Psychometric validation of two patient-reported outcome measures to assess symptom severity and changes in symptoms in hereditary angioedema

Guidelines for management of hereditary angioedema: What is new? What is missing?

Background: Hereditary angioedema is an autosomal dominant disease that presents with recurrent episodic swelling of the submucosal and/or subcutaneous tissues of the cutaneous, gastrointestinal, and respiratory systems. Evaluation and treatment guidelines have been published nationally and internationally to aid the treating provider. Methods: A review of the most cited and most recent updated guidelines was undertaken to review key points and to explore real-world feasibility of incorporating them into clinical practice. The International World Allergy Organization/European Academy of Allergy and Clinical Immunology (WAO/EAACI) Guideline for the Management of Angioedema - The 2017 Revision and Update, and the consensus reports from the Hereditary Angioedema International Working Group, the Joint Task Force on Practice Parameters focused practice parameter update, and the most recently updated US HAEA Medical Advisory Board 2020 Guidelines for the Management of Hereditary Angioedema were reviewed and summarized. Results: Key points that have been consistent throughout the guidelines include recommendations for evaluation and classification of hereditary angioedema as well as evidence-based guidelines for treatment. Further attention is required on the evaluation and continuous assessment of the burden of illness and quality of life (QoL). Conclusion: The guidelines for management of hereditary angioedema provide a framework for the clinician. However, the physician-patient dialog with regard to the patient disease experience, which includes attack frequency, severity, and Qol, must be continually assessed.

Assessment and management of disease burden and quality of life in patients with hereditary angioedema: a consensus report

BACKGROUND

Hereditary angioedema (HAE) is a rare disease characterized by unpredictable, potentially life-threatening attacks, resulting in significant physical and emotional burdens for patients and families. To optimize care for patients with HAE, an individualized management plan should be considered in partnership with the physician, requiring comprehensive assessment of the patient's frequency and severity of attacks, disease burden, and therapeutic control. Although several guidelines and consensus papers have been published concerning the diagnosis and treatment of HAE, there has been limited specific clinical guidance on the assessment of disease burden and quality of life (QoL) in this patient population. Practical guidance is critical in supporting effective long-term clinical management of HAE and improving patient outcomes. The objective of this review is to provide evidence-based guidelines for an individualized assessment of disease burden and QoL in patients with HAE.

METHODS

A consensus meeting was held on February 29, 2020, consisting of 9 HAE experts from the United States and Europe with extensive clinical experience in the treatment of HAE. Consensus statements were developed based on a preliminary literature review and discussions from the consensus meeting.

RESULTS

Final statements reflect the consensus of the expert panel and include the assessment of attack severity, evaluation of disease burden, and long-term clinical management of HAE caused by C1-esterase inhibitor deficiency. Patient-reported outcome measures for assessing HAE attack severity and frequency are available and valuable tools; however, attack frequency and severity are insufficient markers of disease severity unless they are evaluated in the broader context of the effect on an individual patient's QoL. QoL assessments should be individualized for each patient and minimally, they should address the interference of HAE with work, school, social, family, and physical activity, along with access to and burden of HAE treatment. Advances in HAE therapies offer the opportunity for comprehensive, individualized treatment plans, allowing patients to achieve minimal attack burden with reduced disease and treatment burden.

CONCLUSION

This consensus report builds on existing guidelines by expanding the assessment of disease burden and QoL measures for patients with HAE.

New Instrument for the Evaluation of Prodromes and Attacks of Hereditary Angioedema (HAE-EPA)

A disease-specific, patient-reported outcome instrument suitable for evaluation of prodromes and attacks of hereditary angioedema (HAE) is a clinical unmet need. We constructed such instrument and examined its validity, acceptability, and discriminative ability. Sixty-six patients participated in a survey addressing their demographics, social, and medical status. Discriminant content validity involved: (1) construct definition by in-depth cognitive debriefing interviews, (2) item selection identifying relevant categories, and (3) judgment of the format whereby questionnaires were tested on experienced patients and its content/reliability was validated. Prodromes and attacks affecting certain body systems (domains) were organized in "clusters". Internal consistency, content, and convergent validities were analyzed. Analyses of variance and regression models were used to evaluate the discriminative ability of the instrument to differentiate between attacks and prodromes. The study demonstrates very high internal consistency (Cronbach's α: attacks 0.88-0.98, prodromes 0.78-0.98). Analysis of variance confirmed significant differences between all dimensions and in pre-defined clusters (F (4, 61) = 45.74, p < 0.001, Eta² = 0.77). Significant correlations were found between dimensions of prodromes and attacks. Prodromes are associated but differentiated from attacks. Correlations in severity were high for all domains. Interactions were found between prodromes and patients' experience in illness. In conclusion, the new Prodrome-Attack Evaluation questionnaire (HAE-EPA) is capable of distinguishing attacks and prodromes of HAE, as well as determining associations between the two interrelated phenomena. The new instrument achieves the required discriminative ability, acceptability, and content validity/reliability and therefore can be used as a reliable tool for the investigation of prodromes, attacks, and their relationships.

The Enigma of Prodromes in Hereditary Angioedema (HAE)

A prodrome is a premonitory set of signs and symptoms indicating the onset of a disease. Prodromes are frequently reported by hereditary angioedema (HAE) patients, antedating attacks by a few hours or even longer. In some studies, high incidence of prodromes was reported by patients, with considerable number being able to predict oncoming attacks. Regrettably, prodromes have never received a consensual definition and have not been properly investigated in a systematic fashion. Therefore, their nature remains elusive and their contribution to the diagnosis and treatment of disorders is uncertain. The term "prodrome," as used in various pathologies, denotes different meanings, timing, and duration, so it may not be equally suitable for all clinical situations. Perception of a prodrome is unique for each individual patient depending on self-experience. As modern drugs delegate the administration decision to the patients, early detection of a developing attack may help mitigate its severity and allow deployment of appropriate therapy. New diagnostic instruments were recently developed that can assist in defining the attributes of prodromes and their association with attacks. We will review the prodrome phenomenon as exhibited in certain clinical situations, with an emphasis on prodromes of HAE.

Driving towards Precision Medicine for angioedema without wheals

Evidence accumulated over the last two decades indicates that recurrent angioedema without wheals constitutes a diverse family of disorders with a much higher complexity than was previously regarded. Indicatively, during the last two years, novel variants of three genes other than SERPING1 and F12 have been identified in association with hereditary angioedema. Most interestingly, functional studies of at least one of these variants (the variant c.807G > T of ANGPT1 gene) imply the existence of a new disease endotype in which the altered bradykinin metabolism and function does not play a central role. Therefore, using conventional approaches, it seems that the complexity of this disease cannot be sufficiently elucidated and any attempt to interrelate its many diverse aspects seems unrealistic. Similar to other rare and chronic diseases, a Precision Medicine approach, discovering the right target and giving "the right drug, for the right patient, at the right time, every time" seems the optimal future practice. Herein, we review recent data challenging and dictating the need for a switch of angioedema research into high-throughput approaches and we present the expected advantages for better understanding of the disease and patients management.

Optimum Use of Acute Treatments for Hereditary Angioedema: Evidence-Based Expert Consensus

Acute treatment of hereditary angioedema due to C1 inhibitor deficiency has become available in the last 10 years and has greatly improved patients’ quality of life. Two plasma-derived C1 inhibitors (Berinert and Cinryze), a recombinant C1 inhibitor (Ruconest/Conestat alpha), a kallikrein inhibitor (Ecallantide), and a bradykinin B2 receptor inhibitor (Icatibant) are all effective. Durably good response is maintained over repeated treatments and several years. All currently available prophylactic agents are associated with breakthrough attacks, therefore an acute treatment plan is essential for every patient. Experience has shown that higher doses of C1 inhibitor than previously recommended may be desirable, although only recombinant C1 inhibitor has been subject to full dose–response evaluation. Treatment of early symptoms of an attack, with any licensed therapy, results in milder symptoms, more rapid resolution and shorter duration of attack, compared with later treatment. All therapies have been shown to be well-tolerated, with low risk of serious adverse events. Plasma-derived C1 inhibitors have a reassuring safety record regarding lack of transmission of virus or other infection. Thrombosis has been reported in association with plasma-derived C1 inhibitor in some case series. Ruconest was associated with anaphylaxis in a single rabbit-allergic volunteer, but no further anaphylaxis has been reported in those not allergic to rabbits despite, in a few cases, prior IgE sensitization to rabbit or milk protein. Icatibant is associated with high incidence of local reactions but not with systemic effects. Ecallantide may cause anaphylactoid reactions and is given under supervision. For children and pregnant women, plasma-derived C1 inhibitor has the best evidence of safety and currently remains first-line treatment.

Disease Severity, Activity, Impact, and Control and How to Assess Them in Patients with Hereditary Angioedema

Hereditary angioedema (HAE) is a group of rare, potentially life-threatening, and frequently debilitating diseases characterized by recurrent, and often with an unpredictable onset, of swelling attacks. HAE is heterogeneous, with considerable differences between its subtypes, patients, and even within the same patient over time. During the past few years, several new on demand and prophylactic therapies have become available for HAE, allowing for individualized treatment. Therefore, to optimize HAE management, it is important to determine in all patients, the severity of their attacks, their disease activity, its therapeutic control, and its impact on their quality of life. In this manuscript, we review the existing tools to assess these aspects of HAE management, many of which are patient-reported outcome instruments. Also, we outline the current gaps of knowledge and what tools are still missing to allow for a comprehensive assessment of all patients with HAE including children.

The role of the complement system in hereditary angioedema

Hereditary angioedema (HAE) is a rare, but potentially life-threatening disorder, characterized by acute, recurring, and self-limiting edematous episodes of the face, extremities, trunk, genitals, upper airways, or the gastrointestinal tract. HAE may be caused by the deficiency of C1-inhibitor (C1-INH-HAE) but another type of the disease, hereditary angioedema with normal C1-INH function (nC1-INH-HAE) was also described. The patient population is quite heterogeneous as regards the location, frequency, and severity of edematous attacks, presenting large intra- and inter-individual variation. Here, we review the role of the complement system in the pathomechanism of HAE and also present an overview on the complement parameters having an importance in the diagnosis or in predicting the severity of HAE.

Hereditary Angioedema Attacks: Local Swelling at Multiple Sites

Hereditary angioedema (HAE) patients experience recurrent local swelling in various parts of the body including painful swelling of the intestine and life-threatening laryngeal oedema. Most HAE literature is about attacks located in one anatomical site, though it is mentioned that HAE attacks may also involve multiple anatomical sites simultaneously. A detailed description of such multi-location attacks is currently lacking. This study investigated the occurrence, severity and clinical course of HAE attacks with multiple anatomical locations. HAE patients included in a clinical database of recombinant human C1-inhibitor (rhC1INH) studies were evaluated. Visual analog scale scores filled out by the patients for various symptoms at various locations and investigator symptoms scores during the attack were analysed. Data of 219 eligible attacks in 119 patients was analysed. Thirty-three patients (28%) had symptoms at multiple locations in anatomically unrelated regions at the same time during their first attack. Up to five simultaneously affected locations were reported. The observation that severe HAE attacks often affect multiple sites in the body suggests that HAE symptoms result from a systemic rather than from a local process as is currently believed.

Development and content validity testing of a patient-reported outcomes questionnaire for the assessment of hereditary angioedema in observational studies

BACKGROUND

Hereditary Angioedema (HAE), a rare genetic disease, manifests as intermittent, painful attacks of angioedema. Attacks vary in frequency and severity and include skin, abdominal and life-threatening laryngeal swellings. This study aimed to develop a patient reported outcome (PRO) tool for the assessment of HAE attacks, including their management and impact on patients' lives, for use in clinical studies, or by physicians in general practice.

METHODS

The results of open-ended face to face concept elicitation interviews with HAE patients in Argentina (n = 10) and the US (n = 33) were used to develop the first draft questionnaire of the HAE patient reported outcomes questionnaire (HAE PRO). Subsequently, in-depth cognitive debriefing interviews were performed with HAE patients in the UK (n = 10), Brazil (n = 10), Germany (n = 11) and France (n = 12). Following input from eight multinational clinical experts further cognitive interviews were conducted in the US (n = 12) and Germany (n = 12). Patients who experienced abdominal, cutaneous or laryngeal attacks of varying severity levels were included in all rounds of interviews. Across the rounds of interviews patients discussed their HAE attack symptoms, impacts and treatments. Cognitive debriefing interviews explored patient understanding and relevance of questionnaire items. All interviews were conducted face to face following a pre-defined semi-structured interview guide in the patient's native language.

RESULTS

Patients reported a variety of HAE symptoms, attack triggers, warning signs, attack impacts and treatment options which were used to develop the HAE PRO. The HAE PRO was revised and refined following input from patients and clinical experts. The final 18-item HAE PRO provides an assessment of the HAE attack experience including symptoms, impacts, treatment requirements, healthcare resource use and loss of productivity caused by HAE attacks.

CONCLUSIONS

Patient and expert input has contributed to the development of a content valid questionnaire that assesses concepts important to HAE patients globally. HAE patients across cultures consider the HAE PRO a relevant and appropriate assessment of HAE attacks and treatment.

Characterization of anaphylaxis after ecallantide treatment of hereditary angioedema attacks

BACKGROUND

Ecallantide is a human plasma kallikrein inhibitor indicated for treatment of acute attacks of hereditary angioedema for patients 12 years of age and older. Ecallantide is produced in Pichia pastoris yeast cells by recombinant DNA technology. Use of ecallantide has been associated with a risk of hypersensitivity reactions, including anaphylaxis.

OBJECTIVE

The objective of this detailed retrospective data review was to characterize anaphylaxis cases within the ecallantide clinical trials database.

METHODS

Potential cases of hypersensitivity reactions in the ecallantide clinical development program were identified by examining reported adverse events. The National Institute of Allergy and Infectious Disease criteria were used to identify those events that were consistent with anaphylaxis; these cases were then reviewed in detail. Results from investigational antibody testing also were examined.

RESULTS

Among patients who received subcutaneous ecallantide (n = 230 patients; 1045 doses of 30 mg ecallantide), 8 patients (3.5%) had reactions that met the National Institute of Allergy and Infectious Disease criteria for anaphylaxis; none occurred on first exposure to the drug. All 8 reactions had symptom onset within 1 hour of exposure and cutaneous manifestations commonly observed in type I hypersensitivity reactions. All the reactions responded to standard management of type I hypersensitivity reactions and resolved without fatal outcomes. IgE antibody testing to ecallantide or P pastoris was not consistently positive in patients who experienced apparent type I hypersensitivity reactions.

CONCLUSION

Anaphylaxis episodes after subcutaneous ecallantide exposure have clinical features suggestive of type I hypersensitivity reactions. However, anti-ecallantide or anti-P pastoris IgE antibody status was not found to be reliably associated with anaphylaxis.

Abdominal attacks and treatment in hereditary angioedema with C1-inhibitor deficiency

Background

Hereditary angioedema (HAE) is characterized by unpredictable attacks of debilitating subcutaneous and mucosal edema. Gastrointestinal attacks are painful, of sudden onset and often mistaken for acute abdomen leading to unnecessary surgery. The purpose of this study was to analyze symptom presentation of gastrointestinal angioedema in pediatric and adult HAE patients.

Methods

Information collected during the clinical development of ecallantide for treatment of acute HAE attacks included affected anatomic location, accompanying symptoms, medical history, and pain assessments. Efficacy endpoints included Treatment Outcome Score (TOS, maximum score = 100; minimally important difference = 30), a point-in-time measure of treatment response, and time to treatment response.

Results

Forty-nine percent of 521 HAE attacks only involved abdominal symptoms. The most commonly reported abdominal symptoms were distension (77%), cramping (73%) and nausea (67%). The most common pain descriptors were tender, tiring-exhausting, aching, cramping and sickening. White blood cell counts were elevated (>10 × 10⁹/L) in 23% of attacks (mean ± SD: 15.1 ± 11.27 × 10⁹/L). A high proportion of patients reported a history of abdominal surgery, including appendectomy (23%), cholecystectomy (16.4%), and hysterectomy (8.2%). Mean TOS at 4 hours post ecallantide was 77±33 versus 29±65 for placebo. Median time to significant symptom resolution was 165 minutes (95% CI 136, 167) for ecallantide versus >4 hours (95% CI 161, >4 hours) for placebo. Anaphylactic reactions occurred in 6 of the 149 treated patients.

Conclusions

HAE should be considered in the differential diagnosis of patients with recurrent discrete episodes of severe, unexplained crampy abdominal pain associated with nausea.

Trials registration

The data used in the analysis were gathered across multiple clinical trials conducted during the clinical development program for ecallantide. All of the studies were conducted using Good Clinical Practices (GCP) and in accordance with the ethical principles that have their origins in the Declaration of Helsinki. Each site that participated in the clinical trials obtained the appropriate IRB or Ethics Committee approval prior to enrolling any patients. All patients provided written informed consent prior to undergoing any study-related procedures. Pediatric patients provided written assent and their parents or guardians gave written informed consent.

The following trials have been registered at http://www.clinicaltrials.gov: EDEMA2 (identifier NCT01826916); EDEMA3 (identifier NCT00262080); EDEMA4 (identifier NCT00457015); and DX-88/19 (identifier NCT00456508).

Use of ecallantide in pediatric hereditary angioedema

OBJECTIVE

Hereditary angioedema (HAE) due to C1-inhibitor deficiency is a rare autosomal dominant disease that manifests as sudden unpredictable attacks of subcutaneous or submucosal edema affecting the skin, intestine, and upper airway. Ecallantide is a plasma kallikrein inhibitor indicated for treatment of HAE attacks in patients aged 16 years and older. This analysis examines safety and efficacy of ecallantide for treatment of HAE attacks in patients <18 years of age.

METHODS

Data for patients aged 9 to 17 years treated subcutaneously with 30 mg ecallantide or placebo were pooled from 4 clinical studies (2 double-blind, placebo-controlled and 2 open-label). Efficacy end points included 2 HAE-specific patient-reported outcome measures: mean symptom complex severity (MSCS) score and treatment outcome score (TOS). Times to initial improvement, sustained improvement, and complete or near-complete symptom resolution were calculated. Treatment-emergent adverse events were examined.

RESULTS

Overall, 29 pediatric patients were included; 25 of them received ecallantide for 62 total HAE attacks, and 10 received placebo for 10 total attacks. Ecallantide-treated attacks revealed clinically relevant reduction in symptom severity at 4 hours postdosing based on mean change in MSCS score (-1.4 ± 0.9 ecallantide versus -0.9 ± 0.6 placebo) and TOS (73.9 ± 35.50 ecallantide versus 45.0 ± 43.78 placebo). Patients treated with ecallantide showed rapid improvement in symptoms (median time to complete or near-complete symptom resolution: 181 minutes). No serious adverse events related to treatment were observed.

CONCLUSIONS

Ecallantide appears effective for HAE attacks in adolescents, with rapid symptom improvement. No unexpected safety issues were identified.

Analysis of hereditary angioedema attacks requiring a second dose of ecallantide

BACKGROUND

Effective treatment of acute attacks is critical in managing hereditary angioedema (HAE). Ecallantide, a plasma kallikrein inhibitor, is approved for the treatment of HAE attacks. Occasionally, a second dose is needed when treating attacks of HAE.

OBJECTIVE

To evaluate the characteristics of HAE attacks requiring a second dose (dose B) of ecallantide.

METHODS

Data from all ecallantide clinical trials (EDEMA2, EDEMA4, and DX-88/19) that allowed an open-label dose B were included in this analysis. Patient and attack characteristics potentially predictive of dose B after ecallantide were analyzed by logistic regression. A multivariate model was built using a backward selection process, incorporating variables from the univariate model with P < .20 and removing factors with the highest P value until only significant (P < .05) factors remained.

RESULTS

The analysis included 732 ecallantide-treated HAE attacks in 179 patients. Dose B was required in 88 attacks (12.0%), most (80.5%) for incomplete response. By attack location, 31 of 325 abdominal attacks (9.5%), 17 of 158 laryngeal attacks (10.8%), and 40 of 242 peripheral attacks (16.5%) required dose B. On the basis of the univariate analysis, baseline severity (odds ratio = 1.33, P = .15) and peripheral attack (odds ratio = 1.80, P = .01) were identified as potential predictive factors; abdominal attacks had an inverse correlation (odds ratio = 0.64, P = .055). However, the multivariate analysis identified only peripheral attacks as statistically significantly correlated (P < .05) with dose B requirement.

CONCLUSION

A single, 30-mg dose of ecallantide was effective for most HAE attacks (88.0%). Patients with peripheral attacks of HAE were more likely to require a second dose of ecallantide after 4 hours.

TRIAL REGISTRATION

clinicaltrials.gov Identifiers: not applicable for EDEMA2 (trial was conducted before registration requirements were implemented), NCT00457015 for EDEMA4, and NCT00456508 for DX-88/19.

Outcomes after ecallantide treatment of laryngeal hereditary angioedema attacks

BACKGROUND

Hereditary angioedema (HAE) is a rare disorder associated with episodic attacks of well-demarcated angioedema. Attacks that affect the larynx can result in life-threatening airway obstruction.

OBJECTIVES

To examine efficacy and safety of ecallantide treatment for laryngeal HAE attacks.

METHODS

Data were combined from 4 clinical studies (EDEMA2, EDEMA3, EDEMA4, and DX-88/19) evaluating 30 mg of subcutaneous ecallantide for treatment of acute HAE attacks. Efficacy was assessed using 2 validated, HAE-specific, patient-reported outcome measures. The change in Mean Symptom Complex Severity (MSCS) score indicates change in symptom severity; a negative score indicates improvement. The calculated minimally important difference (MID) for change in severity is -0.30. The Treatment Outcome Score (TOS) measures treatment response. A positive score indicates improvement; the calculated MID is 30.

RESULTS

Overall, 98 patients received ecallantide for 220 laryngeal attacks. The mean ± SD change in MSCS score was -1.1 ± 0.73 and -1.6 ± 0.68 at 4 and 24 hours, respectively. The mean ± SD TOS was 73.5 ± 35.8 and 85.5 ± 27.8 at 4 and 24 hours, respectively. Median time to significant improvement was 185 minutes (95% confidence interval, 167-226). One attack required intubation. Four treatment-emergent serious adverse events were reported, including 2 HAE attacks that resulted in hospitalization and 2 anaphylactic reactions. One of these reactions required treatment with epinephrine, but both patients recovered fully. There were no deaths.

CONCLUSION

In this large attack series, ecallantide was effective for treatment of laryngeal HAE attacks. There is a risk of hypersensitivity, including anaphylaxis, consistent with product labeling. As such, ecallantide should be administered under the supervision of a health care professional.

TRIAL REGISTRATION

clinicaltrials.gov Identifiers: not applicable for EDEMA2 (trial was conducted before implementation of registration requirements); NCT00262080 for EDEMA3, NCT00457015 for EDEMA4, and NCT00456508 for DX-88/19.

Hereditary angioedema therapy: kallikrein inhibition and bradykinin receptor antagonism

Current strategies for the treatment of hereditary angioedema (HAE) include targeted inhibition or antagonism of the contact system, which is dysregulated in HAE patients by a C1 esterase inhibitor deficiency. Ecallantide, a plasma kallikrein inhibitor, and icatibant, a selective bradykinin-2 receptor antagonist, have recently been evaluated in clinical studies for the treatment of acute HAE attacks. Both drugs have demonstrated evidence of efficacy and safety in treating acute HAE episodes, with ecallantide approved for use in the United States and icatibant approved for use in Europe. As therapeutic options for HAE expand for both for prophylactic and acute treatment strategies, a number of patient-specific and drug-specific factors have emerged as important considerations when developing individualized HAE management plans. Optimization of HAE therapy will require further integration of new therapies into the current treatment paradigm.

Assessment of rebound and relapse following ecallantide treatment for acute attacks of hereditary angioedema

BACKGROUND

Hereditary angioedema (HAE) is a rare genetic disease characterized by unpredictable and recurring attacks of angioedema. This study assessed potential attack rebound and relapse following treatment with ecallantide, a plasma kallikrein inhibitor approved for HAE attack treatment.

METHODS

Results were integrated from 2 double-blind, placebo-controlled studies of ecallantide treatment for HAE: EDEMA3-DB and EDEMA4. Symptoms were assessed by treatment outcome score (TOS), mean symptom complex severity (MSCS) score, and global response. Patients with improvement at 4 h post-dosing in all three measures followed by any sign of worsening at 24 h were considered to show potential rebound if worsening was beyond baseline or potential relapse if not beyond baseline. Likeliness of rebound or relapse was determined by the number of measures showing worsening and the magnitude of worsening. Patients receiving placebo who met the criteria for rebound/relapse were evaluated for descriptive comparison only.

RESULTS

Significantly more ecallantide-treated patients (42 of 70) compared to placebo (26 of 71) showed improvement in three measures at 4 h and were thus eligible for rebound/relapse (P = 0.006). Of the nine ecallantide-treated patients with signs of worsening at 24 h, none were likely rebound, one was assessed as possible rebound, one as likely relapse, and two as possible relapse. No patient with potential rebound/relapse experienced new symptoms after dosing. Medical intervention was required in one ecallantide-treated patient.

CONCLUSION

Ecallantide was efficacious for treating acute HAE attacks. Relapse was observed in a small proportion of patients, and there was little evidence of rebound.

Content validity of visual analog scales to assess symptom severity of acute angioedema attacks in adults with hereditary angioedema: an interview study

BACKGROUND

Hereditary angioedema (HAE) is a rare, debilitating, potentially life-threatening condition characterized by recurrent acute attacks of edema of the skin, face/upper airway, and gastrointestinal and urogenital tracts. During a laryngeal attack, people with HAE may be at risk of suffocation, while other attacks are often associated with intense pain, disfigurement, disability, and/or vomiting. The intensity of some symptoms is known only to the person experiencing them. Thus, interview studies are needed to explore such experience and patient-reported outcome measures (PROMs) are required for systematic assessment of symptoms in the clinical setting and in clinical trials of treatments for acute HAE attacks.

OBJECTIVE

The aim of this interview study was to assess the content validity and suitability of four visual analog scale (VAS) instruments for use in clinical studies. The VAS instruments were designed to assess symptoms at abdominal, oro-facial-pharyngeal-laryngeal, peripheral, and urogenital attack locations. This is the first known study to report qualitative data about the patient's experience of the rare disorder, HAE.

METHODS

Semi-structured exploratory and cognitive debriefing interviews were conducted with 27 adults with a confirmed clinical/laboratory diagnosis of HAE (baseline plasma level of functional plasma protein C1 esterase inhibitor [C1INH] <50% of normal without evidence for acquired angioedema). There were 17 participants from the US and 10 from Italy, with mean age 42.5 (SD 14.5) years, range 18-72 years, mean HAE duration 21.3 (SD 14.1) years, range 1-45 years, 67% female, and 44% VAS-naïve. Experience of acute angioedema attacks was first explored, noting spontaneous mentions by participants of HAE symptomatology. Cognitive debriefing of the VAS instruments was undertaken to assess the suitability, comprehensibility, and relevance of the VAS items. Asymptomatic participants completed the VAS instruments relevant to their angioedema experience, reporting as if they were experiencing an acute angioedema attack at the time. Interviews were conducted in the clinic setting in the US and Italy over an 8-month period.

RESULTS

Participants mentioned spontaneously almost all aspects of acute angioedema attacks covered by the four VAS instruments, thus providing strong support for inclusion of nearly all VAS items, with no important symptoms missing. Predominant symptoms found to be associated with acute angioedema attacks were edema and pain, and there was evidence of varying degrees of disruption to everyday activities supporting the inclusion of an overall severity item reflecting the disabling effects of HAE symptoms. VAS item wording was understood by participants.

CONCLUSION

This interview study explored and reported the patient experience of HAE attacks. It demonstrated the content validity of the four anatomical location HAE VAS instruments and their suitability for use in clinical trials of recombinant human C1INH (rhC1INH) treatment for ascertaining trial participants' assessments of the severity of acute angioedema symptoms.

Ecallantide for treatment of acute attacks of hereditary angioedema

PURPOSE

The pharmacology, pharmacokinetics, efficacy, safety, dosage, administration, adverse effects, and place in therapy of ecallantide, a kallikrein inhibitor for the treatment of hereditary angioedema (HAE), are reviewed.

SUMMARY

Ecallantide is the first member of the kallikrein inhibitor class approved for the treatment of acute attacks of HAE. Ecallantide works by binding to kallikrein, preventing the conversion of kininogen to bradykinin, which reduces vascular permeability, thus reducing the swelling associated with acute attacks of HAE. Ecallantide has been studied for the treatment of HAE in three Phase II studies and two Phase III studies. These studies were collectively known as the EDEMA (Evaluation of DX-88's Effect in Mitigating Angioedema) studies. Phase III clinical trials found that ecallantide is superior to placebo in ameliorating patient symptoms associated with acute attacks of HAE at any anatomical site. Ecallantide has a favorable safety profile, with the most common adverse effects being gastrointestinal effects, headache, and injection site reactions. The most severe adverse effects of ecallantide are the risk of anaphylaxis and the possible development of antiecallantide antibodies. A risk evaluation and mitigation strategy program has been approved by the Food and Drug Administration to help ensure the safety and efficacy of ecallantide use. The recommended dose is 30 mg given as three separate subcutaneous injections.

CONCLUSION

Ecallantide is a novel agent approved for the treatment of acute attacks of HAE at any anatomical site. It is one of only three medications approved for this indication in the United States, presents a unique mechanism of action, and appears to be safe and effective when used for its labeled indication.

Efficacy assessments in randomized controlled studies of acute therapy for hereditary angioedema

Hereditary angioedema (HAE) is a rare disorder caused by a deficiency of C1 esterase inhibitor, characterized by recurrent, highly variable attacks of subcutaneous or submucosal edema that may affect multiple body sites. Clinical studies of acute HAE therapies have required the use of assessment tools to evaluate both pretreatment attack severity (baseline severity) and changes in symptom severity following treatment (treatment response). This article reviews the range of assessment tools used for efficacy determination of acute HAE therapies, based on a review of relevant clinical studies. Because the goal is relief of symptoms (rather than cure), patient-reported outcomes (PROs) form the basis of these tools. Tools used to evaluate baseline severity typically employ location-specific assessment of symptom severity, using either categorical descriptions (which may be converted into numerical variables) or a visual analog scale (VAS). Some studies define the initial or most symptomatic site as an "index" site for purposes of efficacy determination, while others (such as the Mean Symptom Complex Severity score used in clinical studies of ecallantide) use a composite score that reflects all sites. Assessment of treatment response typically employs the same tool(s) to evaluate baseline severity, and may be either time-based (e.g., time to achievement of minimal or no symptoms) or symptom-based (e.g., degree of symptom relief at predetermined time points). Although it is unlikely that therapies will be compared using identical assessment tools, prospective or retrospective validation ensures the adequacy and relevance of such tools, which should be taken into consideration when therapies are compared.

Prospective, double-blind, placebo-controlled trials of ecallantide for acute attacks of hereditary angioedema

Hereditary angioedema (HAE) is a rare genetic disorder characterized by unpredictable, episodic, incapacitating attacks of well-demarcated angioedema in the absence of urticaria and pruritus. HAE is due to deficient or dysfunctional C1-esterase inhibitor activity, which results in unopposed activation of plasma kallikrein, resulting in increased levels of bradykinin. Ecallantide is a potent and specific plasma kallikrein inhibitor approved for the treatment of acute attacks of HAE affecting any anatomic site. In Phase III clinical trials, subcutaneously administered ecallantide demonstrated significant, rapid and durable symptom relief. Ecallantide was effective for all attack types, including potentially life-threatening laryngeal attacks. The main safety concern is potentially serious hypersensitivity reactions, including anaphylaxis. Ecallantide represents an important treatment option for the management of acute attacks of HAE.

Ecallantide for the treatment of acute attacks in hereditary angioedema

BACKGROUND

Hereditary angioedema is a rare genetic disorder characterized by acute, intermittent, and potentially life-threatening attacks of edema of the skin and mucosa. We evaluated ecallantide, a newly developed recombinant plasma kallikrein inhibitor, for the treatment of acute attacks of angioedema.

METHODS

In this double-blind, placebo-controlled trial, patients with hereditary angioedema presenting with an acute attack were randomly assigned, in a 1:1 ratio, to receive subcutaneous ecallantide, at a dose of 30 mg, or placebo. Two measures of patient-reported outcomes were used to assess the response: treatment outcome scores, which range from +100 (designated in the protocol as significant improvement in symptoms) to -100 (significant worsening of symptoms), and the change from baseline in the mean symptom complex severity score, which range from +2 (representing a change from mild symptoms at baseline to severe symptoms after) to -3 (representing a change from severe symptoms at baseline to no symptoms after). The primary end point was the treatment outcome score 4 hours after study-drug administration. Secondary end points included the change from baseline in the mean symptom complex severity score at 4 hours and the time to significant improvement.

RESULTS

A total of 71 of the 72 patients completed the trial. The median treatment outcome score at 4 hours was 50.0 in the ecallantide group and 0.0 in the placebo group (interquartile range [IQR], 0.0 to 100.0 in both groups; P=0.004). The median change in the mean symptom complex severity score at 4 hours was -1.00 (IQR, -1.50 to 0.00) with ecallantide, versus -0.50 (IQR, -1.00 to 0.00) with placebo (P=0.01). The estimated time to significant improvement was 165 minutes with ecallantide versus more than 240 minutes with placebo (P=0.14). There were no deaths, treatment-related serious adverse events, or withdrawals owing to adverse events.

CONCLUSIONS

Four hours after administration of ecallantide or placebo for acute attacks of angioedema in patients with hereditary angioedema, patient-reported treatment outcome scores and mean symptom complex severity scores were significantly better with ecallantide than with placebo. (Funded by Dyax; ClinicalTrials.gov number, NCT00262080.)

EDEMA4: a phase 3, double-blind study of subcutaneous ecallantide treatment for acute attacks of hereditary angioedema

BACKGROUND

Hereditary angioedema (HAE) is a genetic disorder resulting from low levels of C1-inhibitor activity that manifests as acute attacks of variable and sometimes life-threatening edema. Ecallantide is a novel potent inhibitor of human plasma kallikrein, a key mediator of the excessive formation of bradykinin associated with the signs and symptoms of an HAE attack.

OBJECTIVE

To evaluate the efficacy and safety of ecallantide in the treatment of acute HAE attacks.

METHODS

In this double-blind, placebo-controlled study, patients with a moderate to severe HAE attack were randomized 1:1 to receive 30 mg of subcutaneous ecallantide or placebo. The primary efficacy end point was change from baseline in mean symptom complex severity score 4 hours after dosing. Additional end points included treatment outcome score 4 hours after dosing and maintenance of significant overall improvement through 24 hours.

RESULTS

Ninety-six patients were enrolled. Mean (SD) change from baseline in mean symptom complex severity score 4 hours after dosing was significantly greater with ecallantide use (-0.8 [0.6]) compared with placebo use (-0.4 [0.8]) (P = .01 comparing distributions). Ecallantide therapy was also associated with a significantly larger mean (SD) treatment outcome score 4 hours after dosing vs placebo use (ecallantide: 53.4 [49.7]; placebo: 8.1 [63.2]; P = .003 comparing distributions). The benefit of ecallantide was apparent within 2 hours after dosing and was maintained through 24 hours after dosing. The safety profile was similar between the treatment groups.

CONCLUSION

Ecallantide appears to be an effective and safe treatment for acute attacks of HAE.