Ecallantide

Kalbitor

Ecallantide is a 60-amino-acid recombinant protein engineered from a human protein scaffold using phage-display technology to be a potent and selective inhibitor of plasma kallikrein. Plasma kallikrein is the enzyme that cleaves high-molecular-weight kininogen to generate bradykinin — the peptide responsible for the vascular leak and swelling of hereditary angioedema (HAE). By inhibiting kallikrein, ecallantide chokes off bradykinin production upstream, which is a different point of attack than icatibant, which blocks the bradykinin receptor itself. Its approved use is the treatment of acute attacks of hereditary angioedema in patients aged 12 and older. HAE, most commonly caused by deficiency or dysfunction of C1 esterase inhibitor, leads to unregulated activation of the contact (kallikrein-kinin) system and recurrent episodes of severe swelling of the skin, gastrointestinal tract, and airway. Because C1 inhibitor normally restrains kallikrein, its deficiency lets kallikrein run unchecked — making kallikrein a logical therapeutic target. In pivotal trials (EDEMA), subcutaneous ecallantide significantly reduced symptom severity of acute attacks compared with placebo. A distinctive safety feature sets ecallantide apart from icatibant: it carries a boxed warning for anaphylaxis, because as a protein it can provoke hypersensitivity reactions that can mimic or complicate an HAE attack. For this reason it is administered by a healthcare professional in a setting equipped to manage anaphylaxis, rather than self-injected at home. It was approved by the FDA in 2009 (Kalbitor). It remains a valuable on-demand option, particularly where an upstream kallikrein-blocking mechanism is preferred, and it is used within a specialist-guided HAE plan.