Novel therapies in thrombotic thrombocytopenic purpura

Detection of novel duplication variant in ADAMTS13 gene using chromosomal microarray analysis

We present a case of a child with congenital thrombotic thrombocytopenic purpura found to have a compound heterozygous variant in the ADAMTS13 gene with a novel variant resulting in a large duplication of exons 9-11 of ADAMTS13 This variant was identified through additional molecular testing via a chromosomal microarray analysis. To our knowledge, this assay had not previously been utilised to identify an ADAMTS13 variant and the additional testing was possible through the involvement of a genetic counsellor.

Psychometric evaluation of a patient-reported outcomes instrument for congenital thrombotic thrombocytopenic purpura

BACKGROUND

Congenital thrombotic thrombocytopenic purpura (cTTP) is an ultra-rare, life-threatening hereditary disorder that causes patients to experience significant morbidity and decreased health-related quality of life (HRQoL). A cTTP disease-specific patient-reported outcome (PRO) instrument that is reflective of patients' experiences with the disorder does not currently exist. The objective of this study was to evaluate and validate the psychometric properties of the Congenital Thrombotic Thrombocytopenic Purpura-Patient Experience Questionnaire (cTTP-PEQ), developed using a literature review, interviews with expert clinicians, and qualitative concept elicitation and cognitive debriefing interviews.

METHODS

This prospective, observational study (NCT03519672) was conducted with patients diagnosed with cTTP currently receiving treatment. Patients were enrolled through investigator sites and direct-to-patient recruitment. Individuals completed electronic self-administered PRO measures, including the cTTP-PEQ, at baseline and Day 14 (+ up to 10 days). The cTTP-PEQ consisted of five multi-item domains (Pain/Bruising, Cognitive Impairment, Visual Impairment, Mood, Treatment Burden) and three single-item domains (Fatigue, Headache, Activity Limitation), and assessed symptoms and impact of cTTP in the previous 24 h, 7 days, and 2 weeks. Convergent and discriminant validity were evaluated using Spearman's rank correlation coefficients. Known-groups validity was assessed between patient groups separated by Patient Global Impression of Severity (PGI-S; normal vs. mild/moderate/severe). Internal reliability was assessed using Cronbach's alpha. Test-retest reliability was assessed using intraclass correlation coefficients (ICCs).

RESULTS

Thirty-six patients participated in this study. Convergent validity was confirmed with high-to-moderate correlations (r ≥ 0.4) for 12/15 hypothesized relationships between pairs of domains and/or total scores. Discriminant validity was confirmed with low correlations (r < 0.3) observed for 5/7 hypothesized relationships. Known-groups validity was confirmed with significant differences (p ≤ 0.05) in mean cTTP-PEQ scores between the two PGI-S groups for most domains and items at both timepoints. Cronbach's alpha was 0.88 at baseline and 0.91 at Day 14, confirming internal consistency of the instrument. Test-retest reliability was also confirmed with a high ICC (0.96).

CONCLUSION

This study validates the psychometric properties of the novel cTTP-PEQ for use in research and clinical practice to assess HRQoL among patients with cTTP. This instrument will be particularly useful when assessing cTTP disease burden and the impact of new treatments.

Clinical Features and Risk Factors of Relapse and Mortality in Thrombotic Thrombocytopenic Purpura Patients: A Seven-Year Experience

Background: Thrombotic thrombocytopenic purpura (TTP) is associated with microangiopathic hemolytic anemia, thrombocytopenia, and microvascular thrombosis. No comprehensive report exists on clinical characteristics and risk factors of relapse and mortality in Iranian TTP patients. In this study, we aimed to report clinical features of Iranian TTP patients, to evaluate disease relapse and mortality rate and their associated risk factors. Materials and Methods: This study was a cohort study of patients diagnosed with microangiopathic hemolytic anemia admitted to the Shariati Hospital, Tehran, a referral center for TTP patients, from 2010 to 2017. Demographic, clinical, and laboratory data were recorded and patients were followed for 3 years regarding disease relapse and mortality. Results:  114 patients (80 females, 34 males) with a mean age of 39.3 ± 14.99 years were included.  Hematologic and neurologic symptoms were the most common manifestations. Abnormal laboratory findings at the presentation included thrombocytopenia, anemia, and elevated LDH. All patients were treated with plasma exchange, and 75.5% of them had a response to treatment, while the 3-year relapse and mortality rate was 23.6 and 26.3%.  Lower platelet count was a predictor of disease relapse. Age, hematological, or neurological initial presentation were associated with TTP mortality. Conclusion: Based on the largest study of TTP patients ever in Iran, the demographic and clinical characteristics of Iranian TTP patients are similar to other existing reports. Knowledge of the risk factors for TTP relapse and mortality could be useful to alert hematologists for prompt therapeutic actions when necessary.

Recent advances in therapeutic options for rare hemostatic disorders: selected poster extracts of recent research in hemophilia A, congenital hemophilia with inhibitors, von Willebrand disease, and thrombotic thrombocytopenic purpura presented at the 29th congress of the International Society on Thrombosis and Haemostasis (ISTH 2021, Jul 17-21; virtual congress)

Hemophilia, von Willebrand disease (VWD), and thrombotic thrombocytopenic purpura (TTP) are rare diseases affecting normal hemostasis. Although they differ in their pathogenesis and clinical manifestation, if left undiagnosed and untreated, all these conditions can result in severe long-term consequences and can be potentially life-threatening. This article summarizes a poster series funded by Takeda and presented virtually at the 29th annual congress of the International Society on Thrombosis and Haemostasis (ISTH) in 2021: Data from real-world evidence highlight the importance of joint health and personalized prophylaxis to prevent bleeding for patients with hemophilia, the need to further raise disease awareness in support of timely diagnosis and access to treatment in general practice settings for patients with VWD, and describe the clinical burden for patients with TTP and the importance to advance treatment options for these patients.

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

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

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

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

[Treatment of thrombotic thrombocytopenic purpura]

The review discusses approaches to treatment of acquired thrombotic thrombocytopenic purpuгa (aTTP). In patients with aTTP plasma exchanges, glucocorticosteroids allow to stop an acute attack of TTP, and use of rituximab allows to achieve remission. In recent years, caplacizumab has been used. Treatment options such as cyclosporin A, bortezomib, splenectomy, N-acetylcysteine, recombinant ADAMTS13 are also described. Separately discussed issues of management of patients with TTP during pregnancy, and pediatric patients with TTP.

Clinical Problem Solving and Using New Paths in the Laboratory: Learning from Case Studies

Three selected casuistic studies of individual patient problems from my long-standing professional experience are presented. I intend to highlight the potential contribution of case studies, including new approaches of laboratory investigation, for the advancement of pathophysiological knowledge and would encourage to “rehabilitate” the low academic profile generally attributed to “case reports.”

Juvenile Dermatomyositis (JDM) Complicated by Thrombotic Thrombocytopenic Purpura (TTP) and Purtscher's Retinopathy Responsive to Rituximab: Case Report and Literature Review

Juvenile dermatomyositis (JDM) is a multisystem vasculopathy that infrequently presents with acute complications (1). We report here the case of a 12-year-old girl with JDM who developed Thrombotic Thrombocytopenic purpura (TTP) and Purtscher's retinopathy. This is the second pediatric case of JDM with TTP and Purtscher's retinopathy in the literature. The diagnosis of JDM was based on her clinical presentation (fever, myalgia, proximal muscle weakness, characteristic skin rash and elevated muscle enzymes) (2). Despite improvement of rash, fever and weakness with corticosteroids and intravenous Immunoglobulins (IVIG), the patient developed retinopathy, thrombocytopenia, hemolytic anemia, renal failure, and pulmonary edema within 1 week of initial treatment. A clinical diagnosis of TTP and Purtscher's retinopathy was made and her ADAMTS13 activity was found to be low. Regardless of aggressive treatment with pulse steroid therapy, IVIG, plasmapheresis along with multiple infusions of Fresh Frozen plasma (FFP), her condition deteriorated. In view of her worsening condition, she received one dose of Rituximab and within 48 h, her hematological and retinal involvements improved. Rituximab was given at the same dose once weekly thereafter for 4 total doses. Her disease process was halted, and retinopathy improved significantly in 48 h and continued to gradually improve over 3 weeks of maintenance therapy with cyclosporine, methotrexate, and IVIG and then stabilized. This report documents the association of TTP and Purtscher's retinopathy with JDM, emphasizing that early recognition and prompt treatment with rituximab along with the current standard of care treatment i.e., Vincristine, corticosteroids and plasmapheresis could be of potential benefit in controlling disease activity.

Management of Select Thrombocytopenias

Evaluating, diagnosing, and managing patients with consumptive thrombocytopenia is challenging because of the overlapping nature of many of the diseases that reduce platelet counts. Immune thrombocytopenia (and its variations), drug-induced immune thrombocytopenia, and heparin-induced thrombocytopenia result from autoimmune antibody-mediated destruction of platelets. Thrombotic thrombocytopenia (both congenital and acquired) and the hemolytic uremic syndromes (both typical and atypical) are thrombotic microangiopathies associated with platelet aggregation and consumption along with anemia and renal dysfunction. Rapid history taking, physical assessment, and laboratory evaluation are crucial to accurately managing patients with these disorders. Platelet-associated coagulopathies are infrequently encountered by most providers, and limited exposure to these types of patients, combined with the wide variety of treatment options for reversing bleeding or thrombotic sequelae, makes management difficult. This article reviews the pathophysiology, patient presentation, diagnostic testing, and specific management strategies and challenges of these thrombocytopenias.

Longitudinal assessments of plasma ADAMTS13 biomarkers predict recurrence of immune thrombotic thrombocytopenic purpura

Immune thrombotic thrombocytopenic purpura (iTTP) is primarily caused by immunoglobulin G (IgG)-type autoantibodies that bind and inhibit plasma ADAMTS13 activity and/or accelerate its clearance from circulation. Approximately 50% of patients with iTTP who achieve initial clinical response to therapy experience recurrence (ie, exacerbation and/or relapse); however, a reliable biomarker that predicts such an event is currently lacking. The present study determines the role of longitudinal assessments of plasma ADAMTS13 biomarkers in predicting iTTP exacerbation/recurrence. Eighty-three unique iTTP patients with 97 episodes from the University of Alabama at Birmingham Medical Center between April 2006 and June 2019 were enrolled. Plasma levels of ADAMTS13 activity, antigen, and anti-ADAMTS13 IgG on admission showed no significant value in predicting iTTP exacerbation or recurrence. However, persistently low plasma ADAMTS13 activity (<10 U/dL; hazard ratio [HR], 4.4; 95% confidence interval [CI], 1.6-12.5; P = .005) or high anti-ADAMTS13 IgG (HR, 3.1; 95% CI, 1.2-7.8; P = .016) 3 to 7 days after the initiation of therapeutic plasma exchange was associated with an increased risk for exacerbation or recurrence. Furthermore, low plasma ADAMTS13 activity (<10 IU/dL; HR, 4.8; 95% CI, 1.8-12.8; P = .002) and low ADAMTS13 antigen (<25th percentile; HR, 3.3; 95% CI, 1.3-8.2; P = .01) or high anti-ADAMTS13 IgG (>75th percentile; HR, 2.6; 95% CI, 1.0-6.5; P = .047) at clinical response or remission was also predictive of exacerbation or recurrence. Our results suggest the potential need for a more aggressive approach to achieve biochemical remission (ie, normalization of plasma ADAMTS13 activity, ADAMTS13 antigen, and anti-ADAMTS13 IgG) in patients with iTTP to prevent the disease recurrence.

Antibacterial properties of snake venom components

An increasing problem in the field of health protection is the emergence of drug-resistant and multi-drug-resistant bacterial strains. They cause a number of infections, including hospital infections, which currently available antibiotics are unable to fight. Therefore, many studies are devoted to the search for new therapeutic agents with bactericidal and bacteriostatic properties. One of the latest concepts is to search for this type of substances among toxins produced by venomous animals. In this approach, however, special attention is paid to snake venom because it contains molecules with antibacterial properties. Thorough investigations have shown that the phospholipases A2 (PLA2) and l-amino acids oxidases (LAAO), as well as fragments of these enzymes, are mainly responsible for the bactericidal properties of snake venoms. Some preliminary research studies also suggest that fragments of three-finger toxins (3FTx) are bactericidal. It has also been proven that some snakes produce antibacterial peptides (AMP) homologous to human defensins and cathelicidins. The presence of these proteins and peptides means that snake venoms continue to be an interesting material for researchers and can be perceived as a promising source of antibacterial agents.

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

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

Emerging roles of adjunct therapies in acquired thrombotic thrombocytopenia purpura

Acquired thrombotic thrombocytopenia purpura (aTTP) is caused by autoantibody-mediated severe deficiency of the von Willebrand factor (vWF) cleaving protease ADAMTS13 (a disintegrin and metalloprotease with thrombospondin type 1 repeats, member 13), with subsequent accumulation of ultra-large vWF-multimers that spontaneously form platelet-VWF complexes and microthrombi within the microcirculation. Therapeutic plasma exchange (TPE), by removing autoantibodies and excess ultra-large vWF multimers and replenishing ADAMTS13 activity, remains the urgent primary initial treatment. Although heterogeneity in treatment exists, most centers add upfront immunosuppression with steroids, and many also add upfront rituximab. Refractoriness, exacerbation and relapse are commonly treated with adjunct rituximab. Despite adjunct steroids and rituximab, TTP refractoriness, exacerbation, relapse, morbidity, and mortality remain problematic. Newer adjunct therapies include suppression of ADAMTS13 autoantibody production via plasma cell depletion, inhibition of vWF-platelet interaction, and replenishment of ADAMTS13 function with recombinant ADAMTS13 protein.

The role of ADAMTS-13 and von Willebrand factor in cancer patients: Results from the Vienna Cancer and Thrombosis Study

BACKGROUND

Cancer-associated venous thromboembolism (VTE) is an important complication in the course of a malignant disease. Low ADAMTS-13 (a disintegrin-like and metalloproteinase with thrombospondin type 1 motif 13) and increased von Willebrand Factor (VWF) levels in cancer patients have been described numerously.

OBJECTIVES

Investigation of the influence of ADAMTS-13 and VWF on the probability of VTE and survival in malignancy.

PATIENTS/METHODS

In the framework of the ongoing prospective Cancer and Thrombosis Study (CATS) ADAMTS-13 activity and VWF antigen levels were investigated in cancer patients.

RESULTS

In total, 795 patients with various tumor types (364 female/431 male, median age 62 years) were included; of those, 56 developed VTE and 359 patients died during a median follow-up time of 730 days. The hazard ratio (HR) of VTE per doubling of VWF level was 1.56 (95% confidence interval [CI] 1.13-2.16) in multivariable competing risk analysis. ADAMTS-13 levels showed no correlation with the incidence of VTE in univariate competing risk analysis. The HR of mortality per doubling of VWF level was 1.46 (95% CI 1.28-1.66) and per SD increment of ADAMTS-13was 0.90 (95% CI 0.81-1.00) in multivariable Cox regression analysis. Patients with VWF >75th percentile and concomitant low (<25th percentile) or medium (25-75th percentile) ADAMTS-13 values had the highest probability of mortality (HR 4.31 and 4.75, respectively).

CONCLUSIONS

High VWF levels were significantly associated with the risk of developing VTE in cancer patients, whereas ADAMTS-13 was not. Low ADAMTS-13 and increased VWF levels were independently associated with worse overall survival.

Comparison of the Long-Term Remission of Rituximab and Conventional Treatment for Acquired Thrombotic Thrombocytopenic Purpura: A Systematic Review and Meta-Analysis

The current systematic review and meta-analysis aimed to summarize the results of all available studies to compare the efficacies of rituximab and conventional treatment for acquired thrombotic thrombocytopenic purpura (TTP). Three investigators independently searched studies in the MEDLINE and EMBASE databases published before December 11, 2018. To be included in the meta-analysis, studies needed to be randomized-controlled or cohort studies comparing the efficacies of rituximab and conventional therapy for TTP treatment. The effect estimates and 95% confidence intervals (CIs) from each study were collected, and Mantel-Haenszel methods were used to pool the data. A total of 570 patients from 9 eligible studies were included in the meta-analysis (280 patients in the rituximab arm and 290 in the conventional treatment arm). Patients receiving rituximab in an acute phase to induce disease remission had a significantly lower relapse rate than those given conventional treatment (odds ratio [OR]: 0.40, 95% CI: 0.19-0.85, P = .02, I² = 43%). Similarly, the relapse rate in the rituximab group for preemptive therapy to prevent clinical relapse was also significantly lower than in the control group (OR: 0.09, 95% CI: 0.04-0.24, P < .00001, I² = 11%). Furthermore, the conventional treatment group had a significantly higher mortality rate than the rituximab group during the follow-up (OR: 0.41, 95% CI: 0.18-0.91, P = .03, I² = 0%). Rituximab offered high efficacy for the prevention of relapses and lower mortality rate in cases of acquired TTP.

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

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

Caplacizumab as an emerging treatment option for acquired thrombotic thrombocytopenic purpura

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