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.

Efficacy and Safety of Donidalorsen for Hereditary Angioedema.

BACKGROUND: Hereditary angioedema is a rare disorder characterized by episodic, potentially life-threatening swelling caused by kallikrein-kinin dysregulation. Long-term prophylaxis can stabilize this system. Donidalorsen, an antisense oligonucleotide, specifically reduces prekallikrein expression. METHODS: In this phase 3, double-blind, randomized trial, we assigned patients with hereditary angioedema to receive donidalorsen (80 mg subcutaneously) or placebo once every 4 or 8 weeks. The primary end point was the time-normalized number of investigator-confirmed hereditary angioedema attacks per 4 weeks (attack rate) from week 1 to week 25. RESULTS: A total of 90 patients received donidalorsen every 4 weeks (45 patients), donidalorsen every 8 weeks (23 patients), or placebo (22 patients). The least-squares mean time-normalized attack rate was 0.44 (95% CI, 0.27 to 0.73) in the 4-week group, 1.02 (95% CI, 0.65 to 1.59) in the 8-week group, and 2.26 (95% CI, 1.66 to 3.09) in the placebo group. The mean attack rate from week 1 to week 25 was 81% lower (95% CI, 65 to 89) in the 4-week group than in the placebo group (P<0.001) and 55% lower (95% CI, 22 to 74) in the 8-week group than in the placebo group (P = 0.004); the median reduction in the attack rate from baseline was 90% in the 4-week group, 83% in the 8-week group, and 16% in the placebo group. The mean attack rate during weeks 5 to 25 was 87% lower (95% CI, 72 to 94) in the 4-week group than in the placebo group (P<0.001) and 60% lower (95% CI, 25 to 79) in the 8-week group than in the placebo group. Donidalorsen administered every 4 weeks resulted in an improvement in the least-squares mean total score for the change at week 25 on the Angioedema Quality-of-Life Questionnaire (scores range from 0 to 100, with a score of 100 indicating the worst possible quality of life) that was 18.6 points (95% CI, 9.5 to 27.7) better than that with placebo (P<0.001). The most common adverse events were erythema at the injection site, headache, and nasopharyngitis; 98% of adverse events were mild or moderate in severity. CONCLUSIONS: Donidalorsen treatment reduced the hereditary angioedema attack rate, a finding that supports potential prophylactic use for hereditary angioedema. (Funded by Ionis Pharmaceuticals; OASIS-HAE ClinicalTrials.gov number, NCT05139810.).

Oral Sebetralstat for On-Demand Treatment of Hereditary Angioedema Attacks.

BACKGROUND: Approved on-demand treatments for hereditary angioedema attacks need to be administered parenterally, a route of administration that is associated with delays in treatment or withholding of therapy. METHODS: In this phase 3, double-blind, three-way crossover trial, we randomly assigned participants at least 12 years of age with type 1 or type 2 hereditary angioedema to take up to two oral doses of sebetralstat (300 mg or 600 mg) or placebo for an angioedema attack. The primary end point, assessed in a time-to-event analysis, was the beginning of symptom relief, defined as a rating of "a little better" on the Patient Global Impression of Change scale (ratings range from "much worse" to "much better") at two or more consecutive time points within 12 hours after the first administration of the trial agent. Key secondary end points, assessed in a time-to-event analysis, were a reduction in attack severity (an improved rating on the Patient Global Impression of Severity [PGI-S] scale, with ratings ranging from "none" to "very severe") at two or more consecutive time points within 12 hours and complete attack resolution (a rating of "none" on the PGI-S scale) within 24 hours. RESULTS: A total of 136 participants were assigned to one of six trial sequences, with 110 treating 264 attacks. The time to the beginning of symptom relief with the 300-mg dose and the 600-mg dose was faster than with placebo (P<0.001 and P = 0.001 for the two comparisons, respectively), with median times of 1.61 hours (interquartile range, 0.78 to 7.04), 1.79 hours (1.02 to 3.79), and 6.72 hours (1.34 to >12), respectively. The time to reduction in the attack severity with the 300-mg dose and the 600-mg dose was faster than with placebo (P = 0.004 and P = 0.003), with median times of 9.27 hours (interquartile range, 1.53 to >12), 7.75 hours (2.19 to >12), and more than 12 hours (6.23 to >12). The time to complete resolution was faster with the 300-mg and 600-mg doses than with placebo (P = 0.002 and P<0.001). The percentage of attacks with complete resolution within 24 hours was 42.5% with the 300-mg dose, 49.5% with the 600-mg dose, and 27.4% with placebo. Sebetralstat and placebo had similar safety profiles; no serious adverse events related to the trial agents were reported. CONCLUSIONS: Oral sebetralstat provided faster times to the beginning of symptom relief, reduction in attack severity, and complete attack resolution than placebo. (Funded by KalVista Pharmaceuticals; KONFIDENT ClinicalTrials.gov number, NCT05259917; EudraCT number, 2021-001226-21.).

The future of therapeutic options for hereditary angioedema.

Hereditary angioedema (HAE) is a rare genetic condition causing unpredictable and severe episodes of angioedema that are debilitating and life-threatening. Moreover, HAE can be classified into HAE due to C1-esterase inhibitor deficiency (HAE-C1INH) or HAE with normal C1INH. Moreover, HAE-C1INH is subcategorized as types I and II based on deficient or dysfunctional circulating C1INH protein resulting from inherited or spontaneous mutations in the SERPING1 gene leading to uncontrolled factor XII/plasma kallikrein activation and excessive bradykinin production. Bradykinin-2 receptor activation leads to vasodilation, increased vascular permeability, and smooth muscle contractions, resulting in subcutaneous or submucosal fluid extravasation that can affect the face, extremities, airway, and gastrointestinal and genitourinary systems. Furthermore, HAE with normal C1INH is caused by either a known or unknown genetic mutation, and the mechanisms are less well-established but most forms are thought to be related to bradykinin signaling with a similar presentation as HAE-C1INH despite normal levels of C1INH protein and function. Current HAE management strategies include on-demand and prophylactic treatments which replace C1INH, reduce kallikrein activity, or block bradykinin binding to the bradykinin B2 receptor. With the advent of additional small molecule inhibitors, monoclonal antibodies, RNA-targeted therapies, gene therapies, and gene modification approaches, preclinical studies and human clinical trials are underway to further expand therapeutic options in HAE. This review article will briefly summarize current HAE treatments and provide an overview of potential future therapies for HAE.

Definition, acronyms, nomenclature, and classification of angioedema (DANCE): AAAAI, ACAAI, ACARE, and APAAACI DANCE consensus.

BACKGROUND: Angioedema (AE) manifests with intermittent, localized, self-limiting swelling of the subcutaneous and/or submucosal tissue. AE is heterogeneous, can be hereditary or acquired, may occur only once or be recurrent, may exhibit wheals or not, and may be due to mast cell mediators, bradykinin, or other mechanisms. Several different taxonomic systems are currently used, making it difficult to compare the results of studies, develop multicenter collaboration, and harmonize AE treatment. OBJECTIVE: We developed a consensus on the definition, acronyms, nomenclature, and classification of AE (DANCE). METHODS: The initiative involved 91 experts from 35 countries and was endorsed by 53 scientific and medical societies, and patient organizations. A consensus was reached by online discussion and voting using the Delphi process over a period of 16 months (June 2021 to November 2022). RESULTS: The DANCE initiative resulted in an international consensus on the definition, classification, and terminology of AE. The new consensus classification features 5 types and endotypes of AE and a harmonized vocabulary of abbreviations/acronyms. CONCLUSION: The DANCE classification complements current clinical guidelines and expert consensus recommendations on the diagnostic assessment and treatment of AE. DANCE does not replace current clinical guidelines, and expert consensus algorithms and should not be misconstrued in a way that affects reimbursement of medicines prescribed by physicians using sound clinical judgment. We anticipate that this new AE taxonomy and nomenclature will harmonize and facilitate AE research and clinical studies, thereby improving patient care.

Hereditary angioedema outcomes in US patients switched from injectable long-term prophylactic medication to oral berotralstat.

BACKGROUND: Berotralstat, a first-line, once-daily, oral plasma kallikrein inhibitor for long-term prophylaxis of hereditary angioedema (HAE), is an effective and well-tolerated treatment option. OBJECTIVE: To summarize the safety, effectiveness, and impact on treatment satisfaction in patients who switched from injectable long-term prophylactics to oral berotralstat monotherapy (150 mg daily) at US sites in the international open-label APeX-S study. METHODS: APeX-S was an open-label, Phase II study of berotralstat conducted in 22 countries. Here, we focus on APeX-S patients enrolled at US sites who switched from injectable long-term prophylactics to berotralstat 150 mg once-daily monotherapy. RESULTS: A total of 34 patients discontinued lanadelumab (n = 21), subcutaneous C1 esterase inhibitor (n = 11), or intravenous C1 esterase inhibitor (n = 2) and switched to berotralstat 150 mg monotherapy. Vomiting, diarrhea, and upper respiratory tract infection were the most common adverse events (each 11.8%). Mean monthly attack rates were consistently low after the switch to berotralstat. The mean (SEM) monthly attack rate was 0.29 (0.11) at Month 1, 0.48 (0.15) at Month 6, and 0.58 (0.23) at Month 12. The median attack rate was 0 attack/mo throughout 12 months of treatment. Improvements were observed in the Treatment Satisfaction Questionnaire for Medication from baseline to Month 12 after the switch to berotralstat monotherapy, with the greatest improvements in convenience. CONCLUSION: The transition from injectable prophylactic medication to berotralstat was generally well tolerated. Patients switching to berotralstat monotherapy maintained good control of their HAE symptoms and reported improved treatment satisfaction. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT03472040.

A phase 2 open-label extension study of prekallikrein inhibition with donidalorsen for hereditary angioedema.

BACKGROUND: Hereditary angioedema (HAE) is a potentially fatal disease characterized by unpredictable, recurrent, often disabling swelling attacks. In a randomized phase 2 study, donidalorsen reduced HAE attack frequency and improved patient quality-of-life (ISIS721744-CS2, NCT04030598). We report the 2-year interim analysis of the phase 2 open-label extension (OLE) study (ISIS 721744-CS3, NCT04307381). METHODS: In the OLE, the on-treatment study period consisted of fixed (weeks 1-13, donidalorsen 80 mg subcutaneously every 4 weeks [Q4W]) and flexible (weeks 17-105, donidalorsen 80 mg Q4W, 80 mg every 8 weeks [Q8W], or 100 mg Q4W) dosing periods. The primary outcome was incidence and severity of treatment-emergent adverse events (TEAEs). The secondary outcomes included efficacy, pharmacodynamic, and quality-of-life assessments. RESULTS: Seventeen patients continued in the OLE study. No serious TEAEs or TEAEs leading to treatment discontinuation were reported. Mean monthly HAE attack rate was 96% lower than the study run-in baseline rate (mean, 0.06/month; 95% confidence interval [CI], 0.02-0.10; median, 0.04 on-treatment vs. mean, 2.70/month; 95% CI, 1.94-3.46; median, 2.29 at baseline). Mean monthly attack rate for Q8W dosing (n = 8) was 0.29 (range, 0.0-1.7; 95% CI, -0.21 to 0.79; median, 0.00). Mean plasma prekallikrein and D-dimer concentrations decreased, and Angioedema Quality of Life Questionnaire total score improved from baseline to week 105 with donidalorsen. CONCLUSION: The 2-year interim results of this phase 2 OLE study of donidalorsen in patients with HAE demonstrated no new safety signals; donidalorsen was well tolerated. There was durable efficacy with a 96% reduction in HAE attacks.

Hereditary angioedema in older adults: Understanding the patient perspective.

BACKGROUND: Hereditary angioedema (HAE) is a rare condition characterized by potentially fatal, recurrent episodes of painful swelling. Whereas there are limited studies evaluating the quality of life of individuals with HAE, none have evaluated the impact of HAE on older adults. OBJECTIVE: To evaluate the effect of HAE on older adults through qualitative methodology. METHODS: A group of 3 physicians with extensive research and clinical experience in HAE developed a focus group guidebook highlighting issues of importance to older adults. A total of 17 patients with HAE (type I or II) aged 60 years and older participated in focus groups. Three independent reviewers coded each focus group transcript using a thematic saturation approach. RESULTS: Reviewers identified 7 core themes from the focus groups. The themes identified encompassed the following: (1) challenges with securing medications and insurance concerns; (2) the experience of living with HAE before the advent of newer and more effective therapeutic options; (3) a worsening of HAE attack frequency and severity with aging; (4) the effects of comorbid conditions such as arthritis, memory loss, and irritable bowel syndrome; (5) changes in HAE with menopause; and (6) changing perspective on HAE with age, the effect of HAE on interpersonal relationships including the decision to have children, and goals for future care and research including support groups and a desire to be included in clinical trials. CONCLUSION: Older adults with HAE have specific challenges and concerns that may be unique compared with younger populations. Health care providers should address these to provide optimal care.

Clinical Progress in Hepatic Targeting for Novel Prophylactic Therapies in Hereditary Angioedema.

Hereditary angioedema (HAE) is typically caused by a deficiency of the protease inhibitor C1 inhibitor (C1INH). The absence of C1INH activity on plasma kallikrein and factor XIIa leads to overproduction of the vasoactive peptide bradykinin, with resulting angioedema. As the primary site of C1INH and prekallikrein production, the liver is recognized as an important therapeutic target in HAE, leading to the development of hepatic-focused treatment strategies such as GalNAc-conjugated antisense technology and gene modification. This report reviews currently available data on hepatic-focused interventions for HAE that have advanced into human trials. Donidalorsen is an investigational GalNAc3-conjugated antisense oligonucleotide that binds to prekallikrein mRNA in the liver and reduces the expression of prekallikrein. Phase 2 data with subcutaneous donidalorsen demonstrated a significant reduction in HAE attack rate compared with placebo. Phase 3 trials are underway. ADX-324 is a GalNAc3-conjugated short-interfering RNA being investigated in HAE. BMN 331 is an investigational AAV5-based gene therapy vector that expresses wild-type human C1INH and is targeted to hepatocytes. A single intravenous dose of BMN 331 is intended to replace the defective SERPING1 gene and enable patients to produce functional C1INH. A first-in-human phase 1/2 study is ongoing with BMN 331. NTLA-2002 is an investigational in vivo clustered regularly interspaced short palindromic repeats/Cas9-based therapy designed to knock out the prekallikrein-coding KLKB1 gene in hepatocytes; a phase 1/2 study is ongoing. Findings from these and other ongoing studies are highly anticipated with the expectation of expanding the array of treatment options in HAE.

Evaluation of patient-reported outcome measures for on-demand treatment of hereditary angioedema attacks and design of KONFIDENT, a phase 3 trial of sebetralstat.

BACKGROUND: Hereditary angioedema (HAE) with C1-inhibitor deficiency (HAE-C1-INH) is characterized by recurrent, debilitating episodes of swelling. Sebetralstat, an investigational oral plasma kallikrein inhibitor, demonstrated promising efficacy for on-demand treatment of HAE-C1-INH in a phase 2 trial. We describe the multipronged approach informing the design of KONFIDENT, a phase 3 randomized, placebo-controlled, three-way crossover trial evaluating the efficacy and safety of sebetralstat in patients aged ≥12 years with HAE-C1-INH. METHODS: To determine an optimal endpoint to measure the beginning of symptom relief in KONFIDENT, we engaged patients with HAE on clinical outcome measures and subsequently conducted analyses of phase 2 outcomes. Sample size was determined via a simulation-based approach using phase 2 data. RESULTS: Patient interviews revealed a strong preference (71%) for the Patient Global Impression of Change (PGI-C) over other measures and indicated a rating of "A Little Better" as a clinically meaningful milestone. In phase 2, a rating of "A Little Better" demonstrated agreement with attack severity improvement and resolution on the Patient Global Impression of Severity and had better sensitivity than "Better." Simulations indicated that 84 patients completing treatment would ensure at least 90% power for assessing the primary endpoint of time to beginning of symptom relief defined as a PGI-C rating of at least "A Little Better" for two time points in a row. CONCLUSIONS: Patient feedback and phase 2 data support PGI-C as the primary outcome measure in the phase 3 KONFIDENT trial evaluating sebetralstat, which has the potential to be the first oral on-demand treatment for HAE-C1-INH attacks.

Healthcare utilization of patients with hereditary angioedema treated with lanadelumab and subcutaneous C1-inhibitor concentrate.

Background: New hereditary angioedema (HAE) treatments have become available in recent years for the treatment of HAE due to C1-inhibitor (C1-INH) deficiency, including two subcutaneous (SC) options: a monoclonal antibody (lanadelumab) and a plasma-derived C1-INH concentrate (SC-C1-INH). Limited real-world data on these therapies have been reported. Objective: The objective was to describe new users of lanadelumab and SC-C1-INH, including demographics, healthcare resource utilization (HCRU), costs, and treatment patterns before and after beginning treatment. Methods: This was a retrospective cohort study that used an administrative claims data base. Two mutually exclusive cohorts of adult (ages ≥18 years) new users of lanadelumab or SC-C1-INH with ≥180 days of continuous use were identified. HCRU, costs, and treatment patterns were assessed in the 180-day period before the index date (new treatment use) and up to 365 days after the index date. HCRU and costs were calculated as annualized rates. Results: Forty-seven patients who used lanadelumab and 38 patients who used SC-C1-INH were identified. The most frequently used on-demand HAE treatments at baseline were the same for both cohorts: bradykinin B2 antagonists (48.9% of the patients on lanadelumab, 52.6% of the patients on SC-C1-INH) and C1-INHs (40.4% of the patients on lanadelumab, 57.9% of the patients on SC-C1-INH). More than 33% of the patients continued to fill on-demand medications after treatment initiation. Annualized angioedema-associated emergency department visits and hospitalizations decreased after initiation of treatment, from 1.8 to 0.6 for the patients on lanadelumab and from 1.3 to 0.5 for the patients on SC-C1-INH. Annualized total healthcare costs after treatment initiation in the database were $866,639 and $734,460 for the lanadelumab and SC-C1-INH cohorts, respectively. Pharmacy costs accounted for >95% of these total costs. Conclusion: Although HCRU decreased after the initiation of treatment, angioedema-associated emergency department visits and hospitalizations and on-demand treatment fills were not completely eliminated. This indicates ongoing disease and treatment burden despite use of modern HAE medicines.

Long-term lanadelumab treatment improves health-related quality of life in patients with hereditary angioedema.

BACKGROUND: Hereditary angioedema (HAE) is associated with a substantial disease burden. Lanadelumab reduced the HAE attack rate during 132 weeks of follow-up in the HELP open-label extension (OLE) Study (NCT02741596). OBJECTIVE: To measure the impact of long-term lanadelumab treatment on patient-reported outcomes (PROs). METHODS: Rollover patients (completed the 26-week HELP study [NCT02586805]) and nonrollovers (newly enrolled) received lanadelumab 300 mg every 2 weeks. PROs (Angioedema Quality of Life Questionnaire [AE-QoL], Short Form Health Survey 12-item version 2, Hospital Anxiety and Depression Scale, Work Productivity and Activity Impairment-General Health Questionnaire, and EQ-5D-5L questionnaire) were assessed at baseline (day 0 of HELP OLE) and various time points until the end-of-study visit. The Angioedema Control Test, Treatment Satisfaction Questionnaire for Medication, and Global Impression of Treatment Response were administered starting at week 52. RESULTS: The mean (SD) change in AE-QoL total score from baseline to end-of-study for rollovers (n = 90) was -10.2 (17.9), exhibiting further improvement from HELP in health-related quality of life (HRQoL); 48.9% of rollovers achieved the previously defined 6-point minimal clinically important difference. Nonrollovers (n = 81) reported a change of -19.5 (21.3). Controlled disease (Angioedema Control Test total score ≥10) was reported by 90.2% of rollovers and 95.9% of nonrollovers at the end of the study. Excellent treatment response was reported by 78.7% of patients and 82.4% of investigators. Results from other PROs indicated a slight improvement in anxiety, a high level of satisfaction with treatment, and increased work productivityor activity. CONCLUSION: Clinically meaningful improvement in HRQoL was exhibited with long-term lanadelumab treatment, supporting the benefit of lanadelumab therapy associated with attack prevention. TRIAL REGISTRATION: ClinicalTrials.gov Identifiers: NCT02586805 (HELP Study) and NCT02741596 (HELP open-label extension).

Hereditary Angioedema: Impact of COVID-19 pandemic stress upon disease related morbidity and well-being.

Background: Individuals with hereditary angioedema (HAE) experience stress-related sequelae, including enhanced disease morbidity and reduced quality of life. The pervasive societal strain that surround the coronavirus disease 2019 (COVID-19) pandemic may theoretically pose a disproportionate risk for patients with HAE. Objective: To dissect the interrelationship(s) among the COVID-19 pandemic, stress, and HAE disease-related morbidity and overall well-being. Methods: Subjects with HAE (either due to C1-inhibitor deficiency or with normal C1 inhibitor) as well as non-HAE household members (normal controls) completed online questionnaires that covered the impact of the COVID-19 pandemic on attack frequency, observed effectiveness of HAE medications, stress, and perceived quality of life and/or well-being. The subjects scored each of the questions to reflect their current status as well as their status before being aware of the pandemic. Results: Disease morbidity and psychologic stress outcomes were significantly worse in patients with HAE during the pandemic compared with before they were aware of the pandemic. A COVID-19 infection further increased attack frequency. Control subjects also experienced deterioration of well-being and optimism. A comorbid diagnosis of anxiety, depression, or posttraumatic stress disorder (PTSD) was generally associated with worse outcomes. Women consistently showed greater decrements in wellness during the pandemic compared with men. Women also reported higher levels of comorbid anxiety, depression, or PTSD than men and experienced a higher rate of job loss during the pandemic. Conclusion: The results implicated a deleterious impact of stress in the aftermath of COVID-19 awareness on HAE morbidity. The female subjects were universally more severely affected then were the male subjects. Overall well-being and/or quality of life, and optimism for the future deteriorated after awareness of the COVID-19 pandemic for the subjects with HAE and non-HAE household controls.

An investigational oral plasma kallikrein inhibitor for on-demand treatment of hereditary angioedema: a two-part, randomised, double-blind, placebo-controlled, crossover phase 2 trial.

BACKGROUND: Guidelines recommend effective on-demand therapy for all individuals with hereditary angioedema. We aimed to assess the novel oral plasma kallikrein inhibitor, sebetralstat, which is in development, for on-demand treatment of hereditary angioedema attacks. METHODS: In this two-part phase 2 trial, individuals with type 1 or 2 hereditary angioedema aged 18 years or older were recruited from 25 sites, consisting of specialty outpatient centres, across nine countries in Europe and the USA. Individuals were eligible if they had experienced at least three hereditary angioedema attacks in the past 93 days, were not on prophylactic therapy, and had access to and the ability to self-administer conventional attack treatment. In part 1 of the trial, participants were given a single 600 mg open-label oral dose of sebetralstat to assess safety, pharmacokinetics, and pharmacodynamics of the dose. Part 2 was a randomised, double-blind, placebo-controlled, two-sequence, two-period (2 × 2) crossover trial; participants were randomly assigned (1:1) to either sequence 1, in which they were given a single dose of 600 mg of sebetralstat to treat the first eligible attack and a second dose of placebo to treat the second eligible attack, or sequence 2, in which they were given placebo to treat the first eligible attack and then 600 mg of sebetralstat to treat the second eligible attack. Participants and investigators were masked to treatment assignment. The primary endpoint was time to use of conventional attack treatment within 12 h of study drug administration, which was assessed in all participants who were randomly assigned to treatment and who received study drug for two attacks during part 2 of the study. Safety was assessed in all participants who received at least one dose of study drug, starting in part 1. This study is registered with ClinicalTrials.gov, NCT04208412, and is completed. FINDINGS: Between July 2, 2019, and Dec 8, 2020, 84 individuals were screened and 68 were enrolled in part 1 and received sebetralstat (mean age 38·3 years [SD 13·2], 37 [54%] were female, 31 [46%] were male, 68 [100%] were White). 42 (62%) of 68 participants completed pharmacokinetic assessments. Sebetralstat was rapidly absorbed, with a geometric mean plasma concentration of 501 ng/mL at 15 min. In a subset of participants (n=6), plasma samples obtained from 15 min to 4 h after study drug administration had near-complete protection from ex vivo stimulated generation of plasma kallikrein and cleavage of high-molecular-weight kininogen. In part 2, all 68 participants were randomly assigned to sequence 1 (n=34) or sequence 2 (n=34). 53 (78%) of 68 participants treated two attacks (25 [74%] in the sequence 1 group and 28 [82%] in the sequence 2 group). Time to use of conventional treatment within 12 h of study drug administration was significantly longer with sebetralstat versus placebo (at quartile 1: >12 h [95% CI 9·6 to >12] vs 8·0 h [3·8 to >12]; p=0·0010). There were no serious adverse events or adverse event-related discontinuations. INTERPRETATION: Oral administration of sebetralstat was well tolerated and led to rapid suppression of plasma kallikrein activity, resulting in increased time to use of conventional attack treatment and faster symptom relief versus placebo. Based on these results, a phase 3 trial to evaluate the efficacy and safety of two dose levels of sebetralstat in adolescent and adult participants with hereditary angioedema has been initiated (NCT05259917). FUNDING: KalVista Pharmaceuticals.

Urticaria and Angioedema: Understanding Complex Pathomechanisms to Facilitate Patient Communication, Disease Management, and Future Treatment.

Chronic spontaneous urticaria (CSU) is primarily a T2-dominant disease with a complex genetic background. Skin mast cell activation can be induced not only via the IgE-FcεRI axis but also from several other distinct mechanisms, molecules, and receptors involved in CSU onset, persistence, and exacerbation. These include autoallergy, autoimmunity, central or peripheral neuroimmune dysregulation, activation of both extrinsic and intrinsic coagulation pathways, and microbial infections. Besides mast cells, recent reports suggest the active and direct involvement of basophils and eosinophils. Several biological characteristics or biomarkers have been linked with CSU's known endotypes and may help forecast therapeutic responses. The introduction of biologic therapy for CSU has been a major advance in the last 10 years. The cornerstone of angioedema (AE) pathogenesis is increased vascular permeability and plasma leakage into the deeper dermis and subcutis, either mediated by histamine or bradykinin (BK). C1-inhibitor deficiency, hereditary or acquired, is the primary cause of BK-mediated AE due to increased plasma BK concentration. Other complex conditions have been identified, with some likely involving contact system dysregulation and other putative mechanisms related to vascular endothelial dysfunction. The approval of multiple hereditary-AE-specific therapies for both prevention and acute attacks has revolutionized treatment of this disease. Any new knowledge of the pathogenesis of CSU and AE offers the opportunity to improve patient information, physician-patient communication, prediction of therapeutic responses, selection of precise tailor-made treatment for each patient, and exploration of novel treatment options for those who do not achieve disease control with current medications.

Hereditary Angioedema With Normal C1 Inhibitor: US Survey of Prevalence and Provider Practice Patterns.

BACKGROUND: Hereditary angioedema (HAE) with normal C1-INH (HAE-nl-C1INH) is phenotypically similar to HAE resulting from C1-INH deficiency (HAE-C1INH). Confirmatory diagnostic tests for HAE-nl-C1INH are limited and few clinical study data exist regarding management of the condition. Therefore, survey studies may provide initial estimates of prevalence, diagnosis, and management patterns of this condition. OBJECTIVE: To estimate the prevalence and describe current management patterns for HAE-nl-C1INH in the United States (US). METHODS: We conducted an Internet-based survey of US physicians to estimate the prevalence of the HAE-nl-C1INH population in the United States. Potential participating physicians were identified from the US Hereditary Angioedema Association database and IQVIA Xponent prescription database. Eligible physicians were invited to complete an online survey between June and September 2021. RESULTS: A total of 113 physicians provided data for the estimation of HAE-nl-C1INH prevalence and 81 physicians treating HAE-nl-C1INH patients provided data about treatment patterns. In bias-corrected analysis, we estimated 1,230 to 1,331 HAE-nl-C1INH patients within the United States between May 2019 and April 2020. Mean time to diagnosis for HAE-nl-C1INH was approximately 6 years (range, 2.4-13.5 years). Response to medication was commonly used to inform diagnosis (antihistamine response or nonresponse used by 73% of physician respondents, corticosteroids by 57%, or HAE-specific medications by 74%), and Factor XII genetic testing was used by 43%. CONCLUSIONS: These survey data provide estimates of HAE-nl-C1INH prevalence in the United States as well as current diagnosis and management strategies. Results may be useful for developing studies to assess treatment efficacy and safety, and potentially improve the diagnosis for and management of this patient population.

Hereditary Angioedema During Pregnancy: Considerations in Management.

In recent years, hereditary angioedema (HAE) management has substantially advanced but also become more complex with additional therapeutic options. Pregnancy significantly influences the clinical symptoms of HAE in many women because of estrogen effects or other physiologic factors, and also introduces important safety concerns related to HAE medications. Management of HAE during pregnancy requires clinicians to be familiar with the potential clinical course, triggers, and recommended treatment strategies to provide guidance and optimal medical management to women and families affected by the condition. This review provides an overview of data, considerations, and recommendations related to HAE and pregnancy.

Consider Hereditary Angioedema in the Differential Diagnosis for Unexplained Recurring Abdominal Pain.

Health care providers are likely to encounter patients with recurrent unexplained abdominal pain. Because hereditary angioedema (HAE) is a rare disease, it may not be part of the differential diagnosis, especially for patients who do not have concurrent skin swelling in addition to abdominal symptoms. Abdominal pain is very common in patients with HAE, occurring in up to 93% of patients, with recurrent abdominal pain reported in up to 80% of patients. In 49% of HAE attacks with abdominal symptoms, isolated abdominal pain was the only symptom. Other abdominal symptoms that commonly present in patients with HAE include distension, cramping, nausea, vomiting, and diarrhea. The average time from onset of symptoms to diagnosis is 6 to 23 years. Under-recognition of HAE in patients presenting with predominant gastrointestinal symptoms is a key factor contributing to the delay in diagnosis, increasing the likelihood of unnecessary or exploratory surgeries or procedures and the potential risk of related complications. HAE should be considered in the differential diagnosis for patients with unexplained abdominal pain, nausea, vomiting, and/or diarrhea who have complete resolution of symptoms between episodes. As highly effective targeted therapies for HAE exist, recognition and diagnosis of HAE in patients presenting with isolated abdominal pain may significantly improve morbidity and mortality for these individuals.