Advances in Hereditary Angioedema: The Prevention of Angioedema Attacks With Subcutaneous C1-Inhibitor Replacement Therapy

Shared decision-making in the management of hereditary angioedema: An analysis of patient and physician perspectives

Background: Hereditary angioedema (HAE) is a rare genetic disorder characterized by recurrent, localized episodes of edema. Current treatment guidelines highlight the importance of shared decision-making (SDM) during implementation of HAE management plans. Objective: To determine what constitutes a successful SDM approach in HAE management. Method: Qualitative telephone interviews, which lasted ∼1 hour, were conducted with four HAE physicians and four patients from the APeX-S trial. The physicians were asked to describe the structure and/or content of typical HAE prophylaxis consultations and factors to consider when selecting medications for long-term treatment. Insights from these interviews were used to develop an SDM process diagram. The patients were interviewed to assess how closely the diagram fit their perspectives on the HAE consultation and their involvement in decisions that concerned their care. Interview transcripts were assessed by the interviewer to determine the degree of SDM involvement in each consultation by using qualitative criteria from the literature. Results: Two physicians followed a high-SDM format, and one physician used a "blended" approach. The fourth physician followed a standard (low SDM) format. A successful SDM approach was found to require pre-visit planning, a commitment on behalf of the physician to use SDM methods to learn more about the patient, and empowerment of the patient to reflect on and vocalize his or her preferences and/or needs. Patients engaged in SDM were more likely to proactively request a treatment switch. Conclusion: The adoption of validated HAE-specific treatment decision aids, as well as measures to change the mindsets of patients and physicians, may facilitate successful implementation of SDM in HAE.Clinical Trial Registration: The APeX-S trial was registered with clinicaltrials.gov (NCT03472040).

C1-Inhibitor: Structure, Functional Diversity and Therapeutic Development

Human C1-Inhibitor (C1INH), also known as C1-esterase inhibitor, is an important multifunctional plasma glycoprotein that is uniquely involved in a regulatory network of complement, contact, coagulation, and fibrinolytic systems. C1INH belongs to a superfamily of serine proteinase inhibitor (serpins) and exhibits its inhibitory activities towards several target proteases of plasmatic cascades, operating as a major anti-inflammatory protein in the circulation. In addition to its inhibitory activities, C1INH is also involved in non-inhibitory interactions with some endogenous proteins, polyanions, cells and infectious agents. While C1INH is essential for multiple physiological processes, it is better known for its deficiency with regards to Hereditary Angioedema (HAE), a rare autosomal dominant disease clinically manifested by recurrent acute attacks of increased vascular permeability and edema. Since the link was first established between functional C1INH deficiency in plasma and HAE in the 1960s, tremendous progress has been made in the biochemical characterization of C1INH and its therapeutic development for replacement therapies in patients with C1INH-dependent HAE. Various C1INH biological activities, recent advances in the HAE-targeted therapies, and availability of C1INH commercial products have prompted intensive investigation of the C1INH potential for treatment of clinical conditions other than HAE. This article provides an updated overview of the structure and biological activities of C1INH, its role in HAE pathogenesis, and recent advances in the research and therapeutic development of C1INH; it also considers some trends for using C1INH therapeutic preparations for applications other than angioedema, from sepsis and endotoxin shock to severe thrombotic complications in COVID-19 patients.

The importance of recognizing and managing a rare form of angioedema: hereditary angioedema due to C1-inhibitor deficiency

The majority of angioedema cases encountered in clinical practice are histamine-mediated (allergic); however, some cases are bradykinin-related (non-allergic) and do not respond to standard anti-allergy medications. Among bradykinin-related angioedema, hereditary angioedema (HAE) is a rare, but chronic and debilitating condition. The majority of HAE is caused by deficiency (type 1) or abnormal function (type 2) of the naturally occurring protein, C1-inhibitor (C1-INH)-a major inhibitor of proteases in the contact (kallikrein-bradykinin cascade), fibrinolytic pathway, and complement systems. Failure to recognize HAE and initiate appropriate intervention can lead to years of pain, disability, impaired quality of life (QoL) and, in cases of laryngeal involvement, it can be life-threatening. HAE must be considered in the differential diagnosis of non-urticarial angioedema, particularly for patients with a history of recurrent angioedema attacks, family history of HAE, symptom onset in childhood/adolescence, prodromal signs/symptoms before swellings, recurrent/painful abdominal symptoms, and upper airway edema. Management strategies for HAE include on-demand treatment for acute attacks, short-term prophylaxis prior to attack-triggering events/procedures, and long-term or routine prophylaxis for attack prevention. Patients should be evaluated at least annually to assess need for routine prophylaxis. HAE specific medications like plasma-derived and recombinant C1-INH products, kallikrein inhibitors, and bradykinin B2 receptor antagonists, have improved management of HAE. While the introduction of intravenous C1-INH represented a major breakthrough in routine HAE prophylaxis, some patients fail to achieve adequate control and others have psychological barriers or experience complications related to intravenous administration. Subcutaneous (SC) C1-INH, SC monoclonal antibody (mAb)-based therapies, and an oral kallikrein inhibitor offer effective alternatives for HAE attack prevention and may facilitate self-administration. HAE management should be individualized, with QoL improvement being a key goal. This can be achieved with broader availability of existing options for routine prophylaxis, including greater global availability of C1-INH(SC), mAb-based therapy, oral treatments, and multiple on-demand therapies.