Contact System Activation and Bradykinin Generation in Angioedema: Laboratory Assessment and Biomarker Utilization.

The role of contact system activation has been clearly established in the pathogenesis of hereditary angioedema due to C1 inhibitor deficiency (HAE-C1INH). C1 inhibitor (C1INH)-protease complexes, levels of functional C1INH, plasma kallikrein activation, and cleavage of high-molecular-weight kininogen have each been associated with disease activity. More recently, HAE with normal levels of C1INH (HAE-nl-C1INH) has been recognized. Six genetic mutations have been identified which are linked to HAE-nl-C1INH phenotypes. The majority of individuals with HAE-nl-C1INH fall into the unknown category. There is substantial evidence that bradykinin generation underlies the recurrent attacks of swelling in some of these cohorts.

Summary and future of medicine for hereditary angioedema.

Hereditary angioedema (HAE) is a rare autosomal genetic disease for which there are currently nine FDA-approved drugs. This review summarizes drug treatments for HAE based on four therapeutic pathways: inhibiting the contact system, inhibiting bradykinin binding to B2 receptors, supplying missing C1 inhibitors, and inhibiting plasminogen conversion. The review generalizes the clinical use, pharmacological effects and mechanisms of HAE drugs, and it also discusses possible development directions and targets to enhance understanding of HAE and help researchers.

Sebetralstat (KVD900): A Potent and Selective Small Molecule Plasma Kallikrein Inhibitor Featuring a Novel P1 Group as a Potential Oral On-Demand Treatment for Hereditary Angioedema.

Hereditary angioedema (HAE) is a rare genetic disorder in which patients experience sudden onset of swelling in various locations of the body. HAE is associated with uncontrolled plasma kallikrein (PKa) enzyme activity and generation of the potent inflammatory mediator, bradykinin, resulting in episodic attacks of angioedema. Herein, we disclose the discovery and optimization of novel small molecule PKa inhibitors. Starting from molecules containing highly basic P1 groups, which typically bind to an aspartic acid residue (Asp189) in the serine protease S1 pocket, we identified novel P1 binding groups likely to have greater potential for oral-drug-like properties. The optimization of P4 and the central core together with the particularly favorable properties of 3-fluoro-4-methoxypyridine P1 led to the development of sebetralstat, a potent, selective, orally bioavailable PKa inhibitor in phase 3 for on-demand treatment of HAE attacks.

Isolated angioedema: A review of classification and update on management.

OBJECTIVE: To review the various types of angioedema including diagnosis and treatment. DATA SOURCES: PubMed search of articles in the English language of various types of angioedema. STUDY SELECTIONS: Articles on the subject matter were selected and reviewed. RESULTS: Herein, a case-based approach is presented for discussing the major types of angioedema, including the following: hereditary angioedema types I and II and normal complement, acquired angioedema, angiotensin-converting enzyme-induced angioedema, and histaminergic and nonhistaminergic angioedema. Emerging treatments of hereditary angioedema including targets of prekallikrein, DNA vector technology replacing C1-INH protein, and CRIPSR technology targeting prekallikrein among many others are explored. In addition, other causes and mimickers of angioedema are briefly reviewed. Finally, a novel algorithm is proposed to help guide the treating physician through the workup and management of patients with suspected idiopathic angioedema unresponsive to conventional therapy with antihistamines. CONCLUSION: Over the years, many strides have been made in both understanding the pathophysiology of various types of angioedema and expansion of treatment options. It is important for clinicians to be aware of current and emerging treatment options. We provide a novel practical algorithm to guide clinicians in challenging cases of idiopathic angioedema refractory to antihistamines.

The importance of recognizing and managing a rare form of angioedema: hereditary angioedema due to C1-inhibitor deficiency.

The majority of angioedema cases encountered in clinical practice are histamine-mediated (allergic); however, some cases are bradykinin-related (non-allergic) and do not respond to standard anti-allergy medications. Among bradykinin-related angioedema, hereditary angioedema (HAE) is a rare, but chronic and debilitating condition. The majority of HAE is caused by deficiency (type 1) or abnormal function (type 2) of the naturally occurring protein, C1-inhibitor (C1-INH)-a major inhibitor of proteases in the contact (kallikrein-bradykinin cascade), fibrinolytic pathway, and complement systems. Failure to recognize HAE and initiate appropriate intervention can lead to years of pain, disability, impaired quality of life (QoL) and, in cases of laryngeal involvement, it can be life-threatening. HAE must be considered in the differential diagnosis of non-urticarial angioedema, particularly for patients with a history of recurrent angioedema attacks, family history of HAE, symptom onset in childhood/adolescence, prodromal signs/symptoms before swellings, recurrent/painful abdominal symptoms, and upper airway edema. Management strategies for HAE include on-demand treatment for acute attacks, short-term prophylaxis prior to attack-triggering events/procedures, and long-term or routine prophylaxis for attack prevention. Patients should be evaluated at least annually to assess need for routine prophylaxis. HAE specific medications like plasma-derived and recombinant C1-INH products, kallikrein inhibitors, and bradykinin B2 receptor antagonists, have improved management of HAE. While the introduction of intravenous C1-INH represented a major breakthrough in routine HAE prophylaxis, some patients fail to achieve adequate control and others have psychological barriers or experience complications related to intravenous administration. Subcutaneous (SC) C1-INH, SC monoclonal antibody (mAb)-based therapies, and an oral kallikrein inhibitor offer effective alternatives for HAE attack prevention and may facilitate self-administration. HAE management should be individualized, with QoL improvement being a key goal. This can be achieved with broader availability of existing options for routine prophylaxis, including greater global availability of C1-INH(SC), mAb-based therapy, oral treatments, and multiple on-demand therapies.

Berotralstat: First Approval.

Berotralstat (ORLADEYO™) is an orally administered kallikrein inhibitor, which has been developed by BioCryst Pharmaceuticals for hereditary angioedema (HAE). The inhibition of kallikrein by berotralstat decreases the production of bradykinin, which prevents the localised tissue oedema that occurs during attacks of HAE. Berotralstat has been approved in the USA, and subsequently in Japan, for prophylaxis to prevent attacks of HAE in adults and paediatric patients aged 12 years or older. This article summarises the milestones in the development of berotralstat leading to this first approval for prophylaxis to prevent attacks of HAE.

Antisense Inhibition of Prekallikrein to Control Hereditary Angioedema.

Hereditary angioedema is characterized by recurrent and unpredictable episodes of subcutaneous and mucosal swelling that can be life threatening. IONIS-PKK-LRx is a ligand-conjugated antisense oligonucleotide designed for receptor-mediated delivery to hepatocytes. In a compassionate-use pilot study, two patients with severe bradykinin-mediated angioedema were initially administered weekly subcutaneous injections of the unconjugated parent drug, IONIS-PKKRx, for 12 to 16 weeks, after which they received IONIS-PKK-LRx at a dose of 80 mg every 3 to 4 weeks for 7 to 8 months. Treatment was accompanied by a reduction in the angioedema attack rate. (Funded by Amsterdam UMC.).

Bradykinin and oxidative stress in patients with hereditary angioedema due to C1 inhibitor deficiency.

INTRODUCTION: Hereditary angioedema (HAE) is a rare autosomal dominant disease caused by genetic dysfunction of C1 inhibitor (C1-INH) due to mutations in the SERPING1 gene. The disorder is mediated mainly by bradykinin. The clinical course of the disease is varied and not related to genetic changes. OBJECTIVES: We aimed to evaluate redox homeostasis of peripheral blood mononuclear cells (PBMCs) in patients with HAE due to C1-INH deficiency (C1 INH HAE) by measuring the levels of reactive oxygen species (ROS) of PBMCs as well as plasma advanced glycation end products (AGEs) and advanced oxidation protein products (AOPPs). We also aimed to assess the effect of bradykinin on ROS levels. PATIENTS AND METHODS: We enrolled 30 adults with C1-INH-HAE and 15 healthy individuals. The levels of ROS were measured by flow cytometry, while the plasma levels of AGEs and AOPPs were determined spectrophotometrically by enzyme­ linked immunosorbent assays. RESULTS: Basal and hydrogen peroxide (H2O2)-induced ROS levels were higher in patients with HAE when compared with controls (P = 0.002 and P = 0.001, respectively), indicating abnormalities in redox homeostasis. Plasma AOPP and AGE levels were similar in both groups. Bradykinin reduced basal and H2O2-induced ROS generation in PBMCs only in patients with HAE (P = 0.03). CONCLUSIONS: The higher basal and H2O2-induced ROS levels in patients with C1 INH HAE indicate redox imbalance. However, by reducing basal and H2O2-induced ROS levels, bradykinin shows antioxidant action in this disorder.

Hereditary angioedema: Looking for bradykinin production and triggers of vascular permeability.

Since the Osler's identification of the inherited nature of hereditary angioedema, a huge array of information was collected on pathogenetic mechanisms of the disease. Over the last years, information grew fast, and mutations in different genes, in addition to C1-inhibitor, were found to be causative. All types are inherited as autosomal-dominant traits with incomplete penetrance and little or no genotype-phenotype correlation. As a result, the clinical expression is characterized by a large heterogeneity. The acknowledgement of mechanisms leading to heterogeneity of the clinical phenotype is likely to provide important information not only for a better understanding of the pathogenesis but also for therapy. Regardless of which gene is mutated, similar pathways seem to play a pivotal role, triggering the up-regulation of contact activation system/kallikrein kinin system and giving rise to an unbalanced increase of bradykinin. However, notwithstanding the increase of bradykinin in bloodstream, the phenomenon is localized and no general vascular leakage and oedema is recognized. Thus, it is conceivable that there exist one or more localized factors that stimulate the production of bradykinin, which does not become a systemically event. Uncovering of these factors may shed lights on the missing part of the pathogenesis of hereditary angioedema. The present review, collecting information on pathogenesis from biochemical and genetics investigations, tries to provide a comprehensive view of the pathogenesis of hereditary angioedema. This can allow for a better understanding of the disease and lead to focused investigations that can further improve our knowledge.

Plasminflammation-An Emerging Pathway to Bradykinin Production.

Plasminogen activation is essential for fibrinolysis-the breakdown of fibrin polymers in blood clots. Besides this important function, plasminogen activation participates in a wide variety of inflammatory conditions. One of these conditions is hereditary angioedema (HAE), a rare disease with characteristic attacks of aggressive tissue swelling due to unregulated production and activity of the inflammatory mediator bradykinin. Plasmin was already implicated in this disease decades ago, but a series of recent discoveries have made it clear that plasmin actively contributes to this pathology. Collective evidence points toward an axis in which the plasminogen activation system and the contact system (which produces bradykinin) are mechanistically coupled. This is amongst others supported by findings in subtypes of HAE that are caused by gain-of-function mutations in the genes that respectively encode factor XII or plasminogen, as well as clinical experience with the antifibrinolytic agents in HAE. The concept of a link between plasminogen activation and the contact system helps us to explain the inflammatory side effects of fibrinolytic therapy, presenting as angioedema or tissue edema. Furthermore, these observations motivate the development and characterization of therapeutic agents that disconnect plasminogen activation from bradykinin production.

A review of kallikrein inhibitor lanadelumab in hereditary angioedema.

Hereditary angioedema with C1 esterase inhibitor deficiency is a rare disorder characterized by unpredictable swelling of the face, larynx and gastrointestinal tract. Kallikreins are serine proteases that cleave kininogens to produce bradykinin leading to inflammation. A new prophylactic drug is lanadelumab (DX-2930, SHP-643), a recombinant, fully human IgG1 monoclonal antibody kallikrein inhibitor. Pharmacokinetics show a half-life of 14 days with a dose-dependent effect. Completed trials for lanadelumab include two Phase III studies with updated efficacy in preventing angioedema in hereditary angioedema patients. Ongoing data show the safety of the targeted therapy along with less frequent administration requirements. Information on long-term safety is still needed, as well as, further studies on the correlation of subcutaneous administered dosing requirements and severity of side effects.

Hereditary angioedema in Austria: prevalence and regional peculiarities.

BACKGROUND: Data on the prevalence and clinical features of Austrian patients with hereditary angioedema (HAE) with C1-inhibitor (C1-INH) deficiency (HAE-1) or dysfunction (HAE-2) are lacking. METHODS: Current baseline data were collected in a national survey. The records of HAE patients at the Medical University of Graz were analyzed with regard to clinical characteristics. RESULTS: A total of 137 patients were identified, yielding a prevalence of 1 : 64,396. The median age at the onset of symptoms was 6.5 years, and the median age at the time of correct diagnosis 21.0 years. The median delay in diagnosis was 15.0 years for newly diagnosed patients without a family history of HAE. Patients with a family history of HAE received an immediate diagnosis. HAE patients without a family history of HAE and born before 1960 had to wait a median of 16.0 years until they were diagnosed correctly. Patients born after 1980 still experienced a median diagnostic delay of 6.5 years. CONCLUSION: Patients with this condition still face an excessive diagnostic delay in some parts of Austria, or their disorder may even remain unrecognized by specialists. This underlines the need for better awareness of the disease.

Angiopoietin-1 haploinsufficiency affects the endothelial barrier and causes hereditary angioedema.

BACKGROUND: Different mutations of the angiopoietin-1 gene (ANGPT1) have been associated with the occurrence of hereditary angioedema (HAE). OBJECTIVE: The purpose of the study is to clarify whether the ANGPT1 A119S variant plays its role via haploinsufficiency or a dominant negative effect. METHODS: The ability of ANGPT1 A119S variant to affect the endothelial barrier function was assessed by immunocytochemistry. Inter-endothelial gap formation molecules primarily responsible for cell-cell adhesions of HUVECs, vascular endothelial (VE)-cadherin and ß-catenin, and reorganization of the F-actin cytoskeletal were evaluated. RESULTS: In in vitro conditions mimicking the heterozygous state, the p.A119S variant significantly reduced the capability to bind its natural receptor (80.7% of normal), less than the homozygous condition (59.1%). After stimulation of VEGF or bradykinin, the addiction to equimolar amounts of wtANGPT1 and ANGPT1 p.A119S clearly reduced the expression of VE-cadherin on the endothelial cell surface (31% and 24% respectively). Likewise, cell surface expression of ß-catenin was reduced and severe gap formation between adjacent HUVECs developed. In cultured cells, ß-catenin expression was mostly observed along the cell surface. Treatment with equimolar amounts of wtANGPT1 and ANGPT1 p.A119S failed to restore the reorganization of the F-actin cytoskeletal elements. ANGPT1 p.A119S variant in homozygous condition further diminished VE-cadherin and ß-catenin expression and failed to reduce stress fibre formation significantly affecting the endothelial barrier functionality. CONCLUSIONS AND CLINICAL RELEVANCE: Present data show that in a heterozygous state the p.A119S substitution results in a pathogenic loss of function of the protein due to a mechanism of haploinsufficiency. The ANGPT1 reduced ability to counteract the increment of endothelial permeability produced by inducers, such as VEGF and bradykinin, stimulate vascular leakage and reorganization of the F-actin cytoskeletal elements. As a result, a partial impairment of the ANGPT1 functionality, like when dominant mutations occur, represents a pathophysiological cause of HAE.

A hereditary angioedema screening on an index case: Turkey.

BACKGROUND: Hereditary angioedema (HAE) is characterised by recurrent episodes of angioedema and can be fatal. OBJECTIVE: The present study aimed to screen HAE. METHODS: A total of 60 individuals were screened. The frequency and severity of symptoms were scored from 0 to 8. Measurements were taken of C4 and C1 esterase inhibitor protein (C1-INH) levels. Mutation in the C1 inhibitor gene was examined in 9 patients with HAE. RESULTS: A positive correlation between the C1 esterase inhibitor protein levels and C4 level was detected in the group as a whole (p < 0.001, r = 0.725, n = 60). Anegative correlation between the C1 esterase inhibitor protein level and severity score was observed in the whole group (p < 0.001, r = -0.486, n = 60). A negative correlation was also detected in the entire group between the C4 level and severity score (p = 0.002, r = -0.389, n = 60). In the patients with HAE, a positive correlation between the C1 esterase inhibitor protein level and C4 levels was detected (p = 0.034, r = 0.705, n = 9). A heterozygous c. 601A > T nonsense variant was identified at the C1 esterase inhibitor gene-SERPING1-in patients with Type 1 HAE. CONCLUSION: It is well known that there is a prolonged delay in the diagnosis of HAE. The present study demonstrates that it is very important and even life-saving to screen for HAE on the basis of an index case.

Deletions in SERPING1 Lead to Lower C1 Inhibitor Function: Lower C1 Inhibitor Function Can Predict Disease Severity.

BACKGROUND: How genotype affects phenotype in hereditary angioedema with C1 inhibitor deficiency (C1-INH-HAE) has not been totally clarified. In this study, we investigated the relationship between different types of mutations and various phenotypic characteristics. METHODS: Clinical data from 81 patients from 47 families were recorded. Complement proteins were analyzed from 61 untreated patients. The coding exons and the exon-intron boundaries of the SERPING1 gene were sequenced, and deletion/duplication analysis with multiple ligation dependent probe amplification was performed. The relationship of complement protein with the mutation type was analyzed by using generalized estimating equations. RESULTS: Thirty-five different mutations (15 novel and 2/15 homozygous) were identified. There was no causative mutation in 6 patients (7.4%). Patients with deletion and large deletion had the lowest (5.05%, 0-18.7; 5.8%, 0-16.5%, respectively), and the none mutation group had the highest C1 inhibitor function (23.3%, 11-78%, p < 0.001). C1 inhibitor function levels decreased as the age of the disease progressed (r = -0.352, p = 0.005). Lower C1 inhibitor function levels caused severer disease (r = -0.404, p = 0.001) and more frequent annual attacks (r = -0.289, p = 0.024). In the off-attack period, C1q levels were lower than normal in 9.8% of the patients. CONCLUSION: Deletion mutations may represent the most unfavorable effect on C1 inhibitor function. The earlier disease onset age could be a sign for lower C1 inhibitor function levels in adult life. C1q levels could also be low in C1-INH-HAE patients, as in acquired angioedema. Lower C1 inhibitor function can predict disease severity and may have negative impacts on the course of C1-INH-HAE.

Diagnostic biologique des angioedèmes bradykiniques : les recommandations du CREAK.

Bradykinin mediated angioedema (BK-AE) can be associated either with C1Inhibitor deficiency (hereditary and acquired forms), either with normal C1Inh (hereditary form and drug induced AE as angiotensin converting enzyme inhibitors…). In case of high clinical suspicion of BK-AE, C1Inh exploration must be done at first: C1Inh function and antigenemy as well as C4 concentration. C1Inh deficiency is significant if the tests are below 50 % of the normal values and controlled a second time. In case of C1Inh deficiency, you have to identify hereditary from acquired forms. C1q and anti-C1Inh antibody tests are useful for acquired BK-AE. SERPING1 gene screening must be done if a hereditary angioedema is suspected, even if there is no family context (de novo mutation 15 %). If a hereditary BK-AE with normal C1Inh is suspected, F12 and PLG gene screening is suitable.

Emotional processes and stress in children affected by hereditary angioedema with C1-inhibitor deficiency: a multicenter, prospective study.

BACKGROUND: Hereditary angioedema with C1-inhibitor deficiency (C1-INH-HAE) is characterized by recurrent edema of unpredictable frequency and severity. Stress, anxiety, and low mood are among the triggering factors most frequently reported. Impaired regulation and processing of emotions, also known as alexithymia, may influence outcomes. The aim of this study was to confirm the presence of alexithymia and stress in children with C1-INH-HAE, to determine whether they are also present in children affected by other chronic diseases, and to investigate their relationship with C1-INH-HAE severity. Data from children with C1-INH-HAE (n = 28) from four reference centers in Italy were compared with data from children with type 1 diabetes (T1D; n = 23) and rheumatoid arthritis (RA; n = 25). Alexithymia was assessed using the Alexithymia Questionnaire for Children scale; perceived stress was assessed using the Coddington Life Event Scale for Children (CLES-C). RESULTS: Mean age (standard deviation [SD]) in the C1-INH-HAE, T1D, and RA groups was 11.8 (3.3), 11.7 (2.9), and 11.1 (2.6) years, respectively. Mean C1-INH-HAE severity score was 5.9 (2.1), indicating moderate disease. Alexithymia scores were similar among disease groups and suggestive of difficulties in identifying and describing emotions; CLES-C scores tended to be worse in C1-INH-HAE children. C1-INH-HAE severity was found to correlate significantly and positively with alexithymia (p = 0.046), but not with perceived stress. Alexithymia correlated positively with perceived stress. CONCLUSIONS: Alexithymia is common in children with chronic diseases. In C1-INH-HAE, it may result in increased perceived stress and act as a trigger of edema attacks. Comprehensive management of C1-INH-HAE children should consider psychological factors.

Epidemiology of Bradykinin-mediated angioedema: a systematic investigation of epidemiological studies.

BACKGROUND: Bradykinin-mediated angioedema (Bk-AE) can be life-threatening and requires specific targeted therapies. Knowledge of its epidemiology may help optimize its management. METHODS: We systematically searched the medical literature to identify abstracts of interest indexed between 1948 and March, 2016. We used published national survey data on the proportion of the population treated with angiotensin-converting enzyme inhibitors (ACEI) to derive estimates of the population prevalence of ACEI-AE in the USA, Germany and France. For hereditary angioedema (C1-INH-HAE) and C1-inhibitor related acquired angioedema (C1-INH-AAE), publications had to contain original epidemiologic data collection within a defined geographical area. Hereditary angioedema with normal C1-INH was not included in the analysis due to lack of clearly defined criteria. RESULTS: We identified 4 relevant publications on the prevalence of ACEI-AE, 6 on the prevalence of C1-INH-HAE, and 1 on the prevalence of C1-INH-AAE. The 1st year cumulative incidence of ACEI-AE was estimated to vary between 0.12 (population-based analyses) and 0.30 (meta-analyses of clinical trials) per 100 patient-years. The population prevalence of ACEI-AE was modeled to vary between 7 and 26 in 100,000. The prevalence of C1-INH-HAE was estimated to vary between 1.1 and 1.6 per 100,000. The prevalence of C1-INH-AAE was estimated to be 0.15 per 100,000 in one epidemiological investigation of AAE in Denmark. CONCLUSIONS: Epidemiological evidence on Bk-AE is limited to North America and Europe. ACEI-AE is more common than C1-INH-HAE (~ 10:1), which is more common than C1-INH-AAE (~ 10:1). More studies are needed to comprehensively assess the epidemiological burden of Bk-AE.