Icatibant is a synthetic decapeptide with 5 nonproteinogenic amino acid antagonist targeting the B₂ receptors with a similar affinity to bradykinin. It is resistant to bradykinin-cleaving enzyme degradation and has a potency of 2-3 times higher than earlier B₂ receptors antagonists, thus representing a new class of medication.[A4017,A263041] It was investigated as a potential treatment of hereditary angioedema (HAE) as bradykinin was implicated in HAE swelling; specifically, mice lacking B₂ receptors showed reduced swelling, thus demonstrating bradykinin involvement in the disease pathophysiology.[A4017,A263046] Icatibant was approved by the FDA on August 25, 2011, and by the EMA in 2008 as a treatment for hereditary angioedema.[L49776,L49781] The FDA approval was based on positive results obtained from 3 double-blind, randomized, controlled clinical trials known as FAST 1, 2, and 3, where a median time to almost complete symptom relief was observed to be 8 hours compared to 36 hours for the placebo treatment.[L49776]