Replacement therapy with C1 esterase inhibitors for hereditary angioedema

Angioedema due to hereditary C1 inhibitor deficiency (HAE) is a highly disabling and potentially lethal disease with an estimated prevalence of 1:50,000 in the general population worldwide. Treatment of this condition by replacing the deficient protein started shortly after discovery of the underlying genetic defect. Along with other therapeutic approaches developed over the years, C1 inhibitor replacement therapy maintains a central role for the treatment of angioedema attacks in patients with HAE. Two plasma-derived C1 inhibitors and a recombinant form, produced in transgenic rabbits, have successfully completed controlled trials that reinforced the evidence of the safety and efficacy of this treatment.     

The use of plasma-derived C1 inhibitor in the treatment of hereditary angioedema

C1-inhibitor (C1-INH) deficiency is the genetic defect underlying hereditary angioedema (HAE). Subjects with HAE suffer from recurrent angioedema that may result in death when it affects the larynx, severe abdominal pain when it affects the gastrointestinal mucosa and disfiguration when it affects the skin. The use of plasma-derived C1-INH concentrates to revert angioedema in HAE patients started in the 1970s. Since that time, three different preparations arrived onto the market, two of them are still present. Controlled studies and a large clinical experience indicate that C1-INH concentrate should be considered the treatment of choice for disabling angioedema attacks at any site. Efficacy has also been shown in preventing angioedema induced by invasive medical manoeuvres. Limited experience with repeated weekly infusions indicates that C1-INH can be used for long-term prophylaxis in selected patients. The safety profile is excellent and there are no reports of transmission of viral infections with the preparations available at present. C1-INH is licensed only in a limited number of countries. Clinical trials are ongoing at present to expand registration.     

The use of plasma-derived C1 inhibitor in the treatment of hereditary angioedema

C1-inhibitor (C1-INH) deficiency is the genetic defect underlying hereditary angioedema (HAE). Subjects with HAE suffer from recurrent angioedema that may result in death when it affects the larynx, severe abdominal pain when it affects the gastrointestinal mucosa and disfiguration when it affects the skin. The use of plasma-derived C1-INH concentrates to revert angioedema in HAE patients started in the 1970s. Since that time, three different preparations arrived onto the market, two of them are still present. Controlled studies and a large clinical experience indicate that C1-INH concentrate should be considered the treatment of choice for disabling angioedema attacks at any site. Efficacy has also been shown in preventing angioedema induced by invasive medical manoeuvres. Limited experience with repeated weekly infusions indicates that C1-INH can be used for long-term prophylaxis in selected patients. The safety profile is excellent and there are no reports of transmission of viral infections with the preparations available at present. C1-INH is licensed only in a limited number of countries. Clinical trials are ongoing at present to expand registration.     

Current treatment options for hereditary angioedema due to C1 inhibitor deficiency

Introduction: Hereditary angioedema (HAE) usually results from C1 inhibitor (C1-INH) deficiency or dysfunction. It is a rare autosomal dominant disorder characterized by localized, non-pitting edema of the skin and submucosal tissues of the upper respiratory and gastrointestinal tracts, without significant wheals or pruritus, due to a temporary increase in vascular permeability. Other forms of HAE have been described, but therapies are approved only for HAE with C1-INH deficiency: hence, this review focuses on C1-INH-HAE. Areas covered: The aim of this review article is to present current available therapies for treatment of acute attacks as well as for short- and long-term prophylaxis of hereditary angioedema due to C1 inhibitor deficiency (C1-INH-HAE). The Authors highlight also critical issues on the management of C1-INH-HAE, which is continuously evolving thanks to evidence from clinical trials, post-marketing experience and ongoing studies. Expert opinion: In the last decade, the quality of life of C1-INH-HAE patients has significantly improved due to increased knowledge and awareness of the disease, improved patient support and major progress in pharmacotherapy. Ongoing research will probably provide patients with other new effective therapeutic agents in the near future.     

The central role of endothelium in hereditary angioedema due to C1 inhibitor deficiency

An impairment of the endothelial barrier function underlies a wide spectrum of pathological conditions. Hereditary angioedema due to C1-inhibitor deficiency (C1-INH-HAE) can be considered the “pathophysiological and clinical paradigm” of Paroxysmal Permeability Diseases (PPDs), conditions characterized by recurrent transient primitively functional alteration of the endothelial sieving properties, not due to inflammatory-ischemic-degenerative injury and completely reversible after the acute flare. It is a rare yet probably still underdiagnosed disease which presents with localized, non-pitting swelling of the skin and submucosal tissues of the upper respiratory and gastrointestinal tracts, without significant wheals or pruritus. The present review addresses the pathophysiology of C1-INH-HAE with a focus on the crucial role of the endothelium during contact and kallikrein/kinin system (CAS and KKS) activation, currently available and emerging biomarkers, methods applied to get new insights into the mechanisms underlying the disease (2D, 3D and in vivo systems), new promising investigation techniques (autonomic nervous system analysis, capillaroscopy, flow-mediated dilation method, non-invasive finger plethysmography). Hints are given to the binding of C1-INH to endothelial cells. Finally, crucial issues as the local vs systemic nature of CAS/KKS activation, the episodic nature of attacks vs constant C1-INH deficiency, pros and cons as well as future perspectives of available methodologies are briefly discussed.     

The safety of treatments for angioedema with hereditary C1 inhibitor deficiency

Introduction: Angioedema is a localized and self-limiting edema of the subcutaneous and submucosal tissue. Hereditary angioedema with C1 inhibitor deficiency (C1-INH-HAE) is the best characterized form of hereditary angioedema. In C1-INH-HAE, the reduced plasma levels of C1-INH cause instability of the contact system with release of bradykinin, the key mediator of angioedema. C1-INH-HAE is characterized by recurrent skin swelling, abdominal pain, and potentially life-threatening upper airways obstruction. Knowledge of the molecular mechanisms leading from C1-INH deficiency to angioedema allowed the development of several therapies.

Areas covered: The aim of this review article is to discuss the safety of currently available treatments of C1-INH-HAE. The authors give an insight on the mechanism of action and safety profile of drugs for treatment of acute attacks and for short- and long-term prophylaxis. Evidence from systematic reviews, clinical trials, retrospective studies, and case reports is summarized in this review.

Expert opinion: C1-INH-HAE is a disabling, life-threatening condition that lasts life-long. Different therapeutic approaches with different drugs provide significant benefit to patients. Safety profiles of these therapies are critical for optimal therapeutic decision and need to be known by C1-INH-HAE treating physicians for appropriate risk/benefit evaluation.     

Population pharmacokinetics of recombinant human C1 inhibitor in patients with hereditary angioedema

Aims

To characterize the pharmacokinetics (PK) of recombinant human C1 inhibitor (rhC1INH) in healthy volunteers and hereditary angioedema (HAE) patients.

Methods

Plasma levels of C1INH following 294 administrations of rhC1INH in 133 subjects were fitted using nonlinear mixed-effects modelling. The model was used to simulate maximal C1INH levels for the proposed dosing scheme.

Results

A one-compartment model with Michaelis–Menten elimination kinetics described the data. Baseline C1INH levels were 0.901 [95% confidence interval (CI): 0.839–0.968] and 0.176 U ml⁻¹ (95% CI: 0.154–0.200) in healthy volunteers and HAE patients, respectively. The volume of distribution of rhC1INH was 2.86 l (95% CI: 2.68–3.03). The maximal rate of elimination and the concentration corresponding to half this maximal rate were 1.63 U ml⁻¹ h⁻¹ (95% CI: 1.41–1.88) and 1.60 U ml⁻¹ (95% CI: 1.14–2.24), respectively, for healthy volunteers and symptomatic HAE patients. The maximal elimination rate was 36% lower in asymptomatic HAE patients. Peak C1INH levels did not change upon repeated administration of rhC1INH. Bodyweight was found to be an important predictor of the volume of distribution. Simulations of the proposed dosing scheme predicted peak C1INH concentrations above the lower level of the normal range (0.7 U ml⁻¹) for at least 94% of all patients.

Conclusions

The population PK model for C1INH supports a dosing scheme on a 50 U kg⁻¹ basis up to 84 kg, with a fixed dose of 4200 U above 84 kg. The PK of rhC1INH following repeat administration are consistent with the PK following the first administration.     

C1-Esterase inhibitor: an anti-inflammatory agent and its potential use in the treatment of diseases other than hereditary angioedema

C1-esterase inhibitor (C1-Inh) therapy was introduced in clinical medicine about 25 years ago as a replacement therapy for patients with hereditary angioedema caused by a deficiency of C1-Inh. There is now accumulating evidence, obtained from studies in animals and observations in patients, that administration of C1-Inh may have a beneficial effect as well in other clinical conditions such as sepsis, cytokine-induced vascular leak syndrome, acute myocardial infarction, or other diseases. Activation of the complement system, the contact activation system, and the coagulation system has been observed in these diseases. A typical feature of the contact and complement system is that on activation they give rise to vasoactive peptides such as bradykinin or the anaphylatoxins, which in part explains the proinflammatory effects of either system. C1-Inh, belonging to the superfamily of serine proteinase inhibitors (serpins), is a major inhibitor of the classical complement pathway, the contact activation system, and the intrinsic pathway of coagulation, respectively. It is, therefore, endowed with anti-inflammatory properties. However, inactivation of C1-Inh occurs locally in inflamed tissues by proteolytic enzymes (e.g., elastase) released from activated neutrophils or bacteria thereby leading to increased local activation of the various host defense systems. Here we will give an overview on the biochemistry and biology of C1-Inh. We will discuss studies addressing therapeutic administration of C1-Inh in experimental and clinical conditions. Finally, we will provide an explanation for the therapeutic benefit of C1-Inh in so many different diseases.     

Rhucin, a recombinant C1 inhibitor for the treatment of hereditary angioedema and cerebral ischemia

Pharming NV and Esteve are developing Rhucin, a recombinant human C1 esterase inhibitor. Rhucin is currently undergoing phase III clinical trials in North America and is awaiting regulatory approval in Western Europe for the treatment of prophylactic and acute hereditary angioedema. Pharming is also investigating Rhucin for the potential treatment of cerebral ischemic injury.     

A first of its kind quantitative functional C1-esterase inhibitor lateral flow assay for hereditary angioedema point-of-care diagnostic testing

Hereditary Angioedema (HAE) is a rare, autosomal dominant disease caused by mutations in SERPING1 gene leading to dysfunction/deficiency of C1-esterase inhibitor (C1-INH) protein and subsequent dysregulation of the contact system and bradykinin overproduction. As functional C1-INH (fC1-INH) levels are reduced in HAE types I and II (HAE-I/II), a specific, sensitive and accessible rapid diagnostic method to quantitate fC1-INH is crucial in diagnosing HAE-I/II. Previously, we developed/validated methods to detect fC1-INH levels in human plasma based on functional binding to C1s or FXIIa for C1-INH-based therapies. Quantitative fC1-INH immunoassay methods were converted to the Lateral flow assay (LFA) platform after identifying the best reagent/s pair. The assay was developed and optimized as a first of its kind LFA method for quantifying fC1-INH in human plasma to aid HAE point-of-care diagnosis. Receiver operating characteristic analysis was performed using normal control and HAE subject plasma samples to calculate area-under-curve and a cut-off point to distinguish normal versus HAE subject samples. LFA data was correlated with the conventional diagnostic assay for fC1-INH in HAE plasma samples and profiles matched for individual subjects. Here, we demonstrate a proof-of-concept for the quantitative fC1-INH LFA using normal and HAE plasma samples. We propose that the method could be used as a point-of-care test to diagnose HAE in a variety of settings, such as, a hospital or physician’s office, at home or in an ambulance.     

Acquired angioedema with C1 inhibitor deficiency associated with anticardiolipin antibodies

Acquired angioedema (AAE) with C1 inhibitor deficiency is often associated to B cell lymphoproliferative disorders or autoimmune diseases. We report a case of AAE associated with IgM anti-cardiolipin antibodies, with frequent edematous attacks, that disappeared completely after a slight immunosuppression and danazol therapy.     

The therapeutic potential of a kallikrein inhibitor for treating hereditary angioedema

Hereditary angioedema (HAE) manifests as intermittent, painful attacks of submucosal oedema affecting the larynx, gastrointestinal tract or limbs. Currently, acute treatment is available in Europe but not USA, and requires intravenous administration of a pooled blood product. HAE is most likely caused by dysinhibition of the contact cascade, resulting in overproduction of bradykinin. DX-88 (ecallantide, Dyax Corp.) is a highly specific recombinant plasma kallikrein inhibitor that halts the production of bradykinin and can be dosed subcutaneously. In a placebo-controlled Phase II trial in patients with HAE, DX-88 resulted in significant improvement in symptoms compared with placebo. A Phase III trial is ongoing. This review explains the pathophysiology of HAE and the mechanism by which DX-88, a non-intravenous, nonplasma-derived therapy, might improve the disease, and discusses the clinical course of HAE and available treatments. Finally, it explores the potential value and efficacy of DX-88 in treating HAE.     

The therapeutic potential of a kallikrein inhibitor for treating hereditary angioedema

Hereditary angioedema (HAE) manifests as intermittent, painful attacks of submucosal oedema affecting the larynx, gastrointestinal tract or limbs. Currently, acute treatment is available in Europe but not USA, and requires intravenous administration of a pooled blood product. HAE is most likely caused by dysinhibition of the contact cascade, resulting in overproduction of bradykinin. DX-88 (ecallantide, Dyax Corp.) is a highly specific recombinant plasma kallikrein inhibitor that halts the production of bradykinin and can be dosed subcutaneously. In a placebo-controlled Phase II trial in patients with HAE, DX-88 resulted in significant improvement in symptoms compared with placebo. A Phase III trial is ongoing. This review explains the pathophysiology of HAE and the mechanism by which DX-88, a non-intravenous, nonplasma-derived therapy, might improve the disease, and discusses the clinical course of HAE and available treatments. Finally, it explores the potential value and efficacy of DX-88 in treating HAE.     

Angiotensin II receptor blocker-associated angioedema: on the heels of ACE inhibitor angioedema

Angioedema and cough are known side effects of angiotensin-converting enzyme (ACE) inhibitors. Angiotensin-converting enzyme is a potent inhibitor of kinase II, which facilitates the breakdown of bradykinin. An increase in bradykinin levels results in continued prostaglandin E2 synthesis, vasodilation, increased vascular permeability, and increased interstitial fluid. In contrast, the angiotensin II receptor blockers (ARBs) do not increase bradykinin levels. Angioedema as a complication of ACE inhibitor therapy is not widely recognized; this complication is even less recognized with second-line ARBs. We report angioedema associated with losartan (an ARB) in a patient who had experienced angioedema secondary to enalapril (an ACE inhibitor). Almost half of patients with ARB-associated angioedema also had developed angioedema while receiving ACE inhibitor therapy. Clinicians should exercise caution when using ARBs in patients with a history of angioedema secondary to ACE inhibitors.     

Evaluation of the efficacy and safety of home treatment with the recombinant human C1-inhibitor in hereditary angioedema resulting from C1-inhibitor deficiency

ObjectiveConestat alpha, a C1-inhibitor produced by recombinant technology (rhC1-INH) is an acute treatment for edematous attacks occurring in hereditary angioedema (HAE) with C1-inhibitor deficiency (C1-INH-HAE). Our study evaluated the efficacy and safety of rhC1-INH administered during HAE attacks, and for short-term prophylaxis (STP).Materials & methodOur prospective study analyzed the course of 544 HAE attacks experienced by the 21 C1-INH-HAE patients treated, as well as the outcome of 97 instances of STP implemented with rhC1-INH. Using a purpose-designed questionnaire, the patients recorded relevant, treatment-related information.ResultsTime to the administration of rhC1-INH was 90.0 min (median) after the onset of HAE attacks. The symptoms started to improve as early as 60 min after the injection of rhC1-INH, and the attack resolved 730.0 min after treatment. The interval between the onset of the HAE attack and the administration of rhC1-INH correlated with time until the onset of improvement (R = 0.2053 p < 0.0001), and with time to the complete resolution of symptoms (R = 0.2805, p < 0.0001). Nine patients received STP with rhC1-INH in 97 instances. STP successfully prevented the HAE attack within 72 h of the event on 93/97 occasions. No local and serious systemic adverse events/effects were observed.ConclusionsTreatment with rhC1-INH is effective and safe both for acute management, and for STP. Following the onset of an HAE attack, early administration of rhC1-INH may reduce time to the improvement and to the complete resolution of symptoms. Repeated administration of rhC1-INH does not impair its efficacy.     

Long-term follow up analysis of nadroparin for hereditary angioedema. A preliminary report

Hereditary angioedema is caused by a C1-inhibitor deficiency. It is a life-threatening disease. Its management includes treating acute attacks, short-term prophylaxis, and long-term prophylaxis. We report our experience with nadroparin for the short-term prophylaxis and treatment of angioedema attacks. We indicated treatment with nadroparin 0.3-0.6 mL SC 20 min after the onset of prodromes, then every 8-12 h for 1 day; short-term prophylaxis with 0.3-0.6 mL 1 h before a triggering event and then every 12-24 h for 1 more day. For children, treatment included 0.3 mL SC 20 min after the onset of prodromes, then every 12-24 h for 1 day; short-term prophylaxis was 0.3 mL 1 h before a triggering event and 1 more dose after 24 h. For the treatment, a complete response was considered when nadroparin totally stopped an acute attack within 2 h after injection. Partial response was considered if after 2 h analgesics and/or other therapy were required. Failure was established if after 4 h no response was obtained and fresh frozen plasma and other in-patient measures were required. For short-term prophylaxis, only complete responses and failures were considered. We included 29 adults and 5 children. Functional C1-inhibitor and C4 levels rose after nadroparin. We recorded 256 treatments (89.8% complete responses, 8.2% partial responses, and 1.9% failures), and 102 short-term prophylactic regimens (90.2% complete responses, and 9.8% failures). We found 38 mild adverse events without severe hemorrhagic episodes. If our results are reproduced subsequently, nadroparin may be an alternative for the treatment and short-term prophylaxis of angioedema attacks.     

Biological effects of C1 inhibitor

C1 inhibitor is a serine proteinase inhibitor (serpin) that regulates activation of both the complement and contact systems. Regulation of complement system activation takes place through inactivation of the classical pathway proteases, C1r and C1s, the lectin pathway protease, MASP2, and perhaps via inhibition of alternative pathway activation by reversible binding to C3b. Regulation of contact system activation takes place through inactivation of plasma kallikrein and coagulation factor XIIa. Deficiency of C1 inhibitor results in hereditary angioedema, which is characterized by recurrent episodes of localized angioedema of the skin, gastrointestinal mucosa or upper respiratory mucosa. A variety of clinical, in vitro and animal experiments indicate that the mediator of increased vascular permeability in hereditary angioedema is bradykinin. Animal models suggest that in addition to its utility in therapy of hereditary angioedema, C1 inhibitor may prove useful in a variety of other diseases including septic shock, reperfusion injury, hyperacute transplant rejection, traumatic and hemorrhagic shock, and the increased vascular permeability associated with thermal injury, interleukin-2 therapy and cardiopulmonary bypass. The therapeutic effect in these disease models very likely results from a combination of complement system activation, contact system activation and perhaps from other activities of C1 inhibitor. These other activities include a direct interaction with endotoxin, which may help to prevent endotoxic shock and an interaction with selectin molecules on endothelial cells, which may serve both to concentrate C1 inhibitor at sites of inflammation and to inhibit the transmigration of leukocytes across the endothelium.     

Switch to icatibant in a patient affected by hereditary angioedema with high disease activity: a case report

Icatibant, an antagonist of the bradykinin B2 receptor, was approved for the treatment of acute attacks of hereditary angioedema in the EU in 2008. This paper presents the case of a 65-year-old woman affected by frequent acute attacks of hereditary angioedema who benefitted from a change of therapy to icatibant, following years of treatment with C1-inhibitor.