Thrombotic Thrombocytopenic Purpura: Beyond Empiricism and Plasma Exchange

Repurposing of rituximab biosimilars to treat B cell mediated autoimmune diseases

Rituximab, the first monoclonal antibody approved for the treatment of lymphoma, eventually became one of the most popular and versatile drugs ever in terms of clinical application and revenue. Since its patent expiration, and consequently, the loss of exclusivity of the original biologic, its repurposing as an off-label drug has increased dramatically, propelled by the development and commercialization of its many biosimilars. Currently, rituximab is prescribed worldwide to treat a vast range of autoimmune diseases mediated by B cells. Here, we present a comprehensive overview of rituximab repurposing in 115 autoimmune diseases across 17 medical specialties, sourced from over 1530 publications. Our work highlights the extent of its off-label use and clinical benefits, underlining the success of rituximab repurposing for both common and orphan immune-related diseases. We discuss the scientific mechanism associated with its clinical efficacy and provide additional indications for which rituximab could be investigated. Our study presents rituximab as a flagship example of drug repurposing owing to its central role in targeting cluster of differentiate 20 positive (CD20) B cells in 115 autoimmune diseases.

Cost-consequence analysis of diagnosis and early treatment of acquired thrombotic thrombocytopenic purpura in Colombia

INTRODUCTION

The objective of the study was to evaluate the costs and benefits of early identification and treatment (within 24 hours of admission) of patients with aTTP in Colombia.

METHODS

A cost-consequence analysis was conducted to evaluate the costs and health outcomes of diagnosis and early treament versus no treatment (scenario 1) and late treatment (scenario 2) in a hypothetical cohort of 100 patients with aTTP. The analysis perspective was that of the third-party payer.

RESULTS

In scenario 1, he total cost of early treatment was USD$515,157 compared to USD$293,265 for no treatment. Early treatment avoided 65 deaths in the hypothetical cohort. The cost per death avoided was USD$3,414. In scenario 2, the cost of early treatment was USD$935,507 compared to USD$809,103 in the late start of treatment. By treating patients early, 33 deaths were avoided, 23 patients were estimated to be alive without exacerbations and 16 without relapses. The cost per death avoided was USD$3,879 and the cost per patient alive without exacerbations and relapses was USD$5,611 and USD$7,858, respectively.

CONCLUSIONS

The early identification and treatment of patients with aTTP are associated with benefits in survival and recurrence-free survival, and an incremental cost in the process of care compared to no treatment or late treatment.

Hypertensive Emergency as the Initial Presentation of Acquired Thrombotic Thrombocytopenic Purpura: A Case Report

Thrombotic thrombocytopenic purpura (TTP) is a type of thrombotic microangiopathy (TMA) related to a deficiency of ADAMTS13 protein, which could lead to fatal outcomes. TTP presents a vast array of symptoms, making its diagnosis a challenge to physicians. In this report, we discuss the case of an 80-year-old male who presented with abdominal pain and hypertension with underlying severe thrombocytopenia and hemolysis. Although his presentation could also be secondary to malignant hypertension, he was promptly diagnosed with TTP based on these findings. TTP is a hematologic emergency, and it should be kept in the differential diagnosis when a patient presents with thrombocytopenia and hemolysis with or without accompanying symptoms.

Post-traumatic thrombotic microangiopathy: What trauma surgeons need to know?

Thrombotic microangiopathy (TMA) is characterized by systemic microvascular thrombosis, target organ injury, anemia and thrombocytopenia. Thrombotic thrombocytopenic purpura, atypical hemolytic uremic syndrome and Shiga toxin E-coli-related hemolytic uremic syndrome are the three common forms of TMAs. Traditionally, TMA is encountered during pregnancy/postpartum period, malignant hypertension, systemic infections, malignancies, autoimmune disorders, etc. Recently, the patients presenting with trauma have been reported to suffer from TMA. TMA carries a high morbidity and mortality, and demands a prompt recognition and early intervention to limit the target organ injury. Because trauma surgeons are the first line of defense for patients presenting with trauma, the prompt recognition of TMA for these experts is critically important. Early treatment of post-traumatic TMA can help improve the patient outcomes, if the diagnosis is made early. The treatment of TMA is also different from acute blood loss anemia namely in that plasmapheresis is recommended rather than platelet transfusion. This article familiarizes trauma surgeons with TMA encountered in the context of trauma. Besides, it provides a simplified approach to establishing the diagnosis of TMA. Because trauma patients can require multiple transfusions, the development of disseminated intravascular coagulation must be considered. Therefore, the article also provides different features of disseminated intravascular coagulation and TMA. Finally, the article suggests practical points that can be readily applied to the management of these patients.

Immunogenic hotspots in the spacer domain of ADAMTS13 in immune-mediated thrombotic thrombocytopenic purpura

BACKGROUND

Immune-mediated thrombotic thrombocytopenic purpura (iTTP) is caused by anti-ADAMTS13 autoantibodies inducing a severe deficiency of ADAMTS13. Epitope mapping studies on samples obtained during acute iTTP episodes have shown that the iTTP immune response is polyclonal, with almost all patients having autoantibodies targeting the spacer domain of ADAMTS13.

OBJECTIVES

To identify the immunogenic hotspots in the spacer domain of ADAMTS13.

PATIENTS/METHODS

A library of 11 full-length ADAMTS13 spacer hybrids was created in which amino acid regions of the spacer domain of ADAMTS13 were exchanged by the corresponding region of the spacer domain of ADAMTS1. Next, the full-length ADAMTS13 spacer hybrids were used in enzyme-linked immunosorbent assay to epitope map anti-spacer autoantibodies in 138 samples from acute and remission iTTP patients.

RESULTS

Sixteen different anti-spacer autoantibody profiles were identified with a similar distribution in acute and remission patients. There was no association between the anti-spacer autoantibody profiles and disease severity. Almost all iTTP samples contained anti-spacer autoantibodies against the following three regions: amino acid residues 588-592, 602-610, and 657-666 (hybrids E, G, and M). Between 31% and 57% of the samples had anti-spacer autoantibodies against amino acid regions 572-579, 629-638, 667-676 (hybrids C, J, and N). In contrast, none of the samples had anti-spacer autoantibodies against amino acid regions 556-563, 564-571, 649-656, and 677-685 (hybrids A, B, L, and O).

CONCLUSION

We identified three hotspot regions (amino acid regions 588-592, 602-610, and 657-666) in the spacer domain of ADAMTS13 that are targeted by anti-spacer autoantibodies found in a large cohort of iTTP patients.

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.