A novel therapeutic concept for the treatment of acute angioedema attacks in hereditary angioedema patients: multiple successful treatments even in severe swelling attacks with the bradykinin-B2 receptor antagonist Icatibant

Several forms of angioedema seem to be induced by elevated bradykinin (BK) concentrations. They are either caused by increased BK production, as is the case in hereditary angioedema (HAE) involving the lack of a functional C1-esterase inhibitor, or by reduced BK inactivation (e.g. during ACE-inhibitor treatment). BK-induced angioedema does not respond to the current standard treatment for angioedema caused by increased histamine levels, corticosteroids and antihistamines. Until now acute attacks of HAE have been treated with intravenously administered C1-esterase inhibitor concentrate derived from human plasma. However, no specific treatment has been approved for ACE-inhibitor-induced angioedema. It would be necessary that such an approach inhibits directly the activation of the bradykinin-B2 receptor by BK. During the ongoing international phase III HAE study FAST2, we treated several HAE patients subcutaneously with Icatibant, a specific bradykinin-B2 receptor antagonist. In the open-label part of this study we administered Icatibant for the treatment of 21 acute HAE attacks. Eleven attacks were located in the head-neck region, of which three involved the laryngeal area, six the abdominal and four the genital area. Following treatment with Icatibant, patients reported rapid onset of symptom relief and complete remission of symptoms within a few hours. We were especially impressed by the successful treatment of the edema involving the laryngeal area. The study drug was safe and well tolerated. We have noted short-lived local injection site reactions, which resolved spontaneously without intervention. In our hands Icatibant showed high efficacy for the treatment of acute HAE attacks with a rapid onset of symptom relief. Subcutaneous administration might improve the quality of life for HAE patients. Icatibant could also represent a new therapeutic paradigm for the treatment of ACE-inhibitor-induced angioedema cases but this hypothesis needs to be tested in a clinical study.