Recombinant ADAMTS-13: first-in-human pharmacokinetics and safety in congenital thrombotic thrombocytopenic purpura

Immune Thrombotic Thrombocytopenic Purpura: Pathophysiology, Diagnosis, Therapy and Open Issues

Immune thrombotic thrombocytopenic purpura (iTTP) is a life-threatening thrombotic microangiopathy characterized by microangiopathic hemolytic anemia, thrombocytopenia, and ischemic end-organ injury due to microvascular platelet-rich thrombi. iTTP pathophysiology is based on a severe ADAMTS13 deficiency, the specific von Willebrand factor (vWF)-cleaving protease, due to anti-ADAMTS13 autoantibodies. Early diagnosis and treatment reduce the mortality. Frontline therapy includes daily plasma exchange (PEX) with fresh frozen plasma replacement and immunosuppression with corticosteroids. Caplacizumab has recently been added to frontline therapy. Caplacizumab is a nanobody that binds to the A1 domain of vWF, blocking the interaction of ultra-large vWF multimers with the platelet and thereby preventing the formation of platelet-rich thrombi. Caplacizumab reduces mortality due to ischemic events, refractoriness, and exacerbations after PEX discontinuation. Until now, the criteria for response to treatment mainly took into account the normalization of platelet count and discontinuation of PEX; with the use of caplacizumab leading to rapid normalization of platelet count, it has been necessary to redefine the response criteria, taking into account also the underlying autoimmune disease. Monitoring of ADAMTS13 activity is important to identify cases with a low value of activity (<10IU/L), requiring the optimization of immunosuppressive therapy with the addition of Rituximab. Rituximab is effective in patients with refractory disease or relapsing disease. Currently, the use of Rituximab has expanded, both in frontline treatment and during follow-up, as a pre-emptive approach. Some patients do not achieve ADAMTS13 remission following the acute phase despite steroids and rituximab treatment, requiring an individualized immunosuppressive approach to prevent clinical relapse. In iTTP, there is an increased risk of venous thrombotic events (VTEs) as well as arterial thrombotic events, and most occur after platelet normalization. Until now, there has been no consensus on the use of pharmacological thromboprophylaxis in patients on caplacizumab because the drug is known to increase bleeding risk.

Novel mechanisms of action of emerging therapies of hereditary thrombotic thrombocytopenic purpura

INTRODUCTION

Hereditary thrombotic thrombocytopenic purpura (hTTP) is caused by deficiency of plasma ADAMTS13 activity, resulting from ADAMTS13 mutations. ADAMTS13 cleaves ultra large von Willebrand factor (VWF), thus reducing its multimer sizes. Hereditary deficiency of plasma ADAMTS13 activity leads to the formation of excessive platelet-VWF aggregates in small arterioles and capillaries, resulting in hTTP.

AREAS COVERED

PubMed search from 1956 to 2024 using thrombotic thrombocytopenic purpura and therapy identified 3,675 articles. Only the articles relevant to the topic were selected for discussion, which focuses on pathophysiology, clinical presentations, and mechanisms of action of emerging therapeutics for hTTP. Current therapies include infusion of plasma, or coagulation factor VIII, or recombinant ADAMTS13. Emerging therapies include anti-VWF A1 aptamers or nanobody and gene therapies with adeno-associated viral vector or self-inactivated lentiviral vector or a sleeping beauty transposon system for a long-term expression of a functional ADAMTS13 enzyme.

EXPERT OPINION

Frequent plasma infusion remains to be the standard of care in most parts of the world, while recombinant ADAMTS13 has become the treatment of choice for hTTP in some of the Western countries. The success of gene therapies in preclinical models may hold a promise for future development of these novel approaches for a cure of hTTP.

The history of thrombotic thrombocytopenic purpura research: a narrative review

Background and Objective

Thrombotic thrombocytopenic purpura (TTP) is a rare but debilitating thrombotic microangiopathy that results from severe deficiency of the enzyme ADAMTS13. The disorder was first described in the early 20th century, but the pathophysiology of the disease has only been elucidated in the past three decades. In this narrative review, we will summarize the milestone moments in the history of TTP research and discovery.

Methods

We searched literature using PubMed from 1924 to 2023 using the following free text searches: "thrombotic thrombocytopenic purpura", "Moschcowitz disease", and "thrombotic microangiopathy". We found 6,917 peer-reviewed articles and sorted through these for relevant literature pertinent to the review. A total of 46 articles were included for review and the remainder were excluded.

Key Content and Findings

The history of TTP research was reviewed, with a sampling of major events in the evolution of the understanding of the pathophysiology and treatment of the disease discussed here. There remains much to be learned about the nature of the disease in order to develop more specific and less harmful treatments.

Conclusions

An overview of the major discoveries that have led to our current understanding of TTP reveals the results of collaboration of multiple groups of physicians and scientists through the past century, with additional breakthroughs likely to occur in the future because of that same collaborative spirit.

Imbalance of the von Willebrand Factor - ADAMTS-13 axis in patients with retinal vasculopathy with cerebral leukoencephalopathy and systemic manifestations (RVCL-S)

BACKGROUND

Retinal vasculopathy with cerebral leukoencephalopathy and systemic manifestations (RVCL-S) is an ultra-rare, autosomal-dominant small vessel disease caused by loss-of-function variants in the gene TREX1. Recently, elevated serum levels of von Willebrand Factor Antigen (vWF-Ag) pointed to an underlying endotheliopathy, and microvascular ischemia was suggested to contribute to the neurodegeneration in RVCL-S. Aim of this study was to further elucidate the endotheliopathy in RVCL-S.

METHODS

vWF-Ag and ADAMTS-13 activity were repeatedly measured in two patients with genetically confirmed RVCL-S. Renal biopsy of both RVCL-S patients and autoptic brain, renal, hepatic, and pulmonary specimen of one patient with RVCL-S were examined immunohistochemically in comparison to matched controls. In addition, cerebral methylome analysis was performed in the autoptic brain specimen calculating differentially methylated positions compared to controls.

RESULTS

While vWF-Ag and activity was strongly elevated, ADAMTS-13 activity was low in RVCL-S and further decreased over the course of the disease. Autoptic brain specimen showed signs of thromboinflammation in cerebral small vessels, and vWF-Ag staining was strongly positive in cerebral and renal small vessels in RVCL-S, while only a light to moderate vWF-Ag staining was found in controls. Cerebral methylome analysis yielded 115 differentially methylated CpGs (p < 0.05) in the deceased RVCL-S patient compared to the eight controls without brain pathology. One of the hypomethylated genes coded for ADAMTS-13 (p = 0.00056).

CONCLUSIONS

These findings point to an imbalance of the vWF - ADAMTS-13 axis in patients with RVCL-S, that may finally lead to an accumulation of vWF-Ag in renal and cerebral small vessels. Elevated vWF-Ag levels may serve as an early serum marker reflecting disease activity. If confirmed, therapeutic approaches might aim at an inhibition of vWF-Ag or increase of ADAMTS-13 activity in the future.

Targeting neutrophil extracellular trap accumulation under flow in patients with immune-mediated thrombotic thrombocytopenic purpura

ABSTRACT

Neutrophil NETosis is a unique form of cell death, characterized by the release of decondensed chromatin and antimicrobial contents to the extracellular space, which is involved in inflammation and thrombosis. However, the role of NETosis in the pathogenesis of immune-mediated thrombotic thrombocytopenic purpura (iTTP) and how a targeted therapy affects the accumulation of neutrophil extracellular traps (NETs) under flow remain unknown. Flow cytometry demonstrated that the percentage of neutrophils undergoing NETosis in whole blood from patients with iTTP on admission was significantly increased, with a concurrent decrease in the capacity of inducible NETosis by shigatoxin. After therapy, the percentage of H3Cit+MPO+ neutrophils was significantly reduced, with an improvement in inducible NETosis in these patients. Additionally, little to no NET and thrombus formation was detected underflow in the whole blood from patients with iTTP when platelet counts were very low, but the NET and thrombus formation was dramatically increased following therapy when platelet counts rose to ≥50 × 109/L or were restored to normal with donor platelets. Similarly, there was no thrombus or NET accumulation under flow in the whole blood from vwf-/- mice, but NET accumulation was significantly higher in Adamts13-/- mice than in wild-type mice. Finally, recombinant ADAMTS13 or caplacizumab (or anfibatide) prevented NET and thrombus formation under flow in whole blood from patients with iTTP or from Adamts13-/- mice. These results indicate that neutrophil NETosis and NET formation depend on platelets and von Willebrand factor (VWF) in iTTP, and a targeted therapy such as recombinant ADAMTS13 or caplacizumab may prevent NET and thrombus formation under flow in iTTP.

Cancer progression and tumor hypercoagulability: a platelet perspective

Venous thromboembolism, which is common in cancer patients and accompanies or even precedes malignant tumors, is known as cancer-related thrombosis and is an important cause of cancer- associated death. At present, the exact etiology of the elevated incidence of venous thrombosis in cancer patients remains elusive. Platelets play a crucial role in blood coagulation, which is intimately linked to the development of arterial thrombosis. Additionally, platelets contribute to tumor progression and facilitate immune evasion by tumors. Tumor cells can interact with the coagulation system through various mechanisms, such as producing hemostatic proteins, activating platelets, and directly adhering to normal cells. The relationship between platelets and malignant tumors is also significant. In this review article, we will explore these connections.

Recombinant ADAMTS13 for Immune Thrombotic Thrombocytopenic Purpura

In patients with immune thrombotic thrombocytopenic purpura (iTTP), autoantibodies against the metalloprotease ADAMTS13 lead to catastrophic microvascular thrombosis. However, the potential benefits of recombinant human ADAMTS13 (rADAMTS13) in patients with iTTP remain unknown. Here, we report the clinical use of rADAMTS13, which resulted in the rapid suppression of disease activity and complete recovery in a critically ill patient whose condition had proved to be refractory to all available treatments. We also show that rADAMTS13 causes immune complex formation, which saturates the autoantibody and may promote its clearance. Our data support the role of rADAMTS13 as a novel adjunctive therapy in patients with iTTP.

Recombinant ADAMTS13 in Congenital Thrombotic Thrombocytopenic Purpura

BACKGROUND

Congenital thrombotic thrombocytopenic purpura (TTP) results from severe hereditary deficiency of ADAMTS13. The efficacy and safety of recombinant ADAMTS13 and standard therapy (plasma-derived products) administered as routine prophylaxis or on-demand treatment in patients with congenital TTP is not known.

METHODS

In this phase 3, open-label, crossover trial, we randomly assigned patients in a 1:1 ratio to two 6-month periods of prophylaxis with recombinant ADAMTS13 (40 IU per kilogram of body weight, administered intravenously) or standard therapy, followed by the alternate treatment; thereafter, all the patients received recombinant ADAMTS13 for an additional 6 months. The trigger for this interim analysis was trial completion by at least 30 patients. The primary outcome was acute TTP events. Manifestations of TTP, safety, and pharmacokinetics were assessed. Patients who had an acute TTP event could receive on-demand treatment.

RESULTS

A total of 48 patients underwent randomization; 32 completed the trial. No acute TTP event occurred during prophylaxis with recombinant ADAMTS13, whereas 1 patient had an acute TTP event during prophylaxis with standard therapy (mean annualized event rate, 0.05). Thrombocytopenia was the most frequent TTP manifestation (annualized event rate, 0.74 with recombinant ADAMTS13 and 1.73 with standard therapy). Adverse events occurred in 71% of the patients with recombinant ADAMTS13 and in 84% with standard therapy. Adverse events that were considered by investigators to be related to the trial drug occurred in 9% of the patients with recombinant ADAMTS13 and in 48% with standard therapy. Trial-drug interruption or discontinuation due to adverse events occurred in no patients with recombinant ADAMTS13 and in 8 patients with standard therapy. No neutralizing antibodies developed during recombinant ADAMTS13 treatment. The mean maximum ADAMTS13 activity after recombinant ADAMTS13 treatment was 101%, as compared with 19% after standard therapy.

CONCLUSIONS

During prophylaxis with recombinant ADAMTS13 in patients with congenital TTP, ADAMTS13 activity reached approximately 100% of normal levels, adverse events were generally mild or moderate in severity, and TTP events and manifestations were rare. (Funded by Takeda Development Center Americas and Baxalta Innovations; ClinicalTrials.gov number, NCT03393975.).

How We Interpret Thrombosis with Thrombocytopenia Syndrome?

Platelets play an important role in hemostasis, and a low platelet count usually increases the risk of bleeding. Conditions in which thrombosis occurs despite low platelet counts are referred to as thrombosis with thrombocytopenia syndrome, including heparin-induced thrombocytopenia, vaccine-induced immune thrombotic thrombocytopenia, paroxysmal nocturnal hemoglobinuria, antiphospholipid syndrome, thrombotic microangiopathy (TMA), and disseminated intravascular coagulation. TMA includes thrombotic thrombocytopenic purpura, Shiga toxin-producing Escherichia coli-associated hemolytic uremic syndrome (HUS), and atypical HUS. Patients with these pathologies present with thrombosis and consumptive thrombocytopenia associated with the activation of platelets and the coagulation system. Treatment varies from disease to disease, and many diseases have direct impacts on mortality and organ prognosis if therapeutic interventions are not promptly implemented. Underlying diseases and the results of physical examinations and general laboratory tests as part of a thorough workup for patients should promptly lead to therapeutic intervention before definitive diagnosis. For some diseases, the diagnosis and initial treatment must proceed in parallel. Utilization of not only laboratory tests but also various scoring systems is important for validating therapeutic interventions based on clinical information.

Targeted ADAMTS-13 replacement therapy for thrombotic thrombocytopenic purpura

Thrombotic thrombocytopenic purpura (TTP) is a life-threatening thrombotic disorder associated with a severe deficiency of ADAMTS-13-the protease that cleaves von Willebrand factor. Plasma therapy is the current standard of care for managing acute episodes of TTP, which involves removing patient plasma and replacing it with donor plasma to raise the level of ADAMTS-13 activity. Recently, therapies aimed at replacing ADAMTS-13 have been investigated as possible substitutes or add-ons to plasma therapy for congenital and immune-mediated TTP. Enzyme replacement therapy provides recombinant ADAMTS-13 via intravenous (i.v.) infusion to restore enzyme activity. Recombinant ADAMTS-13-loaded platelets localize to the site of thrombus formation in a more concentrated manner than enzyme replacement or plasma therapy. ADAMTS-13-encoding messenger RNA aims to induce a steady supply of secreted protein and gene therapy is a potentially curative strategy. Overall, targeted ADAMTS-13 replacement therapies may provide better outcomes than plasma therapy by achieving higher levels of ADAMTS-13 activity and a more sustained response with fewer adverse events. Herein, we describe targeted ADAMTS-13 replacement therapies for the treatment of TTP and discuss the advantages and limitations of each approach.

Current and potentially novel antithrombotic treatment in acute ischemic stroke

Acute ischemic stroke (AIS) is the most common type of stroke and requires immediate reperfusion. Current acute reperfusion therapies comprise the administration of intravenous thrombolysis and/or endovascular thrombectomy. Although these acute reperfusion therapies are increasingly successful, optimized secondary antithrombotic treatment remains warranted, specifically to reduce the risk of major bleeding complications. In the development of AIS, coagulation and platelet activation play crucial roles by driving occlusive clot formation. Recent studies implicated that the intrinsic route of coagulation plays a more prominent role in this development, however, this is not fully understood yet. Next to the acute treatments, antithrombotic therapy, consisting of anticoagulants and/or antiplatelet therapy, is successfully used for primary and secondary prevention of AIS but at the cost of increased bleeding complications. Therefore, better understanding the interplay between the different pathways involved in the pathophysiology of AIS might provide new insights that could lead to novel treatment strategies. This narrative review focuses on the processes of platelet activation and coagulation in AIS, and the most common antithrombotic agents in primary and secondary prevention of AIS. Furthermore, we provide an overview of promising novel antithrombotic agents that could be used to improve in both acute treatment and stroke prevention.

Apadamtase Alfa: First Approval

Apadamtase alfa (ADAMTS13, recombinant-krhn; ADZYNMA), a human recombinant form of a disintegrin and metalloproteinase with thrombospondin motifs 13 (ADAMTS13), is being developed by Takeda under license from KM biologics for thrombotic thrombocytopenic purpura (TTP) and sickle cell disease. On 9 November 2023, apadamtase alfa was approved in the USA for prophylactic and on-demand enzyme replacement therapy (ERT) in paediatric and adult patients with congenital TTP. Apadamtase alfa is under regulatory review for congenital TTP in the EU and Japan, and is under clinical development for immune-mediated TTP in several countries worldwide. Clinical development of apadamtase alfa for vaso-occlusive crisis related to sickle cell anaemia is underway in the USA. This article summarizes the milestones in the development of apadamtase alfa leading to this first approval in the USA for congenital TTP.

Kinetic modeling of the plasma pharmacokinetic profiles of ADAMTS13 fragment and its Fc-fusion counterpart in mice

Introduction: Fusion of the fragment crystallizable (Fc) to protein therapeutics is commonly used to extend the circulation time by enhancing neonatal Fc-receptor (FcRn)-mediated endosomal recycling and slowing renal clearance. This study applied kinetic modeling to gain insights into the cellular processing contributing to the observed pharmacokinetic (PK) differences between the novel recombinant ADAMTS13 fragment (MDTCS) and its Fc-fusion protein (MDTCS-Fc). Methods: For MDTCS and MDTCS-Fc, their plasma PK profiles were obtained at two dose levels following intravenous administration of the respective proteins to mice. The plasma PK profiles of MDTCS were fitted to a kinetic model with three unknown protein-dependent parameters representing the fraction recycled (FR) and the rate constants for endocytosis (kup, for the uptake into the endosomes) and for the transfer from the plasma to the interstitial fluid (kpi). For MDTCS-Fc, the model was modified to include an additional parameter for binding to FcRn. Parameter optimization was done using the Cluster Gauss-Newton Method (CGNM), an algorithm that identifies multiple sets of approximate solutions ("accepted" parameter sets) to nonlinear least-squares problems. Results: As expected, the kinetic modeling results yielded the FR of MDTCS-Fc to be 2.8-fold greater than that of MDTCS (0.8497 and 0.3061, respectively). In addition, MDTCS-Fc was predicted to undergo endocytosis (the uptake into the endosomes) at a slower rate than MDTCS. Sensitivity analyses identified the association rate constant (kon) between MDTCS-Fc and FcRn as a potentially important factor influencing the plasma half-life in vivo. Discussion: Our analyses suggested that Fc fusion to MDTCS leads to changes in not only the FR but also the uptake into the endosomes, impacting the systemic plasma PK profiles. These findings may be used to develop recombinant protein therapeutics with extended circulation time.

Cognitive decline in thrombotic thrombocytopenic purpura survivors: The role of white matter health as assessed by MRI

Immune-mediated thrombotic thrombocytopenic purpura (iTTP) is a rare condition caused by severe ADAMTS13 deficiency, leading to platelet aggregation and thrombosis. Despite treatment, patients are prone to cognitive impairment and depression. We investigated brain changes in iTTP patients during remission using advanced magnetic resonance imaging (MRI) techniques, correlating these changes with mood and neurocognitive tests. Twenty iTTP patients in remission (30 days post-haematological remission) were compared with six healthy controls. MRI scans, including standard and specialized sequences, were conducted to assess white matter health. Increased T1 relaxation times were found in the cingulate cortex (p < 0.05), and elevated T2 relaxation times were observed in the cingulate cortex, frontal, parietal and temporal lobes (p < 0.05). Pathological changes in these areas are correlated with impaired cognitive and depressive scores in concentration, short-term memory and verbal memory. This study highlights persistent white matter damage in iTTP patients, potentially contributing to depression and cognitive impairment. Key regions affected include the frontal lobe and cingulate cortex. These findings have significant implications for the acute and long-term management of iTTP, suggesting a need for re-evaluation of treatment approaches during both active phases and remission. Further research is warranted to enhance our understanding of these complexities.

REVIEWING THE DYSREGULATION OF ADAMTS13 AND VWF IN SEPSIS

ABSTRACT

Sepsis is defined as a life-threatening organ dysfunction caused by excessive host response to infection, and represents the most common cause of in-hospital deaths. Sepsis accounts for 30% of all critically ill patients in the intensive care unit (ICU), and has a global mortality rate of 20%. Activation of blood coagulation during sepsis and septic shock can lead to disseminated intravascular coagulation, which is characterized by microvascular thrombosis. Von Willebrand factor (VWF) and ADAMTS13 are two important regulators of blood coagulation that may be important links between sepsis and mortality in the ICU. Herein we review our current understanding of VWF and ADAMTS13 in sepsis and other critical illnesses and discuss their contribution to disease pathophysiology, their use as markers of severe illness, and potential targets for new therapeutic development.

Von Willebrand factor promotes radiation-induced intestinal injury (RIII) development and its cleavage enzyme rhADAMTS13 protects against RIII by reducing inflammation and oxidative stress

Patients with abdominopelvic cancer undergoing radiotherapy commonly develop radiation-induced intestinal injury (RIII); however, its underlying pathogenesis remains elusive. The von Willebrand factor (vWF)/a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13 (ADAMTS13) axis has been implicated in thrombosis, inflammation, and oxidative stress. However, its role in RIII remains unclear. In this study, the effect of radiation on vWF and ADAMTS13 expression was firstly evaluated in patients with cervical cancer undergoing radiotherapy and C57BL/6J mice exposed to different doses of total abdominal irradiation. Then, mice with the specific deletion of vWF in the platelets and endothelium were established to demonstrate the contribution of vWF to RIII. Additionally, the radioprotective effect of recombinant human (rh) ADAMTS13 against RIII was assessed. Results showed that both the patients with cervical cancer undergoing radiotherapy and RIII mouse model exhibited increased vWF levels and decreased ADAMTS13 levels. The knockout of platelet- and endothelium-derived vWF rectified the vWF/ADAMTS13 axis imbalance; improved intestinal structural damage; increased crypt epithelial cell proliferation; and reduced radiation-induced apoptosis, inflammation, and oxidative stress, thereby alleviating RIII. Administration of rhADAMTS13 could equally alleviate RIII. Our results demonstrated that abdominal irradiation affected the balance of the vWF/ADAMTS13 axis. vWF exerted a deleterious role and ADAMTS13 exhibited a protective role in RIII progression. rhADAMTS13 has the potential to be developed into a radioprotective agent.

Laboratory investigation and diagnosis of thrombotic thrombocytopenic purpura

Thrombotic thrombocytopenic purpura (TTP) is a rare and potentially fatal disease for which rapid diagnosis is crucial for patient outcomes. Deficient activity (< 10%) of the liver enzyme, ADAMTS13, is the pathophysiological hallmark of TTP, and measurement of the enzyme activity can establish the diagnosis of TTP with high accuracy. Thus, along with the clinical history, appropriate laboratory assessment of a suspected case of TTP is essential for diagnosis and treatment. Here, we present a review of the available laboratory tests that can assist clinicians in establishing the diagnosis of TTP, with special focus on ADAMTS13 assays, including the measurement of the antigen and activity, and detection of autoantibodies to ADAMTS13.

Dynamic Assessment of Plasma von Willebrand Factor and ADAMTS13 Predicts Mortality in Hospitalized Patients with SARS-CoV-2 Infection

BACKGROUND

Plasma levels of von Willebrand factor (VWF) are significantly elevated in patients with coronavirus disease 2019 (COVID-19). However, dynamic changes and prognostic value of this biomarker in hospitalized patients with COVID-19 have not been determined.

METHODS

A total of 124 patients infected with SARS-CoV-2 were prospectively recruited for the study. Serial blood samples were obtained at the time of admission (D1), 3-4 days following standard-care treatments (D2), and 1-2 days prior to discharge or any time collected prior to death (D3). Plasma VWF antigen, ADAMTS13 antigen, and ADAMTS13 proteolytic activity, as well as the ratio of VWF/ADAMTS13 were determined, followed by various statistical analyses.

RESULTS

On admission, plasma levels of VWF in COVID-19 patients were significantly elevated compared with those in the healthy controls, but no statistical significance was detected among patients with different disease severity. Plasma ADAMTS13 activity but not its antigen levels were significantly lower in patients with severe or critical COVID-19 compared with that in other patient groups. Interestingly, the ratios of plasma VWF antigen to ADAMTS13 antigen were significantly higher in patients with severe or critical COVID-19 than in those with mild to moderate disease. More importantly, plasma levels of VWF and the ratios of VWF/ADAMTS13 were persistently elevated in patients with COVID-19 throughout hospitalization. Kaplan-Meier and Cox proportional hazard regression analyses demonstrated that an increased plasma level of VWF or ratio of VWF/ADAMTS13 at D2 and D3 was associated with an increased mortality rate.

CONCLUSIONS

Persistent endotheliopathy, marked by the elevated levels of plasma VWF or VWF/ADAMTS13 ratio, is present in all hospitalized patients following SARS-CoV-2 infection, which is strongly associated with mortality.

A British Society for Haematology Guideline: Diagnosis and management of thrombotic thrombocytopenic purpura and thrombotic microangiopathies

The objective of this guideline is to provide healthcare professionals with clear, up-to-date and practical guidance on the management of thrombotic thrombocytopenic purpura (TTP) and related thrombotic microangiopathies (TMAs), including complement-mediated haemolytic uraemic syndrome (CM HUS); these are defined by thrombocytopenia, microangiopathic haemolytic anaemia (MAHA) and small vessel thrombosis. Within England, all TTP cases should be managed within designated regional centres as per NHSE commissioning for highly specialised services.

Long-term follow-up of patients with congenital thrombotic thrombocytopenia purpura receiving a plasma-derived factor VIII (Koate) that contains ADAMTS13

BACKGROUND

Hereditary thrombotic thrombocytopenia purpura (hTTP) is an ultra-rare disorder resulting from an inherited deficiency of ADAMTS13, a von Willebrand factor (VWF)-cleaving metalloprotease. The plasma-derived factor VIII/VWF Koate (FVIII/VWFKoate ) has been shown to contain ADAMTS13, allowing for its use to treat hTTP at home by the patient/caregiver.

AIM

Based on prior demonstration of safe and effective use of FVIII/VWFKoate in eight patients with hTTP, we conducted a retrospective study to gather additional data regarding the use of FVIII/VWFKoate for hTTP.

METHODS

This was a multicentre, retrospective, noninterventional chart review of patients who had received FVIII/VWFKoate for the management of hTTP. Data collected included demographics, medical history, relevant family history, past use and tolerability of fresh frozen plasma, and details regarding FVIII/VWFKoate therapy.

RESULTS

The cohort included 11 patients (seven males, four females) with hTTP, ranging in age at study entry from 2 to 28 years. The average duration of FVIII/VWFKoate therapy was 4.8 years (range, 0.5-6.5 years). Among nine patients using FVIII/VWFKoate as prophylaxis, the normalized annual rate of breakthrough TTP episodes ranged from 0.2 to 1.1 episodes/year. All nine patients who received FVIII/VWFKoate prophylaxis had thrombocytopenia recorded at baseline, while eight (88.9%) did not have thrombocytopenia after using FVIII/VWFKoate . There was one AE (unspecified) attributed to FVIII/VWFKoate .

CONCLUSION

These data suggest that FVIII/VWFKoate is a safe and well-tolerated source of the missing ADAMTS13 enzyme in patients with hTTP, producing a marked reduction in thrombocytopenia prevalence, low frequency of TTP episodes, and with the added benefit of self- or caregiver-administration.

Hereditary Thrombotic Thrombocytopenic Purpura

Hereditary thrombotic thrombocytopenic purpura (hTTP), also known as Upshaw-Schulman syndrome, is a rare genetic disorder caused by mutations in the ADAMTS13 gene that leads to decreased or absent production of the plasma von Willebrand factor (VWF)-cleaving metalloprotease ADAMTS13. The result is circulating ultra-large multimers of VWF that can cause microthrombi, intravascular occlusion and organ damage, especially at times of turbulent circulation. Patients with hTTP may have many overt or clinically silent manifestations, and a high index of suspicion is required for diagnosis. For the treatment of hTTP, the goal is simply replacement of ADAMTS13. The primary treatment is prophylaxis with plasma infusions or plasma-derived factor VIII products, providing sufficient ADAMTS13 to prevent acute episodes. When acute episodes occur, prophylaxis is intensified. Recombinant ADAMTS13, which is near to approval, will immediately be the most effective and also the most convenient treatment. In this review, we discuss the possible clinical manifestations of this rare disease and the relevant differential diagnoses in different age groups. An extensive discussion on prophylaxis and treatment strategies is also presented. Unique real patient cases have been added to highlight critical aspects of hTTP manifestations, diagnosis and treatment.

Congenital Thrombotic Thrombocytopenic Purpura: A Rare Cause of Recurrent Thrombocytopenia and Anemia

Congenital thrombotic thrombocytopenic purpura (cTTP) is a rare autosomal recessive microangiopathic disorder caused by inherited mutations in the ADAMTS13 gene. cTTP treatment involves infusing ADAMTS13-rich blood products like fresh frozen plasma (FFP) to replenish levels and prevent disease relapses. Alternative therapies like recombinant ADAMTS13, plasma-derived Factor VIII, or caplacizumab may be used for patients unable to tolerate FFP. We present a case of a five-month-old girl who had recurrent episodes of anemia and thrombocytopenia. She was diagnosed with cTTP based on the presence of low ADAMTS13 activity and the identification of a homozygous likely pathogenic variant in the ADAMTS13 gene. After receiving regular transfusions of FFP, our patient improved significantly and has been asymptomatic for 18 months with no transfusion complications.

Metalloprotease domain latency protects ADAMTS13 against broad-spectrum inhibitors of metalloproteases while maintaining activity toward VWF

BACKGROUND

ADAMTS13 is a circulating metalloprotease that cleaves von Willebrand factor (VWF) in a shear-dependent manner. ADAMTS13 is secreted as an active protease but has a long half-life, suggesting that it is resistant to circulating protease inhibitors. These zymogen-like properties indicate that ADAMTS13 exists as a latent protease that is activated by its substrate.

OBJECTIVES

To investigate the mechanism of ADAMTS13 latency and resistance to metalloprotease inhibitors.

METHODS

Probe the active site of ADAMTS13 and variants using alpha-2 macroglobulin (A2M), tissue inhibitors of metalloproteases (TIMPs), and Marimastat.

RESULTS

ADAMTS13 and C-terminal deletion mutants are not inhibited by A2M, TIMPs, or Marimastat, but cleave FRETS-VWF73, suggesting that the metalloprotease domain is latent in the absence of substrate. Within the metalloprotease domain, mutating the gatekeeper triad (R193, D217, D252) or substituting the calcium-binding (R180-R193) or the variable (G236-S263) loops with corresponding features from ADAMTS5 did not sensitize MDTCS to inhibition. However, substituting the calcium-binding loop and an extended variable loop (G236-S263) corresponding to the S1-S1' pockets with those from ADAMTS5, resulted in MDTCS-GVC5 inhibition by Marimastat, but not by A2M or TIMP3. Substituting the MD domains of ADAMTS5 into full-length ADAMTS13 resulted in a 50-fold reduction in activity compared with the substitution into MDTCS. However, both chimeras were susceptible to inhibition, suggesting that the closed conformation does not contribute to the latency of the metalloprotease domain.

CONCLUSION

The metalloprotease domain protects ADAMTS13 from inhibitors and exists in a latent state that is partially maintained by loops flanking the S1 and S1' specificity pockets.

Association between N-acetylcysteine treatment and in-hospital mortality in adult patients with acquired thrombotic thrombocytopenic purpura: a cohort study

Acquired thrombotic thrombocytopenic purpura (aTTP) is a fatal hematologic disease. Despite the currently high standards of care, some patients who develop refractory or recurrent disease still have a poor prognosis. Although N-acetylcysteine (NAC) is recommended for the treatment of aTTP, its use in aTTP treatment is still controversial. We aimed to evaluate the association of NAC with mortality in patients with aTTP. This was a retrospective cohort study of patients with aTTP with in-hospital mortality as the primary outcome and time to platelet recovery and neurological recovery as secondary outcomes. We used multifactorial COX regression analysis to check for an association of NAC with mortality. Moreover, we performed a sensitivity analysis check the stability of our results. Finally, 89 patients with aTTP were enrolled. After adjusting for potential confounders, we found NAC to be associated with 75% lower in-hospital mortality (HR = 0.25, 95% CI = 0.1-0.64). The results of sensitivity analyses performed remained stable as the risk of in-hospital mortality in patients reduced in patients with comorbid neurological symptoms (HR = 0.23, 95% CI = 0.06-0.89). However, NAC use did not affect the time to platelet recovery (HR = 1.19, 95% CI = 0.57-2.5) or neurological recovery (HR = 0.32, 95% CI = 0.08-1.25) in patients with aTTP. NAC treatment reduces in-hospital mortality in patients with aTTP but does not shorten the time to platelet recovery or neurological recovery.

Autoantibodies enhance ADAMTS-13 clearance in patients with immune thrombotic thrombocytopenic purpura

BACKGROUND

Severe deficiency in ADAMTS-13 (<10%) and the loss of von Willebrand factor-cleaving function can precipitate microvascular thrombosis associated with thrombotic thrombocytopenic purpura (TTP). Patients with immune-mediated TTP (iTTP) have anti-ADAMTS-13 immunoglobulin G antibodies that inhibit ADAMTS-13 function and/or increase ADAMTS-13 clearance. Patients with iTTP are treated primarily by plasma exchange (PEX), often in combination with adjunct therapies that target either the von Willebrand factor-dependent microvascular thrombotic processes (caplacizumab) or the autoimmune components (steroids or rituximab) of the disease.

OBJECTIVES

To investigate the contributions of autoantibody-mediated ADAMTS-13 clearance and inhibition in patients with iTTP at presentation and through the course of the PEX therapy.

PATIENTS/METHODS

Anti-ADAMTS-13 immunoglobulin G antibodies, ADAMTS-13 antigen, and activity were measured before and after each PEX in 17 patients with iTTP and 20 acute TTP episodes.

RESULTS

At presentation, 14 out of 15 patients with iTTP had ADAMTS-13 antigen levels of <10%, suggesting a major contribution of ADAMTS-13 clearance to the deficiency state. After the first PEX, both ADAMTS-13 antigen and activity levels increased similarly, and the anti-ADAMTS-13 autoantibody titer decreased in all patients, revealing ADAMTS-13 inhibition to be a modest modifier of the ADAMTS-13 function in iTTP. Analysis of ADAMTS-13 antigen levels between consecutive PEX treatments revealed that the rate of ADAMTS-13 clearance in 9 out of 14 patients analyzed was 4- to 10-fold faster than the estimated normal rate of clearance.

CONCLUSION

These data reveal, both at presentation and during PEX treatment, that antibody-mediated clearance of ADAMTS-13 is the major pathogenic mechanism that causes ADAMTS-13 deficiency in iTTP. Understanding the kinetics of ADAMTS-13 clearance in iTTP may now enable further optimization of treatment of patients with iTTP.

Clinical Manifestations, Current and Future Therapy, and Long-Term Outcomes in Congenital Thrombotic Thrombocytopenic Purpura

Congenital thrombotic thrombocytopenic purpura (cTTP) is an extremely rare disease characterized by the severe deficiency of a disintegrin and metalloproteinase with thrombospondin type 1 motifs 13 (ADAMTS13), caused by ADAMTS13 mutations. While ADAMTS13 supplementation by fresh frozen plasma (FFP) infusion immediately corrects platelet consumption and resolves thrombotic symptoms in acute episodes, FFP treatment can lead to intolerant allergic reactions and frequent hospital visits. Up to 70% of patients depend on regular FFP infusions to normalize their platelet counts and avoid systemic symptoms, including headache, fatigue, and weakness. The remaining patients do not receive regular FFP infusions, mainly because their platelet counts are maintained within the normal range or because they are symptom-free without FFP infusions. However, the target peak and trough levels of ADAMTS13 to prevent long-term comorbidity with prophylactic FFP and the necessity of treating FFP-independent patients in terms of long-term clinical outcomes are yet to be determined. Our recent study suggests that the current volumes of FFP infusions are insufficient to prevent frequent thrombotic events and long-term ischemic organ damage. This review focuses on the current management of cTTP and its associated issues, followed by the importance of upcoming recombinant ADAMTS13 therapy.

Immune and Hereditary Thrombotic Thrombocytopenic Purpura: Can ADAMTS13 Deficiency Alone Explain the Different Clinical Phenotypes?

Thrombotic thrombocytopenic purpura (TTP) is a thrombotic microangiopathy caused by a hereditary or immune-mediated deficiency of the enzyme ADAMTS13 (a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13). TTPs are caused by the following pathophysiological mechanisms: (1) the presence of inhibitory autoantibodies against ADAMTS13; and (2) hereditary mutations of the ADAMTS13 gene, which is present on chromosome 9. In both syndromes, TTP results from a severe deficiency of ADAMTS13, which is responsible for the impaired proteolytic processing of high-molecular-weight von Willebrand factor (HMW-VWF) multimers, which avidly interact with platelets and subendothelial collagen and promote tissue and multiorgan ischemia. Although the acute presentation of the occurring symptoms in acquired and hereditary TTPs is similar (microangiopathic hemolytic anemia, thrombocytopenia, and variable ischemic end-organ injury), their intensity, incidence, and precipitating factors are different, although, in both forms, a severe ADAMTS13 deficiency characterizes their physiopathology. This review is aimed at exploring the possible factors responsible for the different clinical and pathological features occurring in hereditary and immune-mediated TTPs.

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.

Treatment with recombinant ADAMTS13, alleviates hypoxia/reoxygenation-induced pathologies in a mouse model of human sickle cell disease

BACKGROUND

Sickle cell disease (SCD) is an inherited red blood cell disorder with a causative substitution in the beta-globin gene that encodes beta-globin in hemoglobin. Furthermore, the ensuing vasculopathy in the microvasculature involves heightened endothelial cell adhesion, inflammation, and coagulopathy, all of which contribute to vaso-occlusive crisis (VOC) and the sequelae of SCD. In particular, dysregulation of the von Willebrand factor (VWF) and a disintegrin and metalloproteinase with thrombospondin type 1 motif, member 13 (ADAMTS13) axis has been implicated in human SCD pathology.

OBJECTIVES

To investigate the beneficial potential of treatment with recombinant ADAMTS13 (rADAMTS13) to alleviate VOC.

METHODS

Pharmacologic treatment with rADAMTS13 in vitro or in vivo was performed in a humanized mouse model of SCD that was exposed to hypoxia/reoxygenation stress as a model of VOC. Then, pharmacokinetic, pharmacodynamic, and behavioral analyses were performed.

RESULTS

Administration of rADAMTS13 to SCD mice dose-dependently increased plasma ADAMTS13 activity, reduced VWF activity/antigen ratios, and reduced baseline hemolysis (free hemoglobin and total bilirubin) within 24 hours. rADAMTS13 was administered in SCD mice, followed by hypoxia/reoxygenation stress, and reduced VWF activity/antigen ratios in parallel to significantly (p < .01) improved recovery during the reoxygenation phase. Consistent with the results in SCD mice, we demonstrate in a human in vitro system that treatment with rADAMTS13 counteracts the inhibitory activity of hemoglobin on the VWF/ADAMTS13-axis.

CONCLUSION

Collectively, our data provide evidence that relative ADAMTS13 insufficiency in SCD mice is corrected by pharmacologic treatment with rADAMTS13 and provides an effective disease-modifying approach in a human SCD mouse model.

[Thrombotic thrombocytopenic purpura-a differential diagnostic challenge in an emergency]

Thrombotic thrombocytopenic purpura (TTP), which comprises thrombocytopenia, elevated lactate dehydrogenase levels, and anemia in the combination of organ involvement, is a rare but life-threatening condition associated with an extremely high lethality in the acute phase if left untreated. Using the example of a 49-year-old woman admitted to the hospital with unexplained abdominal symptoms and subfebrile temperatures, recommendations for the emergency situation are presented. Increased awareness of the disease and targeted further diagnostics with determination of the PLASMIC score or ADAMTS13 activity may lead directly to diagnosis of TTP; delayed diagnosis is usually associated with secondary complications.

Differentiating and Managing Rare Thrombotic Microangiopathies During Pregnancy and Postpartum

The most common thrombotic microangiopathy (TMA) of pregnancy is the well-recognized syndrome of preeclampsia with hemolysis, elevated liver enzymes, and low platelet count (HELLP) syndrome. However, rare TMAs, including thrombotic thrombocytopenic purpura, complement-mediated hemolytic-uremic syndrome, and catastrophic antiphospholipid syndrome, may occur during pregnancy or postpartum and present with features similar to those of preeclampsia with severe features. Early recognition and treatment of these infrequently encountered conditions are key for avoiding serious maternal morbidities with long-term sequelae and possible maternal or fetal death. Differentiating between preeclampsia with severe features and these rare TMAs is diagnostically challenging as there is significant overlap in their clinical and laboratory presentation. Given the rarity of these TMAs, high-quality evidence-based recommendations on diagnosis and management during pregnancy are lacking. Using current objective information and recommendations from working groups, this report provides practical clinical approaches to diagnose and manage these rare TMAs. This report also discusses how to manage individuals with a history of these rare TMAs who are planning to conceive. To optimize favorable outcomes, a multidisciplinary approach including obstetricians, maternal-fetal medicine specialists, hematologists, and nephrologists alongside close clinical and laboratory monitoring is vital.

Recombinant ADAMTS13 for Hereditary Thrombotic Thrombocytopenic Purpura

A 27-year-old patient with a history of severe obstetrical complications and arterial thrombosis received a diagnosis of hereditary thrombotic thrombocytopenic purpura (TTP) due to severe ADAMTS13 deficiency when she presented with an acute episode in the 30th week of her second pregnancy. When the acute episode of hereditary TTP became plasma-refractory and fetal death was imminent, weekly injections of recombinant ADAMTS13 at a dose of 40 U per kilogram of body weight were initiated. The patient's platelet count normalized, and the growth of the fetus stabilized. At 37 weeks 1 day of gestation, a small-for-gestational-age boy was delivered by cesarean section. At the time of this report, the patient and her son were well, and she continued to receive injections of recombinant ADAMTS13 every 2 weeks. (Funded by the Swiss National Science Foundation.).

Mechanisms of ADAMTS13 regulation

Recombinant ADAMTS13 is currently undergoing clinical trials as a treatment for hereditary thrombotic thrombocytopenic purpura, a lethal microvascular condition resulting from ADAMTS13 deficiency. Preclinical studies have also demonstrated its efficacy in treating arterial thrombosis and inflammation without causing bleeding, suggesting that recombinant ADAMTS13 may have broad applicability as an antithrombotic agent. Despite this progress, we currently do not understand the mechanisms that regulate ADAMTS13 activity in vivo. ADAMTS13 evades canonical means of protease regulation because it is secreted as an active enzyme and has a long half-life in circulation, suggesting that it is not inhibited by natural protease inhibitors. Although shear can spatially and temporally activate von Willebrand factor to capture circulating platelets, it is also required for cleavage by ADAMTS13. Therefore, spatial and temporal regulation of ADAMTS13 activity may be required to stabilize von Willebrand factor-platelet strings at sites of vascular injury. This review outlines potential mechanisms that regulate ADAMTS13 in vivo including shear-dependency, local inactivation, and biochemical and structural regulation of substrate binding. Recently published structural data of ADAMTS13 is discussed, which may help to generate novel hypotheses for future research.

Thrombotic Thrombocytopenic Purpura: From 1972 to 2022 and Beyond

This review tells the story of my personal experience with thrombotic thrombocytopenic purpura (TTP). It begins with my first encounter with TTP 50 years ago when 2 sisters presented 2 years apart, both pregnant and both died. At that time, I knew nothing about hereditary TTP (hTTP), the risks of pregnancy, or effective treatments. In 1991, a year after I moved to Oklahoma, therapeutic plasma exchange (TPE) was established as an effective treatment. With the availability of effective treatment, the number of patients presenting with suspected TTP soared. The diagnosis of TTP was imprecise. I worked with the Oklahoma Blood Institute (OBI) to understand the management of TTP. Because the OBI provided all TPE procedures for most of Oklahoma, we saw all consecutive patients within a defined geographic area who were identified at a uniform time early in the course of their TTP, without selection or referral bias. It was an inception cohort; this became the Oklahoma TTP Registry. In 2001, we began a very successful collaboration with the University of Bern, Switzerland, to measure ADAMTS13 activity in all of our patients. From our patients, we learned that acquired, autoimmune TTP (iTTP) is a chronic disease with risks for cognitive impairment and depression. Recognition in 2012 of three sisters with hTTP was reminiscent of the beginning of my story. hTTP has risks for multiple severe morbidities, beginning at birth and especially during pregnancy. Future management of both iTTP and hTTP will be more effective and more convenient.

Neutrophil extracellular traps facilitate cancer metastasis: cellular mechanisms and therapeutic strategies

Background

The formation of neutrophil extracellular traps (NETs) was initially discovered as a novel immune response against pathogens. Recent studies have also suggested that NETs play an important role in tumor progression. This review summarizes the cellular mechanisms by which NETs promote distant metastasis and discusses the possible clinical applications targeting NETs.

Method

The relevant literature from PubMed and Google Scholar (2001–2021) have been reviewed for this article.

Results

The presence of NETs has been detected in various primary tumors and metastatic sites. NET-associated interactions have been observed throughout the different stages of metastasis, including initial tumor cell detachment, intravasation and extravasation, the survival of circulating tumor cells, the settlement and the growth of metastatic tumor cells. Several in vitro and in vivo studies proved that inhibiting NET formation resulted in anti-cancer effects. The biosafety and efficacy of some NET inhibitors have also been demonstrated in early phase clinical trials.

Conclusions

Considering the role of NETs in tumor progression, NETs could be a promising diagnostic and therapeutic target for cancer management. However, current evidence is mostly derived from experimental models and as such more clinical studies are still needed to verify the clinical significance of NETs in oncological settings.

Prevalence of neuropsychiatric symptoms and stroke in patients with hereditary thrombotic thrombocytopenic purpura

In this article, Borogovac et al emphasized the burden of stroke and neuropsychiatric symptoms in patients with hereditary thrombotic thrombocytopenic purpura (hTTP) based on an analysis of the International hTTP Registry. Given the rarity of hTTP, patient numbers were small; nevertheless, the prevalence of stroke reached 100% in patients over the age of 50. Nearly all patients also had evidence of neuropsychiatric symptoms. These data confirm the need to diagnose hTTP as early as possible and support the use of prophylaxis to prevent future events.

Recommendations for the diagnosis and treatment of patients with thrombotic thrombocytopenic purpura

Thrombotic thrombocytopenic purpura (TTP) is a thrombotic microangiopathy (TMA) characterized by the development of microangiopathic haemolytic anaemia, thrombocytopenia, and ischaemic organ dysfunction associated with ADAMTS13 levels lower than 10% in most cases. Recently there have been numerous advances in the field of PTT, new, rapid and accessible techniques capable of quantifying ADAMTS13 activity and inhibitors. The massive sequencing systems facilitate the identification of polymorphisms in the ADAMTS13 gene. In addition, new drugs such as caplacizumab have appeared and relapse prevention strategies are being proposed with the use of rituximab. The existence of TTP patient registries allow a deeper understanding of this disease but the great variability in the diagnosis and treatment makes it necessary to elaborate guidelines that homogenize terminology and clinical practice. The recommendations set out in this document were prepared following the AGREE methodology. The research questions were formulated according to the PICO format. A search of the literature published during the last 10 years was carried out. The recommendations were established by consensus among the entire group, specifying the existing strengths and limitations according to the level of evidence obtained. In conclusion, this document contains recommendations on the management, diagnosis, and treatment of TTP with the ultimate objective of developing guidelines based on the evidence published to date that allow healthcare professionals to optimize TTP treatment.

Plasma Proteomics of COVID-19-Associated Cardiovascular Complications: Implications for Pathophysiology and Therapeutics

To gain insights into the mechanisms driving cardiovascular complications in COVID-19, we performed a case-control plasma proteomics study in COVID-19 patients. Our results identify the senescence-associated secretory phenotype, a marker of biological aging, as the dominant process associated with disease severity and cardiac involvement. FSTL3, an indicator of senescence-promoting Activin/TGFβ signaling, and ADAMTS13, the von Willebrand Factor-cleaving protease whose loss-of-function causes microvascular thrombosis, were among the proteins most strongly associated with myocardial stress and injury. Findings were validated in a larger COVID-19 patient cohort and the hamster COVID-19 model, providing new insights into the pathophysiology of COVID-19 cardiovascular complications with therapeutic implications.

Immune‐mediated thrombotic thrombocytopenic purpura in a Jehovah’s Witness – Effectiveness of incorporating extracorporeal immunoadsorption to caplacizumab, steroids and rituximab

We report the case of a Jehovah's Witness adolescent patient with immune‐mediated thrombotic thrombocytopenic purpura after SARS‐Cov2 infection successfully treated without therapeutic plasma exchange (TPE) using caplacizumab, corticosteroids, rituximab, and extracorporeal immunoadsorption (EIA). Further patients for whom TPE is not an option might benefit from this approach.

Our experience in this case suggests that caplacizumab together with corticosteroids, rituximab, and EIA may be an effective treatment option for further patients with i‐TTP who are unable to undergo TPE. EIA is as a treatment in place of TPE contributing to a very rapid removal of autoantibodies against ADAMTS‐13.

Recent advances in the management of immune-mediated thrombotic thrombocytopenic purpura

Immune-mediated thrombotic thrombocytopenic purpura (iTTP) is a potentially life-threatening thrombotic microangiopathy caused by autoantibody-mediated severe ADAMTS13 deficiency. TTP should be suspected in patients with microangiopathic hemolytic anemia and thrombocytopenia without a definite cause. Early detection of iTTP and prompt treatment with plasma exchange and corticosteroids are essential. Rituximab administration should be considered for refractory or relapsed iTTP, and can be used as a first-line adjuvant or preemptive therapy. Treatment with caplacizumab, a novel anti-von Willebrand factor nanobody, resulted in a faster time to platelet count response, significant reduction in iTTP-related deaths, and reduced incidence of refractory iTTP. TTP survivors showed a higher rate of chronic morbidities, including cardiovascular disease and neurocognitive impairment, which can lead to a poor quality of life and higher mortality rate. Meticulous long-term follow-up of TTP survivors is crucial.

Thrombotic microangiopathies: An illustrated review

The thrombotic microangiopathies (TMAs) are a heterogenous group of disorders with distinct pathophysiologies that cause occlusive microvascular or macrovascular thrombosis, and are characterized by microangiopathic hemolytic anemia, thrombocytopenia, and/or end-organ ischemia. TMAs are associated with significant morbidity and mortality, and data on the management of certain TMAs are often lacking. The nomenclature, classification, and management of various TMAs is constantly evolving as we learn more about these rare syndromes. Thorough clinical and laboratory evaluation is essential to distinguish various TMAs and arrive at an accurate diagnosis, which is key for appropriate management. In this illustrated review, we focus on thrombotic thrombocytopenic purpura (TTP), Shiga toxin-associated hemolytic uremic syndrome, complement-mediated hemolytic uremic syndrome, hematopoietic cell transplant-associated TMA, and drug-induced TMA, and describe their incidence, pathophysiology, diagnosis, and management. We also highlight emerging complement-directed therapies under investigation for the management of complement-mediated TMAs.

Molecular Diagnosis Is Vital to the Accurate Classification and Management of Thrombotic Thrombocytopenic Purpura in Children

Thrombotic thrombocytopenic purpura (TTP) is a rare but potentially life-threatening hematologic disease, presenting a myriad of diagnostic and management challenges in children. Here, we provide a review of this disorder and discuss 2 exemplary cases of TTP occurring in adolescents, emphasizing the need for consideration of late-onset congenital TTP (cTTP). We demonstrate the importance of early confirmation of ADAMTS13 enzyme deficiency and the presence or absence of ADAMTS13 inhibitor in order to rapidly initiate the appropriate life-saving therapies. Ultimately, molecular testing is paramount to distinguishing between congenital and acquired immune-mediated TTP.

Cardioprotective properties of Artemisia herba alba nanoparticles against heart attack in rats: A study of the antioxidant and hypolipidemic activities

Recently, pharmaceutical scientists' interest has increased to find novel pharmaceutical natural substances with potent antioxidant capacity and very low side effects to be used safely in preventive medicine. One of the most common types of diseases with a large spread globally is cardiovascular diseases, which cause a high rate of deaths annually. The present study evaluated the use of Artemisia herba alba leaves' extract (AHALE) and AHALE zinc oxide nanoparticles (AHALE-ZnONPs) against isoproterenol (ISO) inducing myocardial infarction (MI) in male rats. Several groups of Wistar male rats fed a high-fat diet (HFD) were pretreated with several doses of AHALE or AHALE-ZnONPs for one month followed by exposure to ISO for two days. After treatment, samples of the rats' heart tissues and blood were collected for several molecular biological and biochemical analyses. Heart enzymes, antioxidant enzymes, lipid peroxidation compounds, lipid markers, activities, ROS generation, apoptosis, DNA damage and expression of lipid metabolism genes were analyzed in rats pretreated with AHALE or AHALE-ZnONPs followed by exposure to ISO. The results showed an increase in the levels of AST, ALT, LDH, CK, CK-MB, and cTnT (heart markers), elevation in TG, TC, and LDL levels (lipid profile markers), levels of TBARS and LOOH (lipid peroxidation products), ROS generation, DNA damage, apoptosis, and upregulation of PPAR-α, ADD1, FASN, and ACC genes in animals exposed to ISO in comparison with the control animals. Moreover, a decrease in antioxidant enzyme activities, including GPx, GRx, and GST, was observed in animals exposed to ISO in comparison with control rats. In male rats pretreated with AHALE or AHALE-ZnONPs followed by exposure to ISO, the oxidative stress induced by ISO was prevented. The results suggest that Artemisia extract could be considered for use as one of the natural compounds for prevention of atherosclerosis and heart diseases due to its high antioxidant and hypolipidemic activities. The reduced oxidative stress of Artemisia extract may be a result of the existence of flavonoids and phenolic substances.

Coagulation and inflammation in cancer: Limitations and prospects for treatment

The development of so-called immune checkpoint inhibitors (ICIs), which target specific molecular processes of tumour growth, has had a transformative effect on cancer treatment. Widespread use of antibody-based medicines to inhibit tumour cell immune evasion by modulating T cell responses is becoming more common. Despite this, response rates are still low, and secondary resistance is an issue that arises often. In addition, a wide range of serious adverse effects is triggered by enhancing the immunological response. As a result of an increased mortality rate, a higher prevalence of thrombotic complications is connected with an increased incidence of immunological reactions, complement activation, and skin toxicity. This suggests that the tumour microenvironment's interaction between coagulation and inflammation is important at every stage of the tumour's life cycle. The coagulation system's function in tumour formation is the topic of this review. By better understanding the molecular mechanisms in which tumour cells circulate, plasmatic coagulation and immune system cells are engaged, new therapy options for cancer sufferers may be discovered.