Icatibant

Icatibant is a synthetic decapeptide analog of bradykinin that acts as a potent and selective competitive antagonist of the bradykinin B2 receptor. Developed by Jerini (later acquired by Shire, now Takeda) and approved by the FDA in 2011, icatibant is marketed as Firazyr for the treatment of acute attacks of hereditary angioedema (HAE) in adults.

Hereditary angioedema is a rare genetic disorder caused by deficiency or dysfunction of C1-esterase inhibitor (C1-INH), which results in uncontrolled activation of the contact system and excessive bradykinin generation. Bradykinin acts on B2 receptors on endothelial cells to increase vascular permeability, causing the characteristic episodes of subcutaneous and submucosal edema affecting the skin, gastrointestinal tract, and potentially the airway. Laryngeal attacks can be life-threatening if not treated promptly.

Icatibant was designed with five non-natural amino acid substitutions that make it resistant to the enzymatic degradation pathways that rapidly inactivate native bradykinin, while converting it from an agonist to a potent antagonist. By blocking B2 receptor activation by endogenous bradykinin, icatibant directly addresses the pathophysiological mechanism of HAE attacks, rapidly reducing vascular permeability and resolving edema.

The FAST (For Angioedema Subcutaneous Treatment) clinical trials demonstrated that icatibant significantly shortened the time to symptom relief compared to placebo in acute HAE attacks. The median time to onset of symptom relief was approximately 2 hours with icatibant versus 12 hours with placebo, and patient-rated symptom severity scores improved significantly faster. The drug is designed for self-administration, allowing patients to treat attacks promptly at home without requiring an emergency department visit.