Ecallantide (Kalbitor): Uses, Evidence, and Side Effects

People experiencing a sudden hereditary angioedema attack need treatments with a clear evidence base and a known safety profile. Ecallantide, sold as Kalbitor, is one such option approved specifically for this rare condition.

Key takeaways

• Ecallantide (brand name Kalbitor) is a plasma kallikrein inhibitor approved for acute hereditary angioedema attacks.
• It is approved for patients 12 years of age and older.
• The label carries a boxed warning.
• At least 13 clinical trials have studied ecallantide, including a completed Phase 3 trial in HAE.
• FAERS reports for ecallantide are dominated by its indicated condition, hereditary angioedema, alongside headache and malaise.

What Ecallantide Is

Ecallantide is classified as a plasma kallikrein inhibitor. Hereditary angioedema results from mutations affecting C1-esterase-inhibitor, a protein that normally regulates the complement system and the contact system pathway involved in blood clotting. People with this condition have low C1-INH activity and low C4 levels, which allows the kallikrein-kinin system to become overactive. By inhibiting plasma kallikrein, ecallantide interrupts a pathway involved in the swelling attacks characteristic of this disorder.

What Ecallantide Is Approved For

Ecallantide, marketed as Kalbitor, is indicated for treatment of acute attacks of hereditary angioedema in patients 12 years of age and older. This is a rare genetic disorder, and the approval is specific to managing these acute episodes rather than preventing them long term. The label for Kalbitor carries a boxed warning.

What the Evidence Shows

Ecallantide has been studied across at least 13 registered clinical trials. A completed Phase 3 trial, "Efficacy Study of DX-88 (Ecallantide) to Treat Acute Attacks of Hereditary Angioedema (HAE)," supported its use in this population. Other trials explored different applications, including a terminated Phase 1 study in macular edema and a terminated Phase 2 study evaluating blood loss during cardiac surgery, though these did not lead to approvals in those areas.

Reported Side Effects

Reports submitted to FAERS for ecallantide most frequently reference hereditary angioedema itself, the condition it treats, along with off label use and reports of the drug being ineffective. Beyond these, the most commonly reported reactions include malaise, headache, and general pain, with hypersensitivity and dose omission issues also noted. These are counts of submitted reports, not confirmed rates of incidence or proof that the drug caused the reaction.