CRISPR-Cas9 In Vivo Gene Editing of KLKB1 for Hereditary Angioedema.

BACKGROUND: Hereditary angioedema is a rare genetic disease that leads to severe and unpredictable swelling attacks. NTLA-2002 is an in vivo gene-editing therapy based on clustered regularly interspaced short palindromic repeats (CRISPR)-CRISPR-associated protein 9. NTLA-2002 targets the gene encoding kallikrein B1 (KLKB1), with the goal of lifelong control of angioedema attacks after a single dose. METHODS: In this phase 1 dose-escalation portion of a combined phase 1-2 trial of NTLA-2002 in adults with hereditary angioedema, we administered NTLA-2002 at a single dose of 25 mg, 50 mg, or 75 mg. The primary end points were the safety and side-effect profile of NTLA-2002 therapy. Secondary and exploratory end points included pharmacokinetics, pharmacodynamics, and clinical efficacy determined on the basis of investigator-confirmed angioedema attacks. RESULTS: Three patients received 25 mg of NTLA-2002, four received 50 mg, and three received 75 mg. At all dose levels, the most common adverse events were infusion-related reactions and fatigue. No dose-limiting toxic effects, serious adverse events, grade 3 or higher adverse events, or clinically important laboratory findings were observed after the administration of NTLA-2002. Dose-dependent reductions in the total plasma kallikrein protein level were observed between baseline and the latest assessment, with a mean percentage change of -67% in the 25-mg group, -84% in the 50-mg group, and -95% in the 75-mg group. The mean percentage change in the number of angioedema attacks per month between baseline and weeks 1 through 16 (primary observation period) was -91% in the 25-mg group, -97% in the 50-mg group, and -80% in the 75-mg group. Among all the patients, the mean percentage change in the number of angioedema attacks per month from baseline through the latest assessment was -95%. CONCLUSIONS: In this small study, a single dose of NTLA-2002 led to robust, dose-dependent, and durable reductions in total plasma kallikrein levels, and no severe adverse events were observed. In exploratory analyses, reductions in the number of angioedema attacks per month were observed at all dose levels. (Funded by Intellia Therapeutics; ClinicalTrials.gov number, NCT05120830.).

Evolution of Guidelines for the Management of Hereditary Angioedema due to C1 Inhibitor Deficiency

Hereditary angioedema (HAE) is a severe and disabling condition characterized by recurrent episodes of subcutaneous or mucosal swelling in the skin and respiratory and gastrointestinal tracts. HAE due to C1-esterase inhibitor deficiency (C1-INH-HAE) is the most prevalent subtype. The present Iberian study compared C1-INH-HAE treatment guidelines published between 2010 and 2022 to identify the main differences in therapeutic approaches for on-demand treatment and short- and long-term prophylaxis (LTP). HAE guidelines evolved with the availability of new treatments and with a change in the management paradigm towards an individualized, patient-centered approach, where quality of life (QOL) is central. A parallel trend was observed towards increasingly frequent home-based treatment, which potentially facilitates timely interventions, provides greater flexibility and convenience, and is associated with increased QOL, enabling patients to lead more normal lives. Most innovations over the years were made for LTP, together with the advent of new therapies and awareness of patients’ needs. Several prophylactic therapies with a high level of evidence became available, although formal head-to-head comparisons are lacking. The treatment goals became more ambitious, ranging from a reduction in the frequency, severity, and duration of attacks to achieving total disease control and normalization of patients’ lives. The document also addresses relevant items such as changes in terminology (eg, the introduction of designations as “first-line”) and the introduction of patient-reported outcome measures to assess patients’ perceptions of their self-experienced QOL and well-being. Unmet needs in the management of C1-INH-HAE are identified (AU)

El angioedema hereditario (AEH) es una enfermedad grave e incapacitante, caracterizada por episodios recurrentes de edema subcutáneo en la piel o en las mucosas de los tractos respiratorio y gastrointestinal. El AEH por déficit del C1-inhibidor (AEH-C1-INH) es el subtipo más prevalente. En el presente estudio ibérico se han comparado las guías/recomendaciones de tratamiento del AEH-INH-C1, publicadas entre 2010 y 2022 para identificar las principales diferencias en cuanto a los enfoques terapéuticos para el tratamiento a demanda y la profilaxis a corto y largo plazo (PLP). A nivel mundial, las directrices sobre el AEH evolucionaron con la disponibilidad de nuevos tratamientos y con un cambio en el paradigma de gestión hacia un enfoque individualizado y centrado en el paciente en el que la calidad de vida (CdV) es fundamental. En consonancia con ello, se observó una tendencia creciente hacia el tratamiento domiciliario, ya que facilita potencialmente las intervenciones precoces, proporciona mayor flexibilidad y comodidad, y se asocia a una mayor calidad de vida, permitiendo a los pacientes llevar una vida normal. La PLP es el indicador que más innovaciones ha experimentado a lo largo de los años, paralelamente a la disponibilidad de nuevas terapias y a la toma de conciencia de las necesidades de los pacientes. Se dispone de varias terapias profilácticas con un alto nivel de evidencia, aunque faltan estudios específicos de comparaciones directas entre ellas. Los objetivos del tratamiento se han ido haciendo más ambiciosos, desde la reducción de la frecuencia, gravedad y duración de los ataques, hasta lograr el control total de la enfermedad y la normalización de la vida de los pacientes en la actualidad (AU)

Factor VII activating protease (FSAP) is not essential in the pathophysiology of angioedema in patients with C1 inhibitor deficiency.

BACKGROUND: Excessive bradykinin (BK) generation from high molecular weight kininogen (HK) by plasma kallikrein (PK) due to lack of protease inhibition is central to the pathophysiology of hereditary angioedema (HAE). Inadequate protease inhibition may contribute to HAE through a number of plasma proteases including factor VII activating protease (FSAP) that can also cleave HK. OBJECTIVE: To investigate the interaction between FSAP and C1 inhibitor (C1Inh) and evaluate the potential role of FSAP in HAE with C1Inh deficiency. MATERIALS AND METHODS: Plasma samples from 20 persons with HAE types 1 or 2 in remission were studied and compared to healthy controls. We measured and compared antigenic FSAP levels, spontaneous FSAP activity, FSAP generation potential, activation of plasma pre-kallikrein (PPK) by FSAP, and the formation of FSAP-C1Inh and FSAP-alpha2-antiplasmin (FSAP-α2AP) complexes. Furthermore, we measured HK cleavage and PK activation after activation of endogenous pro-FSAP and after addition of exogenous FSAP. RESULTS: In plasma from HAE patients, there is increased basal FSAP activity compared to healthy volunteers. HAE plasma exhibits decreased formation of FSAP-C1Inh complexes and increased formation of FSAP-α2AP complexes in histone-activated plasma. Although exogenous FSAP can cleave HK in plasma, this was not seen when endogenous plasma pro-FSAP was activated with histones in either group. PK was also not activated by FSAP in plasma. CONCLUSION: In this study, we established that FSAP activity is increased and the pattern of FSAP-inhibitor complexes is altered in HAE patients. However, we did not find evidence suggesting that FSAP contributes directly to HAE attacks.

Angioedema Without Wheals: Challenges in Laboratorial Diagnosis.

Angioedema is a prevailing symptom in different diseases, frequently occurring in the presence of urticaria. Recurrent angioedema without urticaria (AE) can be hereditary (HAE) and acquired (AAE), and several subtypes can be distinguished, although clinical presentation is quite similar in some of them. They present with subcutaneous and mucosal swellings, affecting extremities, face, genitals, bowels, and upper airways. AE is commonly misdiagnosed due to restricted access and availability of appropriate laboratorial tests. HAE with C1 inhibitor defect is associated with quantitative and/or functional deficiency. Although bradykinin-mediated disease results mainly from disturbance in the kallikrein-kinin system, traditionally complement evaluation has been used for diagnosis. Diagnosis is established by nephelometry, turbidimetry, or radial immunodiffusion for quantitative measurement of C1 inhibitor, and chromogenic assay or ELISA has been used for functional C1-INH analysis. Wrong handling of the samples can lead to misdiagnosis and, consequently, mistaken inappropriate approaches. Dried blood spot (DBS) tests have been used for decades in newborn screening for certain metabolic diseases, and there has been growing interest in their use for other congenital conditions. Recently, DBS is now proposed as an efficient tool to diagnose HAE with C1 inhibitor deficiency, and its use would improve the access to outbound areas and family members. Regarding HAE with normal C1 inhibitor, complement assays' results are normal and the genetic sequencing of target genes, such as exon 9 of F12 and PLG, is the only available method. New methods to measure cleaved high-molecular-weight kininogen and activated plasma kallikrein have emerged as potential biochemical tests to identify bradykinin-mediated angioedema. Validated biomarkers of kallikrein-kinin system activation could be helpful in differentiating mechanisms of angioedema. Our aim is to focus on the capability to differentiate histaminergic AE from bradykinin-mediated AE. In addition, we will describe the challenges developing specific tests like direct bradykinin measurements. The need for quality tests to improve the diagnosis is well represented by the variability of results in functional assays.

The crux of C1-INH testing in everyday lab work.

BACKGROUND: The determination of functional C1-INH is complex and depends on methodology, sample transport, and storage conditions. In clinical practice, we encounter individuals with pathological values which then cannot be proved true, and HAE patients in whom the values were wrongly found to be normal under non-optimum conditions. We aimed to test realistic real-life sample processing conditions for accurate C1-INH determination. METHODS: We conducted two national inter-laboratory comparisons with optimal sample preparation but different dispatch conditions. We also investigated variations of temperature and time, and their influence on C1-INH. RESULTS: C1-INH levels showed a significantly wider dispersion under suboptimal transport conditions than under optimal conditions (p < 0.00001). Two putatively healthy patient samples turned out to be pathological. Contrary to our expectations, we found no significant trend in a specific direction when the variables of temperature, time and sample material were combined and varied under realistic conditions. However, the range of variation in [%] functionality was markedly greater in supposedly healthy volunteers. Thus, under experimental conditions we obtained false pathological results that were not far from reality. CONCLUSION: C1- INH determination is crucial for the diagnosis of HAE. Time, temperature, and sample handling have a significant impact on this laboratory value, sometimes leading to incorrect values, inaccurate diagnoses, and inappropriate therapies. This underlines the importance of proper handling of samples. If a patient has ambiguous C1-INH values despite optimized conditions, thus hindering a conclusive diagnosis of HAE, we recommend genetic testing.

Anti-C1-Inhibitor Autoantibody Detection by ELISA.

Enzyme-linked immunosorbent assay (ELISA) is a quantitative analytical method used to measure the concentration of molecules in biological fluids through antigen-antibody reactions. Here we describe the measurement of anti-C1-inhibitor autoantibodies by an indirect ELISA. In this method patients' sera are incubated in a microplate coated with plasma derived C1-inhibitor.

COVID-19 as a trigger of acute attacks in people with hereditary angioedema.

Acute attacks could occur during the convalescent phase of COVID-19 illness, more commonly in patients with a history of frequent attacks. However it is unclear whether the acute attacks during the convalescent phase are specifically triggered by COVID-19 or not.

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.

Hereditary Angioedema with and Without C1-Inhibitor Deficiency in Postmenopausal Women.

PURPOSE: Most types of hereditary angioedema (HAE) are worsened by endogenous or exogenous estrogens. Conversely, androgens can improve HAE with abnormal C1-Inhibitor (C1-INH) by increasing C1-INH concentrations. Menopause is associated with an extinction of ovarian estrogenic and androgenic secretion. There is currently insufficient information on postmenopausal women with HAE. The objective of this study was to describe the activity of HAE in postmenopausal women. METHODS: This was a French retrospective, multicenter study in postmenopausal women with HAE with or without C1-INH deficiency/dysfunction. The patients were classified before and after menopause with a previously validated HAE disease severity score. RESULTS: We included 65 women from 13 centers in France. The mean age was 62.7± 9.2 years, and the mean time between menopause and inclusion was 12.5± 9.1 years. HAE was associated with C1-INH deficiencyin 88% (n = 57) of the patients, a mutation of factor 12 in 8% (n = 5), a mutation in plasminogen gene in one, and unknown HAE for two. The HAE course was not different after menopause in 46.1% (n = 30), improved in 38.5% (n = 25), and worsened in 15.4% (n = 10). Improvement was correlated with estrogen sensitivity of angioedema before menopause (p = 0.06 for improvement vs no effect or worsening). In addition, we observed that only ten women received treatment (transdermal or oral estradiol+ progestogen) for their menopause symptoms. Among them, only 3 experienced worsening of symptoms (2 on transdermal and 1 on oral estradiol). CONCLUSION: Following menopause, most women with HAE remain stable but some worsen. Improvement was mainly observed in patients with previous estrogen sensitivity. More research is required in menopausal women with HAE to better understand how to manage climacteric symptoms.

Can the neutrophil-lymphocyte ratio predict type 1 hereditary angioedema attacks?

The neutrophil-lymphocyte ratio is a simple and easily used parameter for the assessment of inflammation. We aimed to determine the predictive potential of the neutrophil-lymphocyte ratio regarding episode occurrence in patients with hereditary angioedema. Sixty-six patients with Type 1 hereditary angioedema and 60 healthy controls were included in the study. The laboratory results of the patients in their episode-free periods were similar to those of the healthy controls. The median of neutrophil-lymphocyte ratio was higher during episodes when compared to normal periods (3.5 versus 2.0, p < .001). A significant positive correlation was present between the episode count and the neutrophil-lymphocyte ratio calculated during the episodes (r = 0.557, p < .001). We can conclude that the neutrophil-lymphocyte ratio, which is cheap and easy to calculate, can be used by clinicians as a predictive parameter for prediction of the episode count in patients with hereditary angioedema.

Pharmacokinetics, Pharmacodynamics, and Exposure-Response of Lanadelumab for Hereditary Angioedema.

Hereditary angioedema (HAE) with C1 inhibitor deficiency is a rare disorder characterized by unpredictable, potentially life-threatening recurrent angioedema attacks. Lanadelumab is a fully human monoclonal antibody with selective binding to active plasma kallikrein, and prevents the formation of cleaved high molecular weight kininogen (cHMWK) and bradykinin, thereby preventing HAE attacks. The clinical pharmacology of lanadelumab was characterized following subcutaneous administration in 257 subjects (24 healthy subjects and 233 patients with HAE). The pharmacokinetics of lanadelumab were described using a one-compartment model with first-order rate of absorption and linear clearance, showing slow absorption and a long half-life (14.8 days). A covariate analysis retained body weight and health status on apparent clearance (CL/F) and body weight on volume of distribution (V/F). Population estimates of CL/F and V/F were 0.0249 L/hour (0.586 L/day) and 12.8 L, respectively. An indirect-response Imax model showed 53.7% maximum suppression in cHMWK formation with a low potential for interactions with concomitant medications (analgesic, anti-inflammatory, and antirheumatic medications). A 300 mg dose administered Q2W was associated with a mean steady-state minimum concentration (Cmin,ss ; 25.4 µg/mL) that was ~ 4.5-fold higher than the half-maximal inhibitory concentration for cHMWK reduction (5.71 µg/mL). Exposure-response analyses suggest that 300 mg Q2W dosing was associated with a significantly reduced HAE attack rate, prolonged time to first attack after treatment initiation, and lower need for concomitant medications. The response was comparable across patient body weight groups. Findings from this analysis support the dosing rationale for lanadelumab to prevent attacks in patients with HAE.

A focus on the use of subcutaneous C1-inhibitor for treatment of hereditary angioedema.

INTRODUCTION: HAE is a very debilitating disease that causes significant distress for patients not only during an acute attack but also constant fear for a subsequent attack. It is important to address long-term prophylactic (LTP) therapy to prevent attacks, decrease morbidity and increase the quality of life. When discussing LTP, the drug burden, convenience and efficacy must be taken into account. AREAS COVERED: We review the literature and the different phases of clinical trials leading up to approval by the US FDA of subcutaneous highly concentrated C1-Inhibitor (SC-C1-INH), called Haegarda. The dose approved is of 60 IU/kg twice weekly showing significant improvement in the reduction of attacks and need for on-demand therapy for attacks with minimal side effects. EXPERT OPINION: SC-C1-INH has added significantly to the armamentarium of physicians that treat HAE. The ability to achieve a steady state of C1-INH above 40% function is key to the success of the drug. The drug burden is an SC injection twice a week that exceeds the newly approved lanadelumab. The benefit may be that the protein that is deficient in HAE is replaced and with this the complement, fibrinolytic, coagulation pathways, and contact system are also regulated; however, evidence that this is of benefit is still lacking.

Perioperative Management of Patients With Hereditary Angioedema With Special Considerations for Cardiopulmonary Bypass.

Hereditary angioedema (HAE) is a rare autosomal dominant disorder mostly due to the deficiency of C1-esterase inhibitor (C1-INH). Reduced C1-INH activity below ~38% disrupts homeostasis of bradykinin (BK) formation by increasing kallikrein activation and causes recurrent angioedema attacks affecting the face, extremities, genitals, bowels, oropharynx, and larynx. HAE symptoms can be debilitating and potentially life-threatening. The recent clinical developments of biological and pharmacological agents have immensely improved acute and long-term care of patients with moderate-to-severe HAE. The therapies are given as on-demand and/or prophylaxis, and self-administration is highly recommended and performed with some agents via intravenous or subcutaneous route. Perioperative clinicians need to be familiar with the symptoms and diagnosis of HAE as well as available therapies because of the potential need for airway management, sedation, or anesthesia for various medical and surgical procedures and postoperative care. Cardiovascular surgery using cardiopulmonary bypass is a unique condition in which heparinized blood comes into direct contact with an artificial surface while pulmonary circulation, a major reserve of angiotensin-converting enzyme (ACE), becomes excluded. These changes result in systemic kallikrein activation and BK formation even in non-HAE patients. The objectives of this review are (1) to review pathophysiology of HAE and laboratory testing, (2) to summarize pertinent pharmacological data on the prophylactic and on-demand treatment strategies, and (3) to discuss available clinical data for perioperative management in cardiovascular surgery.

Bradykinin and oxidative stress in patients with hereditary angioedema due to C1 inhibitor deficiency.

INTRODUCTION: Hereditary angioedema (HAE) is a rare autosomal dominant disease caused by genetic dysfunction of C1 inhibitor (C1-INH) due to mutations in the SERPING1 gene. The disorder is mediated mainly by bradykinin. The clinical course of the disease is varied and not related to genetic changes. OBJECTIVES: We aimed to evaluate redox homeostasis of peripheral blood mononuclear cells (PBMCs) in patients with HAE due to C1-INH deficiency (C1 INH HAE) by measuring the levels of reactive oxygen species (ROS) of PBMCs as well as plasma advanced glycation end products (AGEs) and advanced oxidation protein products (AOPPs). We also aimed to assess the effect of bradykinin on ROS levels. PATIENTS AND METHODS: We enrolled 30 adults with C1-INH-HAE and 15 healthy individuals. The levels of ROS were measured by flow cytometry, while the plasma levels of AGEs and AOPPs were determined spectrophotometrically by enzyme­ linked immunosorbent assays. RESULTS: Basal and hydrogen peroxide (H2O2)-induced ROS levels were higher in patients with HAE when compared with controls (P = 0.002 and P = 0.001, respectively), indicating abnormalities in redox homeostasis. Plasma AOPP and AGE levels were similar in both groups. Bradykinin reduced basal and H2O2-induced ROS generation in PBMCs only in patients with HAE (P = 0.03). CONCLUSIONS: The higher basal and H2O2-induced ROS levels in patients with C1 INH HAE indicate redox imbalance. However, by reducing basal and H2O2-induced ROS levels, bradykinin shows antioxidant action in this disorder.

sgp120 and the contact system in hereditary angioedema: A diagnostic tool in HAE with normal C1 inhibitor.

Mutations in Factor XII, plasminogen gene, angiopoietin-1 gene and kininogen 1 gene have been found in some patients with hereditary angioedema with normal C1 inhibitor (HAE-nl-C1inh), but the underlying disease mechanisms remain unclear. Additionally, there are no accepted biomarkers for this disease. Because the contact system has been implicated in hereditary angioedema with C1 inhibitor deficiency (HAE-C1inh), we studied the fragmentation patterns of serum glycoprotein 120 (sgp120), a protein that is highly susceptible to cleavage by kallikrein, in 31 HAE-C1inh and 13 HAE-nl-C1inh patient plasma samples. Compared to normal controls, the majority of plasma samples from patients with HAE-C1inh contained fragmented sgp120. These samples also showed increased kallikrein amidolytic activity indicating spontaneous contact system activation. In contrast, most samples from HAE-nl-C1inh patients exhibited intact sgp120. However, if these samples were incubated at 4 °C in plastic, significant sgp120 fragmentation and spontaneous contact system activation were observed. Concurrently, there was C1 inhibitor fragmentation that generated the nonfunctional 94 kD fragment and a reduction in C1 inhibitor function. Normal samples did not show sgp120 or C1 inhibitor fragmentation after incubation. We sequenced sgp120 and found it to be identical to inter-alpha-trypsin inhibitor heavy chain 4 (ITIH4). These results suggest that sgp120 or ITIH4 is cleaved when the contact system is activated and that this cleavage could be used as a biomarker in patients with HAE-nl-C1inh.

Self-administration of icatibant in acute attacks of Type I hereditary angioedema: A case report and review of hereditary angioedema.

Hereditary angioedema (HAE) is a rare group of genetic disease characterized by non-itchy swelling of subcutaneous and submucosal tissues of the extremities, genitalia, gastrointestinal tract, and upper airways, which can be life threatening. Moreover, unpredictability and recurrence of HAE attacks significantly affect patients' quality of life. Short- and long-term prophylaxis is used to decrease the severity and frequency of attacks, but during severe or potentially severe acute episodes, treatment with C1-INH replacement or icatibant is mandatory. Icatibant is a selective bradykinin B2 receptor antagonist that has been licensed for self-administration at home, resulting in earlier treatment of the attack and quicker recovery, less emergency admittance with a significant improvement of patients' quality of life, and decrease of health care costs. The authors present a case of a young woman, affected by Type I HAE, who has been successfully treated with icatibant on demand at home, resulting in reduction of emergency admissions and improvement of quality of life. The authors also review the different types HAE, their clinical aspects, diagnosis, and management.