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

Prolonging the circulatory half-life of C1 esterase inhibitor via albumin fusion

Hereditary Angioedema (HAE) is an autosomal dominant disease characterized by episodic swelling, arising from genetic deficiency in C1-esterase inhibitor (C1INH), a regulator of several proteases including activated Plasma kallikrein (Pka). Many existing C1INH treatments exhibit short circulatory half-lives, precluding prophylactic use. Hexahistidine-tagged truncated C1INH (trC1INH lacking residues 1-97) with Mutated N-linked Glycosylation Sites N216Q/N231Q/N330Q (H6-trC1INH(MGS)), its murine serum albumin (MSA) fusion variant (H6-trC1INH(MGS)-MSA), and H6-MSA were expressed in Pichia pastoris and purified via nickel-chelate chromatography. Following intravenous injection in mice, the mean terminal half-life of H6-trC1INH(MGS)-MSA was significantly increased versus that of H6-trC1INH(MGS), by 3-fold, while remaining ~35% less than that of H6-MSA. The extended half-life was achieved with minimal, but significant, reduction in the mean second order rate constant of Pka inhibition of H6-trC1INH(MGS)-MSA by 33% relative to that of H6-trC1INH(MGS). Our results validate albumin fusion as a viable strategy for half-life extension of a natural inhibitor and suggest that H6-trC1INH(MGS)-MSA is worthy of investigation in a murine model of HAE.

Current and Emerging Therapeutics in Hereditary Angioedema

Angioedema is characterized by transient movement of fluid from the vasculature into the interstitial space leading to subcutaneous or submucosal non-pitting edema. Current evidence suggests that most angioedema conditions can be grouped into 2 categories: mast cell-mediated (previously termed histaminergic) or bradykinin-mediated angioedema. Although effective therapies for mast cell-mediated angioedema have existed for decades, specific therapies for bradykinin-mediated angioedema have more recently been developed. In recent years, rigorous studies of these therapies in treating hereditary angioedema (HAE) have led to regulatory approvals of medication for HAE management thereby greatly expanding HAE treatment options.

Plasma-derived C1 esterase inhibitor pharmacokinetics and safety in patients with hereditary angioedema

Background

Over 40 years of use demonstrates that complement 1 esterase inhibitor (C1-INH) concentrate is effective and well tolerated for acute edema attacks and prophylaxis in patients with hereditary angioedema. OCTA-C1-INH is a new stable, virus-inactivated, nanofiltrated concentrate of C1-INH derived from human plasma.

Objective

We investigated the pharmacokinetics and safety profile of new C1-INH in people with hereditary angioedema during an attack-free period.

Methods

In this prospective, multicenter, open-label, single-arm study, adults with hereditary angioedema type I/II received a single intravenous dose of 20 IU/kg C1-INH. Blood samples were taken ≤30 minutes before infusion, and 0, 0.25, 1, 2, 6, 12, 24, 48, 72, 120, 144, and 168 hours after infusion. The primary end point was assessing the pharmacokinetic parameters of C1-INH measured by C1-INH activity. Safety end points were also examined.

Results

Twenty patients received a single dose of 20 IU/kg new C1-INH with a mean (standard deviation) total dose of 1457.3 (356.51) IU. Mean (standard deviation) area under the curve normalized by dose was 51.6 (17.9) h∙IU/mL/IU, maximum blood concentration was 1.14 (0.989) IU/mL, incremental recovery was 0.0466 (0.051) (IU∙kg)/(IU∙mL), half-life was 0.598 (0.716) hours, and time to maximum concentration was 0.598 (0.716) hours. No thromboembolic events were recorded. No treatment-emergent adverse events were rated as severe/serious.

Conclusion

PK parameters of new C1-INH were in line with those reported for other C1-INH concentrates. New C1-INH demonstrated a favorable safety profile in patients with C1-INH deficiency. Further studies are warranted to determine the effectiveness and longer-term safety of new C1-INH.

The international WAO/EAACI guideline for the management of hereditary angioedema - The 2021 revision and update

Hereditary Angioedema (HAE) is a rare and disabling disease for which early diagnosis and effective therapy are critical. This revision and update of the global WAO/EAACI guideline on the diagnosis and management of HAE provides up-to-date guidance for the management of HAE. For this update and revision of the guideline, an international panel of experts reviewed the existing evidence, developed 28 recommendations, and established consensus by an online DELPHI process. The goal of these recommendations and guideline is to help physicians and their patients in making rational decisions in the management of HAE with deficient C1-inhibitor (type 1) and HAE with dysfunctional C1-inhibitor (type 2), by providing guidance on common and important clinical issues, such as: 1) How should HAE be diagnosed? 2) When should HAE patients receive prophylactic on top of on-demand treatment and what treatments should be used? 3) What are the goals of treatment? 4) Should HAE management be different for special HAE patient groups such as children or pregnant/breast feeding women? 5) How should HAE patients monitor their disease activity, impact, and control? It is also the intention of this guideline to help establish global standards for the management of HAE and to encourage and facilitate the use of recommended diagnostics and therapies for all patients.

The international WAO/EAACI guideline for the management of hereditary angioedema-The 2021 revision and update

Hereditary angioedema (HAE) is a rare and disabling disease for which early diagnosis and effective therapy are critical. This revision and update of the global WAO/EAACI guideline on the diagnosis and management of HAE provides up-to-date guidance for the management of HAE. For this update and revision of the guideline, an international panel of experts reviewed the existing evidence, developed 28 recommendations, and established consensus by an online DELPHI process. The goal of these recommendations and guideline is to help physicians and their patients in making rational decisions in the management of HAE with deficient C1 inhibitor (type 1) and HAE with dysfunctional C1 inhibitor (type 2), by providing guidance on common and important clinical issues, such as: (1) How should HAE be diagnosed? (2) When should HAE patients receive prophylactic on top of on-demand treatment and what treatments should be used? (3) What are the goals of treatment? (4) Should HAE management be different for special HAE patient groups such as children or pregnant/breast-feeding women? and (5) How should HAE patients monitor their disease activity, impact, and control? It is also the intention of this guideline to help establish global standards for the management of HAE and to encourage and facilitate the use of recommended diagnostics and therapies for all patients.

C1-Inhibitor: Structure, Functional Diversity and Therapeutic Development

Human C1-Inhibitor (C1INH), also known as C1-esterase inhibitor, is an important multifunctional plasma glycoprotein that is uniquely involved in a regulatory network of complement, contact, coagulation, and fibrinolytic systems. C1INH belongs to a superfamily of serine proteinase inhibitor (serpins) and exhibits its inhibitory activities towards several target proteases of plasmatic cascades, operating as a major anti-inflammatory protein in the circulation. In addition to its inhibitory activities, C1INH is also involved in non-inhibitory interactions with some endogenous proteins, polyanions, cells and infectious agents. While C1INH is essential for multiple physiological processes, it is better known for its deficiency with regards to Hereditary Angioedema (HAE), a rare autosomal dominant disease clinically manifested by recurrent acute attacks of increased vascular permeability and edema. Since the link was first established between functional C1INH deficiency in plasma and HAE in the 1960s, tremendous progress has been made in the biochemical characterization of C1INH and its therapeutic development for replacement therapies in patients with C1INH-dependent HAE. Various C1INH biological activities, recent advances in the HAE-targeted therapies, and availability of C1INH commercial products have prompted intensive investigation of the C1INH potential for treatment of clinical conditions other than HAE. This article provides an updated overview of the structure and biological activities of C1INH, its role in HAE pathogenesis, and recent advances in the research and therapeutic development of C1INH; it also considers some trends for using C1INH therapeutic preparations for applications other than angioedema, from sepsis and endotoxin shock to severe thrombotic complications in COVID-19 patients.

Etiology and predictors of cluster attacks of hereditary angioedema that recur despite pharmaceutical treatment

Introduction: Hereditary angioedema (HAE) is a disease that leads to recurrent swelling of the skin and mucous membranes, including the upper airway tract. Apart from being deadly, these attacks can be debilitating, which leads to a poor quality of life in patients. Clinicians are occasionally confronted with patients who have recurrent attacks despite treatment with C1 esterase inhibitor concentrate or β₂-receptor antagonists. The goal of this study was to investigate repeated attacks that occur 48 hours to 7 days ("cluster attacks") after treatment, to determine why they occur and the factors that may be associated with them, and thus to prevent their occurrence. Methods: We conducted a multicenter mixed retrospective-prospective study with data acquired from all documented attacks in our patients with collective (n = 132) between 2015 and 2018. Results: Eighty-five percent (n = 132) of our total patient collective (N = 156) agreed to participate in the study. Nine percent of these patients (n = 12) had cluster attacks, with a total of 48 cluster attacks. The data procured from the patients were mixed retrospective-prospective. Approximately 72% of all the cluster attacks were caused by exogenous stimuli (41% due to psychological stress, 29% due to physical stimuli, and 2% due to menstruation). Cluster attacks occurred in 7% of the patients who received prophylactic therapy in comparison with 12.5% of patients who received on-demand therapy. Cluster attacks comprised 48.4% of all the attacks that patients with cluster-attacks (n= 9) experienced. In addition, the patients who were underdosing their C1 esterase inhibitor treatment had cluster attacks more often. A lower "time to repeated attack" was seen in the patients who received on-demand therapy compared with those who received prophylactic therapy. Discussion: The percentage of the patients who had attacks as a result of exogenous triggers was higher in the cluster-attack group (70.5%) compared with the general HAE population (30-42%). Repeated attacks, therefore, were strongly associated with external triggers. The patients who received prophylactic treatment and who experienced cluster attacks were highly likely to have been underdosing, which may explain the repeated attacks despite treatment. In the patients prone to cluster attacks, prophylaxis should be considered.

Therapeutic SERPINs: Improving on Nature

Serine proteases drive important physiological processes such as coagulation, fibrinolysis, inflammation and angiogenesis. These proteases are controlled by serine protease inhibitors (SERPINs) that neutralize their activity. Currently, over 1,500 SERPINs are known in nature, but only 37 SERPINs are found in humans. Thirty of these are functional protease inhibitors. The inhibitory potential of SERPINs is in perfect balance with the proteolytic activities of its targets to enable physiological protease activity. Hence, SERPIN deficiency (either qualitative or quantitative) can lead to disease. Several SERPIN resupplementation strategies have been developed to treat SERPIN deficiencies, including concentrates derived from plasma and recombinant SERPINs. SERPINs usually inhibit multiple proteases, but only in their active state. Over the past decades, considerable insights have been acquired in the identification of SERPIN biological functions, their inhibitory mechanisms and specificity determinants. This paves the way for the development of therapeutic SERPINs. Through rational design, the inhibitory properties (selectivity and inhibitory potential) of SERPINs can be reformed and optimized. This review explores the current state of SERPIN engineering with a focus on reactive center loop modifications and backbone stabilization. We will discuss the lessons learned from these recombinant SERPINs and explore novel techniques and strategies that will be essential for the creation and application of the future generation of therapeutic SERPINs.

Population pharmacokinetics of recombinant human C1 esterase inhibitor in children with hereditary angioedema

BACKGROUND

Recombinant human C1 esterase inhibitor (rhC1-INH) is indicated in the United States for the treatment of acute hereditary angioedema (HAE) attacks in adolescents and adults; it is also indicated in Europe for children aged 2 years and older. A need exists for further insight into potential pharmacokinetic (PK) differences in functional C1-INH levels by age (ie, children, adolescents, and adults).

OBJECTIVE

To perform population PK modeling to predict C1-INH levels by age after by age rhC1-INH administration.

METHODS

Data from a phase 2 pediatric trial (children aged 4-13 years at screening) were added to a database of 6 trials in adults and adolescents. An unpublished population PK model was refined and used to simulate C1-INH exposure.

RESULTS

Analysis included 153 individuals (14 healthy volunteers; 139 patients with HAE) and 1788 functional C1-INH measurements (59 from 20 patients in the pediatric trial). Bodyweight (population weight, 16-128 kg) was a key predictor of C1-INH volume of distribution. Age was not a predictor of C1-INH PK after the inclusion of bodyweight in the model. Simulations of the recommended rhC1-INH dosing regimen (bodyweight <84 kg, 50 U/kg; ≥84 kg, 4200 U) revealed that overall C1-INH exposure was comparable among age groups. Predicted peak functional C1-INH concentrations were at or above the lower level of normal (≥0.7 U/mL) for 99.8% of adults (≥18 years), 99.8% of adolescents (14-17 years), and 96.0% of children (2-13 years).

CONCLUSION

The analyses support the same weight-based rhC1-INH dosing for HAE attacks in children as currently recommended for adolescents and adults. These results support clinical trial data, which revealed similar safety and efficacy profiles across these age groups.

ARGX-117, a therapeutic complement inhibiting antibody targeting C2

Background

Activation of the classical and lectin pathway of complement may contribute to tissue damage and organ dysfunction of antibody-mediated diseases and ischemia-reperfusion conditions. Complement factors are being considered as targets for therapeutic intervention.

Objective

We sought to characterize ARGX-117, a humanized inhibitory monoclonal antibody against complement C2.

Methods

The mode-of-action and binding characteristics of ARGX-117 were investigated in detail. Furthermore, its efficacy was analyzed in in vitro complement cytotoxicity assays. Finally, a pharmacokinetic/pharmacodynamic study was conducted in cynomolgus monkeys.

Results

Through binding to the Sushi-2 domain of C2, ARGX-117 prevents the formation of the C3 proconvertase and inhibits classical and lectin pathway activation upstream of C3 activation. As ARGX-117 does not inhibit the alternative pathway, it is expected not to affect the antimicrobial activity of this complement pathway. ARGX-117 prevents complement-mediated cytotoxicity in in vitro models for autoimmune hemolytic anemia and antibody-mediated rejection of organ transplants. ARGX-117 exhibits pH- and calcium-dependent target binding and is Fc-engineered to increase affinity at acidic pH to the neonatal Fc receptor, and to reduce effector functions. In cynomolgus monkeys, ARGX-117 dose-dependently reduces free C2 levels and classical pathway activity. A 2-dose regimen of 80 and 20 mg/kg separated by a week, resulted in profound reduction of classical pathway activity lasting for at least 7 weeks.

Conclusions

ARGX-117 is a promising new complement inhibitor that is uniquely positioned to target both the classical and lectin pathways while leaving the alternative pathway intact.

The international WAO/EAACI guideline for the management of hereditary angioedema-The 2017 revision and update

Hereditary Angioedema (HAE) is a rare and disabling disease. Early diagnosis and appropriate therapy are essential. This update and revision of the global guideline for HAE provides up-to-date consensus recommendations for the management of HAE. In the development of this update and revision of the guideline, an international expert panel reviewed the existing evidence and developed 20 recommendations that were discussed, finalized and consented during the guideline consensus conference in June 2016 in Vienna. The final version of this update and revision of the guideline incorporates the contributions of a board of expert reviewers and the endorsing societies. The goal of this guideline update and revision is to provide clinicians and their patients with guidance that will assist them in making rational decisions in the management of HAE with deficient C1-inhibitor (type 1) and HAE with dysfunctional C1-inhibitor (type 2). The key clinical questions covered by these recommendations are: (1) How should HAE-1/2 be defined and classified?, (2) How should HAE-1/2 be diagnosed?, (3) Should HAE-1/2 patients receive prophylactic and/or on-demand treatment and what treatment options should be used?, (4) Should HAE-1/2 management be different for special HAE-1/2 patient groups such as pregnant/lactating women or children?, and (5) Should HAE-1/2 management incorporate self-administration of therapies and patient support measures?

On the value of therapeutic interventions targeting the complement system in acute myocardial infarction

The complement system plays an important role in the inflammatory response subsequent to acute myocardial infarction (AMI). The aim of this study is to create a systematic overview of studies that have investigated therapeutic administration of complement inhibitors in both AMI animal models and human clinical trials. To enable extrapolation of observations from included animal studies toward post-AMI clinical trials, ex vivo studies on isolated hearts and proof-of-principle studies on inhibitor administration before experimental AMI induction were excluded. Positive therapeutic effects in AMI animal models have been described for cobra venom factor, soluble complement receptor 1, C1-esterase inhibitor (C1-inh), FUT-175, C1s-inhibitor, anti-C5, ADC-1004, clusterin, and glycosaminoglycans. Two types of complement inhibitors have been tested in clinical trials, being C1-inh and anti-C5. Pexelizumab (anti-C5) did not result in reproducible beneficial effects for AMI patients. Beneficial effects were reported in AMI patients for C1-inhibitor, albeit in small patient groups. In general, despite the absence of consistent positive effects in clinical trials thus far, the complement system remains a potentially interesting target for therapy in AMI patients. Based on the study designs of previous animal studies and clinical trials, we discuss several issues which require attention in the design of future studies: adjustment of clinical trial design to precise mechanism of action of administered inhibitor, optimizing the duration of therapy, and optimization of time point(s) on which therapeutic effects will be evaluated.

Recombinant human C1 esterase inhibitor in the management of hereditary angioedema

Hereditary angioedema (HAE), a rare autosomal dominant genetic disorder, is caused by a deficiency in functional C1 esterase inhibitor (C1-INH). This potentially life-threatening condition manifests as recurrent attacks of subcutaneous and submucosal swelling of the skin, gastrointestinal tract and larynx. The management of HAE includes treatment of acute episodes, short-term prophylaxis in preparation for exposure to known triggers and long-term prophylaxis to decrease the incidence and severity of HAE attacks. Four products are approved in the USA for the treatment of acute attacks of HAE, including one human plasma-derived C1-INH therapy, a recombinant human C1-INH product (rhC1-INH), a plasma kallikrein inhibitor and a bradykinin B2 receptor antagonist. In addition, one human plasma-derived C1-INH therapy and danazol are approved for prophylaxis of HAE attacks. rhC1-INH, extracted from the milk of transgenic rabbits, is a glycoprotein of 478 amino acids with an identical amino acid sequence to the endogenous human C1-INH protein. Population pharmacokinetic analysis of rhC1-INH supports an intravenous dosing strategy of 50 U/kg (maximum 4200 U). The safety and efficacy of rhC1-INH in the treatment of acute attacks in patients with HAE were demonstrated in three randomized, double-blind, placebo-controlled studies and two open-label extension studies. In a pilot prophylaxis study, weekly administration of rhC1-INH 50 U/kg for 8 weeks reduced the incidence of HAE attacks and was well tolerated. Administration of rhC1-INH has not been associated with the development of anti-drug antibodies or antibodies to anti-host-related impurities.

The effect of weight on the efficacy and safety of C1 esterase inhibitor concentrate for the treatment of acute hereditary angioedema

BACKGROUND

Despite the worldwide obesity epidemic, there have been very few studies investigating the influence of body weight on treatment dosing and outcomes in patients with hereditary angioedema (HAE).

OBJECTIVE

The purpose of this analysis was to determine whether the standard weight-based dosing recommendation of C1 esterase inhibitor (C1-INH) concentrate (20 IU/kg) is adequate in HAE patients with a high body mass index (BMI).

METHODS

Data from patients treated for HAE attacks with 20 IU/kg of C1-INH concentrate were retrospectively analyzed from the open-label IMPACT2 study (International Multicenter Prospective Angioedema C1-INH Trial). Patients were categorized according to BMI as being normal body weight, overweight, or obese. Efficacy end points were time to onset of symptom relief and time to complete resolution of symptoms. The safety profile was evaluated according to adverse events occurring within 7 to 9 days of treatment.

RESULTS

Of 57 patients, 24 (42%) were of normal body weight, 20 (35%) were overweight, and 13 (23%) were obese. Median (95% CI) time to onset of symptom relief was 0.37 hour (0.29-0.57) in normal-weight patients, 0.48 hour (0.39-0.53) in overweight patients, and 0.58 hour (0.41-0.94) in obese patients. Median time (95% CI) to complete resolution of symptoms was 15.2 hours (9.3-23.2) in normal-weight patients, 22.6 hours (11.3-44.6) in overweight patients, and 11.0 hours (5.6-23.6) in obese patients (differences not significant). There were no relevant differences in the incidence of adverse events in normal-weight patients (54%), overweight patients (30%), and obese patients (54%).

CONCLUSIONS

Treatment of HAE attacks with weight-based doses of C1-INH concentrate provided reliable treatment response, regardless of body weight, in these patients with HAE.

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.

Pharmacokinetics of plasma-derived C1-esterase inhibitor after subcutaneous versus intravenous administration in subjects with mild or moderate hereditary angioedema: the PASSION study

Background

Hereditary angioedema (HAE) is a rare disease caused by C1-esterase inhibitor (C1-INH) deficiency, characterized by periodic attacks of acute edema affecting subcutaneous (SC) tissues and mucous membranes. Human C1-INH concentrate given intravenously (IV) is effective and safe, but venous access may be difficult. We compared SC and IV administration of human pasteurized C1-INH concentrate with respect to pharmacokinetics, pharmacodynamics, and safety.

Study Design and Methods

This was a prospective, randomized, open-label, crossover study. Twenty-four subjects with mild or moderate HAE were randomly assigned during an attack-free interval to receive 1000 units of human pasteurized C1-INH concentrate IV or SC. Plasma levels of C1-INH activity and antigen, C4 antigen, cleaved high-molecular-weight kininogen (clHK), and C1-INH antibodies were measured.

Results

The mean relative bioavailability of functional C1-INH after SC administration was 39.7%. Maximum C1-INH activity after SC administration occurred within 48 hours and persisted longer than after IV administration. C4 antigen levels increased and clHK levels decreased after IV and SC administration, indicating the pharmacodynamic action of C1-INH. The mean half-life of functional C1-INH was 62 hours after IV administration and 120 hours after SC administration (p = 0.0595). C1-INH concentrate was safe and well tolerated when administered via both routes. As expected, SC administration resulted in a higher incidence of injection site reactions, all of which were mild.

Conclusion

With a relative bioavailability of 39.7%, SC administration of human pasteurized C1-INH yields potentially clinically relevant and sustained plasma levels of C1-INH and is safe and well tolerated.

WAO Guideline for the Management of Hereditary Angioedema

Hereditary Angioedema (HAE) is a rare disease and for this reason proper diagnosis and appropriate therapy are often unknown or not available for physicians and other health care providers. For this reason we convened a group of specialists that focus upon HAE from around the world to develop not only a consensus on diagnosis and management of HAE, but to also provide evidence based grades, strength of evidence and classification for the consensus. Since both consensus and evidence grading were adhered to the document meets criteria as a guideline. The outcome of the guideline is to improve diagnosis and management of patients with HAE throughout the world and to help initiate uniform care and availability of therapies to all with the diagnosis no matter where the residence of the individual with HAE exists.

C1-INH concentrate for treatment of acute hereditary angioedema: a pediatric cohort from the I.M.P.A.C.T. studies

BACKGROUND

We analyzed the clinical response of pediatric and adolescent hereditary angioedema (HAE) patients to pdC1-INH in the International Multicenter Prospective Angioedema C1-INH Trials (I.M.P.A.C.T.) 1 and 2.

METHODS

Patients included in this post hoc analysis of prospectively collected data were between 10 and 18 yr old with type I or II HAE and a documented history of abdominal or facial attacks. Patients received a single injection of pdC1-INH concentrate (Berinert(®) , CSL Behring, Marburg, Germany) 20 U/kg. Efficacy end-points were time from the administration of study drug to onset of symptom relief and time to complete relief of all symptoms.

RESULTS

Seven pediatric patients were included in I.M.P.A.C.T.1 with only 1 attack analyzed per patient. Median time to onset of relief was 0.42 h and to complete resolution was 8.08 h. No patient experienced a worsening of symptoms during the 0-4-h assessment period. Nine patients who experienced a total of 115 attacks were included in the analysis of I.M.P.A.C.T.2. Abdominal attacks were rated as 'severe' more frequently than were other types of attacks. The number of attacks per patient ranged from 2 to 42, and study participation ranged from 1 to 38 months. Median times to onset of symptom relief and to complete symptom resolution were 0.49 h and 14.1 h, respectively. Of 4 treatment-emergent adverse events in both studies, only 2 were considered related to treatment.

CONCLUSIONS

Study results showed that outcomes with pdC1-INH treatment of HAE in pediatric patients are comparable with outcomes in adults.

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.

Therapeutic approaches in hereditary angioedema

Hereditary angioedema (HAE) is characterized by acute attacks of edema with multiple localizations, the laryngeal angioedema being the most potentially lethal. In HAE, C1-INH impairments cause episodic increase in kallikrein activity leading to attacks of angioedema. Several therapies have recently become available to treat or to prevent HAE attacks, and others are under evaluation for this indication. Plasma-derived C1-INH, bradykinin receptor antagonists (icatibant), kallikrein inhibitors (ecallantide), or recombinant C1-INH is authorized on the market for HAE attack therapy or prophylaxis. Some of these compounds can be used exclusively to treat HAE attacks, whereas others can also be used as prophylactic therapies. Such therapies, although not available worldwide, can improve disease outcome due to their different mechanisms of action.

Recent developments in the treatment of acute abdominal and facial attacks of hereditary angioedema: focus on human C1 esterase inhibitor

Hereditary angioedema (HAE) is a potentially fatal genetic disorder typified by a deficiency (type I) or dysfunction (type II) of the C1-inhibitor (C1-INH) and characterized by swelling of the extremities, face, trunk, abdominal viscera, and upper airway. Type III is normal estrogen-sensitive C1-INH HAE. Bradykinin, the main mediator of HAE, binds to endothelial B2 receptors, increasing vascular permeability and resulting in edema. HAE management includes short- and long-term prophylaxis. For treating acute episodes, C1-INH concentrate is recommended with regression of symptoms achieved in 30-90 min. Infusions of 500-1000 U have been used in Europe for years. Two plasma-derived C1-INH concentrates have been licensed recently in the United States: Berinert(®) for treating acute attacks and Cinryze(®) for prophylaxis in adolescent/adult patients. A recombinant C1-INH that is being considered for approval (conestat alfa) exhibited significant superiority versus placebo. Ecallantide (Kalbitor(®)) is a selective kallikrein inhibitor recently licensed in the United States for treating acute attacks in patients aged >16 years. It is administered in three 10-mg subcutaneous injections with the risk of anaphylactic reactions. Icatibant (Firazyr(®)) is a bradykinin B2 receptor competitor. It is administered subcutaneously as a 30-mg injection and approved in Europe but not in the United States.