versus 16 (IQR, 9.5-23.5) days in the historical cohort: (p = .002). The median number of plasma exchanges and the length of days requiring them, between the caplacizumab group versus the historical cohort, was 6 (IQR, 6-10) versus 19.5 (IQR, 12.5-29.5) plasma exchanges (p = .006); and 9 (IQR, 8.5-13.5) versus 22 (15-31) days (p = .049), respectively. There were no refractory cases in the caplacizumab group in comparison with 37.5 % in the historical cohort. None of patients treated with caplacizumab experienced a recurrence after 1081 (IQR, 511-3125) days of follow-up. Safety was in line with data reported in clinical trials, with mild adverse events (mostly grade≤2).

CONCLUSION

We provided real-world evidence in the treatment of aTTP, confirming the results obtained in clinical trials. Caplacizumab reduced the time to platelet count recovery and the number and length of plasma exchanges.

Brazilian experience with caplacizumab in acquired thrombotic thrombocytopenic purpura: outcomes of the expanded access program

Acquired thrombotic thrombocytopenic purpura (aTTP) is a rare disease with an acute and severe clinical presentation. The anti-von Willebrand factor caplacizumab was licensed for adults with aTTP based on prospective controlled trials. However, until now, there was no Brazilian experience with this new treatment modality. This retrospective, multicenter, single-arm, expanded access program (EAP) with caplacizumab, plasma exchange (PEX), and immunosuppression was conducted between 02/24/21 and 04/14/21, and enrolled 5 Brazilian patients with aTTP. EAP allowed access to caplacizumab in Brazil and real-world data was collected, at a time when the medication was not commercially available in Brazil. The median age was 31 years old, most patients were women (80%), and neurological manifestation was observed in 80% of cases. The median of laboratory tests was hemoglobin (Hb) of 11 g/dL, platelets (16.1 × 10⁹/L), lactic dehydrogenase (LDH) of 1471 U/L, creatinine (0.7 mg/dL), ADAMTS13 activity lower than 0.71%, and PLASMIC score of 6. All patients received immunosuppression, PEX, and caplacizumab. Until clinical response was achieved, the median was 3 sessions of PEX and 3 days of treatment. The median time of caplacizumab use was 35 days, with platelet normalization in 2 days after starting the drug. The median total length of stay was 8 days. All patients achieved clinical response and clinical remission, with a good safety profile. There was rapid clinical response, few PEX sessions were necessary, and there were short hospital stay, absence of refractoriness, little exacerbation, no death, and resolution of signs and symptoms at diagnosis.

Therapeutic plasma exchange-free treatment for first-episode TTP: A systematic review

OBJECTIVE

Thrombotic thrombocytopenic purpura (TTP) is a thrombotic microangiopathy (TMA), and therapeutic plasma exchange (TPE) is currently the standard treatment. However, TPE sometimes cannot be implemented. The aim of this study was to systematically review patients with a first TTP episode who were treated without TPE.

METHOD

The PubMed, Embase, Web of Science and Cochrane Library databases were searched by two investigators independently to collect case reports and clinical studies on TTP patients treated without TPE. After removing duplicate records and records that did not meet the inclusion criteria, the patients' data of eligible studies, including the basic characteristics, treatment regimens, and outcomes were extracted for further analysis.

RESULTS

A total of 5338 potentially relevant original studies were identified, from which 21 studies, including 14 cases, 3 case series and 4 retrospective studies, met eligibility requirements and were included. Treatment regimens in the absence of TPE were found to vary based on individual information. Most patients recovered, with normal platelet counts and ADAMT13 activity at discharge. In the meta-analysis of retrospective studies, the TPE-free group had no higher mortality than the TPE-treated group.

CONCLUSION

Our study shows that TPE-free treatment may not increase the mortality of TTP patients, which provides a new treatment concept for patients with first episodes of TTP. However, the current evidence is not high due to the lack of randomized controlled trials, so more well-designed prospective clinical trials are warranted to investigate the safety and efficacy of TPE-free treatment regimens in TTP patients.

Thrombotic thrombocytopenic purpura in caplacizumab era - An individualized approach

Thrombotic thrombocytopenic purpura (TTP) is a rare disease characterized by a severe deficiency (< 10 % activity) of ADAMTS13 enzyme due to an autoantibody (aTTP) or genetic defect leading to congenital TTP (cTTP). The management of aTTP has evolved over the last 30 years, beginning with plasma exchange (PLEX) being the standard of care, leading to gradual aggressive immunosuppression therapies to manage exacerbations and relapses. Although PLEX had reversed the mortality from > 90 % to < 10-20 %, early deaths do occur in severe aTTP, especially when there is a delay in diagnosis and/or PLEX initiation. There is growing evidence that aTTP is often associated with the long-term neuropsychiatric sequela, probably associated with brain damage caused by microthromboses. Recently, a disease-modifying agent, caplacizumab, a potent nanobody that inhibits the interaction between the A1 domain of von Willebrand factor with GPIb on platelets, was approved by various agencies for the treatment of aTTP. Two clinical trials showed its efficacy in rapidly correcting platelet counts and preventing exacerbations because caplacizumab was continued for 30 days post-PLEX, irrespective of ADAMTS13 recovery. However, caplacizumab was associated with higher and unusual bleeding side effects compared to the placebo due to a severe acquired von Willebrand syndrome that persisted for the duration of therapy. Because of its longer half-life coupled with early aggressive rituximab therapy, it is prudent to use caplacizumab judiciously to avoid serious bleeds and to reduce costs. This manuscript provides a rational approach for using caplacizumab, an important disease-modifying agent.

Frontiers in pathophysiology and management of thrombotic thrombocytopenic purpura

Thrombotic thrombocytopenic purpura (TTP) is a fatal disease in which platelet-rich microthrombi cause end-organ ischemia and damage. TTP is caused by markedly reduced ADAMTS13 (a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13) activity. Hereditary or congenital TTP (cTTP) is caused by ADAMTS13 gene mutations. In acquired or immune TTP (iTTP), ADAMTS13 activity is reduced by anti-ADAMTS13 autoantibodies. TTP is characterized by thrombocytopenia, hemolytic anemia, fever, renal dysfunction, and neuropsychiatric symptoms. Therapeutic plasma exchange (TPE) and immunosuppressive therapy are the mainstays of treatment. As untreated TTP has a high mortality rate, immediate initiation of TPE is recommended when TTP is suspected. Conventionally, corticosteroids have been used for immunosuppressive therapy. Current drug therapies include rituximab, an anti-CD20 antibody that is effective in newly diagnosed cases and refractory cases, as well as for relapse prevention, and caplacizumab, an anti- von Willebrand factor (VWF) nanobody that inhibits the binding of platelets to VWF and prevents microthrombi formation. Recombinant human ADAMTS13 is a promising treatment for cTTP. Although these therapeutic advances have improved the outcomes of TTP, early diagnosis and prompt initiation of appropriate therapy are necessary to achieve these outcomes.

Caplacizumab as rescue therapy in refractory TTP involving neurologic features

BACKGROUND

The role of caplacizumab in the routine treatment of immune thrombotic thrombocytopenic purpura (iTTP) remains to be established.

CASE SUMMARY

A 56-year-old woman was transferred to our center with iTTP and neurologic features. At the outside hospital, she was initially diagnosed and managed as Immune Thrombocytopenia (ITP). Upon transfer to our center, daily plasma exchange, steroids, and rituximab were initiated. After an initial improvement, refractoriness became evident with a decline in platelet count and continued neurologic abnormalities. Initiation of caplacizumab resulted in rapid hematologic and clinical responses.

CONCLUSION

Caplacizumab is a valuable treatment modality in iTTP, particularly in cases associated with refractoriness or neurologic features.

Caplacizumab for treating subacute intra-stent thrombus occurring despite efficacious double anti-platelet treatment and anticoagulation: a case report

Background

Acute and subacute stent thromboses are a rare complication associated with high mortality and morbidity occurring in ∼1.5% of patients treated with primary percutaneous intervention for ST-elevation myocardial infarction (STEMI). Recent publications describe a potential role of the von Willebrand factor (VWF) in thrombus formation at sites of critical coronary stenosis in STEMI.

Case summary

We describe a 58-year-old woman with STEMI at initial presentation, who suffered subacute stent thrombosis despite good stent expansion, efficacious dual antiplatelet therapy, and therapeutic anticoagulation. Because of very high VWF values, we administered N-acetylcysteine in order to depolymerize VWF, but the drug was not well tolerated. Since the patient was still symptomatic, we used caplacizumab in order to prevent VWF from interacting with platelets. Under this treatment, the clinical and angiographic course was favourable.

Discussion

Considering a modern view of intracoronary thrombus pathophysiology, we describe an innovative treatment approach, which eventually ended in a favourable outcome.

Semi-selective plasma filtration applied to the treatment of acquired thrombotic thrombocytopenic purpura following bnt162b2 administration

Following the widespread use of anti SARS-CoV-2 vaccines, there have been reports of thrombocytopenia developing after the administration of different types of vaccine. We report a case of a 63-year-old male who developed neurological symptoms after receiving the second dose of the bnt162b2 vaccine. Blood tests performed upon admission to the Emergency Department revealed severe thrombocytopenia and microangiopathic hemolytic anemia. ADAMTS13 activity was undetectable and antibody titer was high. Due to the rapid neurological deterioration, steroid therapy with prednisone was started at an initial dose of 1 mg/kg/day. Rituximab therapy was started to prevent the formation of new antibodies. Given the slow response to this therapy, we added Caplacizumab, (a monoclonal antibody anti-Von Willebrand factor) in order to inhibit platelet hyperaggregation, combined with standard plasma exchange. The patient experienced repeated episodes of intolerance to fresh frozen plasma (FFP). Switching from plasma exchange to plasma filtration, remission was attained in this unusual case of vaccine-related thrombocytopenia with microangiopathic hemolytic anemia.

The efficacy and safety of caplacizumab in Japanese patients with immune-mediated thrombotic thrombocytopenic purpura: an open-label phase 2/3 study

Caplacizumab is an anti-von Willebrand factor humanized single-variable-domain immunoglobulin fragment whose efficacy and safety in immune-mediated thrombotic thrombocytopenia purpura (iTTP) have been demonstrated in international studies. This prospective, open-label phase 2/3 study evaluated caplacizumab 10 mg administered daily during plasma exchange and for 30 days afterward, in combination with immunosuppressive treatment, in Japanese adults with a clinical diagnosis of iTTP (new or recurrent). The primary endpoint was prevention of iTTP recurrence; key secondary endpoints included time to platelet count response, time to organ damage normalization, and safety. Among 21 treated patients, 1 of 15 (6.7%) evaluable patients developed iTTP recurrence. Median time to normalization was 2.79 days for platelet count and 2.65 days for organ damage markers (n = 15). Treatment-emergent adverse events (TEAEs) were mostly mild to moderate in severity; the most frequently reported caplacizumab-related TEAEs were increased alanine aminotransferase, epistaxis, and gastrointestinal hemorrhage (all in 9.5% of patients). At least one bleeding event was reported in 7 of 21 patients (33%). Caplacizumab was effective in Japanese patients with iTTP, with a low rate of iTTP recurrence, rapid normalization of platelet counts and organ damage markers, and no unexpected TEAEs. Trial registration: ClinicalTrials.gov identifier, NCT04074187.

[Novel treatment strategies for acquired thrombotic thrombocytopenic purpura]

Thrombotic thrombocytopenic purpura (TTP) is a poor prognosis disease caused by platelet thrombi produced in the microvessels throughout the body. The thrombus is mainly composed of von Willebrand factor (VWF) and platelets. Acquired TTP is an autoimmune disease wherein autoantibodies against ADAMTS13, a VWF-cleaving enzyme, are produced and ADAMTS13 activity is markedly decreased. Plasma exchange using fresh-frozen plasma as a replacement fluid effective against acquired TTP was reported in 1991. Since then, plasma exchange and corticosteroids have been the standard of care in Japan. Caplacizumab, which is a monoclonal antibody against the VWF A1 domain, finally became available for use in 2022, and the number of cases is still increasing in Japan. A clinical trial of recombinant ADAMTS13 product is being conducted for congenital TTP, and an era is expected to come in the future when plasma exchange will no longer be necessary.

[Refractory thrombotic thrombocytopenic purpura]

Thrombotic thrombocytopenic purpura (TTP) remains a serious illness with potentially life-threatening complications. The following case of a TTP patient describes a serious relapse with exacerbation in spite of adequately initiated therapy and highlights the necessity of interdisciplinary expertise in the treatment of the disease.

Caplacizumab Use in a TTP Case Unresponsive to Conventional Therapy

Introduction Thrombotic Thrombocytopenic Purpura (TTP) is a rare but life-threatening disorder caused by severely reduced activity of ADAMTS13, causing platelet adhesion and formation of small-vessel platelet-rich thrombi, thrombocytopenia, and microangiopathic haemolytic anaemia. Diagnosis A 48-year-old female presented with acute generalized petechial rash, bruises, and fatigue. Bloods revealed thrombocytopenia, anaemia, 10% schistocytes. Her plasmic score was seven, and ADAMT13 was &lt;5. Treatment Patient initially responded to plasma exchange and steroids, but thrombocytopenia recurred on day six of treatment, needing the addition of further immunosuppressive drugs and Caplacizumab. Conclusion TTP cases unresponsive to conventional regimens can represent a challenging situation; however, poor outcomes could potentially be avoided with a novel therapy like Caplacizumab. In our patient, this medication was well tolerated, and platelet count normalized after two days of its introduction.

Successful use of a second course of caplacizumab in relapsed thrombotic thrombocytopenic purpura

There is limited data on the use of caplacizumab beyond the initial treatment course. We describe a patient case demonstrating the efficacy of a second course of caplacizumab in a patient with relapsed acquired thrombotic thrombocytopenic purpura (TTP). A 25-year-old female was treated for an initial event of TTP with steroids, plasma exchange, rituximab, and caplacizumab. Caplacizumab was continued 30 days post plasma exchange, which was on day 46 of treatment, at which time platelets had improved to 292 x 10⁹/L. Two weeks after completion of the first caplacizumab course, on day 60, she was readmitted with platelets of 5 x 10⁹/L. Daily plasma exchange and steroids were started on admission, with rituximab added on day 65. On day 67, the decision was made to re-initiate caplacizumab due to a platelet count of 21 x 10⁹/L. By day 72, platelets improved to 273 x 10⁹/L and the patient was able to be discharged and completed her second 30-day post plasma exchange course of caplacizumab without complications or further relapses.

[Treatment of immune-mediated thrombotic thrombocytopenic purpura: A decisive turning point]

Immune-mediated thrombotic thrombocytopenic purpura (iTTP) is a rare and life-threatening thrombotic microangiopathy characterized by severe deficiency of ADAMTS13, the enzyme that cleaves von Willebrand factor multimers. Recent insights into iTTP pathophysiology have led to the development of new therapies targeting ADAMTS13 replacement, anti-ADAMTS13 antibodies, and von Willebrand factor-platelet interactions. New maximalist therapeutic strategies are emerging based on triple therapy. While plasma exchange remains the cornerstone therapy of the acute phase, the introduction of front-line immunosuppressive treatments, corticosteroids and rituximab, has led to a reduction in exacerbations and relapses but without any significant improvement in survival. Caplacizumab, a bivalent humanized anti-von Willebrand factor nanobody, is poised to revolutionize the treatment of the acute phase. By inhibiting the interaction between von Willebrand factor multimers and platelets, caplacizumab prevents platelets adhesion, prevents the formation of new microthrombi and protects organs from ischemia. Its early combination with plasma exchange and immunosuppressive therapy prevents unfavorable outcomes and reduces the burden of care. Supported by repeated ADAMTS13 assays, rituximab prevents relapse in patients with persistent or recurrent ADAMTS13 deficiency in clinical remission. This review examines how advances in diagnostics and targeted therapies are changing the current treatment paradigm in both the acute and remission phases and are contributing to dramatically improve the iTTP prognosis.

Refractory acquired thrombotic thrombocytopenic purpura in a patient with sickle cell trait successfully treated with caplacizumab

Methods: We report a case of a 20-year-old Nigerian male who presented with acquired thrombotic thrombocytopenic purpura (aTTP) and sickle cell trait. The coexistence of published cases of TTP and sickle cell hemoglobinopathies is rare.Results: Despite the initial treatment with plasma exchange and glucocorticoids, our patient relapsed and also required caplacizumab which resulted in successful remission.Discussion: We conclude by reviewing the cases of TTP in patients with sickle cell hemoglobinopathies and review how vaso-occlusive crises with multiorgan injury can mimic TTP.Conclusion: Ours is the first published case of aTTP with confirmed ADAMTS13 autoantibodies in a patient with a sickle cell hemoglobinopathy and contributes to the literature on the successful use of caplacizumab in clinical practice.

Effectiveness of Caplacizumab Nanobody in Acquired Thrombotic Thrombocytopenic Purpura Refractory to Conventional Treatment

Acquired thrombocytopenic thrombotic purpura (aTTP) is an autoantibody-mediated disease against the enzyme A Disintegrin and Metalloprotease domain with ThromboSpondin-1 type motif 13, which until now has been treated with plasma exchange (PEX) and corticosteroids. A 29-year-old female patient, who presented with aTTP in the context of pregnancy, has developed multiple relapses after treatment with PEX, corticosteroids, and rituximab. Recently, caplacizumab, a nanobody against von Willebrand factor, has been approved for the treatment of aTTP. In our patient, caplacizumab achieved better disease control, with a lower platelet count restoration time, days of PEX and hospitalization duration, as compared to standard therapy, reproducing the results of clinical trials. Caplacizumab represents a significant advance in the treatment of aTTP, especially in cases of recurrent relapses.

[Pathogenesis and novel treatment of thrombotic thrombocytopenic purpura]

The key clinical symptoms of thrombotic thrombocytopenic purpura (TTP) are severe thrombocytopenia, microangiopathic hemolytic anemia, and organ ischemia/infarction due to microthrombi. Hemolytic anemia in TTP is characterized by mechanical damage to red blood cells. TTP is caused by a severe deficiency of ADAMTS13 activity, which is caused by mutations in the ADAMTS13 gene (congenital TTP) or by autoantibodies affecting the function or clearance of ADAMTS13 (immune TTP). Patients with congenital TTP receive fresh frozen plasma (FFP) transfusion for the supplementation of ADAMTS13. Meanwhile, those with immune TTP receive plasma exchange therapy using FFP for the supplementation of ADAMTS13 and the removal of anti-ADAMTS13 autoantibodies. Corticosteroid therapy is concurrently administered to suppress autoantibody production. In terms of novel treatment, the use of rituximab, a humanized anti-CD20 monoclonal antibody, in patients with immune TTP was approved by the Japanese health insurance in 2020. Novel and promising drugs are currently developed. A first-in-human study of recombinant ADAMTS13 for congenital TTP was reported in 2017. Caplacizumab is a humanized nanobody that inhibits the interaction between von Willebrand factor and platelets. This drug can prevent early thrombus formation and organ damage in patients with immune TTP. Therefore, these novel drugs can improve mortality in patients with TTP.

High-resolution structure of the vWF A1 domain in complex with caplacizumab, the first nanobody-based medicine for treating acquired TTP

von Willebrand factor (vWF) is a huge oligomeric glycoprotein involved in blood homeostasis. However, this protein is also implicated in acquired thrombotic thrombocytopenic purpura (TTP). The blocking of its binding with platelets has been recognized as an attractive therapeutic strategy for treating acquired TTP. Caplacizumab, a bivalent single-domain antibody (VHH), is the first FDA-approved nanobody drug against vWF for the treatment of acquired TTP. Here, we describe the crystal structure of the A1 domain of vWF in complex with the caplacizumab nanobody at the resolution of 1.60 Å. This structure elucidates the precise epitope and binding mode of caplacizumab. Unexpectedly, caplacizumab binds to the bottom face of the vWF A1 domain and does not create any steric clash with platelet-receptor glycoprotein Ib (GPIb) bound to vWF. However, its binding can stabilize the different conformation within the N-terminus and α1β2 loop from the GPIb bound structure, suggesting that the mechanisms of caplacizumab would not be the direct competition of GPIb binding to vWF A1 domain but the conformational arrestment of vWF in an inappropriate state to platelet adhesion. This high-resolution structure would provide helpful information for the design of improved anti-vWF therapeutics for the treatment of acquired TTP.

An Early Unexpected Immune Thrombotic Thrombocytopenic Purpura Relapse Associated with SARS-CoV-2 Infection: A Case Report and Literature Review

SARS-CoV-2 has been reported as a possible triggering factor for the development of several autoimmune diseases and inflammatory dysregulation. Here, we present a case report of a woman with a history of systemic lupus erythematosus and antiphospholipid syndrome, presenting with concurrent COVID-19 infection and immune thrombotic thrombocytopenic purpura (TTP). The patient was treated with plasma exchange, steroids, and caplacizumab with initial good response to therapy. The course of both TTP and COVID-19 disease was mild. However, after ADAMTS-13 activity was normalized, the patient experienced an early unexpected TTP relapse manifested by intravascular hemolysis with stable platelet counts requiring further treatment. Only 3 cases of COVID-19 associated TTP were reported in the literature thus far. We summarize the literature and suggest that COVID-19 could act as a trigger for TTP, with good outcomes if recognized and treated early.

Thrombotic thrombocytopenic Purpura: A nurse's perspective on a decade of treatment in Sheffield, United Kingdom

TTP is a rare, life threatening condition, with an annual incidence of 3-11 cases per million people. A deficiency of a vWF multimer cleaving protein, ADAMTS13 is the cause of the condition. Quick & accurate diagnosis is crucial in the safe & effective treatment of individuals presenting with this condition. First line treatment is the removal of the resulting ulta-large vWF multimers left in the circulation by the lack of ADAMTS13 & immunosuppression of antibodies against ADAMTS13. In the last 3 years, introduction of a targeted therapy called Caplacizumab has seen a change in treatment. This paper provides an overview of the experience of the Sheffield, UK treatment team in the changes in TTP treatment pathways in the region. Finally exploring the impact introducing Caplacizumab into routine management has had on patient care & outcomes from a local nurse's perspective.

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.

Effective and safe off-label use of caplacizumab treatment in a middle-aged obese male

This study shows clinical efficacy and safety profile of an off-label use of caplacizumab for the treatment of immune-mediated thrombotic thrombocytopenic purpura in a middle-aged obese male patient manifesting aphasia, weakness and unconsciousness. Routine blood tests revealed haemolytic anaemia, severe thrombocytopenia (platelet count=20×10⁹/L) and moderate creatinine increase. Diagnosis was based on the clinical judgement and laboratory determinations (undetectable ADAMTS13 activity and presence of anti-ADAMTS13 antibodies). The patient underwent plasma-exchange and an adjunctive treatment with prednisone (1mg/Kg/day), but the occurrence of a refractory and exacerbated form of disease suggested also using rituximab (375mg/m² weekly for 4 weeks) and caplacizumab as salvage treatments. The caplacizumab was given at 10mg/day subcutaneously without the first intravenous bolus. Because von Willebrand factor inhibition, platelet count recovery and remission of symptoms were achieved, use of caplacizumab with this scheme appeared to be as effective as the approved one. Although this is an off-label use, this case highlights the potential of this new treatment, in terms of drug's efficacy and safety.

Successful use of caplacizumab in a case of refractory acquired thrombotic thrombocytopenic purpura following subacute thyroiditis

Acquired thrombotic thrombocytopenic purpura (aTTP) is a rare condition mainly characterized by microangiopathic hemolytic anemia, thrombocytopenia, reported in approximately three cases per one million adults per year. Some reports describing co-occurrence of aTTP and other autoimmune disorders, as Graves' thyroiditis, are reported. To the best of our knowledge this is the first report describing co-occurrence of subacute thyroiditis and aTTP. The patient was refractory to conventional therapy with plasma exchange, steroids and rituximab but was successfully treated with the addition of caplacizumab, an anti-VWF bivalent variable-domain-only immunoglobulin fragment that inhibits interaction between VWF multimers and platelets.

Successful management of three patients with autoimmune thrombotic thrombocytopenic purpura with paradigm-changing therapy: Caplacizumab, steroids, plasma exchange, rituximab, and intravenous immunoglobulins (CASPERI)

Autoimmune thrombotic thrombocytopenic purpura (aTTP) is a severe disease caused by the production of autoantibodies against von Willebrand factor (vWF)-cleaving ADAMTS13 (a disintegrin and metalloproteinase with thrombospondin-1 motifs; 13th member of the family). In 2018, caplacizumab was approved for the treatment of patients with acute aTTP in conjunction with plasma exchange (PE) and immunosuppressive therapy. Immunosuppressive standard of care includes mainly steroids whereas rituximab is usually reserved for refractory cases. We report three patients with a first acute episode of aTTP who were successfully treated with a paradigm-changing scheme including standard of care (caplacizumab, steroids and PE) plus upfront therapy with rituximab and intravenous immunoglobulins (CASPERI). Rituximab was added 1-4 days after diagnosis, when ADAMTS13 autoantibodies were detected and intravenous immunoglobulins were administered after performing PE using albumin as replacement solution. Successful outcome was observed in all three patients: platelet recovery (>150 × 10⁹/L) was observed after 3, 4, and 5 days from diagnosis; ADAMTS13 activity >5% and ADAMTS13 autoantibodies were negative after 14, 15, and 21 days from diagnosis. In conclusion, caplacizumab, steroids, PE (using fresh frozen plasma or albumin as replacement solution and adding intravenous immunoglobulins) plus upfront rituximab therapy was a safe and efficient combination to induce remission in case of acute aTTP.

Delayed Thrombotic Complications in a Thrombotic Thrombocytopenic Purpura Patient Treated With Caplacizumab

Thrombotic thrombocytopenic purpura (TTP) is a rare and unpredictable disease with a high mortality rate (90%) if untreated. It results from systemic microvascular thrombosis and leads to profound thrombocytopenia, hemolytic anemia and organ failure of varying severity. However, macrovascular thrombosis has been described in very rare cases. Caplacizumab has emerged as a promising new drug for the management of TTP. We report the case of a patient with idiopathic refractory TTP treated with caplacizumab who developed thrombotic complications upon discontinuation of treatment.

[Diagnosis and treatment of thrombotic thrombocytopenic purpura]

Thrombotic thrombocytopenic purpura (TTP) is a life-threatening disease in which platelets are consumed and thrombotic microangiopathy develops in multiple organs due to a severe deficiency of the metalloproteinase, ADAMTS13. TTP should be suspected in any case associated with thrombocytopenia and hemolytic anemia; TTP can be diagnosed in cases of profound reduction in ADAMTS13 activity (to <10% of the normal level). Congenital TTP involves mutations in the ADAMTS13 gene, whereas acquired or autoimmune TTP results from the actions of inhibitory autoantibodies against the ADAMTS13 protein. Plasma exchange together with corticosteroids is an effective treatment for acquired TTP; plasma exchange removes autoantibodies and provides ADAMTS13 supplementation, whereas corticosteroids further suppress autoantibody generation. Rituximab was recently approved in Japan for use in refractory or relapsing TTP. Likewise, caplacizumab, an anti-von Willebrand factor, may contribute to disease control and overall survival by preventing ongoing thrombosis and acute end-organ damage.

Thrombotic Thrombocytopenic Purpura, Heparin-Induced Thrombocytopenia, and Disseminated Intravascular Coagulation

Hemostatic abnormalities are common among critically ill patients and are associated with a high risk of bleeding. The abnormalities range from isolated thrombocytopenia or prolongation of global coagulation assays to complex disease states, such as thrombotic microangiopathic syndromes, and can be associated with a wide range of conditions, including trauma, surgery, acute disease processes, cardiopulmonary bypass, and exposure to drugs and blood products. Prompt identification of underlying causes is important because treatment strategies vary. Moreover, prompt initiation of both supportive and specific treatments is vital to decrease the morbidity and mortality in the intensive care unit.

Thrombotic Thrombocytopenic Purpura: Beyond Empiricism and Plasma Exchange

For many years after its first description in 1924, thrombotic thrombocytopenic purpura was an intriguing puzzle for clinicians and researchers, not only for its unique pathology, perplexing changes in von Willebrand factor multimers, and high rate of rapid fatality but also for its dramatic response to plasma infusion or exchange. The discovery of ADAMTS13 (a disintegrin and metalloprotease with thrombospondin type 1 repeats member-13) and its deficiency in patients with thrombotic thrombocytopenic purpura, due to inhibitory autoantibodies or genetic mutations, provides a mechanistic scheme for understanding its pathogenesis. This new knowledge quickly led to the use of rituximab to promote its remission and prevent recurrence. Recombinant ADAMTS13 is also under development to replace plasma infusion as the therapy for hereditary thrombotic thrombocytopenic purpura. Recently, caplacizumab, a bivalent nanobody targeting the glycoprotein 1b binding epitope of von Willebrand factor A1 domain, was approved as an addition to the current regimen of plasma exchange and immunomodulation for adult patients of acquired thrombotic thrombocytopenic purpura. This review discusses how the new treatment may improve patient outcomes and its potential pitfalls.

Caplacizumab for relapsing thrombotic thrombocytopenic purpura

BACKGROUND

Thrombotic thrombocytopenic purpura (TTP) is an ultra-rare disorder in childhood and belongs to the microangiopathic hemolytic anemias (MAHA) and the thrombotic microangiopathies (TMA). In the acquired form, autoantibodies against ADAMTS13 inhibit cleaving of von Willebrand factor (vWF) multimers, thereby promoting their interaction with thrombocytes, causing TMA and MAHA. A recently introduced nanobody, caplacizumab, inhibits the binding of platelets to vWF.

CASE-DIAGNOSIS/TREATMENT

During a first episode, a 10-year-old girl was admitted for TTP. Plasma exchange (PE) and immunosuppressive therapy with corticosteroids and mycophenolate mofetil were initiated. The course was complicated by catheter-associated septicemia and a very slow hematological and clinical recovery. Platelet count became normal at day 40 after admission and treatment initiation. Three years later, the child presented again with TTP. During this second episode, caplacizumab was introduced together with PE and immunosuppressive therapy within 4 days after admission. With this regimen, platelet count normalized within 3 days of treatment, and PE treatment could be stopped after a total of 14 days. The child could be discharged and caplacizumab was continued on an outpatient basis until day 30 after initiation. Adverse events during the use of caplacizumab were not encountered.

CONCLUSIONS

Caplacizumab treatment was safe and effective in a child with relapsing, autoantibody-mediated TTP. With respect to this potentially life-threatening condition, the add-on use of caplacizumab represents a novel option to reduce morbidity and mortality and improve quality of life in children and adolescents with TTP.

Caplacizumab to treat immune-mediated thrombotic thrombocytopenic purpura

Immune-mediated thrombotic thrombocytopenic purpura (iTTP) is a rare and life-threatening disease characterized by microangiopathic hemolytic anemia, thrombocytopenia and multiorgan failure, resulting from autoantibody-mediated severe A disintegrin and metalloproteinase with thrombospondin motifs 13 (ADAMTS13) deficiency. In spite of treatment with plasma exchange and immunosuppression, patients remain at risk of exacerbations, refractoriness and death. Caplacizumab (Cablivi; Ablynx, a Sanofi company), a nanobody targeting von Willebrand factor (vWF), has been recently approved in the E.U. and the U.S. as the first therapeutic specifically indicated for the treatment of adults experiencing an episode of iTTP. Caplacizumab blocks the interaction of all multimers with platelets and, therefore, has an immediate effect on platelet aggregation and the ensuing formation and accumulation of platelet-rich microthrombi. This immediate effect of caplacizumab has the potential to protect the patient from tissue ischemia and organ dysfunction while the underlying disease process resolves. We detail here the preclinical and clinical data on caplacizumab for iTTP, including the recent studies that led to approval by the U.S. Food and Drug Administration (FDA) in 2019.

Caplacizumab: a change in the paradigm of thrombotic thrombocytopenic purpura treatment

Introduction: Immune thrombotic thrombocytopenic purpura (iTTP) is an immune-mediated deficiency in von Willebrand factor-cleaving protease ADAMTS13 allowing unrestrained adhesion of von Willebrand factor multimers to platelets and microthrombosis. Caplacizumab, an anti-von Willebrand factor humanized, bivalent single-domain nanobody preventing its binding to the platelet has been investigated and approved for use in the treatment of iTTP. Areas covered: The purpose of this article is to summarize the available clinical data on the efficacy and safety of caplacizumab in iTTP and to provide our opinion on the place of caplacizumab in current treatment regimens. Expert opinion: Caplacizumab is a new drug with a complementary mechanism of action with respect to the standard available therapeutics. It demonstrated efficacy in clinical trials through a faster platelet count normalization and protection of patients from exacerbations and refractoriness. Caplacizumab is well tolerated with minor bleeds as the most important side effect. The efficacy of caplacizumab now needs to be assessed in real-life but definitely, this drug opens hope for a significant improvement in iTTP prognosis at the very early, critical step of the disease.

Clinical pharmacology of caplacizumab for the treatment of patients with acquired thrombotic thrombocytopenic purpura

Introduction: Caplacizumab is a humanized anti-von Willebrand Factor (vWF) Nanobody® for the treatment of acquired Thrombotic Thrombocytopenic Purpura (aTTP). Caplacizumab targets the A1-domain of vWF, inhibiting the interaction between vWF and platelets. Clinical studies conducted in aTTP patients confirmed the rapid and sustained complete suppression of the vWF activity using an initial intravenous dose of 10 mg, and a maintenance subcutaneous 10 mg daily dosing regimen, with corresponding favorable efficacy and safety profiles. Areas covered: The pharmacokinetics of caplacizumab are non-linear, characterized by a target-mediated disposition and the exposure is dependent upon drug and target concentration over time. The pharmacokinetics of caplacizumab are predictable when considering the turn-over of the circulating vWF and its modulation by the drug over time. Renal and hepatic impairment are not expected to influence the exposure to the drug, and no direct or indirect drug-drug pharmacokinetic interactions are anticipated based on the mechanism of action and the specificity of the pharmacodynamic effect of caplacizumab. Expert opinion: Caplacizumab prevents the interaction between vWF and platelets, offering a direct and rapid therapeutic intervention to stop microthrombosis. The combination of caplacizumab with plasma exchange and immunosuppression represents an important, potentially life-saving advance in the treatment of aTTP patients.

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.