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.

HDX-MS study on garadacimab binding to activated FXII reveals potential binding interfaces through differential solvent exposure

Hageman factor (FXII) is an essential component in the intrinsic coagulation cascade and a therapeutic target for the prophylactic treatment of hereditary angioedema (HAE). CSL312 (garadacimab) is a novel high-affinity human antibody capable of blocking activated FXII activity that is currently undergoing Phase 3 clinical trials in HAE. Structural studies using hydrogen/deuterium exchange coupled to mass spectrometry revealed evidence of interaction between the antibody and regions surrounding the S1 specificity pocket of FXII, including the 99-loop, 140-loop, 180-loop, and neighboring regions. We propose complementarity-determining regions (CDRs) in heavy-chain CDR2 and CDR3 as potential paratopes on garadacimab, and the 99-loop, 140-loop, 180-loop, and 220-loop as binding sites on the beta chain of activated FXII (β-FXIIa).

A phase I, first-in-human, randomized dose-escalation study of anti-activated factor XII monoclonal antibody garadacimab

Factor XII (FXII) is the principal initiator of the plasma contact system and has proinflammatory and prothrombotic activities. This single‐center, first‐in‐human phase I study aimed to assess the safety and tolerability of single escalating doses of garadacimab, a monoclonal antibody that specifically inhibits activated FXII (FXIIa), in healthy male volunteers. Volunteers were randomized to eight cohorts, with intravenous (i.v.) doses of 0.1, 0.3, 1, 3, and 10 mg/kg and subcutaneous (s.c.) doses of 1, 3, and 10 mg/kg. Six volunteers in each cohort received garadacimab or placebo in a ratio of 2:1. Follow‐up for safety lasted 85 days after dosing. Blood samples were collected throughout for pharmacokinetic/pharmacodynamic analysis. Forty‐eight volunteers were enrolled: 32 received garadacimab and 16 received placebo. Most volunteers experienced at least one treatment‐emergent adverse event (TEAE), predominantly grade 1. No serious TEAEs, deaths, or TEAEs leading to discontinuation were reported. No volunteers tested positive for garadacimab antidrug antibodies. Garadacimab plasma concentrations increased in a dose‐dependent manner. Sustained inhibition of FXIIa‐mediated kallikrein activity beyond day 28 resulted from 3 and 10 mg/kg garadacimab (i.v. and s.c.). A dose‐dependent increase in activated partial thromboplastin time with no change in prothrombin time was demonstrated. Garadacimab (single‐dose i.v. and s.c.) was well‐tolerated in healthy volunteers. Dose‐dependent increases in plasma concentration and pharmacodynamic effects in relevant kinin and coagulation pathways were observed. These results support the clinical development of garadacimab, including in phase II studies in hereditary angioedema and coronavirus disease 2019 (COVID‐19).

Factor XII(a) inhibitors: a review of the patent literature

Introduction: Blood coagulation factor XII (FXII) is an emerging and potentially safe drug target, which dysregulation is associated with thrombosis, hereditary angioedema, and (neuro)inflammation. At the same time, FXII-deficiency is practically asymptomatic. Industrial and academic institutions have developed a number of potential therapeutic agents targeting either FXII zymogen or its active form FXIIa for the treatment of thrombotic and inflammatory conditions associated with the activity of this enzyme.Areas covered: A short overview of the FXII(a) structure and function, underlining its suitability as a drug target, is given. The article reviews patents reported over the last three decades on FXII(a)-targeting therapeutic agents. These agents include small molecules, proteins, peptides, oligonucleotides, siRNAs, and monoclonal antibodies.Expert opinion: The performed analysis of patents revealed that many FXII(a) inhibitors are in the early preclinical stage, while several already showed efficacy in vivo animal models of thrombosis, sepsis, hereditary angioedema, and multiple sclerosis. Two anti-FXIIa agents namely tick protein Ir-CPI and monoclonal antibody CSL312 are currently in human clinical trials. The results of these trials and further studies of FXII(a) pathophysiological functions will encourage the development of new FXII(a) inhibitors.

Optimizing hereditary angioedema management through tailored treatment approaches

Hereditary angioedema (HAE) is a rare but serious and potentially life threatening autosomal dominant condition caused by low or dysfunctional C1 esterase inhibitor (C1-INH) or uncontrolled contact pathway activation. Symptoms are characterized by spontaneous, recurrent attacks of subcutaneous or submucosal swellings typically involving the face, tongue, larynx, extremities, genitalia or bowel. The prevalence of HAE is estimated to be 1:50,000 without known racial differences. It causes psychological stress as well as significant socioeconomic burden. Early treatment and prevention of attacks are associated with better patient outcome and lower socioeconomic burden. New treatments and a better evidence base for management are emerging which, together with a move from hospital-centered to patient-centered care, will enable individualized, tailored treatment approaches.

Efficacy of C1 esterase inhibitor concentrate in treatment of cutaneous attacks of hereditary angioedema

BACKGROUND

Although treatment with C1 esterase inhibitor (C1-INH) concentrate is well established for hereditary angioedema (HAE) attacks in general, data that assess its efficacy for cutaneous attack treatment are sparse.

OBJECTIVE

To assess efficacy of plasma-derived, nanofiltered C1-INH concentrate for cutaneous attack treatment by comparing treated attacks from the uncontrolled I.M.P.A.C.T.2 study with historical data for untreated attacks.

METHODS

Cutaneous attack data from patients with HAE who were treated for cutaneous edema with 20 IU/kg body weight C1-INH concentrate in the uncontrolled I.M.P.A.C.T.2 study (38 patients) were compared with data from untreated patients from an historical data base (46 patients) and included subset analyses for facial edema (treated group, 21 patients; untreated group, 33 patients) and peripheral edema (30 patients in each group). Average attack duration (AAD) per patient was the efficacy end point used to compare treated and untreated patients. Differences were assessed with a Wilcoxon test (primary analysis) and a log-rank test; AAD per patient was analyzed descriptively and graphically with Kaplan-Meier curves.

RESULTS

The AAD per patient of all cutaneous attacks or facial and peripheral cutaneous attack subsets was significantly faster with C1-INH treatment than without treatment (Wilcoxon and log-rank tests, both p < 0.0001 for all comparisons). Mean AADs per patient for all, facial, and peripheral attacks were 2.04, 1.45, and 2.16 days, respectively, in the C1-INH-treated group, and were 3.74, 4.45, and 2.98 days, respectively, in the untreated group. Kaplan-Meier curves corroborated the observed group differences.

CONCLUSION

Treatment of cutaneous HAE attacks (all attacks or facial and peripheral attack subsets) with 20 IU/kg C1-INH concentrate provided faster attack resolution compared with no treatment.

Hereditary angioedema caused by c1-esterase inhibitor deficiency: a literature-based analysis and clinical commentary on prophylaxis treatment strategies

Hereditary angioedema (HAE) caused by C1-esterase inhibitor deficiency is an autosomal-dominant disease resulting from a mutation in the C1-inhibitor gene. HAE is characterized by recurrent attacks of intense, massive, localized subcutaneous edema involving the extremities, genitalia, face, or trunk, or submucosal edema of upper airway or bowels. These symptoms may be disabling, have a dramatic impact on quality of life, and can be life-threatening when affecting the upper airways. Because the manifestations and severity of HAE are highly variable and unpredictable, patients need individualized care to reduce the burden of HAE on daily life. Although effective therapy for the treatment of HAE attacks has been available in many countries for more than 30 years, until recently, there were no agents approved in the United States to treat HAE acutely. Therefore, prophylactic therapy is an integral part of HAE treatment in the United States and for selected patients worldwide. Routine long-term prophylaxis with either attenuated androgens or C1-esterase inhibitor has been shown to reduce the frequency and severity of HAE attacks. Therapy with attenuated androgens, a mainstay of treatment in the past, has been marked by concern about potential adverse effects. C1-esterase inhibitor works directly on the complement and contact plasma cascades to reduce bradykinin release, which is the primary pathologic mechanism in HAE. Different approaches to long-term prophylactic therapy can be used to successfully manage HAE when tailored to meet the needs of the individual patient.

Cinryze (C1-inhibitor) for the treatment of hereditary angioedema

Cinryze is a pasteurized, nanofiltered plasma derived concentrate of C1-inhibitor (pdC1-INH) licensed for the prophylactic treatment of hereditary angioedema. In a double-blind placebo-controlled crossover trial to evaluate Cinryze as prophylaxis, the frequency of attacks was halved (6.26 per 12 weeks on Cinryze versus 12.73 per 12 weeks on placebo). Furthermore, attacks were generally milder and of shorter duration. For treatment of acute attacks in patients receiving Cinryze, 1000 units, within 4 h of the start of an attack, the estimated time to the onset of unequivocal relief was reduced to 2 h, compared with more than 4 h in those treated with placebo. Cinryze and other similar products are going to change the future management of hereditary angioedema and have potential in other areas of medicine.

C1 esterase inhibitor concentrate in 1085 Hereditary Angioedema attacks--final results of the I.M.P.A.C.T.2 study

BACKGROUND

The placebo-controlled study International Multicentre Prospective Angioedema C1-INH Trial 1 (I.M.P.A.C.T.1) demonstrated that 20 U/kg C1 esterase inhibitor (C1-INH) concentrate (Berinert®; CSL Behring, Marburg, Germany) is effective in treating acute abdominal and facial Hereditary Angioedema (HAE) attacks.

METHODS

I.M.P.A.C.T.2 was an open-label extension study of I.M.P.A.C.T.1 to evaluate the safety and efficacy of long-term treatment with 20 U/kg C1-INH for successive HAE attacks at any body location. Efficacy outcomes included patient-reported time to onset of symptom relief (primary) and time to complete resolution of all symptoms (secondary), analysed on a per-patient and per-attack basis. Safety assessments included adverse events, vital signs, viral safety and anti-C1-INH antibodies.

RESULTS

During a median study duration of 24 months, 1085 attacks were treated in 57 patients (10-53 years of age). In the per-patient analysis, the median time to onset of symptom relief was 0.46 h and was similar for all types of attacks (0.39-0.48 h); the median time to complete resolution of symptoms was 15.5 h (shortest for laryngeal attacks: 5.8 h; 12.8-26.6 h for abdominal, peripheral and facial attacks). Demographic factors, type of HAE, intensity of attacks, time to treatment, use of androgens and presence of anti-C1-INH antibodies had no clinically relevant effect on the efficacy outcomes. There were no treatment-related safety concerns. No inhibitory anti-C1-INH antibodies were detected in any patient.

CONCLUSIONS

A single dose of 20 U/kg C1-INH concentrate is safe and provides reliable efficacy in the long-term treatment of successive HAE attacks at any body location.

C1 Esterase Inhibitor (Human) for the Treatment of Acute Hereditary Angioedema

Hereditary angioedema (HAE) is a relatively rare disease characterized by acute episodes of swelling. These swellings can be disfiguring, painful and life-threatening. Since the symptoms occur in different areas and most patients experience a delay in their diagnosis, resulting in unnecessary suffering and dangerous situations. HAE can have a tremendous impact on the quality of life. The major genetic deficiency in this disorder is either an absent or nonfunctional C1INH which regulates the complement, fibrinolitic, kalikrein and plasmin pathways.

Risk of laryngeal edema and facial swellings after tooth extraction in patients with hereditary angioedema with and without prophylaxis with C1 inhibitor concentrate: a retrospective study

OBJECTIVE

Tooth extractions may trigger clinical symptoms of hereditary angioedema due to C1 inhibitor deficiency (HAE-C1-INH). The aim of this study was to determine how many tooth extractions were followed by symptoms of HAE-C1-INH in patients with and without preoperative short-term prophylaxis with C1 inhibitor concentrate.

STUDY DESIGN

Tooth extractions and clinical symptoms of HAE-C1-INH were determined from clinical record files of 171 patients with HAE-C1-INH.

RESULTS

Facial swelling or potentially life-threatening laryngeal edema, or both, occurred in 124/577 tooth extractions (21.5%) without prophylaxis. Similar symptoms occurred in a fewer proportion of patients undergoing extractions (16/128; 12.5%) after short-term prophylaxis with C1 inhibitor concentrate. The graded dose-response relationship was significant at P < .05.

CONCLUSIONS

Short-term prophylaxis with C1 inhibitor concentrate significantly reduces the risk of HAE-C1-INH symptoms after tooth extraction. In some patients, however, facial swellings and laryngeal edema symptoms may occur despite prophylaxis.

Hereditary angioedema: beyond international consensus - circa December 2010 - The Canadian Society of Allergy and Clinical Immunology Dr. David McCourtie Lecture

Background

The 2010 International Consensus Algorithm for the Diagnosis, Therapy and Management of Hereditary Angioedema was published earlier this year in this Journal (Bowen et al. Allergy, Asthma & Clinical Immunology 2010, 6:24 - http://www.aacijournal.com/content/6/1/24). Since that publication, there have been multiple phase III clinical trials published on either prophylaxis or therapy of hereditary angioedema and some of these products have changed approval status in various countries. This manuscript was prepared to review and update the management of hereditary angioedema.

Objective

To review approaches for the diagnosis and management of hereditary angioedema (HAE) circa December 2010 and present thoughts on moving from HAE management from international evidence-based consensus to facilitate more local health unit considerations balancing costs, efficacies of treatments, and risk benefits. Thoughts will reflect Canadian and international experiences.

Methods

PubMed searches including hereditary angioedema and diagnosis, therapy, management and consensus were reviewed as well as press releases from various pharmaceutical companies to early December 2010.

Results

The 2010 International Consensus Algorithms for the Diagnosis, Therapy and Management of Hereditary Angioedema is reviewed in light of the newly published phase III Clinical trials for prevention and therapy of HAE. Management approaches and models are discussed.

Conclusions

Consensus approach and double-blind placebo controlled trials are only interim guides to a complex disorder such as HAE and should be replaced as soon as possible with large phase IV clinical trials, meta analyses, data base registry validation of approaches including quality of life and cost benefit analyses, safety, and head-to-head clinical trials investigating superiority or non-inferiority comparisons of available approaches. Since not all therapeutic products are available in all jurisdictions and since health care delivery approaches and philosophy vary between countries, each health care delivery sector will likely devise their own algorithms based on local practicalities for implementing evidence-based guidelines and standards for HAE disease management. Quality-of-life and cost affordability benefit conclusions will likely vary between countries and health care units. Data base registries for rare disorders like HAE should be used to detect early adverse events for new therapies and to facilitate phase IV clinical trials and encourage superiority and non-inferiority comparisons of HAE management approaches.

Prospective study of C1 esterase inhibitor in the treatment of successive acute abdominal and facial hereditary angioedema attacks

BACKGROUND

hereditary angioedema (HAE) is a rare disorder characterized by a quantitative or functional deficiency of C1 esterase inhibitor (C1-INH), resulting in periodic attacks of acute edema at various body locations. The symptoms of these painful attacks can be treated effectively with C1-INH concentrate.

OBJECTIVE

to document the efficacy and safety of a weight-based dose of C1-INH concentrate in the treatment of successive HAE attacks at abdominal and facial locations.

METHODS

acute facial and abdominal attacks were each treated with C1-INH concentrate using a single intravenous dose of 20 U/kg body weight. Efficacy end points included patient-reported time to onset of symptom relief and time to complete resolution of all symptoms. Safety was assessed by monitoring adverse events and assaying for markers of viral infection.

RESULTS

we treated 663 abdominal attacks in 50 patients and 43 facial attacks in 16 patients (a total of 706 attacks in 53 patients). The median time to onset of relief for all attacks was 19.8 minutes, with a median time to complete resolution of 11.0 hours. The median time to onset of relief was 19.8 minutes for abdominal attacks and 28.2 minutes for facial attacks, indicating efficacy for both types of attack. No treatment-related serious adverse events occurred, and C1-INH concentrate was well tolerated. No human immunodeficiency virus, hepatitis virus, or parvovirus B19 infections arose during the study.

CONCLUSION

the C1-INH concentrate dose of 20 U/kg provides rapid, effective, and safe treatment for successive HAE attacks at abdominal and facial locations.

Population pharmacokinetics of plasma-derived C1 esterase inhibitor concentrate used to treat acute hereditary angioedema attacks

BACKGROUND

C1 esterase inhibitor (C1-INH) replacement is recommended as a first-line therapy for acute edema attacks in hereditary angioedema (HAE). Only limited pharmacokinetic analyses of the administered C1-INH in plasma are available.

OBJECTIVE

To investigate retrospectively the population pharmacokinetics of a plasma-derived C1-INH (pC1-INH) concentrate used to treat acute HAE attacks in a randomized, placebo-controlled phase 2/3 study in patients with HAE.

METHODS

Acute abdominal and facial attacks were treated with either a pC1-INH concentrate (Berinert) at single intravenous doses of 10 or 20 U/kg body weight or placebo. Plasma sampling was conducted 0, 1, and 4 hours after dosing. A nonlinear retrospective population pharmacokinetic model was obtained using the assumption of a 1-compartment model.

RESULTS

The final population pharmacokinetic model was based on data from 97 patients treated with 10 or 20 U/kg of pC1-INH concentrate. The estimated mean half-life was 32.7 hours (90% confidence interval, 16.6-48.8 hours), and the estimated mean clearance was 0.92 mL/kg/h (90% confidence interval, 0.50-1.33 mL/kg/h).

CONCLUSIONS

The half-life of the same pC1-INH concentrate reported in a previous study was confirmed by this retrospective population pharmacokinetic analysis in patients treated for acute HAE attacks. In contrast to other treatment options with shorter half-lives, the long half-life of pC1-INH concentrate may provide an extended period of protection, even after the symptoms of an attack have subsided.

Characterization of acute hereditary angioedema attacks during pregnancy and breast-feeding and their treatment with C1 inhibitor concentrate

OBJECTIVE

The objective of the study was to investigate the rates and characteristics of hereditary angioedema (HAE) attacks associated with pregnancy, delivery, and the postpartum period and their treatment with C1 esterase inhibitor (INH) concentrate.

STUDY DESIGN

This was an observational study including 22 women with type I HAE, with data collected before, during, and after 35 pregnancies (37 children) based on patient diaries, interviews, and case report forms.

RESULTS

In 83% of pregnancies, attack rates increased during pregnancy; highest mean rates occurred in the second and third trimesters. C1-INH concentrate effectively controlled attacks and was safe for mothers and children. Low-plasma C1-INH activity during pregnancy tended to be associated with an increased chance of giving birth to a child with HAE.

CONCLUSION

Increased attack rates during pregnancy in women with HAE are well controlled with C1-INH concentrate, indicating the clear benefit of integrating the availability of C1-INH concentrate into the management plan for these women during pregnancy and delivery.

On demand treatment and home therapy of hereditary angioedema in Germany - the Frankfurt experience

BACKGROUND

Manifestation of acute edema in hereditary angioedema (HAE) is characterized by interindividual and intraindividual variability in symptom expression over time. Flexible therapy options are needed.

METHODS

We describe and report on the outcomes of the highly individualized approach to HAE therapy practiced at our HAE center in Frankfurt (Germany).

RESULTS

The HAE center at the Frankfurt University Hospital currently treats 450 adults with HAE or AAE and 107 pediatric HAE patients with highly individualized therapeutic approaches. 73.9% of the adult patients treat HAE attacks by on-demand therapy with pasteurized pd C1-INH concentrate, 9.8% use additional prophylaxis with attenuated androgens, 1% of the total patient population in Frankfurt has been treated with Icatibant up to now. In addition adult and selected pediatric patients with a high frequency of severe attacks are instructed to apply individual replacement therapy (IRT) with pasteurized pd C1-INH concentrate. Improvement on Quality of Life items was shown for these patients compared to previous long-term danazol prophylaxis. Home treatment of HAE patients was developed in the Frankfurt HAE center in line with experiences in hemophilia therapy and has so far been implemented over a period of 28 years. At present 248 (55%) of the adult patients and 26 (24%) of the pediatric patients are practicing home treatment either as on demand or IRT treatment.

CONCLUSIONS

In conclusion, the individualized home therapies provided by our HAE center, aim to limit the disruption to normal daily activities that occurs for many HAE patients. Furthermore, we seek to optimize the economic burden of the disease while offering a maximum quality of life to our patients.

HAE international home therapy consensus document

Hereditary angioedema (C1 inhibitor deficiency, HAE) is associated with intermittent swellings which are disabling and may be fatal. Effective treatments are available and these are most useful when given early in the course of the swelling. The requirement to attend a medical facility for parenteral treatment results in delays. Home therapy offers the possibility of earlier treatment and better symptom control, enabling patients to live more healthy, productive lives. This paper examines the evidence for patient-controlled home treatment of acute attacks ('self or assisted administration') and suggests a framework for patients and physicians interested in participating in home or self-administration programmes. It represents the opinion of the authors who have a wide range of expert experience in the management of HAE.

Human C1-esterase inhibitor concentrate (Berinert)

Human C1-esterase inhibitor concentrate (C1-INH concentrate) is derived from human plasma and is indicated for the treatment of acute episodes of hereditary angioedema. Intravenous C1-INH concentrate provided rapid symptom relief in patients with acute abdominal or facial episodes associated with type I or II hereditary angioedema, according to the results of the randomized, double-blind, multicenter, placebo-controlled IMPACT-1 trial. The median time to the onset of symptom relief was significantly shorter with C1-INH concentrate 20 U/kg than with placebo (0.5 vs 1.5 hours). A subsequent noncomparative extension trial (IMPACT-2) showed the ongoing efficacy of 'on-demand' treatment with C1-INH concentrate; overall, the onset of symptom relief occurred in a median 30 minutes. Several additional studies demonstrated the efficacy of intravenous C1-INH concentrate in patients with laryngeal edema, skin swellings, or abdominal episodes associated with type I or II hereditary angioedema. Self-administered home therapy with intravenous C1-INH concentrate significantly improved health-related quality of life in patients with hereditary angioedema. Dermatology Life Quality Index and Short Form 36-item Health Survey scores were significantly improved from baseline by self-administered home therapy with C1-INH concentrate. Intravenous C1-INH concentrate was well tolerated in patients with hereditary angioedema, with no confirmed cases of viral transmission.

Prospective study of rapid relief provided by C1 esterase inhibitor in emergency treatment of acute laryngeal attacks in hereditary angioedema

Introduction

Hereditary angioedema (HAE) is a rare disorder characterized by C1 esterase inhibitor (C1-INH) deficiency, resulting in periodic attacks of acute edema that can be life-threatening if they occur in the laryngeal region. We assessed the efficacy of C1-INH concentrate in the emergency treatment of rarely occurring acute laryngeal HAE attacks in a prospective, open-label clinical study.

Methods

Acute laryngeal attacks were each treated with C1-INH concentrate (Berinert) at a single dose of 20 U/kg body weight. Efficacy endpoints included time to onset of symptom relief and time to complete resolution of all symptoms, each based on the patient's assessment.

Results

All 39 laryngeal attacks in 16 patients were treated successfully. The median time to onset of symptom relief was 15 min. The median time to complete resolution of all symptoms was 8.25 h. No treatment-related serious adverse events occurred, and the treatment was well tolerated. The administration of C1-INH concentrate was not associated with any viral infections.

Conclusion

C1-INH concentrate is an effective and safe emergency treatment for providing reliable and rapid relief from the potentially life-threatening symptoms of laryngeal HAE attacks.

Treatment of type I and II hereditary angioedema with Rhucin, a recombinant human C1 inhibitor

Hereditary and acquired angioedema are of outstanding clinical importance, as edematous attacks associated with these conditions can thrust afflicted patients into mortal danger. Currently, C1 inhibitor concentrate - a human blood product - is available as a replacement therapy. In view of the limited number of donors, as well as the risk of transmission of blood-borne infections, it is a reasonable expectation to develop a therapeutic alternative based on recombinant technology, which would eliminate all these shortcomings. Pharming (Leiden, The Netherlands) has developed Rhucin, a recombinant human C1 inhibitor, as a proprietary product, which is currently being evaluated in Phase III clinical trials. Ongoing studies conducted within the framework of the development program are almost complete and their interim findings are reassuring. This should facilitate successful regulatory approval in the near future, which is indispensable in order to make Rhucin available for patients with hereditary angioedema or other disorders amenable to C1 inhibitor replacement.

Recurrent angioedema and the threat of asphyxiation

BACKGROUND

Recurrent angioedema may affect the skin or, less commonly, the tongue, gastrointestinal tract, and larynx. Angioedema is a clinical sign that can be produced by a variety of diseases. Asphyxiation due to edematous obstruction of the upper airway is rare, but, for the affected patients, it is a permanent risk.

METHODS

Review of the literature based on a selective search and the authors' decades of experience treating patients with angioedema in a dedicated ambulatory care unit.

RESULTS

Hereditary angioedema due to C1 esterase inhibitor deficiency has been intensively studied, and nearly all steps in its pathogenesis are known, from the causative gene defect all the way to the clinical presentation of angioedema. Bradykinin is the main mediator in this pathway. New treatment options (icatibant; C1-inhibitor concentrate for self-administration and long-term treatment) have helped patients considerably. In recent years, a new type of hereditary angioedema has been described, resulting not from a lack of C1 inhibitor, but rather from mutations of coagulation factor XII or other, as yet unidentified genetic abnormalities. There are major differences in the pharmacological treatment of the different diseases that cause angioedema. In an emergency, when severe upper airway obstruction can be life-threatening, immediate treatment is needed to keep the upper airway open.

CONCLUSION

In patients with recurrent angioedema, the diagnostic classification of the underlying disorder as a particular type of hereditary or acquired angioedema is a prerequisite for appropriate treatment.

Pharmacokinetic analysis of human plasma-derived pasteurized C1-inhibitor concentrate in adults and children with hereditary angioedema: a prospective study

BACKGROUND

Hereditary angioedema (HAE) is a rare and potentially life-threatening disease presenting with acute edema of subcutaneous tissues and/or mucous membranes. Patients with HAE have abnormally low or dysfunctional C1-inhibitor (C1-INH). Preventing the progression of acute attacks is the main goal of C1-INH replacement therapy; knowledge of the C1-INH concentrate half-life is of crucial importance. This pharmacokinetic study was conducted to investigate the pharmacokinetics of pasteurized human plasma-derived C1-INH concentrate (pC1-INH).

STUDY DESIGN AND METHODS

This was a prospective, single-center study of six children and 34 adults with an established diagnosis of HAE. On-demand treatment with pC1-INH was administered to all children, whereas adults received either pC1-INH on-demand treatment or individual replacement therapy (IRT). Functional C1-INH plasma levels were fitted to a single-compartment model with nonlinear regression, and the area under the curve was standardized to a dose equivalent of 15 U/kg body weight of pC1-INH concentrate.

RESULTS

The median half-life of functional C1-INH plasma levels in pediatric patients receiving on-demand therapy was 32.9 hours (mean, 31.5 hr). In adults, the median half-lives of functional C1-INH plasma levels after on-demand therapy were 39.1 hours (mean, 47.8 hr) and 30.9 hours (mean 33.3 hr) for patients on IRT. The median times to achieve maximum plasma activity after administration were 0.6 hour for children, 1.0 hour for adults receiving on-demand treatment, and 0.5 hour for adults on IRT.

CONCLUSIONS

pC1-INH concentrate has a long median terminal elimination half-life and rapidly reaches maximum plasma concentrations. This rapid onset of clinical efficacy is essential in patients suffering from HAE.

Hereditary angioedema: increased number of attacks after frequent treatments with C1 inhibitor concentrate

OBJECTIVE

C1 inhibitor concentrate is regarded as effective and safe in treating acute attacks of hereditary angioedema caused by C1 inhibitor deficiency. This study investigated the course of disease in 3 women treated frequently with C1 inhibitor concentrate.

METHODS

Three women are described who received C1 inhibitor concentrate for the treatment of acute attacks of hereditary angioedema and experienced an increase in the frequency of attacks during that treatment period. In a control group of 24 patients aged more than 60 years with hereditary angioedema, the natural course of disease was determined.

RESULTS

The 3 women (ages 50, 69, and 72 years) had received C1 inhibitor concentrate for 27, 18, and 22 years, respectively, for acute abdominal and skin attacks. Before this treatment, all attacks were severe. The treatment was always effective: The attacks were mild, and the duration of the attacks was shortened. During the treatment period, the number of attacks increased slowly but continuously, starting at the onset of treatment and paralleling the course of treatment. At the end of the observation period, the number of attacks increased by 4-fold, 12-fold, and 5-fold in the 3 women, respectively. No factors known to increase the frequency of attacks in hereditary angioedema were found in these patients. The control group did not show a similar increase in attacks during a comparable period of time.

CONCLUSION

A possible explanation for the increase in the frequency of attacks may lie in the large number of injections of C1 inhibitor concentrate.

Clinical Immunology Review Series: An approach to the patient with angio-oedema

Angio-oedema is a common reason for attendance at the accident and emergency department and for referral to immunology/allergy clinics. Causative factors should always be sought, but a large proportion of patients have the idiopathic form of the disease. A minority of patients represent a diagnostic and treatment challenge. Failure to identify the more unusual causes of angio-oedema may result in life-threatening situations. Common and rare causes of angio-oedema will be discussed in this article, as well as the diagnostic and treatment pathways for the management of these patients. A comprehensive history and close monitoring of response to treatment are the most cost-effective diagnostic and treatment tools.