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, epsilon-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.