Caplacizumab in adult patients with acquired thrombotic thrombocytopenic purpura

COVID-Induced Thrombotic Thrombocytopenic Purpura: A Case Report and Treatment-Focused Review

Thrombotic thrombocytopenic purpura (TTP) is a rare disease that is part of a vast spectrum of thrombotic microangiopathies (TMAs). Despite the rarity of TTP, clinicians must maintain a high suspicion of this disease. The condition is characterized by fever, low platelets, hemolytic anemia, renal abnormalities, and neurological dysfunction. However, all these symptoms are not necessarily present in all the patients. In this review, we describe a case of a 51-year-old female who presented to the emergency department (ED) with chief complaints of dizziness and lightheadedness, subsequently leading to a diagnosis of TTP, caused as a result of COVID-19. This review raises awareness so that there is early recognition of any hematological manifestations associated with COVID-19, reducing the morbidity and mortality associated with the disease. Due to the unpredictability of COVID-19 and its complications, robust research is needed to understand the mechanism and determine which patients are more at risk for adverse outcomes.

Concomitant presentation of thrombotic thrombocytopenic purpura, immune thrombocytopenia, and autoimmune hemolytic anemia in a patient with newly diagnosed systemic lupus erythematosus

Thrombocytopenia is always of concern when encountered in emergency settings. We report a case of a 29-year-old women in whom a unique constellation of hematological disorders occurred. The patient had been diagnosed with idiopathic immune thrombocytopenia (ITP) in 2007, with a history of several thrombocytopenic flares. She now presented with homonymous hemianopia accompanied by thrombocytopenia and microangiopathic hemolytic anemia (MAHA) and was soon after diagnosed with a posterior stroke. Symptoms were more reminiscent of acquired thrombotic thrombocytopenic purpura (aTTP) rather than ITP. Immediate treatment with plasma exchange and caplacizumab curtailed MAHA, and progressive ischemic disease was averted. ADAMTS-13 testing confirmed the diagnosis of immune-mediated aTTP. Repeated testing for ITP, however, also showed IgG-loaded thrombocytes with the former known anti-GPIIb/IIIa specificity. Furthermore, autoimmune hemolytic anemia (AIHA) could be detected by direct antiglobulin test showing IgG and complement loading of the patient's erythrocytes. The autoimmune background of all three entities suggested an underlying systemic disease. Indeed, systemic lupus erythematosus (SLE) serology was strongly positive allowing for the diagnosis of SLE. ITP and AIHA as well as aTTP can be secondary to SLE, but emergence of all three disorders has not been reported at the same time.

Successful Treatment of Refractory Thrombotic Thrombocytopenic Purpura (TTP) With Caplacizumab: A Case Report

We report a female patient who presented with generalized weakness, episodes of altered mental status and slurred speech, and a history of systemic lupus erythematosus. Initial investigations showed profound thrombocytopenia and schistocytosis on peripheral blood smear. PLASMIC score was promptly calculated, and plasma exchange with steroids was initiated based on the initial high PLASMIC score. Bone marrow examination showed hypocellular marrow without any other obvious abnormalities. The patient's platelet counts initially improved but had a quick decline, on which, rituximab and subsequently caplacizumab were introduced. The patient was discharged after stabilization with plasma exchange (PLEX) therapy as needed on an outpatient basis.

HUS and TTP: traversing the disease and the age spectrum

Hemolytic uremic syndrome (HUS) and thrombotic thrombocytopenia purpura (TTP) are rare diseases sharing a common pathological feature, thrombotic microangiopathy (TMA). TMA is characterized by microvascular thrombosis with consequent thrombocytopenia, microangiopathic hemolytic anemia and/or multiorgan dysfunction. In the past, the distinction between HUS and TTP was predominantly based on clinical grounds. However, clinical presentation of the two syndromes often overlaps and, the differential diagnosis is broad. Identification of underlying pathogenic mechanisms has enabled the classification of these syndromes on a molecular basis: typical HUS caused by Shiga toxin-producing Escherichia coli (STEC-HUS); atypical HUS or complement-mediated TMA (aHUS/CM-TMA) associated with genetic or acquired defects leading to dysregulation of the alternative pathway (AP) of complement; and TTP that results from a severe deficiency of the von Willebrand Factor (VWF)-cleaving protease, ADAMTS13. The etiology of TMA differs between pediatric and adult patients. Childhood TMA is chiefly caused by STEC-HUS, followed by CM-TMA and pneumococcal HUS (Sp-HUS). Rare conditions such as congenital TTP (cTTP), vitamin B12 metabolism defects, and coagulation disorders (diacylglycerol epsilon mutation) present as TMA chiefly in children under 2 years of age. In contrast secondary causes and acquired ADAMT13 deficiency are more common in adults. In adults, compared to children, diagnostic delays are more frequent due to the wide range of differential diagnoses. In this review we focus on the three major forms of TMA, STEC-HUS, aHUS and TTP, outlining the clinical presentation, diagnosis and management of the affected patients, to help highlight the salient features and the differences between adult and pediatric patients which are relevant for management.

A Biomolecular Toolbox for Precision Nanomotors

The application of nanomotors for cancer diagnosis and therapy is a new and exciting area of research, which when combined with precision nanomedicine, promises to solve many of the issues encountered by previous development of passive nanoparticles. The goal of this article is to introduce nanomotor and nanomedicine researchers to the deep pool of knowledge available regarding cancer cell biology and biochemistry, as well as provide a greater appreciation of the complexity of cell membrane compositions, extracellular surfaces, and their functional consequences. A short description of the nanomotor state-of-art for cancer therapy and diagnosis is first provided, as well as recommendations for future directions of the field. Then, a biomolecular targeting toolbox has been collated for researchers looking to apply their nanomaterial of choice to a biological setting, as well as providing a glimpse into currently available clinical therapies and technologies. This toolbox contains an overview of different classes of targeting molecules available for high affinity and specific targeting and cell surface targets to aid researchers in the selection of a clinical disease model and targeting methodology. It is hoped that this review will provide biological context, inspiration, and direction to future nanomotor and nanomedicine research.

Selective targeting BMP2 and 4 in SMAD4 negative esophageal adenocarcinoma inhibits tumor growth and aggressiveness in preclinical models

Purpose

Abnormalities within the Sonic Hedgehog (SHH), Bone Morphogenetic Protein (BMP) and SMAD4 signalling pathways have been associated with the malignant behavior of esophageal adenocarcinoma (EAC). We recently developed two specific llama-derived antibodies (VHHs), C4C4 and C8C8, which target BMP4 and BMP2/4, respectively. Here we aimed to demonstrate the feasibility of the VHHs for the treatment of EAC and to elucidate its underlying mechanism.

Methods

Gene Set Enrichment Analysis (GSEA) was performed on a TCGA dataset, while expression of SHH, BMP2/4 and SMAD4 was validated in a cohort of EAC patients. The effects of the VHHs were tested on the recently established SMAD4(-) ISO76A primary EAC cell line and its counterpart SMAD4(+) ISO76A. In a patient-derived xenograft (PDX) model, the VHHs were evaluated for their ability to selectively target tumor cells and for their effects on tumor growth and survival.

Results

High expression of BMP2/4 was detected in all SMAD4 negative EACs. SHH upregulated BMP2/4 expression and induced p38 MAPK signaling in the SMAD4(-) ISO76A cells. Inhibition of BMP2/4 by VHHs decreased the aggressive and chemo-resistant phenotype of the SMAD4(-) ISO76A but not of the SMAD4(+) ISO76A cells. In the PDX model, in vivo imaging indicated that VHHs effectively targeted tumor cells. Both VHHs significantly inhibited tumor growth and acted synergistically with cisplatin. Furthermore, we found that C8C8 significantly improved survival of the mice.

Conclusions

Our data indicate that increased BMP2/4 expression triggers aggressive non-canonical BMP signaling in SMAD4 negative EAC. Inhibiting BMP2/4 decreases malignant behavior and improves survival. Therefore, VHHs directed against BMP2/4 hold promise for the treatment of SMAD4 negative EAC.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13402-022-00689-2.

Thrombotic Thrombocytopenia Masquerading As COVID-19 Infection

Thrombotic thrombocytopenic purpura (TTP) is a rare and challenging diagnosis that consists of thrombotic microangiopathy due to complete or severe deficiency of ADAMTS13 protease that can present at any age. It is very important to have a suspicion concerning this disease as mortality can be very high if it goes unnoticed. This case describes a patient that presented with gastrointestinal symptoms and hematuria and was found to have COVID-19 and TTP. 

We present a case of a 40-year-old female with no past medical history who presented to the Emergency Department with complaints of abdominal pain, nausea, vomiting, and dark urine. The patient workup revealed a platelet count of 4000. The patient was also noted to be COVID-19 positive. Upon further workup, the TTP diagnosis was confirmed. She responded appropriately to plasmapheresis and steroids.

COVID-19 seems to be linked to a wide range of hematologic conditions including but not limited to TTP. In view that TTP can have significant mortality if untreated, we must be suspicious about this condition in COVID-19 cases. The aim of this case report is to highlight the importance of having a low threshold for making a diagnosis of TTP if labs are significant for hemolytic anemia. Our aim is also to emphasize that the treatment should be initiated if schistocytes are seen on the peripheral smear without awaiting laboratory results confirming low levels of ADAMTS13, given the fatal nature of the condition if left untreated.

Acquired Thrombotic Thrombocytopenic Purpura Following Inactivated COVID-19 Vaccines: Two Case Reports and a Short Literature Review

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) outbreak in December 2019, causing millions of deaths all over the world, and the lack of specific treatment for severe forms of coronavirus disease 2019 (COVID-19) have led to the development of vaccines in record time, increasing the risk of vaccine safety issues. Recently, several cases of thrombotic thrombocytopenic purpura (TTP) have been reported following COVID-19 vaccination. TTP is a rare disease characterized by thrombocytopenia, microangiopathic hemolytic anemia and ischemic end-organ lesions. It can be either congenital or acquired. Various events such as viral infections, medication, pregnancy, malignancies, and vaccinations may cause TTP. Here, we report two cases of acquired TTP following Sinopharm COVID-19 vaccine (BBIBP-CorV) and Sinovac COVID-19 vaccine (CoronaVac). Diagnosis was based on clinical presentation and confirmed with a severe reduction in the activity of von Willebrand factor-cleaving protease ADAMTS-13 and the presence of inhibitory autoantibodies. The two patients were successfully treated with corticosteroids, plasma exchange therapy and rituximab in the acute phase. In the literature, the reported cases of TTP induced by COVID-19 vaccination occurred after Adenoviral Vector DNA- and SARS-CoV-2 mRNA-Based COVID-19 vaccines. To the best of our knowledge, this is the first report of acquired TTP after inactivated virus COVID-19 vaccination.

Nanobodies: from structure to applications in non-injectable and bispecific biotherapeutic development

The increasing demand for convenient, miniaturized and multifunctional antibodies necessitates the development of novel antigen-recognition molecules for biological and medical studies. Nanobodies, the functional variable regions of camelid heavy-chain-only antibodies, as a new tool, complement the conventional antibodies and are in the stage of rapid development. The outstanding advantages of nanobodies include a stable structure, easy production, excellent water solubility, high affinity toward antigens and low immunogenicity. With promising application potential, nanobodies are now increasingly applied to various studies, including protein structure analysis, microscopic imaging, medical diagnosis, and drug development. The approval of the first nanobody drug Caplacizumab by the FDA disclosed the therapeutic potential of nanobodies. The outbreak of COVID-19 accelerated the development of nanobody drugs in non-injectable and bispecific biotherapeutic applications. Herein, we reviewed recent studies on the nanobody structure, screening and their applications in protein structure analysis and nanobody drugs, especially on non-injectable nanobody and bispecific nanobody development.

Monoclonal antibodies used for the management of haematological disorders

INTRODUCTION

Monoclonal antibodies Ab (MoAb) are increasingly becoming part of therapeutic armamentarium for haematologists and haemato-oncologists. This review brings together commonly used antibodies in one place for brevity and novel understanding.

AREAS COVERED

Pubmed and Scopus databases were explored focusing on MoAb in clinical haematological practice. Emphasis was given to current review articles. The data base was searched from 1997 till present. 24 different antibodies, most of which are in use were discussed. Antibodies are used for diverse conditions i.e. malignant and benign haematological conditions, treatment at various phases of stem cell transplantation. These antibodies were used both alone or in combination with various chemotherapy, targeted small molecules or as immunoconjugates. Some of the side effect profiles of these antibodies were common and some were unique. Unusual infections or organ dysfunctions were noted. Improved function of antibodies by protein engineering is also advancing rapidly. Dosage, frequency and route of administration depended on the convenience and condition for which the antibody is used.

EXPERT OPINION

: MoAbs are increasingly used in haematology practice either alone or in combination with other types of therapy for improved out come in various haematological conditions.

Immune thrombotic thrombocytopenic purpura: Personalized therapy using ADAMTS-13 activity and autoantibodies

Recently, treatment of immune-mediated thrombotic thrombocytopenic purpura (ITTP) has changed with the advent of caplacizumab in clinical practice. The International Working Group (IWG) has recently integrated the ADAMTS-13 activity/autoantibody monitoring in consensus outcome definitions. We report three ITTP cases during the coronavirus disease 2019 pandemic, that received a systematic evaluation of ADAMTS-13 activity and autoantibodies. We describe how the introduction of caplacizumab and ADAMTS-13 monitoring could change the management of ITTP patients and discuss whether therapeutic choices should be based on the clinical response alone. ADAMTS-13 activity/antibodies were assessed every 5 days. Responses were evaluated according to updated IWG outcome definitions. These kinetics, rather than clinical remission, guided the therapy, allowing early and safe caplacizumab discontinuation and sensible administration of rituximab. Caplacizumab was cautiously discontinued after achieving ADAMTS-13 complete remission. These cases illustrate that prospective ADAMTS-13 evaluation and use of updated IWG definitions may improve real-life patients' management in the caplacizumab era.

Caplacizumab Model-Based Dosing Recommendations in Pediatric Patients With Acquired Thrombotic Thrombocytopenic Purpura

Acquired thrombotic thrombocytopenic purpura (aTTP) is a rare and life‐threatening autoimmune thrombotic microangiopathy. Caplacizumab, evaluated in phase II and III studies in adults, shortens the time to platelet count response and reduces aTTP exacerbations, has a favorable safety profile, and can potentially reduce refractoriness and mortality associated with aTTP. Since no children with aTTP were enrolled in these clinical trials, caplacizumab has been initially approved for use only in adult patients with aTTP (10 mg). Pediatric dosing recommendations were developed using model‐based simulations. A semimechanistic pharmacokinetic/pharmacodynamic population model has been developed describing the interaction between caplacizumab and von Willebrand factor antigen (vWF:Ag) following intravenous and subcutaneous administration of caplacizumab in different adult populations, at various dose levels, using nonlinear mixed‐effects modeling. Based on the allometrically scaled pharmacokinetic/pharmacodynamic model, different dosing regimens were simulated in 8000 children (aged 2‐18 years). Simulated caplacizumab exposures and vWF:Ag levels across different age categories were compared to an adult reference group. A simulated daily dose of 5 mg in children weighing <40 kg and of 10 mg in children weighing ≥40 kg resulted in similar exposures and vWF:Ag suppression across age and weight groups. Despite the lack of pediatric clinical data, the results of this modeling and simulation analysis constituted the basis for the European extension of indication for caplacizumab (10 mg) to adolescents aged >12 years and with a body weight ≥40 kg. This represents a rare case in which regulatory authorities have deemed a modeling and simulation study robust enough to approve a variation of indication.

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.

Cost effectiveness of caplacizumab in acquired thrombotic thrombocytopenic purpura

Acquired thrombotic thrombocytopenic purpura (TTP) is a life-threatening disease characterized by thrombotic microangiopathy leading to end-organ damage. The standard of care (SOC) treatment is therapeutic plasma exchange (TPE) alongside immunomodulation with steroids, with increasing use of rituximab ± other immunomodulatory agents. The addition of caplacizumab, a nanobody targeting von Willebrand factor, was shown to accelerate platelet count recovery and reduce TPE treatments and hospital length of stay in TTP patients treated in 2 major randomized clinical trials. The addition of caplacizumab to SOC also led to increased bleeding from transient reductions in von Willebrand factor and increased relapse rates. Using data from the 2 clinical trials of caplacizumab, we performed the first-ever cost-effectiveness analysis in TTP. Over a 5-year period, the projected incremental cost-effectiveness ratio (ICER) in our Markov model was $1 482 260, significantly above the accepted 2019 US willingness-to-pay threshold of $195 300. One-way sensitivity analyses showed the utility of the well state and the cost of caplacizumab to have the largest effects on ICER, with a reduction in caplacizumab cost demonstrating the single greatest impact on lowering the ICER. In a probabilistic sensitivity analysis, SOC was favored over caplacizumab in 100% of 10 000 iterations. Our data indicate that the addition of caplacizumab to SOC in treatment of acquired TTP is not cost effective because of the high cost of the medication and its failure to improve relapse rates. The potential impact of caplacizumab on health system cost using longer term follow-up data merits further study.

Fatal cerebral hemorrhage in a patient with thrombotic thrombocytopenic purpura with a normal platelet count during treatment with caplacizumab

Acquired thrombotic thrombocytopenic purpura (aTTP) is a thrombotic microangiopathy with a severe mortality and morbidity. Caplacizumab has recently been approved in the Netherlands as a new therapeutic option in patients with life-threatening organ failure due to aTTP. We describe the case of a 50 year old patient with aTTP who was referred to our hospital for treatment with caplacizumab. After undergoing treatment with plasmapheresis, prednisolone, rituximab and caplacizumab, her platelet count recovered and she was ready to be discharged. Unfortunately, before discharge she developed a fatal intra-cerebral hemorrhage. Fatal hemorrhage as an adverse event of caplacizumab has not been described before. Up to now there is no evidence-based treatment for caplacizumab induced heavy bleeding.

Therapeutic Antibodies Targeting Potassium Ion Channels

Monoclonal antibodies combine specificity and high affinity binding with excellent pharmacokinetic properties and are rapidly being developed for a wide range of drug targets including clinically important potassium ion channels. Nonetheless, while therapeutic antibodies come with great promise, K⁺ channels represent particularly difficult targets for biologics development for a variety of reasons that include their dynamic structures and relatively small extracellular loops, their high degree of sequence conservation (leading to immune tolerance), and their generally low-level expression in vivo. The process is made all the more difficult when large numbers of antibody candidates must be screened for a given target, or when lead candidates fail to cross-react with orthologous channels in animal disease models due to their highly selective binding properties. While the number of antibodies targeting potassium channels in preclinical or clinical development is still modest, significant advances in the areas of protein expression and antibody screening are converging to open the field to an avalanche of new drugs. Here, the opportunities and constraints associated with the discovery of antibodies against K⁺ channels are discussed, with an emphasis on novel technologies that are opening the field to exciting new possibilities for biologics development.

Unique aspects of adaptive immunity in camelids and their applications

Members of the Camelidae have unique adaptive immunological features that are not widely observed in other species. All camelids are known to have three distinct IgG isotypes - IgG1, IgG2 and IgG3. While IgG1 has a conventional antibody structure, both IgG2 and IgG3 are devoid of light chains and instead possess hypervariable regions in their heavy chain (VHH), while lacking the typical CH1 domain found in heavy chains. VHH domains are increasingly being utilized as "next generation" antibodies, as they have unique biochemical and structural properties including high pH stability as well as a lower molecular weight allowing for increased tissue penetration. These features of VHH domains offer a number of advantages for both biotechnology and clinical applications and are commonly termed "nanobodies". A second unique aspect of the camelid adaptive response is involves T cell-mediated immunity. Characterization of gamma delta (ꝩδ) T cells in camelid species has found they use somatic hypermutation in their T cell receptor gamma (TRG) and delta (TRD) loci to increase the structural stability of their ꝩδ T receptor. The use of somatic hyper mutation to increase the diversity of their T cell repertoire, is a feature that has not been observed in other mammalian species. In addition, in alpacas there is a unique subset of ꝩδ T cells called Vꝩ9Vδ2 T cells. Activation of these cells is dependent upon phosphoantigen (PAg)-mediated interaction with B7-like butyrophilin molecules (BTN-3). This makes alpacas the first species outside of primates to be identified with this unique subset and activation mechanism. Here we review some fundamentals of camelid adaptive immunity that make them distinct from other vertebrate species and their potential applications to human therapies.

Caplacizumab for Acute Thrombotic Thrombocytopenic Purpura

Acute thrombotic thrombocytopenic purpura (aTTP) is a rare microangiopathic hemolytic anemia. Standard of care currently includes plasma exchange and immunosuppressive agents, including glucocorticoids, vincristine, and rituximab. Even with these therapies, relapse occurs in 36% of patients, and mortality ranges from 10% to 20%. Caplacizumab is a novel agent approved for the treatment of adult patients with aTTP in conjunction with plasma exchange and immunosuppressive therapies. It works by binding to the A1 domain of von Willebrand factor (VWF), blocking platelets from binding to VWF and aggregating. In clinical trials, patients who received caplacizumab compared with placebo were more likely to have a normalization of their platelet count, a lower rate of recurrence, and a lower incidence of the composite of aTTP-related death, recurrence, or major thromboembolic event. The side effect profile is rather benign and includes epistaxis, headache, and gingival bleeding. Caplacizumab is only available through specialty pharmacy services due to its high cost. Providers should be aware of and prepared for the prior authorization process required to assist their patients in gaining access to the medication. Currently, there is no formal consensus regarding caplacizumab's place in therapy for patients with aTTP, but it remains an option for refractory cases.

Clínica neurológica fluctuante: ¿Llamo al neurólogo o al hematólogo?

Objetivos

Resaltar el papel del laboratorio clínico y la pronta comunicación con el servicio de Hematología en el diagnóstico y la rapidez en la instauración del tratamiento de una patología hematológica tan urgente como la Púrpura Trombótica Trombocitopénica (PTT).

Caso clínico

Varón de edad avanzada derivado a Urgencias hospitalarias por su médico de Atención Primaria por trastorno de emisión del lenguaje, asimetría facial y disminución de fuerza en extremidad superior, por lo que se activa el código ictus. Sin embargo, los hallazgos de laboratorio (anemia y trombocitopenia, creatinina, bilirrubina total y LDH elevadas, test de Coombs directo negativo) y presencia de esquistocitos en el frotis de sangre periférica, acaban derivando en un diagnóstico completamente diferente: microangiopatía trombótica tipo PTT.

Conclusiones

La primera orientación diagnóstica de ictus hemisférico izquierdo fue rechazada ante los signos de anemia hemolítica no autoinmune, trombocitopenia sin causa aparente y presencia de esquistocitos. No debemos olvidar que esta patología puede cursar con afectación multiorgánica y características clínicas muy variables. Aunque su diagnóstico definitivo se basa en la determinación de actividad de ADAMTS-13, debido a la elevada mortalidad es necesario instaurar tratamiento de forma inmediata tras su sospecha.

Fluctuating neurological symptoms: should I call the neurologist or the hematologist?

Objectives

The objective of this study was to highlight the role of the clinical laboratory and the relevance of reporting the case immediately to the unit of hematology for the diagnosis and early administration of treatment in the presence of such an urgent hematologic disease as thrombotic thrombocytopenic purpura (TTP).

Case presentation

An elderly patient was referred to the emergency department of our hospital by his general practitioner for speech difficulty, facial asymmetry and weakness in the upper limb. Stroke code was activated. However, laboratory findings (anemia, thrombocytopenia, elevated creatinine, total bilirubin and LDH, negative direct Coombs test) and presence of schistocytes in the peripheral blood smear test were consistent with a completely different diagnosis: TTP thrombotic microangiopathy.

Conclusions

The first diagnostic approach of left hemispheric stroke was not confirmed in the laboratory, with findings of nonautoimmune hemolytic anemia, thrombocytopenia without apparent cause and presence of schistocytes. We should not forget that the clinical manifestations of this condition are widely variable and may include multiorganic dysfunction. Although confirmation of diagnosis is based on ADAMTS-13, its associated high mortalitiy requires immediate treatment on mere suspicion.

Critical Care COVID-19 Patient with a Picture of Thrombotic Thrombocytopenic Purpura

Background

Thrombotic thrombocytopenic purpura (TTP) is an uncommon haematological disease which can occur at any age and may present with COVID-19. This case describes a COVID-19 complication associated with a presentation resembling TTP.

Case description

A 51-year-old man who had received a kidney transplant and was on immunosuppressant medication, was admitted to a critical care unit with severe COVID-19 pneumonia/acute respiratory distress syndrome (ARDS) which required intubation, mechanical ventilation and inotropic support. The course was complicated by the classic pentad of thrombocytopenia, intravascular haemolysis, acute kidney injury, neurological symptoms and fever, which prompted the diagnosis of probable TTP. After five sessions of therapeutic plasma exchange, the patient's general status improved, he was weaned off mechanical ventilation and his renal panel and haemolytic markers normalized.

Conclusion

TTP is a life-threatening condition which requires urgent management with therapeutic plasma exchange. This case highlights some possible complications of COVID-19 generally and in immunocompromised patients specifically. The potential role of plasma exchange in COVID-19 patients without a positive diagnosis of TTP (the so-called 'TTP resembling presentation') is an area of further research.

LEARNING POINTS

COVID-19 can manifest as a picture of thrombotic thrombocytopenic purpura (TTP) which requires therapeutic plasma exchange as in other cases of TTP.Further research is required on the use of therapeutic plasma exchange in severe COVID-19 with cytokine storm.

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.

Factors Affecting the Formation and Treatment of Thrombosis by Natural and Synthetic Compounds

Venous thromboembolism (VTE) refers to deep vein thrombosis (DVT), whose consequence may be a pulmonary embolism (PE). Thrombosis is associated with significant morbidity and mortality and is the third most common cardiovascular disease after myocardial infarction and stroke. DVT is associated with the formation of a blood clot in a deep vein in the body. Thrombosis promotes slowed blood flow, hypoxia, cell activation, and the associated release of many active substances involved in blood clot formation. All thrombi which adhere to endothelium consist of fibrin, platelets, and trapped red and white blood cells. In this review, we summarise the impact of various factors affecting haemostatic disorders leading to blood clot formation. The paper discusses the causes of thrombosis, the mechanism of blood clot formation, and factors such as hypoxia, the involvement of endothelial cells (ECs), and the activation of platelets and neutrophils along with the effects of bacteria and reactive oxygen species (ROS). Mechanisms related to the action of anticoagulants affecting coagulation factors including antiplatelet drugs have also been discussed. However, many aspects related to the pathogenesis of thrombosis still need to be clarified. A review of the drugs used to treat and prevent thrombosis and natural anticoagulants that occur in the plant world and are traditionally used in Far Eastern medicine has also been carried out.

Prospect of SARS-CoV-2 spike protein: Potential role in vaccine and therapeutic development

The recent outbreak of the betacoronavirus SARS-CoV-2 has become a significant concern to public health care worldwide. As of August 19, 2020, more than 22,140,472 people are infected, and over 781,135 people have died due to this deadly virus. In the USA alone, over 5,482,602 people are currently infected, and more than 171,823 people have died. SARS-CoV-2 has shown a higher infectivity rate and a more extended incubation period as compared to previous coronaviruses. SARS-CoV-2 binds much more strongly than SARS-CoV to the same host receptor, angiotensin-converting enzyme 2 (ACE2). Previously, several methods to develop a vaccine against SARS-CoV or MERS-CoV have been tried with limited success. Since SARS-CoV-2 uses the spike (S) protein for entry to the host cell, it is one of the most preferred targets for making vaccines or therapeutics against SARS-CoV-2. In this review, we have summarised the characteristics of the S protein, as well as the different approaches being used for the development of vaccines and/or therapeutics based on the S protein.

Brain Delivery of Single-Domain Antibodies: A Focus on VHH and VNAR

Passive immunotherapy, i.e., treatment with therapeutic antibodies, has been increasingly used over the last decade in several diseases such as cancers or inflammation. However, these proteins have some limitations that single-domain antibodies could potentially solve. One of the main issues of conventional antibodies is their limited brain penetration because of the blood-brain barrier (BBB). In this review, we aim at exploring the different options single-domain antibodies (sDAbs) such as variable domain of heavy-chain antibodies (VHHs) and variable new antigen receptors (VNARs) have already taken to reach the brain allowing them to be used as therapeutic, diagnosis or transporter tools.

New Therapeutic Targets and Treatment Options for Thrombotic Microangiopathy: Caplacizumab and Ravulizumab

OBJECTIVE

To review the efficacy and safety of caplacizumab and ravulizumab for thrombotic microangiopathy.

DATA SOURCES

A literature search from January 2011 to May 2020 was performed using the key terms caplacizumab (or ALX-0681), ravulizumab (or ALXN1210), atypical hemolytic uremic syndrome (aHUS), acquired thrombotic thrombocytopenic purpura (aTTP), and thrombotic microangiopathy.

STUDY SELECTION AND DATA EXTRACTION

Relevant clinical trials and articles in the English language were identified and reviewed.

DATA SYNTHESIS

aTTP and aHUS are syndromes of thrombotic microangiopathy manifested by excessive platelet aggregation and endothelial cell destruction, with subsequent thrombocytopenia, hemolysis, and multiorgan failure. Current standard therapy for aTTP is therapeutic plasma exchange (TPE) to remove von Willebrand factor (vWF) multimers and anti-ADAMTS13 autoantibodies. As an adjunctive therapy to TPE, caplacizumab inhibits binding of vWF to platelets and prevents new microthrombi formation. It reduces thromboembolic event rate and days of TPE and delays relapse. Headache and epistaxis were the most common adverse events. aHUS develops because of dysregulation of the alternative complement pathway, followed by constitutive activation of complement components that causes thrombosis and end-organ damage. Short-term initial evaluation with ravulizumab, a long-acting complement inhibitor, demonstrates rapid hematological and renal improvement, with sustained complement inhibition and tolerable adverse effects.

RELEVANCE TO PATIENT CARE AND CLINICAL PRACTICE

This review describes the pharmacology, pharmacokinetics, cost consideration, and clinical studies for caplacizumab and ravulizumab for thrombotic microangiopathy. Place of therapy is also discussed.

CONCLUSION

Targeted therapies with caplacizumab and ravulizumab are expected to reduce the burden of exacerbation, refractory disease, recurrence, and possibly death for thrombotic microangiopathy.

[Thrombotic microangiopathy in rheumatology: a link between thrombosis and autoimmunity]

Uncontrolled hypercoagulation and inflammation (thromboinflammation), which are both independent and closely related and amplifying each other pathological processes, form the basis for pathogenesis of a wide range of diseases and complications, including immuno-inflammatory (autoimmune) rheumatic diseases, with the development of potentially fatal injuries of internal organs. Thrombotic microangiopathy is one of the most prominent prototypes of thromboinflammatory pathological conditions. The close link between environmental factors, hemostasis genetic defects and the complement system, inflammation and autoimmunity as pathogenetic mechanisms of microthrombosis draws particular attention to studying thrombotic microangiopathy in immuno-inflammatory rheumatic diseases, primarily systemic lupus erythematosus, antiphospholipid syndrome and scleroderma renal crisis. In future, these studies may be important for expanding the idea of the role of autoimmune mechanisms in pathogenesis of critical hemostasis disorders in human diseases, and for developing new approaches to therapy. Recently, special attention has been paid to the treatment of systemic lupus erythematosus and antiphospholipid syndrome with eculizumab, which is humanized monoclonal IgG2/4k antibody that blocks the complement component C5a and the membrane attack complex (C5b-9) formation, and which is registered for the treatment of atypical hemolytic uremic syndrome, paroxysmal nocturnal hemoglobinuria, as well as severe forms of myasthenia gravis and neuromyelitis optica. Further studies in this direction will create prerequisites for improving the prognosis not only in patients with orphan disorders, but also for widespread human diseases.