Hereditary angioedema (HAE) is a rare disorder characterized by recurrent attacks of swelling that may involve multiple anatomical locations. In the majority of patients, it is caused by a functional or quantitative defect in the C1 inhibitor (C1-INH), which is an important regulator of the complement, fibrinolytic, kallikrein-kinin and coagulation systems. Standard treatments used for other types of angioedema are ineffective for HAE. Traditional therapies for HAE, including fresh frozen plasma, ε-aminocaproic acid and danazol, may be well tolerated and effective in some patients; however, there are limitations both in their safety and efficacy.
Several novel therapies have completed phase III trials in the US, including: (i) plasma-derived C1-INH replacement therapies (Berinert P® and Cinryze®); (ii) a recombinant C1-INH replacement therapy (conestat alfa; Rhucin®); (iii) a kallikrein inhibitor (ecallantide [DX-88]); and (iv) a bradykinin-2-receptor antagonist (icatibant). Both Berinert P® and Cinryze® are reported to have excellent efficacy and safety data from phase III trials. Currently, only Cinryze® has been approved for prophylactic use in the US. US FDA approval for other novel agents to treat HAE and for the use of Cinryze® in the treatment of acute attacks is pending.