Ecallantide (Kalbitor) is a 60 amino-acid recombinant protein synthesized in the Pichia pastoris strain of yeast. It binds specifically to plasma kallikrein, inhibiting its activity. As a result, kallikrein is unable to cleave high-molecular-weight kininogen to release bradykinin, one of the key effector molecules leading to symptoms in hereditary angioedema.
Ecallantide is administered subcutaneously. It must be administered in a healthcare setting due to an anaphylaxis rate of 3.9% of treated patients.
In 2009, ecallantide was approved by the FDA for the treatment of acute attacks of hereditary angioedema in patients 16 years of age and older. It has been shown to be effective in improving symptoms of an acute attack within 4 hours of administration and decreasing the need for additional medical intervention 24 hours after administration. More recently, ecallantide has also been shown to be effective in ACE inhibitor-induced angioedema. In 2014, the FDA approved an expansion of the indication of ecallantide to include patients 12 years of age and older. Plasma-derived C1INH, recombinant C1INH, and ecallantide are the only agents license for the treatment of pediatric patients. Ecallantide is also effective in the prevention of blood loss from cardiothoracic surgery.
In addition to anaphylaxis, adverse reactions to ecallantide include headache, nausea, fatigue, diarrhea, upper respiratory tract infection, injection site reactions, nasopharyngitis, vomiting, pruritus, abdominal pain, and pyrexia.