Elevated plasma levels of vascular permeability factors in C1 inhibitor-deficient hereditary angioedema

BACKGROUND

Hereditary angioedema with C1 inhibitor deficiency (C1-INH-HAE) is a rare inherited genetic disease characterized by recurrent swelling episodes of the skin, gastrointestinal tract, and upper airways. Angioedema attacks result from increased vascular permeability due to the release of bradykinin from high molecular weight kininogen. Currently, there are no biomarkers predicting the frequency of angioedema attacks. Vascular permeability is modulated by several factors, including vascular endothelial growth factors (VEGFs) and angiopoietins (Angs). As increased circulating levels of VEGFs and Angs have been observed in diseases associated with higher vascular permeability (e.g., systemic capillary leak syndrome and sepsis), we sought to analyze plasma concentrations of VEGFs and Angs in patients with C1-INH-HAE.

METHODS

Sixty-eight healthy controls and 128 patients with C1-INH-HAE were studied. Concentrations of angiogenic (VEGF-A, Ang1, Ang2), anti-angiogenic (VEGF-A165b ) and lymphangiogenic (VEGF-C) factors were evaluated by ELISA. C1-INH functional activity was assessed by EIA.

RESULTS

Plasma concentrations of VEGF-A, VEGF-C, Ang1, and Ang2 were higher in patients with C1-INH-HAE in remission than in healthy controls. Concentration of VEGF-A was further increased in patients with lower C1-INH functional activity. Patients with C1-INH-HAE experiencing more than 12 angioedema attacks per year were characterized by higher plasma levels of VEGF-A, VEGF-C, and Ang2 compared with the other patients.

CONCLUSIONS

We hypothesize that VEGFs and Angs induce a state of 'vascular preconditioning' that may predispose to angioedema attacks. In addition, the identification of increased plasma levels of VEGFs and Angs in patients with C1-INH-HAE may prompt the investigation of VEGFs and Angs as biomarkers of C1-INH-HAE severity.

The Complement System

The human complement system (C) acts to lyse susceptible cells, to promote phagocytosis of target particles, and to solubilize immune-complexes, its activation generates peptides that mediate features of the inflammatory response. It is comprised of a series of plasma zymogens, activated by proteolytic cleavage in a cascade manner, and of plasma and cell membrane control proteins. Activation is achieved by two independent routes: the classical pathway, started by immunoglobulins, and the alternative pathway, started by cell membrane components. Both of them promote the generation of an enzyme-complex (C3 convertase) able to cleave the pivotal protein of the complement system, C3, thus initiating the common pathway with the formation of the lytic complex (Figure 1).

In this paper we will briefly review the physiologic phenomena related to the complement activation and its role in pathogenesis of illness particularly focusing on the studies carried out in our laboratory.

Efficacy of on-demand treatment in reducing morbidity in patients with hereditary angioedema due to C1 inhibitor deficiency

BACKGROUND

Angioedema due to hereditary deficiency of C1 inhibitor causes temporarily disability. Guidelines recommend early on-demand treatment of attacks to reduce morbidity. In this prospective observational study, we evaluated the efficacy of on-demand approach.

METHODS

From January 2009 to August 2014, data on attacks and treatments were collected from 227 patients from our centre in Milan.

RESULTS

A total of 4244 attacks were reported; 50% were treated with approved therapies (pdC1-INH or icatibant), 15% were with tranexamic acid, and 35% were not treated. Attack locations were peripheral cutaneous (46%), abdominal (34%), multiple (12%), facial (5%) and laryngeal (3%). Attack severities were moderate (48%), mild (28%) and severe (24%). Median attack duration (data available for 2393 attacks) with approved therapies was 10 h, significantly shorter than without treatment (45 h) or with tranexamic acid (38 h). Most of the treatments were self-administered: 93% with icatibant and 59% with pd-C1-INH. Median attack duration with icatibant was 8 and 11.5 h with pd-C1 INH. Median time from onset of symptoms to drug administration was 1 h with icatibant and 2 h with pd-C1INH and median time from drug administration to complete resolution was 5.5 and 8 h, respectively. Second treatment was required in 12.7% of icatibant-treated attacks and in 1.9% of pdC1-INH-treated attacks.

CONCLUSION

This study provides evidence that on-demand treatment is effective in reducing disease-related morbidity. The use of on-demand treatment in Italy has increased up to 50% of attacks in the last years, reflecting a better adherence to international guidelines.

Phase II study results of a replacement therapy for hereditary angioedema with subcutaneous C1-inhibitor concentrate

BACKGROUND

Hereditary angioedema (HAE) due to C1 inhibitor deficiency manifests as recurrent swelling attacks that can be disabling and sometimes fatal. Long-term prophylaxis with twice-weekly intravenous injections of plasma-derived C1-inhibitor (pdC1-INH) has been established as an effective treatment. Subcutaneous (SC) administration of pdC1-INH has not been studied in patients with HAE.

METHODS

This open-label, dose-ranging, crossover study (COMPACT Phase II) was conducted in 18 patients with type I or II HAE who received two of twice-weekly 1500, 3000, or 6000 IU SC doses of highly concentrated volume-reduced CSL830 for 4 weeks each. The mean trough plasma levels of C1-INH functional activity, C1-INH and C4 antigen levels during Week 4, and overall safety and tolerability were evaluated. The primary outcome was model-derived steady-state trough C1-INH functional activity.

RESULTS

After SC CSL830 administration, a dose-dependent increase in trough functional C1-INH activity was observed. C1-INH and C4 levels both increased. The two highest dose groups (3000 and 6000 IU) achieved constant C1-INH activity levels above 40% values, a threshold that was assumed to provide clinical protection against angioedema attacks. Compared with intravenous injection, pdC1-INH SC injection with CSL830 showed a lower peak-to-trough ratio and more consistent exposures. All doses were well tolerated. Mild-to-moderate local site reactions were noted with pain and swelling being the most common adverse event.

CONCLUSIONS

Subcutaneous volume-reduced CSL830 was well tolerated and led to a dose-dependent increase in physiologically relevant functional C1-INH plasma levels. A clinical outcome study of SC CSL830 in patients with HAE warrants further investigation.

Presentation, diagnosis and treatment of angioedema without wheals: a retrospective analysis of a cohort of 1058 patients

BACKGROUND

The first classification of angioedema without wheals was recently reported and comprises different forms of the disease distinguished by aetiology, mediator of oedema and inheritance.

METHODS

In total, 1725 consecutive patients with angioedema without wheals were examined at our centre between 1993 and 2012. We excluded from the analysis 667 patients because of incomplete data or because angioedema was related to a specific factor.

RESULTS

According to the new classification of angioedema, the 1058 patients included in this analysis were diagnosed with hereditary (HAE; n = 377) or acquired angioedema (AAE; n = 681). The former group included HAE with C1-inhibitor (C1-INH) deficiency (C1-INH-HAE; n = 353) and HAE with normal C1-INH levels (n = 24), of which six had a factor XII mutation (FXII-HAE) and 18 had disease of unknown origin (U-HAE). The AAE group included disease with C1-INH deficiency (C1-INH-AAE; n = 49), AAE related to angiotensin-converting enzyme inhibitor treatment (n = 183), idiopathic histaminergic (IH-AAE; n = 379) and idiopathic nonhistaminergic angioedema (InH-AAE; n = 70). We compared hereditary and AAE with uncertain aetiopathogenesis: the FXII-HAE and U-HAE groups pooled (FXII/U-HAE) versus InH-AAE. The median age at onset of FXII/U-HAE and InH-AAE was 26 and 38 years, respectively. In addition, 56% of patients with FXII/U-HAE and 81% of those with InH-AAE reported more than five attacks per year (median duration of 48 h). The location of angioedema in patients with FXII/U-HAE versus those with InH-AAE was the following: face, 70% versus 86%; tongue, oral cavity or larynx, 55% versus 68%; limbs, 70% versus 56%; and gastrointestinal mucosa, 50% versus 20%. Prophylaxis with tranexamic acid was effective in all six patients with U-HAE and in 37 of 38 with InH-AAE who were started on this treatment.

CONCLUSION

Our findings in this cohort of patients with angioedema provide new information on the clinical characteristics, diagnosis and treatment of this disease.

Classification, diagnosis, and approach to treatment for angioedema: consensus report from the Hereditary Angioedema International Working Group

Angioedema is defined as localized and self-limiting edema of the subcutaneous and submucosal tissue, due to a temporary increase in vascular permeability caused by the release of vasoactive mediator(s). When angioedema recurs without significant wheals, the patient should be diagnosed to have angioedema as a distinct disease. In the absence of accepted classification, different types of angioedema are not uniquely identified. For this reason, the European Academy of Allergy and Clinical Immunology gave its patronage to a consensus conference aimed at classifying angioedema. Four types of acquired and three types of hereditary angioedema were identified as separate forms from the analysis of the literature and were presented in detail at the meeting. Here, we summarize the analysis of the data and the resulting classification of angioedema.

Review of recent guidelines and consensus statements on hereditary angioedema therapy with focus on self-administration

Consensus meetings and the resulting recommendations shape treatment choices in rare diseases such as hereditary angioedema (HAE) because they combine the experience of prescribing physicians and the patients who are receiving therapy. Self-administration of HAE therapy was recognised as a potential treatment option in the first consensus publication in 2003. Recent studies have confirmed that self-administration of therapy resolves attacks quickly, safely and minimises burden of disease; however, the discovery of inconsistent treatment approaches is a concern and warrants investigation into the barriers that prevent adherence with current recommendations.

Icatibant treatment for acquired C1-inhibitor deficiency: a real-world observational study

Icatibant, a bradykinin B2 receptor antagonist, is an established treatment for acute attacks of hereditary angioedema (HAE) with C1-inhibitor (C1-INH) deficiency. We describe our experience with icatibant in eight patients with angioedema because of acquired C1-INH deficiency (AAE). Forty-eight moderate-to-severe attacks were treated with subcutaneous icatibant 30 mg; two moderate attacks resolved without treatment. The median (range) duration of treated attacks (onset to complete resolution) was 9.33 (1.67-39.00) h; durations of the untreated attacks were 72 and 96 h. Symptom improvement following icatibant treatment occurred in 0.5 (0.25-2.10) h and complete resolution in 6.75 (0.50-30.75) h. A single icatibant injection achieved complete symptom resolution in 47 attacks; one facial attack required a second injection. One peripheral attack responded less quickly than other treated attacks. Five patients reported transient injection site reactions. Icatibant appeared to provide effective symptom relief and was generally well tolerated.

Alterations of coagulation and fibrinolysis in patients with angioedema due to C1-inhibitor deficiency

Patients with functional deficiency of C1-inhibitor (C1-INH) suffer from recurrent acute attacks (AA) of localized oedema associated with activation of the contact system, complement and fibrinolysis. To unravel further the role of coagulation and fibrinolysis in the pathophysiology of C1-INH deficiency, we performed simultaneous thrombin and plasmin generation measurements in plasma from patients with hereditary angioedema (HAE) due to C1-INH deficiency during AA (n = 23), in remission (R) (n = 20) and in controls (n = 20). During AA thrombin generation after in-vitro activation of plasma was higher than in controls, as demonstrated by shorter thrombin peak-time (P < 0·05), higher thrombin peak-height (P < 0·001) and increased area under the curve (AUC) (P < 0·05). Additionally, elevated levels of prothrombin fragment 1+2 (P < 0·0001) were observed in non-activated plasma from the same patients. In contrast, in activated plasma from patients during AA plasmin generation estimated as plasmin peak-height (P < 0·05) and plasmin potential (P < 0·05) was reduced, but non-activated plasma of the same patients showed elevated plasmin-anti-plasmin (PAP) complexes (P < 0·001). This apparent discrepancy can be reconciled by elevated soluble thrombomodulin (sTM) (P < 0·01) and thrombin activatable fibrinolysis inhibitor (TAFI) in patients during AA providing possible evidence for a regulatory effect on fibrinolysis. Plasminogen activator inhibitor-1 (PAI-1) was reduced in patients during AA indicating, together with the observed reduction of plasmin generation, the consumption of fibrinolytic factors. In conclusion, our results support the involvement of coagulation and fibrinolysis in the pathophysiology of HAE and show the possible application of simultaneous measurement of thrombin and plasmin generation to evaluate different clinical conditions in HAE patients.

Evidence-based recommendations for the therapeutic management of angioedema owing to hereditary C1 inhibitor deficiency: consensus report of an International Working Group

Angioedema owing to hereditary deficiency of C1 inhibitor (HAE) is a rare, life-threatening, disabling disease. In the last 2 years, the results of well-designed and controlled trials with existing and new therapies for this condition have been published, and new treatments reached the market. Current guidelines for the treatment for HAE were released before the new trials and before the new treatments became available and were essentially based on observational studies and expert opinion. To provide evidence-based HAE treatment guidelines supported by the new studies, a conference was held in Gargnano del Garda, Italy, from September 26 to 29, 2010. The meeting hosted 58 experienced HAE expert physicians, representatives of pharmaceutical companies and representatives of HAE patients' associations. Here, we report the topics discussed during the meeting and evidence-based consensus about management approaches for HAE in adult/adolescent patients.

Target levels of functional C1-inhibitor in hereditary angioedema

BACKGROUND

  Hereditary angioedema (HAE) is a heterozygous deficiency of first component of complement-inhibitor (C1INH). Insufficient C1INH activity leads to uncontrolled activation of plasma cascade systems, which results in acute angioedema attacks in patients with HAE. Plasma-derived or recombinant C1INH products are approved for the treatment of such angioedema attacks. The target level of C1INH activity needed to achieve optimal efficacy, however, remains unknown. We determined the plasma level of C1INH associated with optimal clinical efficacy in the treatment of angioedema attacks.

METHODS

  Efficacy and pharmacokinetic data were reviewed from recently published placebo-controlled randomized trials in the treatment of HAE with either plasma-derived or recombinant C1INH products, tested at various doses.

RESULTS

  A dose-dependent effect was observed on time to the beginning of relief of symptoms, on time to resolution of symptoms, and on the response rate within 4 h. Optimal efficacy of C1INH therapy is achieved at doses ≥50 U/kg. This dose increases plasma C1INH activity in almost all patients to values ≥0.7 U/ml (70% of normal), the lower limit of the normal range. The differences in half-lives of the various C1INH products do not have an obvious effect on clinical efficacy.

CONCLUSION

  A review of the efficacy and pharmacokinetic data from recently published controlled studies in the treatment of HAE attacks suggests that efficacy of C1INH therapy is optimal when C1INH activity levels are restored to the normal range.

New topics in bradykinin research

Bradykinin has been implicated to contribute to allergic inflammation and the pathogenesis of allergic conditions. It binds to endothelial B(1) and B(2) receptors and exerts potent pharmacological and physiological effects, notably, decreased blood pressure, increased vascular permeability and the promotion of classical symptoms of inflammation such as vasodilation, hyperthermia, oedema and pain. Towards potential clinical benefit, bradykinin has also been shown to exert potent antithrombogenic, antiproliferative and antifibrogenic effects. The development of pharmacologically active substances, such as bradykinin receptor blockers, opens up new therapeutic options that require further research into bradykinin. This review presents current understanding surrounding the role of bradykinin in nonallergic angioedema and other conditions seen by allergists and emergency physicians, and its potential role as a therapeutic target.

Standard care impact on angioedema because of hereditary C1 inhibitor deficiency: a 21-month prospective study in a cohort of 103 patients

BACKGROUND

  Hereditary angioedema (HAE) due to the deficiency of C1 inhibitor (C1-INH) causes chronically recurrent cutaneous, abdominal and laryngeal angioedema that are disabling and potentially life-threatening.

OBJECTIVE

  We designed a prospective study to quantify the residual disease in patients with HAE treated according to the existing consensus documents.

METHODS

  Data were collected from diaries recording occurrence, duration, location and treatment of acute angioedema attacks. A total of 386 semesters properly completed were analyzed. Forty-seven of 103 patients were on prophylactic treatment, 41 with attenuated androgens and six with tranexamic acid. A total of 1532 angioedema attacks (one every 45.3 days) were registered.

RESULTS

  Peripheral attacks were the most frequent (698), followed by abdominal (503) and combined locations (232), laryngeal edema was less common (99). Patients on prophylaxis with attenuated androgens had 7.7 attacks/year lasting 1.47 days, those on tranexamic acid had 8.1 attacks/year lasting 1.59 days, and those without prophylaxis had 8.9 attacks/year lasting 1.68. Plasma-derived C1-INH was used by 44 patients to treat a total of 376 acute attacks that resolved faster (1.1 day) than those not treated (1.85 day) or treated with tranexamic acid (1.79 day). No adverse events related to C1-INH infusion were reported.

CONCLUSION

  Our data demonstrate that tranexamic acid is not effective in the treatment of acute attacks and indicate that under the current therapeutic approach, the HAE related disability is effectively but partially reduced. Incomplete success does not appear to depend on limited efficacy of the drugs but on their limited use that can be overcome by implementing specific treatment strategies.

The acquired deficiency of C1-inhibitor: lymphoproliferation and angioedema

Acquired deficiency of C1 inhibitor (C1-INH) with angioedema symptoms (acquired angioedema, AAE) is characterized by local increase in vascular permeability (angioedema) of the skin and the gastrointestinal and oro-pharyngo-laryngeal mucosa. The mediator of symptoms is bradykinin, a potent vasoactive peptide, released from high molecular weight kininogen when it is cleaved by plasma kallikrein a serine protease controlled by C1-INH. Autoantibodies inactivating C1-INH are detected in the majority of patients and account for the deficiency. Irrespectively to the presence of anti-C1-INH autoantibodies lymphoproliferative diseases, ranging from benign monoclonal gammopathies to malignant lymphoma, are frequently associated with AAE. Demonstration that monoclonal components correspond to anti-C1-INH autoantibodies and correlation between course of lymphoma and course of AAE provide strong support to consider the two diseases expression of the same pathologic process.

Plasma biomarkers of acute attacks in patients with angioedema due to C1-inhibitor deficiency

BACKGROUND

Cl-inhibitor (C1-INH) deficiency leads to recurrent attacks of mucocutaneous edema and may be inherited (hereditary angioedema [HAE]) or acquired (acquired angioedema [AAE]), which have the same clinical picture characterized by angioedema involving the skin, gastrointestinal tract, and larynx. Although cutaneous swelling is evident, abdominal angioedema is still a diagnostic challenge and attacks can mimic surgical emergencies. There is currently no laboratory marker for identifying angioedema attacks.

OBJECTIVE

As coagulation and fibrinolysis are activated during angioedema attacks, we assessed if plasma measurements of prothrombin fragment F1 + 2 (marker of thrombin generation) and D-dimer (marker of fibrin degradation) can be useful for the diagnosis of angioedema because of C1-INH deficiency, especially in case of hidden locations as abdominal attacks.

METHODS

In addition to complement, we measured plasma levels of F1 + 2 and D-dimer in 28 patients with C1-INH deficiency during acute attacks and remission, 35 patients without C1-INH deficiency during abdominal colics, and 20 healthy subjects.

RESULTS

Plasma F1 + 2 levels were higher in patients with C1-INH deficiency during remission than in healthy controls (P = 0.001), and further increased during cutaneous and abdominal attacks (P = 0.0001); patients without C1-INH deficiency had normal F1 + 2 levels during abdominal colics. Plasma D-dimer levels were higher in patients with C1-INH deficiency during remission than in controls (P = 0.012) and increased during angioedema attacks, reaching higher levels than in patients without C1-INH deficiency during colics (P = 0.002).

CONCLUSIONS

During acute angioedema attacks, patients with C1-INH deficiency have high prothrombin fragment F1 + 2 and D-dimer levels, the measurement of which may have an important diagnostic value.