Current and emerging biologics for the treatment of hereditary angioedema

Managing Diagnosis, Treatment, and Burden of Disease in Hereditary Angioedema Patients with Normal C1-Esterase Inhibitor

Hereditary angioedema (HAE) is a rare, chronic, and debilitating genetic disorder characterized by recurrent and unpredictable swelling episodes that primarily affect the subcutaneous and/or submucosal tissues of the extremities, larynx, face, abdomen, and genitals. Most cases of HAE are caused by mutations in the serpin family G member 1 gene (SERPING1), which encodes C1-esterase inhibitor (C1-INH) protein. Mutations in SERPING1 lead to deficient (type I HAE-C1-INH) or dysfunctional (type II HAE-C1-INH) C1-INH protein and subsequent dysregulation of the kallikrein-bradykinin cascade. However, some patients present with a third type of HAE (HAE-nI-C1-INH), which was first described in the year 2000 and is characterized by an absence of mutations in SERPING1. Although mutations in the coagulation factor XII, angiopoietin-1, plasminogen, kininogen-1, myoferlin, and heparan sulfate-glucosamine 3-O-sulfotransferase-6 genes have been identified in some patients with HAE-nI-C1-INH, genetic cause is still unknown in many cases, hindering full elucidation of the pathology of this HAE subtype. Diagnosis of HAE-nI-C1-INH is also further complicated by the fact that patients typically demonstrate normal plasma levels of C1-INH and complement component 4 protein and normal C1-INH functionality during laboratory analysis. Therefore, we review the challenges associated with diagnosing, treating, and living with HAE-nI-C1-INH. We conclude that raising awareness of the presenting features of HAE-nI-C1-INH within the clinical setting and among the general public is critical to aid earlier suspicion and diagnosis of the disease. Furthermore, adopting an individualized approach to HAE-nI-C1-INH treatment is essential to help address the current and significant unmet needs in this patient population.

Emerging drugs for the treatment of hereditary angioedema due to C1-inhibitor deficiency

INTRODUCTION

Hereditary angioedema due to C1-inhibitor (C1-INH-HAE) is a rare disease characterized by unpredictable swelling attacks that may be life-threatening when affecting the upper airways. Understanding the pathophysiology of HAE and the mechanism of bradykinin-mediated angioedema allowed the development of new therapies for the treatment of HAE: clinical trials are ongoing to expand the number of drugs available for on-demand treatment and prophylaxis.

AREAS COVERED

Authors discuss the products that have been used to treat this disease for many years and present the most recently marketed products and those which are under development.

EXPERT OPINION

Significant therapeutic progress has been made in HAE. In particular, drugs targeting specific molecules involved in the angioedema formation were developed and studies with new drugs are ongoing. In the coming years, more effective therapies with easier administration route options for on-demand treatment and long-term prophylaxis will be available to treat this disease and the variety of patients. Gene therapy strategies may offer a definitive treatment. High costs of current and new drugs may be a limiting factor for their availability, especially in developing countries.

Orphan Drug Use in Patients With Rare Diseases: A Population-Based Cohort Study

Background: Orphan drugs are used for the diagnosis, prevention and treatment of rare diseases that, in the European Union, are defined as disorders affecting no more than 5 persons in 10,000. So far, a total of around 800 orphan medicinal products have been approved by the European Medicines Agency, however the utilization profile of orphan drugs has yet to be explored. This study aimed at assessing the utilization profile of orphan drugs authorized for marketing by the Italian Medicines Agency using population-based data.

Methods: A total of 21 orphan drugs used in outpatient settings, approved in the European Union before or during the 2008–2018 period and involving 15 rare diseases, were included in the study. The monitored population included patients with one of the conditions surveilled by the population-based Tuscany Registry of Rare Diseases and diagnosed between 2000–2018. A multi-database approach was applied, by linking data from the registry with information collected in drug prescriptions databases. The prevalence and intensity of use were estimated for the selected orphan drugs and other non-orphan medications, used to treat the same rare disease and for which a change in the prevalence of use was hypothesized after authorization of the orphan drug.

Results: For some diseases (acquired aplastic anemia, tuberous sclerosis complex, most metabolic diseases) a low prevalence of orphan drugs use was observed (range between 1.1–12.5%). Conversely, orphan drugs were frequently used in hemophilia B, Wilson disease and idiopathic pulmonary fibrosis (maximum of 78.3, 47.6 and 41.8%, respectively). For hemophilia B and Leber’s hereditary optic neuropathy, there are currently no other medications used in clinical practice in addition to orphan drugs. Six orphan drugs were used for the treatment of pulmonary arterial hypertension, appearing the elective therapy for this disease, albeit with different utilization profiles (range of prevalence 1.7–55.6%).

Conclusion: To the best of our knowledge, this is the first study investigating the utilization profile of orphan drugs prescribed in a defined geographical area, and providing relevant information to monitor over time potential changes in the prevalence of these medications as well as in the health care decision making.

Where we are with acquired angioedema due to C1 inhibitor deficiency: A systematic literature review

Acquired angioedema due to C1 inhibitor deficiency (C1-INH-AAE) is a rare disease characterized by adult-onset recurrent non-urticarial angioedema with low levels of C1-INH. It is associated with lymphoproliferative disorders, and treatments are off-label with variable success. We conducted a systematic literature review to include patients with C1-INH-AAE identified in PubMed and Embase databases between January 2006 and February 2021. Clinical features of these patients were summarized, and factors associated with disease remission were explored. A total of 121 patients were included in the current study with a median age at diagnosis of 64 years and 45.5% being male. An associated disease was recorded in 94 patients (77.7%), and lymphoproliferative disorder was the most reported (59/94, 62.8%). Anti-C1-INH autoantibodies were present in 45 of 71 patients (63.4%). Factors impacting disease remissions included age (odds ratio [OR] 0.951, 95% confidence interval [CI] 0.909-0.994, p = 0.027), male (OR 0.327, 95% CI 0.124-0.866, p = 0.025), presence of monoclonal gammopathy (OR 0.133, 95% CI 0.041-0.429, p = 0.001), requirement of specific on-demand treatment (OR 0.216, 95% CI 0.066-0.709, p = 0.012) and rituximab use (OR 2.865, 95% CI 1.038-7.911, p = 0.042). A total of nine patients (7.4%) died at last follow up and most were unrelated to C1-INH-AAE. Our results imply that C1-INH-AAE is primarily associated with underlying B or plasma cell abnormalities, and clone-directed therapies could be promising options for its long-term management.

Physician and patient perspectives on the management of hereditary angioedema: a survey on treatment burden and needs

Hereditary angioedema (HAE) is a rare disorder caused by genetic mutations that lead to recurrent episodes of swelling in various parts of the body. Prophylactic treatment is common for patients with HAE, and the therapeutic options have expanded in recent years. The current standard of care for prophylactic HAE therapies is subcutaneous treatment, which can be self-administered at home, greatly improving patient quality of life. As new therapies emerge, it is important for patients and physicians to discuss the risks and benefits associated with each treatment to develop an individualized approach to HAE management. We conducted surveys of patients with HAE and physicians who treat patients with HAE to identify prescribing trends for prophylactic HAE treatments and the impact that such treatments has on patients. Our results confirmed that newer, subcutaneous therapies are prescribed for HAE prophylaxis more frequently than other therapies in the United States and that treatment burdens still exist for patients with HAE. We found that physicians and patients were not always aligned on how treatment choices affect patients' lives, which may mean that there are opportunities for enhanced patient-physician dialog and shared decision-making in HAE management in the United States.

A Robust Bioassay of the Human Bradykinin B2 Receptor that Extends Molecular and Cellular Studies: The Isolated Umbilical Vein

Bradykinin (BK) has various physiological and pathological roles. Medicinal chemistry efforts targeted toward the widely expressed BK B₂ receptor (B₂R), a G-protein-coupled receptor, were primarily aimed at developing antagonists. The only B₂R antagonist in clinical use is the peptide icatibant, approved to abort attacks of hereditary angioedema. However, the anti-inflammatory applications of B₂R antagonists are potentially wider. Furthermore, the B₂R antagonists notoriously exhibit species-specific pharmacological profiles. Classical smooth muscle contractility assays are exploited over a time scale of several hours and support determining potency, competitiveness, residual agonist activity, specificity, and reversibility of pharmacological agents. The contractility assay based on the isolated human umbilical vein, expressing B₂R at physiological density, was introduced when investigating the first non-peptide B₂R antagonist (WIN 64338). Small ligand molecules characterized using the assay include the exquisitely potent competitive antagonist, Pharvaris Compound 3 or the partial agonist Fujisawa Compound 47a. The umbilical vein assay is also useful to verify pharmacologic properties of special peptide B₂R ligands, such as the carboxypeptidase-activated latent agonists and fluorescent probes. Furthermore, the proposed agonist effect of tissue kallikrein on the B₂R has been disproved using the vein. This assay stands in between cellular and molecular pharmacology and in vivo studies.

Therapeutic Lessons to be Learned From the Role of Complement Regulators as Double-Edged Sword in Health and Disease

The complement system is an important part of the innate immune system, providing a strong defense against pathogens and removing apoptotic cells and immune complexes. Due to its strength, it is important that healthy human cells are protected against damage induced by the complement system. To be protected from complement, each cell type relies on a specific combination of both soluble and membrane-bound regulators. Their importance is indicated by the amount of pathologies associated with abnormalities in these complement regulators. Here, we will discuss the current knowledge on complement regulatory protein polymorphisms and expression levels together with their link to disease. These diseases often result in red blood cell destruction or occur in the eye, kidney or brain, which are tissues known for aberrant complement activity or regulation. In addition, complement regulators have also been associated with different types of cancer, although their mechanisms here have not been elucidated yet. In most of these pathologies, treatments are limited and do not prevent the complement system from attacking host cells, but rather fight the consequences of the complement-mediated damage, using for example blood transfusions in anemic patients. Currently only few drugs targeting the complement system are used in the clinic. With further demand for therapeutics rising linked to the wide range of complement-mediated disease we should broaden our horizon towards treatments that can actually protect the host cells against complement. Here, we will discuss the latest insights on how complement regulators can benefit therapeutics. Such therapeutics are currently being developed extensively, and can be categorized into full-length complement regulators, engineered complement system regulators and antibodies targeting complement regulators. In conclusion, this review provides an overview of the complement regulatory proteins and their links to disease, together with their potential in the development of novel therapeutics.

Antisense Inhibition of Prekallikrein to Control Hereditary Angioedema

Hereditary angioedema is characterized by recurrent and unpredictable episodes of subcutaneous and mucosal swelling that can be life threatening. IONIS-PKK-L_Rx is a ligand-conjugated antisense oligonucleotide designed for receptor-mediated delivery to hepatocytes. In a compassionate-use pilot study, two patients with severe bradykinin-mediated angioedema were initially administered weekly subcutaneous injections of the unconjugated parent drug, IONIS-PKK_Rx, for 12 to 16 weeks, after which they received IONIS-PKK-L_Rx at a dose of 80 mg every 3 to 4 weeks for 7 to 8 months. Treatment was accompanied by a reduction in the angioedema attack rate. (Funded by Amsterdam UMC.).

Lanadelumab for the prevention of attacks in hereditary angioedema

Introduction: Hereditary angioedema (HAE) with C1 esterase inhibitor deficiency (C1-INH-HAE) is a rare disease that manifests with cutaneous and/or submucosal swellings due to uncontrolled activation of the contact/kinin system. Attacks recur with unpredictable frequency and severity, laryngeal edema is potentially lethal, and the disease burden may severely disrupt patients' lives.Areas covered: This review provides an overview of lanadelumab, a human monoclonal antibody targeted against plasma kallikrein that was recently approved for prevention of symptoms in C1-INH-HAE.Expert opinion: The phase III HELP Study demonstrated the efficacy of lanadelumab in reducing HAE attacks. These positive results are being further confirmed in the open-label extension study. This agent addresses some of the limitations of existing prophylactic options as tolerability issues, the need for intravenous administration and frequent dosing. Therefore, lanadelumab can profoundly improve the quality of life of patients with C1-INH-HAE.

Driving towards Precision Medicine for angioedema without wheals

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