Current and Prospective Targets of Pharmacologic Treatment of Hereditary Angioedema Types 1 and 2

Characteristics of Patients with Hereditary Angioedema Who Reduced Lanadelumab Treatment Administration Frequency: A Retrospective Observational Study of US Claims Data

BACKGROUND

Lanadelumab is the only long-term prophylaxis indicated for reduced administration frequency in patients with hereditary angioedema who have been well controlled for > 6 months. Understanding the characteristics of patients who reduce administration frequency will help identify populations where frequency modifications may be appropriate.

OBJECTIVE

We aimed to describe characteristics of patients who did and did not reduce lanadelumab administration frequency to inform real-world dosing regimens, and characteristics indicative of sustained frequency reduction.

METHODS

A retrospective observational study using healthcare insurance data in the USA from the Merative™ MarketScan® Commercial and Medicare Databases identified patients persistent on lanadelumab for ≥ 18 months. Reduced administration frequency was defined as a ≥ 25% decrease in lanadelumab costs during months 7-12 or 13-18 versus 0-6. Hereditary angioedema attack triggers/symptoms and hereditary angioedema-related healthcare encounters, treatment, and costs were assessed.

RESULTS

Of 54 identified patients, 25 reduced administration frequency. Two patients returned to initial dosing frequency during months 13-18 after reducing during months 7-12. Patients who reduced administration frequency experienced fewer hereditary angioedema attack triggers/symptoms before lanadelumab initiation (baseline) and during months 0-6 than those who did not; they also had a lower mean number of hereditary angioedema-related inpatient admissions, emergency room visits, and outpatient visits during baseline, had fewer claims for acute treatment (60.0% vs 65.5%) and prior long-term prophylaxis (20.0% vs 27.6%), and had lower mean hereditary angioedema treatment costs at baseline ($139,520 vs $233,815) than those who did not.

CONCLUSIONS

This real-world analysis suggests that patients with less frequent hereditary angioedema-related healthcare encounters, lower disease activity, and lower costs within 6 months before lanadelumab initiation are more likely to achieve reduced dosing frequency.

Unveiling the Complexities of Hereditary Angioedema

Hereditary angioedema (HAE) is a rare and potentially life-threatening genetic disorder, constituting approximately 2% of all clinical cases of angioedema, with a global prevalence estimated between 1 in 50,000 and 1 in 150,000 individuals. The condition affects individuals of all genders and ethnic backgrounds without significant variation. HAE is classified into three types. Type I HAE, which accounts for 85% of cases, is characterized by a deficiency of the C1 esterase inhibitor (C1-INH) gene. Type II HAE, making up 15% of cases, involves a dysfunctional C1-INH. Type III HAE, which represents about 5% to 10% of cases, is often estrogen-dependent and although several mutations have been identified, it typically involves normal C1-INH activity. Despite the differences in C1-INH functionality, all three types of HAE manifest with similar clinical symptoms. HAE leads to recurrent episodes of non-pruritic angioedema, which occurs in the absence of urticaria. Breakthroughs in understanding HAE pathophysiology have revolutionized treatment, leading to the development of highly targeted therapies for both acute management and long-term prevention. Meanwhile, cutting-edge advancements in omics technologies are unlocking new possibilities for biomarker discovery, paving the way for more precise diagnoses and personalized treatment strategies that could significantly enhance patient outcomes. This review will delve into the intricate pathophysiology, diverse clinical presentations, and diagnostic challenges of HAE while exploring emerging biomarkers and innovative approaches to therapeutic management and prevention strategies. Additionally, it will underscore the vital importance of screening family members of affected individuals, even when symptoms are not present.

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.

Once-Daily Oral Berotralstat for Long-Term Prophylaxis of Hereditary Angioedema: The Open-Label Extension of the APeX-2 Randomized Trial

BACKGROUND

Berotralstat is a first-line, once-daily oral plasma kallikrein inhibitor approved for prophylaxis of hereditary angioedema (HAE) attacks in patients 12 years or older.

OBJECTIVE

This analysis examined the safety and effectiveness of long-term prophylaxis with berotralstat.

METHODS

APeX-2 was a phase 3, parallel-group, multicenter trial in patients with HAE caused by C1-inhibitor deficiency (NCT03485911). Part 1 was a randomized, double-blind, placebo-controlled evaluation of 150 and 110 mg of berotralstat over 24 weeks. In part 2, berotralstat-treated patients continued the same treatment, and placebo-treated patients were re-randomized to 150 or 110 mg of berotralstat for 24 weeks. In part 3, all patients were treated with open-label berotralstat at 150 mg, which could be continued for up to an additional 4 years. In part 3, the primary endpoint was long-term safety and tolerability. Secondary endpoints included HAE attack rates and quality of life (QoL).

RESULTS

Eighty-one patients entered part 3. Treatment-emergent adverse events (TEAEs) occurred in 82.7% of patients, with most being mild or moderate in severity. The most common TEAEs were nasopharyngitis, urinary tract infection, abdominal pain, arthralgia, coronavirus infection, and diarrhea. Drug-related TEAEs occurred in 14.8% of patients, but none were serious. For patients who completed 96 weeks of berotralstat treatment (n = 70), the mean (standard error) change in attack rate from baseline was -2.21 (0.20) attacks/mo. Clinically meaningful improvements in QoL were also observed, with the largest improvements in the functioning domain.

CONCLUSION

Berotralstat was generally well tolerated, provided rapid and sustained reductions in HAE attacks and improved QoL over 96 weeks.

An expert panel's review on patients with hereditary angioedema switching from attenuated androgens to oral prophylactic therapy

Background: Hereditary angioedema (HAE) is a rare condition marked by swelling episodes in various body parts, including the extremities, upper airway, face, intestinal tract, and genitals. Long-term prophylaxis (LTP), prescribed to control recurring HAE attacks, is integral to its management. Previously, attenuated androgens (AAs) were the only oral LTP options. However, in 2020, berotralstat, an oral plasma kallikrein inhibitor, was approved in the United States. A 2018 survey of adults with HAE type I or type II showed that almost all the patients who used prophylactic HAE medication preferred oral treatment (98%) and felt that it fit their lifestyle better than injectable treatment (96%). Still, guidelines lack consensus on transitioning patients from AAs to alternative oral prophylactic therapy. Objective: This paper aims to share expert insights and patient feedback on transitioning from AAs to berotralstat, an alternative oral prophylactic therapy, from the perspective of clinicians with extensive experience in treating patients with HAE. Methods: A panel of five HAE specialists convened for a virtual half-day roundtable discussion in April 2023. Results: Discussions about transitioning from AAs to berotralstat were prompted by routine consultations, patient inquiries based on independent research, ineffective current treatment, or worsening AA-related adverse effects. For patients who switched from AAs, the physicians reported that the decision was influenced by the alternative therapy's ability to prevent HAE attacks, its safety, and the once-daily administration schedule. All expert panel members identified fewer AA-related adverse effects; better quality of life; and less severe, shorter, and less frequent HAE attacks as clinical or patient goals they hoped to achieve through the treatment switch. Conclusion: The emergence of new, highly specific LTP drugs for HAE calls for the development of comprehensive recommendations and guidelines for transitioning from AAs to alternative oral prophylactic therapy. The expert panel highlighted key factors to consider during the development of such guidelines.

The analysis of the effect of the COVID-19 pandemic on patients with hereditary angioedema type I and type II

Due to the similarity between the pathomechanism of SARS-CoV-2 infections and hereditary angioedema due to C1-inhibitor deficiency (C1-INH-HAE), a possibility emerged that C1-INH-HAE may worsen the course of the infection, or that the infection may influence the severity of angioedema (HAE) attacks in C1-INH-HAE patients. Our study aimed to evaluate the effects of the COVID-19 pandemic on the quality of life (QoL) of Hungarian C1-INH-HAE patients, and to survey the acute course of the infection, post COVID symptoms (PCS), vaccination coverage and the side effects of vaccines in this patient population. 93 patients completed our questionnaire between 1st July 2021 and 31st October 2021. In this same period and between March 2019 and March 2020, 63 patients completed the angioedema quality of life questionnaire (AE-QoL). Out of those patients infected with SARS-CoV-2 in the examined period (18/93 patients; 19%), 5% required hospitalization, 28% experienced HAE attacks in the acute phase of the infection, and 44% experienced PCS. A total number of 142 doses of vaccines were administered to the patients. Serious vaccine reactions did not occur in any case, 4 (5%) out of the 73 vaccinated patients experienced HAE attacks. No significant difference (p = 0.59) was found in the median of the AE-QoL total score, or in the number of HAE attacks prior and during the pandemic. Based on our study, HAE patients did not experience more serious SARS-CoV-2 infection, and it did not aggravate the course of HAE either. Changes in the QoL were not significant, and vaccines were safe in HAE patients.

Cold Urticaria Syndromes: Diagnosis and Management

Cold urticaria is a chronic condition causing episodic symptoms of cold-induced wheals or angioedema in response to direct or indirect exposure to cold temperatures. Whereas symptoms of cold urticaria are typically benign and self-limiting, severe systemic anaphylactic reactions are possible. Acquired, atypical, and hereditary forms have been described, each with variable triggers, symptoms, and responses to therapy. Clinical testing, including response to cold stimulation, helps define disease subtypes. More recently, monogenic disorders characterized by atypical forms of cold urticaria have been described. Here, we review the different forms of cold-induced urticaria and related syndromes and propose a diagnostic algorithm to aid clinicians in making a timely diagnosis for the appropriate management of these patients.

A multicenter chart review of patient characteristics, treatment, and outcomes in hereditary angioedema: unmet need for more effective long-term prophylaxis

BACKGROUND

Hereditary angioedema (HAE) is a rare disease characterized by unpredictable, recurring subcutaneous or submucosal swelling. Without effective therapy, HAE can negatively impact patients' quality of life. Management of HAE includes on-demand treatment of attacks and short- and long-term prophylaxis (LTP) to prevent attacks. Newer therapies may be more tolerable and effective in managing HAE; however, therapies such as androgens are still widely used in some countries owing to their relative ease of access and adequate disease control for some patients. This study evaluated the characteristics, treatment patterns, clinical outcomes, and healthcare resource utilization of a multinational cohort of patients with HAE, with a focus on understanding reasons for recommending or discontinuing available therapies.

METHODS

A retrospective chart review was conducted at 12 centers in six countries and included data from patients with HAE type 1 or 2 who were ≥ 12 years of age at their first clinical visit. The relationship between LTP use and attack rates was evaluated using a multivariable Poisson regression model. Data were collected between March 2018 and July 2019.

RESULTS

Data from 225 patients were collected (62.7% female, 86.2% White, 90.2% type 1); 64.4% of patients had their first HAE-related visit to the center prior to or during 2014. Treatment patterns varied between countries. Overall, 85.8% of patients were prescribed on-demand treatment and 53.8% were prescribed LTP, most commonly the androgen danazol (53.7% of patients who used LTP). Plasma-derived C1 inhibitor (Cinryze^®) was used by 29.8% of patients for LTP. Patients who received LTP had a significantly lower rate of HAE attacks than patients who did not receive any LTP (incidence rate ratio (95% confidence interval) 0.90 (0.84-0.96)). Androgens were the most commonly discontinued therapy (51.3%), with low tolerability cited as the most frequent reason for discontinuation (50.0%).

CONCLUSIONS

Overall, findings from this study support the use of LTP in the prevention of HAE attacks; a lower rate of attacks was observed with LTP compared with no LTP. However, the type of LTP used varied between countries, with tolerability and accessibility to specific treatments playing important roles in management decision-making.

Efficacy and safety of garadacimab, a factor XIIa inhibitor for hereditary angioedema prevention (VANGUARD): a global, multicentre, randomised, double-blind, placebo-controlled, phase 3 trial

BACKGROUND

Hereditary angioedema is a rare and potentially life-threatening genetic disease that is associated with kallikrein-kinin system dysregulation. Garadacimab (CSL312), a novel, fully-human monoclonal antibody that inhibits activated factor XII (FXIIa), is being studied for the prevention of hereditary angioedema attacks. The aim of this study was to evaluate the efficacy and safety of once-monthly subcutaneous administrations of garadacimab as prophylaxis for hereditary angioedema.

METHODS

VANGUARD was a pivotal, multicentre, randomised, double-blind, placebo-controlled, phase 3 trial that recruited patients (aged ≥12 years) with type I or type II hereditary angioedema across seven countries (Canada, Germany, Hungary, Israel, Japan, the Netherlands, and the USA). Eligible patients were randomly assigned (3:2) to receive garadacimab or placebo for 6 months (182 days) by an interactive response technology (IRT) system. Randomisation was stratified by age (≤17 years vs >17 years) and baseline attack rate (1 to <3 attacks per month vs ≥3 attacks per month) for the adult group. The randomisation list and code were kept by the IRT provider during the study, with no access by site staff and funding representatives. All patients and investigational site staff, and representatives from the funder (or their delegates) with direct interaction with the study sites or patients, were masked to treatment assignment in a double-blind fashion. Randomly assigned patients received a 400-mg loading dose of subcutaneous garadacimab as two 200-mg injections or volume-matched placebo on day 1 of the treatment period, followed by five additional self-administered (or caregiver-administered) monthly doses of 200-mg subcutaneous garadacimab or volume-matched placebo. The primary endpoint was the investigator-assessed time-normalised number of hereditary angioedema attacks (number of hereditary angioedema attacks per month) during the 6-month treatment period (day 1 to day 182). Safety was evaluated in patients who received at least one dose of garadacimab or placebo. The study is registered with the EU Clinical Trials Register, 2020-000570-25 and ClinicalTrials.gov, NCT04656418.

FINDINGS

Between Jan 27, 2021, and June 7, 2022, we screened 80 patients, 76 of whom were eligible to enter the run-in period of the study. Of 65 eligible patients with type I or type II hereditary angioedema, 39 were randomly assigned to garadacimab and 26 to placebo. One patient was randomly assigned in error and did not enter the treatment period (no dose of study drug received), resulting in 39 patients assigned to garadacimab and 25 patients assigned to placebo being included. 38 (59%) of 64 participants were female and 26 (41%) were male. 55 (86%) of 64 participants were White, six (9%) were Asian (Japanese), one (2%) was Black or African American, one (2%) was Native Hawaiian or Other Pacific Islander, and one (2%) was listed as other. During the 6-month treatment period (day 1 to day 182), the mean number of investigator-confirmed hereditary angioedema attacks per month was significantly lower in the garadacimab group (0·27, 95% CI 0·05 to 0·49) than in the placebo group (2·01, 1·44 to 2·57; p<0·0001), corresponding to a percentage difference in means of -87% (95% CI -96 to -58; p<0·0001). The median number of hereditary angioedema attacks per month was 0 (IQR 0·00-0·31) for garadacimab and 1·35 (1·00-3·20) for placebo. The most common treatment-emergent adverse events were upper-respiratory tract infections, nasopharyngitis, and headaches. FXIIa inhibition was not associated with an increased risk of bleeding or thromboembolic events.

INTERPRETATION

Monthly garadacimab administration significantly reduced hereditary angioedema attacks in patients aged 12 years and older compared with placebo and had a favourable safety profile. Our results support the use of garadacimab as a potential prophylactic therapy for the treatment of hereditary angioedema in adolescents and adults.

FUNDING

CSL Behring.

The role of vasoactive peptides in skin homeostasis-focus on adiponectin and the kallikrein-kinin system

Vasoactive peptides often serve a multitude of functions aside from their direct effects on vasodynamics. This article will review the existing literature on two vasoactive peptides and their involvement in skin homeostasis: adiponectin and-as the main representative of the kallikrein-kinin system-bradykinin. Adiponectin is the most abundantly expressed adipokine in the human organism, where it is mainly localized in fat depots including subcutaneous adipose tissue, from where adiponectin can exert paracrine effects. The involvement of adiponectin in skin homeostasis is supported by a number of studies reporting the effects of adiponectin in isolated human keratinocytes, sebocytes, fibroblasts, melanocytes, and immune cells. Regarding skin pathology, the potential involvement of adiponectin in psoriasis, atopic dermatitis, scleroderma, keloid, and melanogenesis is discussed in this article. The kallikrein-kinin system is composed of a variety of enzymes and peptides, most of which have been identified to be expressed in the skin. This also includes the expression of bradykinin receptors on most skin cells. Bradykinin is one of the very few hormones that is targeted by treatment in routine clinical use in dermatology-in this case for the treatment of hereditary angioedema. The potential involvement of bradykinin in wound healing, psoriasis, and melanoma is further discussed in this article. This review concludes with a call for additional preclinical and clinical studies to further explore the therapeutic potential of adiponectin supplementation (for psoriasis, atopic dermatitis, wound healing, scleroderma, and keloid) or pharmacological interference with the kallikrein-kinin system (for wound healing, psoriasis, and melanoma).

CU06-1004 alleviates vascular hyperpermeability in a murine model of hereditary angioedema by protecting the endothelium

BACKGROUND

Over-release of the vasoactive peptide bradykinin (BK) due to mutation in the SERPING1 gene is the leading cause of hereditary angioedema (HAE). BK directly activates endothelial cells and increases vascular permeability by disrupting the endothelial barrier, leading to angioedema affecting face, lips, extremities, gastrointestinal tract, and larynx. Although various pharmacological treatment options for HAE became available during the last decade, they are presently limited and pose a major economic burden on patients. To identify additional therapeutic options for HAE, we evaluated the effect of CU06-1004, an endothelial dysfunction blocker, on BK-induced vascular hyperpermeability and the HAE murine model.

METHODS

To investigate the effect of CU06-1004 on BK-induced vascular hyperpermeability in vivo, we pre-administrated WT mice with the drug and then induced vascular leakage through intravenous injection of BK and observed vascular alternation. Then, SERPING1 deficient mice were used for a HAE murine model. For an in vitro model, the HUVEC monolayer was pre-treated with CU06-1004 and then stimulated with BK.

RESULTS

Bradykinin disrupted the endothelial barrier and formed interendothelial cell gaps, leading to hyperpermeability in vivo and in vitro. However, CU06-1004 treatment protected the endothelial barrier by suppressing Src and myosin light chain activation via BK and alleviated hyperpermeability.

CONCLUSION

Our study shows that CU06-1004 oral administration significantly reduced vascular hyperpermeability in the HAE murine model by protecting the endothelial barrier function against BK stimulation. Therefore, protecting endothelium against BK with CU06-1004 could serve as a potential prophylactic/therapeutic approach for HAE patients.

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.

Long-term prophylaxis in hereditary angioedema management: Current practices in France and unmet needs

Background: Hereditary angioedema (HAE) is characterized by unpredictable and potentially life-threatening attacks of cutaneous and submucosal swelling. Over the past decade, new agents, based on a better understanding of the underlying biologic mechanisms of HAE, have changed the face of long-term prophylaxis (LTP). Objective: The objective was to describe current practices and unmet needs with regard to LTP for HAE in expert centers in France. Methods: The study was conducted in France in 2020. Based on their experience with patients with HAE who had visited their center at least once in the past 3 years, physicians from 25 centers who are expert in the management of HAE were requested to fill in a questionnaire that encapsulated their active patient list, criteria for prescribing LTP, and medications used. They were asked about potential unmet needs with currently available therapies. They were asked to express their expectations with regard to the future of HAE management. Results: Analysis was restricted to 20 centers that had an active patient file and agreed to participate. There were 714 patients with C1 inhibitor (C1-INH) deficiency, of whom 423 (59.2%) were treated with LTP. Altered quality of life triggered the decision to start LTP, as did the frequency and severity of attacks. Ongoing LTP included androgens (28.4%), progestins (25.8%), lanadelumab (25.3%), tranexamic acid (14.2%), intravenous C1-INHs (5.6%), and recombinant C1-INH (0.7%). Twenty-nine percent of the patents with LTP were considered to still have unmet needs. Physicians' concerns varied among therapies: poor tolerability for androgens and progestins, a lack of efficacy for tranexamic acid and progestins, dosage form, and high costs for C1-INHs and lanadelumab. Physicians' expectations encompassed more-efficacious and better-tolerated medications, easier treatment administration for the sake of improved quality of life of patients, and less-expensive therapies. Conclusion: Despite the recent enrichment of the therapeutic armamentarium for LTP, physicians still expressed unmet needs with currently available therapies.

Treatment of hereditary angioedema—single or multiple pathways to the rescue

Hereditary angioedema (HAE) is a rare disease caused by mutations in the SERPING1 gene. This results in deficient or dysfunctional C1 esterase inhibitor (C1-INH) and affects multiple proteases involved in the complement, contact-system, coagulation, and fibrinolytic pathways. Current options for the treatment and prevention of HAE attacks include treating all affected pathways via direct C1-INH replacement therapy; or specifically targeting components of the contact activation system, in particular by blocking the bradykinin B₂ receptor (B2R) or inhibiting plasma kallikrein, to prevent bradykinin generation. Intravenously administered plasma-derived C1-INH (pdC1-INH) and recombinant human C1-INH have demonstrated efficacy and safety for treatment of HAE attacks, although time to onset of symptom relief varied among trials, specific agents, and dosing regimens. Data from retrospective and observational analyses support that short-term prophylaxis with intravenous C1-INH products can help prevent HAE attacks in patients undergoing medical or dental procedures. Long-term prophylaxis with intravenous or subcutaneous pdC1-INH significantly decreased the HAE attack rate vs. placebo, although breakthrough attacks were observed. Pathway-specific therapies for the management of HAE include the B2R antagonist icatibant and plasma kallikrein inhibitors ecallantide, lanadelumab, and berotralstat. Icatibant, administered for treatment of angioedema attacks, reduced B2R-mediated vascular permeability and, compared with placebo, reduced the time to initial symptom improvement. Plasma kallikrein inhibitors, such as ecallantide, block the binding site of kallikrein to prevent cleavage of high molecular weight kininogen and subsequent bradykinin generation. Ecallantide was shown to be efficacious for HAE attacks and is licensed for this indication in the United States, but the labeling recommends that only health care providers administer treatment because of the risk of anaphylaxis. In addition to C1-INH replacement therapy, the plasma kallikrein inhibitors lanadelumab and berotralstat are recommended as first-line options for long-term prophylaxis and have demonstrated marked reductions in HAE attack rates. Investigational therapies, including the activated factor XII inhibitor garadacimab and an antisense oligonucleotide targeting plasma prekallikrein messenger RNA (donidalorsen), have shown promise as long-term prophylaxis. Given the requirement of lifelong management for HAE, further research is needed to determine how best to individualize optimal treatments for each patient.

Pharmacological suppression of the kallikrein kinin system with KVD900: An orally available plasma kallikrein inhibitor for the on-demand treatment of hereditary angioedema

BACKGROUND

Hereditary angioedema (HAE) is a rare genetic disease that leads to recurrent episodes of swelling and pain caused by uncontrolled plasma kallikrein (PKa) activity. Current guidelines recommend ready availability of on-demand HAE treatments that can be administered early upon attack onset. This report describes the pharmacological and pharmacodynamic properties of the novel oral small-molecule PKa inhibitor KVD900 as a potential on-demand treatment for HAE.

METHODS

Pharmacological properties of KVD900 on PKa and closely related serine proteases were characterized using kinetic fluorogenic substrate activity assays. Effects of KVD900 on PKa activity and kallikrein kinin system activation in whole plasma were measured in the presence of dextran sulphate (DXS)-stimulation using a fluorogenic substrate and capillary immunoassays to quantify high molecular weight kininogen (HK), plasma prekallikrein and Factor XII cleavage. Pharmacodynamic effects of orally administered KVD900 were characterized in plasma samples from six healthy controls in a first in human phase 1 clinical trial and from 12 participants with HAE in a phase 2 clinical trial.

RESULTS

KVD900 is a selective, competitive and reversible inhibitor of human PKa enzyme with a Ki of 3.02 nM. The association constant (Kon ) of KVD900 for PKa is >10 × 106  M-1  s-1 . Oral administration of KVD900 in a first-in-human clinical trial achieved rapid and near complete inhibition of DXS-stimulated PKa enzyme activity and HK cleavage and reduced plasma prekallikrein and Factor XII activation in plasma. In individuals with HAE, orally administered KVD900 inhibited DXS-stimulated PKa activity in plasma by ≥95% from 45 min to at least 4 h post-dose and provided rapid protection of HK from cleavage.

CONCLUSION

KVD900 is a fast-acting oral PKa inhibitor that rapidly inhibits PKa activity, kallikrein kinin system activation and HK cleavage in plasma. On-demand administration of KVD900 may provide an opportunity to halt the generation of bradykinin and reverse HAE attacks.

SERPING1 Variants and C1-INH Biological Function: A Close Relationship With C1-INH-HAE

Hereditary angioedema with C1 Inhibitor deficiency (C1-INH-HAE) is caused by a constellation of variants of the SERPING1 gene (n = 809; 1,494 pedigrees), accounting for 86.8% of HAE families, showing a pronounced mutagenic liability of SERPING1 and pertaining to 5.6% de novo variants. C1-INH is the major control serpin of the kallikrein–kinin system (KKS). In addition, C1-INH controls complement C1 and plasminogen activation, both systems contributing to inflammation. Recognizing the failed control of C1s protease or KKS provides the diagnosis of C1-INH-HAE. SERPING1 variants usually behave in an autosomal-dominant character with an incomplete penetrance and a low prevalence. A great majority of variants (809/893; 90.5%) that were introduced into online database have been considered as pathogenic/likely pathogenic. Haploinsufficiency is a common feature in C1-INH-HAE where a dominant-negative variant product impacts the wild-type allele and renders it inactive. Small (36.2%) and large (8.3%) deletions/duplications are common, with exon 4 as the most affected one. Point substitutions with missense variants (32.2%) are of interest for the serpin structure–function relationship. Canonical splice sites can be affected by variants within introns and exons also (14.3%). For noncanonical sequences, exon skipping has been confirmed by splicing analyses of patients' blood-derived RNAs (n = 25). Exonic variants (n = 6) can affect exon splicing. Rare deep-intron variants (n = 6), putatively acting as pseudo-exon activating mutations, have been characterized as pathogenic. Some variants have been characterized as benign/likely benign/of uncertain significance (n = 74). This category includes some homozygous (n = 10) or compound heterozygous variants (n = 11). They are presenting with minor allele frequency (MAF) below 0.00002 (i.e., lower than C1-INH-HAE frequency), and may be quantitatively unable to cause haploinsufficiency. Rare benign variants could contribute as disease modifiers. Gonadal mosaicism in C1-INH-HAE is rare and must be distinguished from a de novo variant. Situations with paternal or maternal disomy have been recorded (n = 3). Genotypes must be interpreted with biological investigation fitting with C1-INH expression and typing. Any SERPING1 variant reminiscent of the dysfunctional phenotype of serpin with multimerization or latency should be identified as serpinopathy.

Inhibition of Prekallikrein for Hereditary Angioedema

BACKGROUND

Hereditary angioedema is characterized by recurrent and unpredictable swellings that are disabling and potentially fatal. Selective inhibition of plasma prekallikrein production by antisense oligonucleotide treatment (donidalorsen) may reduce the frequency of attacks and the burden of disease.

METHODS

In this phase 2 trial, we randomly assigned, in a 2:1 ratio, patients with hereditary angioedema with C1 inhibitor deficiency to receive four subcutaneous doses of either donidalorsen (80 mg) or placebo, with one dose administered every 4 weeks. The primary end point was the time-normalized number of investigator-confirmed angioedema attacks per month (attack rate) between week 1 (baseline) and week 17. Secondary end points included quality of life, as measured with the Angioedema Quality of Life Questionnaire (scores range from 0 to 100, with higher scores indicating worse quality of life), and safety.

RESULTS

A total of 20 patients were enrolled, of whom 14 were randomly assigned to receive donidalorsen and 6 to receive placebo. The mean monthly rate of investigator-confirmed angioedema attacks was 0.23 (95% confidence interval [CI], 0.08 to 0.39) among patients receiving donidalorsen and 2.21 (95% CI, 0.58 to 3.85) among patients receiving placebo (mean difference, -90%; 95% CI, -96 to -76; P<0.001). The mean change from baseline to week 17 in the Angioedema Quality of Life Questionnaire score was -26.8 points in the donidalorsen group and -6.2 points in the placebo group (mean difference, -20.7 points; 95% CI, -32.7 to -8.7). The incidence of mild-to-moderate adverse events was 71% among patients receiving donidalorsen and 83% among those receiving placebo.

CONCLUSIONS

Among patients with hereditary angioedema, donidalorsen treatment resulted in a significantly lower rate of angioedema attacks than placebo in this small, phase 2 trial. (Funded by Ionis Pharmaceuticals; ISIS 721744-CS2 ClinicalTrials.gov number, NCT04030598.).

Small molecule drugs for atopic dermatitis, rheumatoid arthritis, and hereditary angioedema

OBJECTIVE

To review recent trends in the development of targeted small molecule drugs (SMDs) for the treatment of immunologically driven disorders, including atopic dermatitis, rheumatoid arthritis, and hereditary angioedema.

DATA SOURCES

Data sources included peer-reviewed published literature from the PubMed database, published abstracts from scientific and medical meetings, and medication information from the Drugs@FDA database.

STUDY SELECTIONS

Articles with primary or retrospective trial results, articles with patient or physician survey results, articles providing expert perspectives, and commentary on chronic immunologic disorders, Food and Drug Administration package inserts, and abstracts from scientific meetings were selected.

RESULTS

Targeted biological therapies have greatly improved response rates and symptom relief for patients with long-term immunologically driven disorders over the past 2 decades. However, recent advances in the understanding of molecular pathways involved in the pathogenesis of these disorders have led to the development of novel targeted SMDs, such as tofacitinib and berotralstat, that can be delivered orally or topically. Few head-to-head studies that compare the safety and efficacy of biologics to SMDs in immunologically driven disorders exist, although some studies suggest that oral and topical modes of administration are preferred by patients and may improve patient quality of life over time.

CONCLUSION

Scientific advances have led to an increase in the development of targeted SMDs for the treatment of chronic immunologic disorders, which may revolutionize the management of these diseases. Head-to-head studies and real-world evidence are needed to fully compare treatment attributes between biologics and SMDs, including safety, efficacy, adherence, impact on quality of life, and cost-effectiveness.